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 In October, 2002, the American Dental Association (ADA) released a Scientific Assessment entitled “Evaluation of Mercury in Dental Facility Wastewater.” The report argued that dental offices were not a significant source of mercury contamination, and that existing practices were sufficient to keep mercury emissions low.

The Association of Municipal Sewage Authorities released a critique of the ADA report in December, 2002, taking issue with most of its findings.  It is long and detailed, but here are a few nuggets:

The report incorrectly implies that publicly owned treatment works (POTWs) are designed to handle dental mercury.

The report makes definitive statements and assumptions about the bioavailability of mercury in dental amalgam with little or no supporting evidence.

...the cost per pound of removing mercury in dental facility wastewater via amalgam separators ($45,500 to $139,000 per pound, according to the report) could be compared to the cost per pound for POTWs to remove the same mercury (approximately $21 million per pound). 
 
 
 
Report is shown below.
 
AMSA Review of American Dental Association (ADA) Scientific Assessment 
“Evaluation of Mercury in Dental Facility Wastewater” October 2002 
General Comments 
1. The report incorrectly implies that publicly owned treatment works (POTWs) are 
designed to handle dental mercury.  The report must be revised to reflect that this not 
the case.  When Congress created the National Pollutant Discharge Elimination 
System (NPDES) permitting system, it required POTWs to achieve technology based 
treatment requirements (secondary treatment), which were not intended to remove 
toxic pollutants from wastewater.  Instead, the control of toxics from indirect 
dischargers was to be accomplished via local pretreatment requirements (See CWA 
Section 307(b)(1)) and Federal effluent guidelines (See CWA Section 307(a)(2)). 
Congress clearly recognized that removal of toxic pollutants by POTWs was the 
exception, not the rule, and that sewer uses must comply with local and Federal 
pretreatment requirements as necessary to maintain the integrity of the POTW 
wastewater treatment systems (See U.S.C. Section 1342(b)(8){TA \l "33 U.S.C. 
Section 1342(b)(8)" \s "33 U.S.C. Section 1324(b)(8)" \c 4}).  Mercury from dental 
facilities, even if incidentally removed as part of a POTW's treatment system, still 
makes its way into the environment and is not "treated" contrary to the statements in 
the report.  Mercury wastes are incompatible and must be removed at the source. 
2. As POTW discharges are a small fraction of the national mercury problem, AMSA 
agrees that dental amalgam in wastewater is a small percentage of the national 
mercury problem.  But the report must note that dentists remain a significant source 
of mercury for POTWs, and POTWs must comply with very stringent total mercury 
limits through permit requirements or ultimately through the implementation of total 
maximum daily loads (TMDLs).  Many states also have adopted virtual elimination 
policies for mercury that require local agencies, including POTWs, to undertake all 
available means to reduce mercury releases to the environment.  An AMSA study 
estimates that on average dentists contribute between 35 and 40% of the influent 
mercury received by POTWs
1
.  Given the huge costs of removing mercury once it 
becomes part of a POTW’s wastestream (estimates as much $21 million per pound 
have been made), it makes sense to implement all reasonable and cost effective source 
control options for reducing the discharge of mercury to POTWs, including programs 
for dentists. 
3. The report makes definitive statements and assumptions about the bioavailability of 
mercury in dental amalgam with little or no supporting evidence.  AMSA believes 
that there is too much uncertainty associated with the bioavailability of mercury in the 
environment from all sources to include such assumptions in the report’s calculations.  
                                                          
1
 “Mercury Source Control and Pollution Prevention Program Evaluation.”  Prepared for the Association of 
Metropolitan Sewerage Agencies (AMSA), under Cooperative Agreement with the U.S. Environmental Protection 
Agency, by Larry Walker Associates.  March 2002. AMSA Comments on ADA Scientific Assessment 
December 17, 2002 
Page 2 
Accordingly, AMSA believes the report’s calculations should be based solely on total 
mercury. 
The report's text should, however, have a general discussion of the uncertainty 
associated with the bioavailability of mercury.  This could include a statement that 
mercury in amalgam has relatively low bioavailability, but it should also include an 
acknowledgment that the bioavailability of this mercury can increase in the 
environment through, for example, dissolution and methylation and that the potential 
for this happening has been demonstrated by some studies.  It could also refer to EPA 
estimates of the fraction of total mercury in the environment that is methylmercury, 
citing the criterion document but acknowledging that whether mercury from amalgam 
is ultimately more or less bioavailable than these estimates is unknown
2
There should also be an acknowledgement that any considerations of bioavailability 
are irrelevant for POTWs that are implementing programs to achieve compliance with 
water quality based effluent limits for total mercury.  POTWs beneficially reusing 
their biosolids will also be concerned with total mercury.  Furthermore, for a POTW 
that incinerates or otherwise heat treats its solids, the process could affect the form of 
any mercury amalgam in the solids.  Thus, bioavailability of mercury in dental 
amalgam discharged to a particular POTW may vary. 
4. The purpose of the assessment was to evaluate contributions of mercury to the 
environment from the discharge of wastewater during placement and removal of 
dental amalgams.  In preparing the summary, the author must be very careful not to 
generalize the results to include all emissions from dental amalgams, as the report 
does not consider air emissions during placement and removal of amalgams (0.7 
tons/year for 1994-95, per the U.S. EPA, 1997
3
), nor does it consider mercury from 
amalgam that contaminates human waste from teeth grinding, or mercury air 
emissions from cremation of human remains with amalgam fillings.  
5. ADA should acknowledge that their model of the national impact of dental discharges 
is based on little to no real data.   ADA’s contractor, ENVIRON International 
Corporation, uses assumptions and extrapolation, even when real data could be used.  
This approach could be used to reach many different conclusions.  It is misleading to 
suggest that conclusions drawn from such limited data are the product of “rigorous 
scientific analysis.”  In particular, the authors’ assumptions concerning the efficiency 
of amalgam separators and the “bioavailability” of amalgam released into the 
environment are arbitrary and unsupported by real data.   Substituting different data 
on these points, but otherwise using the authors’ model, leads to very different 
                                                          
2
 Water Quality Criterion for the Protection of Human Health: Methylmercury. EPA 823-R-01-001. U.S. 
Environmental Protection Agency. January 2001. 
3
Mercury Study Report to Congress.  EPA-452/R-97-003.  U.S. Environmental Protection Agency.  Washington,               
  D.C. 1997. AMSA Comments on ADA Scientific Assessment 
December 17, 2002 
Page 3 
conclusions from those presented in the report.   With those two changes, one could 
conclude that amalgam separators are in fact a highly cost effective mechanism for 
reducing mercury loadings to POTWs. 
6. Paragraph 5 of Section 1 regarding “…a later version…”  and “…that further versions 
of this assessment will be prepared as additional comments are provided…” should be 
inserted as the first paragraph in the Executive Summary. 
There is no mention of the DRAFT nature of the report within the Executive 
Summary. Within the last paragraph of the Executive Summary there is mention of 
working with others on a National Action Plan.  However, this last paragraph does not 
mention that the main report (regarding numbers and significance of loadings) is still 
under review.  Also, the Cover Page of the document should indicate that the 
assessment is a “DRAFT.” 
Specific Comments 
Executive Summary: 
The ADA concludes that the dental community releases small amounts of mercury when 
compared to various facilities that may release mercury.  While the ADA maintains that the 
total quantity of mercury released to all environmental media is minimal, analysis by the City 
of Wichita (Wichita, Kansas) has found that the dental community is the largest source 
contributor of mercury to the POTW.  These findings are consistent with studies conducted 
by AMSA and other AMSA members.  POTWs are not designed to carry, treat and remove 
mercury, and are required to meet stringent effluent discharge criteria as well as biosolids 
land application criteria.     
The Executive Summary provides specific numbers of various specialties in the dental 
profession.  Further clarification is needed on the amount of individual offices versus offices 
with numerous dentists on the same vacuum.  The report does not take into account the fact 
that some specialties, although infrequently, do remove amalgam in certain situations during 
certain procedures. 
Executive Summary, Paragraph 2: 
“The mercury contained in dental amalgam, and its release during normal restorative 
procedures, is a source of mercury that has received particular scrutiny.” 
As this report only considers the release to wastewater of dental amalgam, this sentence 
should read, “The mercury released to wastewater from dental amalgam during normal 
restorative procedures is a source of mercury that has received particular scrutiny.”  
Alternatively, the ADA could broaden its analysis to consider air emissions of mercury from 
dental facilities as well as wastewater discharges. AMSA Comments on ADA Scientific Assessment 
December 17, 2002 
Page 4 
Executive Summary, Paragraph 2:   
“the present paper quantifies, through a scientifically valid and comprehensive approach, the 
relative contribution of: (1) mercury from dental facilities that enters surface water as 
compared to the total amount of mercury entering surface water from other sources.”   
The report does not quantify mercury from dental facilities that enters surface water, as it 
does not include estimates of mercury from air emissions at dental facilities that may enter 
surface waters.  Additionally, as written, the report does not compare the mercury from 
dental facilities to the total amount of mercury entering surface waters from other sources, 
but rather very narrowly compares the mercury in wastewater from dental facilities in the 
United States to the total amount of mercury emitted into the air from anthropogenic sources 
in the United States in the mid-1990s.  Not all of the mercury emitted to the air in the United 
States is deposited in the United States.  Rather, the Mercury Study Report to Congress
clearly states that computer simulations indicate that only about one-third of the U.S. 
anthropogenic mercury emissions are deposited in the lower 48 states of the U.S.  
Additionally, the Mercury Study Report to Congress upon which the comparison is made 
does not quantify the amount of mercury air emissions which enters water bodies, but rather 
only discusses told amounts emitted in the U.S. and deposited in the U.S.  Not all mercury 
from air emissions will reach water bodies, as some of the mercury will adhere to soils or be 
taken up by plants before it reaches a water body.   
This phrase should therefore read, “the present paper compares … releases of mercury in 
dental facility wastewater to total air emissions of mercury in the United States in the mid-
1990s.”  Even so, the statement would remain somewhat misleading, as only a third of the 
mercury emitted in the United States is actually deposited in the United States, and the 
amount of this mercury that enters surface waters is unknown. 
Executive Summary, Paragraph 2:  
“the present paper quantifies, through a scientifically valid and comprehensive approach, the 
relative contribution of: … (2) the amount of mercury in municipal sludge attributable to 
wastewater discharged from dental facilities” 
The current version of the report does not determine the percentage of mercury in municipal 
sludge attributable to wastewater discharged from dental facilities.  The report does indicate 
that the mercury concentration in POTW biosolids from dental facility wastewater is 0.49 
mg/kg.  As POTW biosolids have 1 to 3 mg/ dry kg of mercury, this represents 16% to 50% 
of the mercury in them.  Additionally, the objectives of the study in the Executive Summary
should match the objectives of the study as listed in Section 1.  No mention is made of 
studying relative biosolids concentrations in the study objectives as presented in Section 1.  
This numbered item should be deleted from the paragraph or changes should be made to 
ensure the objectives throughout the report are consistent.   AMSA Comments on ADA Scientific Assessment 
December 17, 2002 
Page 5 
Executive Summary, Paragraph 2: 
It is stated that “few studies have been conducted in a holistic manner.” And that: 
“Therefore, the present paper quantifies, through a scientifically valid and comprehensive 
approach, the relative contribution of: (1 – 3) (see text)”.  The last paragraph of Section 1 
discusses the “limits to this assessment.”  Section 1 states that “this assessment is not 
intended to be a precise model of mercury behavior in the environment….”  Section 1 goes 
on to mention that others “are studying fate and transport mechanisms applicable to 
mercury.”  These comments are valid within the Introduction, and therefore should be 
included within the Executive Summary.  
Executive Summary, Paragraph 2:  
“the present paper quantifies, through a scientifically valid and comprehensive approach, the 
relative contribution of: … (3) the contribution of mercury from dental facilities to the levels 
of methylmercury in the environment.” 
Again, the scope of this report is limited to the examination of mercury in wastewater from 
dental facilities, not the entire environmental contribution of dental facilities (as it neglects 
air emissions from dental facilities).  Additionally, no attempt is made in the report to 
determine the actual quantity of methylmercury currently present in the environment that has 
resulted from dental facility wastewater discharges.  Rather, the current wastewater 
discharges from dental facilities are compared to total air emission rates in the United States.  
To break out methylmercury contributions, the author simply assumed that all air emissions 
of mercury are available for conversion to methylmercury, while only half the mercury 
discharged from POTWs due to dental amalgam is available for this conversion.  There is no 
scientific basis for the assumption of only half of the dental mercury being bioavailable for 
methylmercury conversion.  Rather, the author relies on several very short-term studies (53 
days or less) that show small amounts of methylation of mercury in amalgams.  The author 
does not present any evidence to show that all mercury entering wastewater from dental 
amalgams will not methylate, given long enough durations.  Until such evidence can be 
produced, the attempt to translate total mercury from dental offices to methylmercury should 
not be made.  As stated above, the reports calculations should be presented solely based on 
total mercury.  Therefore, the phrase quoted above should be dropped from the report.  
Alternatively, all of Paragraph 2 of the Executive Summary should be altered to reflect the 
actual objectives of the report, as presented in Section 1, paragraph 4. 
Executive Summary, Paragraph 4:  
“Based on measured capture efficiencies of chair-side traps and vacuum filters, we calculated 
the industry-wide capture efficiency to be a weighted average of 77.8% using Best 
Management Practices (BMPs).” 
The use of the figure “77.8%” implies a degree of precision in the calculations that is beyond 
the scope of the report.  There is a large degree of uncertainty in the numbers for chair-trap AMSA Comments on ADA Scientific Assessment 
December 17, 2002 
Page 6 
removal efficiency, vacuum filter removal efficiency, and the number of dentists using 
vacuum filters.  It would be more appropriate to use the figure “78%” in place of “77.8%” 
Additionally, the industry-wide capture efficiency was calculated assuming that 100% of 
dentists employed BMPs.  It is unrealistic to expect that every single dentist maintains 
his/her chair-side trap and vacuum filter in perfect accordance with manufacturer’s 
instructions.  Rather, it would be more appropriate to assume some reasonable number of 
dentists do not employ full BMPs.   
Executive Summary, Paragraph 6:  
“We have estimated that up to half of the 0.53 tons of mercury could be converted to 
methylmercury in the environment.”  As discussed above, the authors give no basis for their 
assumption that half of the dental amalgam discharged from POTWs will never convert to 
methylmercury, regardless of the amount of time spent in the environment.   
Executive Summary, Paragraph 7:  
“The total annual loading of dental-related methylmercury was estimated to be 1.04 tons” 
  
The total annual loading of dental-related methylmercury was never quantified in the report.  
“Dental-related” methylmercury would include mercury air emissions from dentists as well 
as mercury in human waste from amalgam fillings and air emissions from crematoria from 
the incineration of human remains.  Additionally, it is beyond the scope of the report to 
discuss the amount of mercury from dental facilities that may eventually turn into 
methylmercury, as discussed above.  The authors give no basis for their assumption that half 
of the dental amalgam discharged from POTWs will never convert to methylmercury, 
regardless of the amount of time spent in the environment.   
Executive Summary, Paragraph 7:  
“…representing less than 0.7% of the total bioavailable mercury released in the U.S. (based 
on the data contained in the EPA’s 1997 Mercury Study Report to Congress).” 
Once again, the scope of the report does not allow quantification, in a scientifically valid 
manner, of the amount of bioavilable mercury.  The report should be limited to a discussion 
of total mercury, unless evidence can be produced that dental mercury does not methylate 
given long enough time periods. 
As to the 0.7% figure, it is a comparison not with “total bioavilable mercury released in the 
U.S.”, but rather to the total amount of mercury emitted into the air in the United States in 
the mid-1990s.  
Executive Summary, Paragraph 8:  
“When a significantly decreased BMP compliance was assumed, the conclusion of our 
assessment does not change.” AMSA Comments on ADA Scientific Assessment 
December 17, 2002 
Page 7 
While the overall conclusion of the report may not change, it is important to note that the 
calculated amount of mercury released to the environment changes substantially, almost 
doubling, when decreased BMP compliance is assumed.   
Executive Summary, Paragraph 8:  
“Wastewater from dental facilities is not a substantial contributor to methylmercury in the 
environment.” 
As this report does not present enough evidence to establish the degree to which mercury in 
dental facility wastewater methylates in the environment, this sentence should be worded, 
“Wastewater from dental facilities is not a substantial contributor to mercury in the 
environment.” 
Executive Summary, Paragraph 9:  
“… the use of amalgam separators only reduces the national loading of bioavailable mercury 
from amalgam entering surface water by 0.57 to 0.97 tons.” 
Again, the report does not present enough evidence to establish the degree to which mercury 
in dental facility wastewater from amalgam is bioavailable.  Additionally, the report does not 
address all mercury loadings from amalgam to surface waters but rather only those from 
dental facility wastewater, as it neglects other routes for amalgam to enter surface water such 
as amalgam in human waste from the grinding of fillings.  Change calculations to address 
total mercury only.  See General Comment 3 for approach to address bioavailability of 
mercury from dental amalgam. 
Executive Summary, Paragraph 10:  
“The USEPA has determined that regulation of mercury from other industries is not 
warranted at costs significantly less than the costs we calculate here.” 
This conclusion is not discussed in the text of the report.  It should be deleted unless specific 
references are provided. 
Executive Summary, Paragraph 11:  
“However, the fact that dental facilities are not the primary or even a significant source of 
methylmercury…” 
The reference to methylmercury should be dropped from this statement.  Additionally, the 
conclusion as written is overly broad.  Dental facilities may be the primary source of mercury 
influent to POTWs in some locations.  In that case, they are certainly a significant source of 
mercury.  Determination of significance depends on many factors.  For a persistent, 
bioaccumulative, and toxic pollutant such as mercury, even small amounts can be of AMSA Comments on ADA Scientific Assessment 
December 17, 2002 
Page 8 
significance.  Better wording would be, “However, the fact that wastewater discharges from 
dental facilities are only a small source of mercury emissions in the United States….”  
Executive Summary, Paragraph 11:  
It is stated that: “This assessment was prepared to provide an objective tool…” The 
Executive Summary should make it clear to the reader that this is still a draft. 
Executive Summary, Paragraph 12:   
“…planning to engage in a dialogue with the USEPA, states, and sewerage management 
authorities to determine a fair and equitable role for the dental community in reducing 
mercury releases entering the environment.”   
Again, this statement is beyond the scope of this report.  This report is not meant to address 
all mercury releases to the environment from the dental community, as numerous pathways 
for dental amalgam to enter the environment are ignored.  This statement should be amended 
to read, “planning to engage in a dialogue with the USEPA, states, and sewerage 
management authorities to determine a fair and equitable role for the dental community in 
reducing mercury releases to wastewater from dental facilities.”   
The report neglects one of the primary concerns of the sewer management authorities, which 
is to ensure that wastewater discharged from their facilities meets all Federal, state, and local 
regulations, including mercury discharge limitations.  As the report does not address the 
relative contribution of dental wastewater mercury versus other sources of mercury entering 
POTWs, it is not likely to be useful to sewer management authorities.  A more useful 
document for these entities would be a report estimating the impact of dental wastewater and 
amalgam separators on mercury concentrations in POTW effluent and biosolids.   
Section 1: 
This section states that the mercury present in dental amalgams is not readily converted to 
the organic form in the environment.  This is an assumption based on the few studies 
available and does not take into account the various conditions encountered in the POTW.  
Until further studies are performed that are of a longer duration and which take into account 
more specific variables, this statement cannot be made or defended.  See General Comment 
3. 
Section 1, Paragraph 2:  
“Although it is reported that the dental industry uses approximately 30 tons of mercury 
annually in dental amalgams, they are not a major source of mercury releases to the 
environment.” 
This sentence is a conclusion.  It should be taken out of the introduction section. AMSA Comments on ADA Scientific Assessment 
December 17, 2002 
Page 9 
Section 1, Paragraph 2:  
“Nor is the mercury contained in amalgams present as methylmercury, or readily converted 
to this organic form in the environment.” 
Specific references should be provided for these statements, or they should be removed from 
the introduction.  See General Comment 3. 
Section 1, Paragraph 4:  
“Specifically, we have identified the following two overall objectives: 1. Estimate the 
influence of dental amalgam discharges on the levels of methylmercury in the environment, 
and 2. Determine the costs versus the benefits of further reductions in dental amalgam 
discharges.” 
As discussed above, a discussion of methylmercury sources is beyond the scope of this 
report.  Additionally, the report does not discuss the influence of dental amalgam discharges 
on the levels of mercury in the environment, but rather is limited to a comparison of the 
discharge of mercury in dental facility wastewater versus overall air emissions of mercury in 
the United States in the mid-1990s.  Furthermore, the cost analysis in the report should be 
referred to as a cost-effectiveness analysis, not a cost benefit analysis, as it simply estimates 
a cost per pound of mercury removed by amalgam separators.  To perform a cost-benefit 
analysis, the cost of the reductions would have to be compared to the benefits of performing 
the reductions in terms of improvements in environmental conditions or human health.  It 
might also be helpful to compare the costs of removing mercury by amalgam separators to 
the costs of removing mercury from POTWs.  For example, the cost per pound of removing 
mercury in dental facility wastewater via amalgam separators ($45,500 to $139,000 per 
pound, according to the report) could be compared to the cost per pound for POTWs to 
remove the same mercury (approximately $21 million per pound).   
This sentence should be amended to read, “Specifically, we have identified the following two 
overall objectives: 1. Compare the release of mercury in dental facility wastewater to the 
total air emissions of mercury in the United States in the mid-1990s, and 2.  Determine the 
cost-effectiveness of installation of amalgam separators on dental facility wastewater.  
Section 1, Paragraph 4: 
Wording related to “…support partisan positions.” should be deleted.  This type of language 
is not appropriate for a technical report.  
Section 2, Paragraph 2:  
“The following are the individual elements that will be addressed to achieve the first 
objective: … The amount of mercury in amalgam released from POTWs that could be 
converted to methylmercury.” AMSA Comments on ADA Scientific Assessment 
December 17, 2002 
Page 10 
As the report does not address, in a scientifically defensible manner, the amount of dental 
amalgam that can potentially be converted to methylmercury, the bullet item referring to 
methylmercury should be deleted.  See General Comment Number 3. 
Section 3: 
There is some confusion regarding the number of dentists used throughout the report.  
AMSA believes that a more accurate count of dentists should include all general dentists 
(private, government/military, etc).  AMSA believes the number used later in the report to 
estimate the high-end number of separators that may be required, 133,092, is a more accurate 
estimate of the total number of general practice dentists, and should be used throughout the 
report for the total number of dentists.  AMSA believes the report should also indicate 
whether this number includes individuals at dental schools.  
It should be noted that further on in the report (Section 8. Mercury Released to POTWs), the 
estimate of 6.34 tons appears to be valid. 
Based on the study conducted by the Metropolitan Council Environmental Services (MCES) 
(St. Paul, Minnesota) and the Minnesota Dental Association (MDA), the following 
calculation can be made: 
(133,092 general dentists)(234 mg Hg/day)(48 weeks/year)(4 days/week)(1 kg/1,000,000 
mg)  =  5980 kg/year  =  13,155 pounds/year  =  6.58 tons/year 
The report estimates by headcounts, removal rates, etc. (a mass balance approach) that 6.34 
tons/year would be released.  The 6.58 and 6.34 values are very close.   
Section 3, Paragraph 1:  
“Therefore it is estimated that approximately 92,957 active general practice dentists place 
amalgam.” 
Amend this calculation to include all general practice dentists (i.e., 133,092).  See Comment 
on Section 3 above regarding the total number of general practice dentists.  The total number 
should not be limited to private general practice dentists.  So 133,092*0.76=101,150 general 
practice dentists that place amalgams. 
Section 6, Paragraph 1:   
“Dividing the 66 million amalgam placements identified by the ADA in 1999 by the 92,957 
general dentists conducting the procedures, we estimate that each general dentist conducts an 
average of about 713 amalgam placements per year.” 
As the number of amalgam placements per year is taken from 1999, and this number for 
placements is used as the basis for the dental wastewater mercury release calculations, the 
dental wastewater mercury releases should be compared to air emissions from 1999.  As AMSA Comments on ADA Scientific Assessment 
December 17, 2002 
Page 11 
1999 air emissions are not available, the mid-1990 air emission estimates should be amended 
to reflect air regulations that have significantly lowered the magnitude of mercury air 
emissions from several categories of businesses. 
Additionally, correct these numbers to reflect all general practice dentists that place 
amalgams, not just private dentists. 
Section 6, Paragraph 1:  
“… we calculate an average annual placement rate of about 711 amalgam placements/active 
general dentist/year.  Again, good internal correctional with the 713 amalgam 
placements/active general dentist/year identified by the ADA.” 
Correct these numbers to reflect all general practice dentists that place amalgams, not just 
private dentists. 
Section 7, Paragraph 1: 
 “… we calculate an overall industry-wide capture efficiency of 77.8.” 
The use of the figure “77.8%” implies a degree of precision in the calculations that is beyond 
the scope of the report.  There is a large degree of uncertainty in the numbers for chair-trap 
removal efficiency, vacuum filter removal efficiency, and the number of dentists using 
vacuum filters.  It would be more appropriate to use the figure “78%” in place of “77.8%” 
Additionally, the industry-wide capture efficiency was calculated assuming that 100% of 
dentists employed BMPs.  It is unrealistic to expect that every single dentist maintains 
his/her chair-side trap and vacuum filter in perfect accordance with manufacturer’s 
instructions.  Rather, it would be more appropriate to assume some reasonable number of 
dentists do not employ full BMPs.   
Section 7, Paragraph 1: 
The phrase “Best Management Practices” is vague.   “Management practices” implies active 
measures, but as used here, it appears to refer to the existence of chair-side traps and vacuum 
filters, which are passive devices that are standard and necessary elements of existing 
vacuum systems.  There is little, if anything, in the way of “practices” a dentist could adopt 
to improve the efficiency of these devices.  The only relevant “management practices” are 
the proper cleaning and disposal procedures for the solids captured in those devices.    
The terms “conventional coarse traps and filters” would be clearer and more neutral.  At a 
minimum, the report could define “BMPs” as “proper management of conventional coarse 
traps and filters.”  In addition, the report should note that the “percentage removals” cited by 
the report do not represent potential reductions in the existing loading of mercury to POTWs.  
Surveys conducted by the Massachusetts Water Resources Authority (Charlestown, 
Massachusetts) indicate that most dentists in the Authority’s service area already use such AMSA Comments on ADA Scientific Assessment 
December 17, 2002 
Page 12 
practices.  If this is true, “BMPs” would largely represent conventional practices already in 
use in some communities, so the removals cited may reflect a portion of what is already 
being achieved nationwide.  Thus, a program to promote proper management of solids from 
conventional devices might not have much impact on current, site-specific POTW loadings. 
Section 8: 
It should be mentioned in Section 8 of this report, which summarizes the release to POTWs, 
that if a clinic switches to a “turbine” or “dry” vacuum system that does not use a vacuum 
filter, there will be an increase in the release of amalgam and mercury to POTWs. 
Given that dry systems are more economical to use over their life (save electricity and 
water), this is the dominant trend in the Minneapolis/St. Paul metropolitan area.  This report 
should comment on whether or not this trend is occurring nationwide.  
This information should be mentioned elsewhere in the report, especially in the Executive 
Summary. 
Section 8, Paragraph 1: 
The report’s estimate of 6.34 tons of mercury going to POTWs appears to be reasonable, but 
it would be preferable if the estimate were checked against what might be calculated from 
actual observed discharges.   One recommendation would be to use average daily discharge 
reported in the study by MCES
4
: 234 mg/dentist/day. 
MCES’s study is not the only source of empirical data.  The study by Larry Walker 
Associates for AMSA
5
 (the “AMSA study”), calculated an average loading value of 56 
mg/dentist/day, using data from several different studies, suggesting a total loading value 
about 25% that of the MCES study.  MWRA’s sampling has found a broad range of variation 
in dental discharges, yielding loading estimates consistent with both the AMSA study, at the 
low end, and the MCES study at the high end.  However, the MCES study was the most 
detailed and controlled, and should be regarded as credible evidence that the higher end 
estimate represents at least some of the discharges actually taking place.  Furthermore, there 
is other data from Cailas and Drummond published by the Illinois Waste Management and 
Research Center that shows higher values than the MCES data. 
The report does not compare its estimate of 6.34 tons discharged by dentists to wastewater 
with loadings from any other dischargers to POTWs, but nothing in the report contradicts the 
findings of the AMSA study concerning relative significance of dentists’ contribution of 
mercury to POTWs.  The AMSA study did not attempt to generate a national loadings 
estimate, but it did attempt to model the potential for reductions from different sources at 
                                                          
4
 Evaluation of Amalgam Removal Equipment and Dental Clinic Loadings to the Sanitary Sewer.  Metropolitan 
Council of Environmental Services (“MCES”), St. Paul, MN (2001) 
5
 “Mercury Source Control and Pollution Prevention Program Evaluation.”  Prepared for the Association of 
Metropolitan Sewerage Agencies (AMSA), under Cooperative Agreement with the U.S. Environmental Protection 
Agency, by Larry Walker Associates.  March 2002. AMSA Comments on ADA Scientific Assessment 
December 17, 2002 
Page 13 
representative POTWs, and dentists were consistently the source where the largest reductions 
are possible.  The AMSA study concluded that the percent of influent mercury values 
coming from dentists varied from 25% to 100%, depending on the value used for dentists, 
and in the end found an average dental contribution of between 35 and 40%. 
Section 9, Paragraph 3: 
The idea that dental mercury in “beneficially re-used sludge” should be treated as if it were 
not released to the environment is unwarranted.  If a sludge product is used as fertilizer, its 
contents technically enter the environment.  AMSA cannot agree that compliance with 
applicable limits for mercury means that mercury amalgam discharged to a POTW can be 
disregarded.  The pretreatment program requirements of state and Federal law require 
POTWs to maintain and enforce regulatory limits for toxic pollutants, including mercury, 
even when the POTW is in compliance with applicable limits.  Furthermore, in some parts of 
the country, the presence of certain pollutants, even within the regulatory limits, may limit 
the management options available to a POTW.  
Section 9, Paragraph 3: 
The use of 40% for the amount going to grit is not valid.  Apparently the 40% comes from a 
combination of theoretical and sampling data, but the report does not make it clear where the 
estimate comes from.  Data from Balogh and Johnson 1998 show that 7% to 48% of the 
mercury entering a wastewater treatment plant may go out with the grit.  This work was done 
in support of a MCES and MDA study coordinated by Claude Anderson (MCES) titled: 
Community-Wide Dental Mercury Study, 2001.  The write-up for the Community-Wide study 
indicated that 7% was believed to be more representative for the eight MCES wastewater 
treatment plants.  Also, not all POTWs have grit removal as part of their overall treatment 
processes, and thus this generalized removal factor cannot be applied to a nationwide 
estimate. 
The report should use a range of 7% - 48% for its calculations or use an average of 7% and 
48%, giving 28%, instead of 40%.  AMSA strongly recommends that the report show what 
the range was if it cites Balogh and Johnson 1998. 
The report states that “as much as 40% of the amalgam particles entering a POTW may be 
removed in the grit chamber.”  Stating “as much as” implies that they are using the upper 
end, or close to the upper end, of a range as the amount to base a calculation.  This does not 
seem appropriate. 
As with beneficially reused biosolids, the report should not discount the mercury removed in 
the grit chamber.  Grit may be landfilled or, in some cases, added to the biosolids and sent 
for land application and is not sequestered in some way.   AMSA Comments on ADA Scientific Assessment 
December 17, 2002 
Page 14 
Section 9, Paragraph 3: 
The September 2002 version of this report (Revision 1) compared the estimated 0.49 mg/dry 
kg to 5 mg/dry kg for wastewater treatment plant sludge. AMSA had (verbally) indicated to 
ADA and ENVIRON that 5mg/dry kg was too high.  In this revised version, the reference to 
5 mg/dry kg was not modified (lowered), but rather this reference was apparently eliminated 
altogether.  Although AMSA does not have a precise figure, we estimate a range of 1 – 3 
mg/dry kg. 
Section 9, Paragraph 3 and 4: 
Between these two paragraphs, a reference should be added regarding the Community-Wide 
Dental Mercury Study.  This study found that there was a 29% - 44% decline in the mercury 
levels of sludge by installing amalgam separators at the clinics. (Since the separators did not 
remove all of the amalgam or mercury, the overall percent loading contribution from the 
clinics would have been higher than 29% - 44%.) 
Section 10: 
In this section the author states that grit chamber solids are managed as solid waste and 
disposed of in Subtitle D solid waste landfills.  This is not the case for grit chamber solids 
from all POTWs (example provided by City of Wichita).  In some cases, solids are 
incorporated with biosolids and land applied, which presents a new set of issues concerning 
the fate of amalgam in biosolids. 
Section 10, Paragraph 2:   
The report states that “there have been few, if any, rigorous studies on the environmental 
behavior of dental amalgam or amalgamated mercury.”  There have been remarkably few 
studies, but it would be false to state that there have been no studies.  The report does not cite 
any of the studies that are actually available, and has not presented the actual findings of the 
studies that are cited.   
The four studies cited in Table 1 on page 9, are short term studies of solubility under specific 
conditions.  The studies by Senkpiel, et al, are studies of dissolved mercury in dental 
wastewater and anaerobic sludge.  Heintze, et al, is a study of methylation of mercury from 
dental amalgam when exposed in vitro to oral streptococci.  The authors reported that they 
did find methylmercury, and concluded that “The results indicate that organic mercury 
compounds may be found in the oral cavity.”  (This reviewer was not able to obtain a copy of 
“Beckert, 1988”).  
There are many other studies on the solubility of mercury in dental wastewater.  Earlier in 
the report, the authors cite Drummond, 1995, and Naleway, et al, 1994, studies which 
reported dissolved and colloidal fractions of 5-10%.  Other studies can be found at the AMSA Comments on ADA Scientific Assessment 
December 17, 2002 
Page 15 
website of the International and American Associations for Dental Research.  For example, 
Berdouses, et al,
6
 found that  
While the age of the amalgam and the amalgam type influence the extent of mercury 
release during the initial non-steady-state conditions, the steady-state value of 
mercury daily dose due to a single amalgam filling is 0.03 micrograms/day, which is 
well below the calculated threshold-limiting value (TLV) of 82.29 micrograms/day 
considered dangerous for occupational exposure in the United States.  
The research literature also includes numerous studies showing the affects of various factors, 
such as acidity, abrasion and heat, which increase the solubility of mercury in amalgam.  For 
example, Certisimo, et al,
7
 demonstrated that commercial tooth whitening products can 
increase the solubility of mercury from amalgam.  Stone, et al,
8
 demonstrated that oxidizing 
substances used for cleaning dental vacuum lines can dissolve a substantial portion of the 
mercury in amalgam.  Dr. Stone and his colleagues at the Naval Dental Research Institute 
have also demonstrated that mercury in dental wastewater can become methylated in holding 
tanks downstream by bacteria present in the oral flora.
9
There are at least three studies showing that fish placed in a tank with amalgam show 
significant uptake of mercury in their livers or muscle tissue.
10
  These studies demonstrate 
that mercury in amalgam will be taken up by the aquatic food chain.   
In the face of such results, there is no justification for the assumptions made in the report.  
See General Comment 3 for approach to address bioavailability of mercury from dental 
amalgam. 
                                                          
6
  “Mercury release from dental amalgams: an in vitro study under controlled chewing and brushing in an artificial 
mouth,”  E. Berdouses, T. K. Vaidyanathan, A. Dastane, C. Weisel, M. Houpt and Z. Shey, Department of 
Prosthodontics and Biomaterials, UMDNJ-NJ Dental School, Newark 07103, USA, et al.   Available at 
www.iadr.com. 
7
  “The Effect of Bleaching Agents on Mercury Release from Spherical Dental Amalgam,”  F.J. Certosimo, F.J. 
Robertello, M.V. Dishman, R.E. Bogacki, and M. Wexel, Virginia Commonwealth University, USA. Available at 
www.iadr.com. 
8
  “Line Cleanser/Disinfectant Effects on Soluble Mercury Content of Dental Wastewater,”  M. E. Stone, E. D. 
Pederson, R. A. Auxer, and S. L. Davis, The Naval Dental Research Institute, 310-A B Street, Building 1-H, Great 
Lakes, IL 60088-5259, USA.  Available at www.dentalmercury.com. 
9
  “Methylmercury Content of Dental-Unit Wastewater,”  M.E.Stone, M.E. Cohen, S.Z. Schade, J.C. Kuehne, Naval 
Dental Research Institute, USA. Available at www.dentalmercury.com.. 
10
   "Mercury Concentrations in Fish from Dental Amalgam" ("Anrikning I fisk av kvicksilver fran tandamalgam") 
Rapport SNV PM 1072 States Naturvardsverk, Stockholm, Sweden, 1978 (English version available from the 
Swedish Natural Environmental Protection Agency Library );  "Microcosm Environmental Analysis of Dental 
Waste Water," J.L. Drummond, BM Francis, MD Cailas, and TY Wu (University of Chicago and UrbanaChampagne, Il.)(Abstract #688, published in the Journal of Dental Research, 1988); “Uptake and accumulation of 
mercury from dental amalgam in the common gold fish, Carassius auratus,”  C.J. Kennedy. Department of 
Biological Sciences, Simon Fraser University. Environmental Pollution 121 (2003) 321–326.AMSA Comments on ADA Scientific Assessment 
December 17, 2002 
Page 16 
Section 10, Paragraph 2:  
“After reviewing all of the literature, a default bioavailability factor of 50% was chosen 
based on best scientific judgment.  There have been few, if any, rigorous studies on the 
environmental behavior of dental amalgam or amalgamated mercury (McGroddy and 
Chapman 1997).  All of these studies have weaknesses, as well as strengths.  EPA and state 
regulatory agencies assume for simplicity that all of the total mercury that enters the 
environment may be converted to methylmercury.”    
Given the extremely small amount of data available on methylation of mercury in the 
environment, there is no sound scientific basis for a choice of 50% as the percentage of 
mercury in dental amalgam wastewater that is bioavailable.  Clearly, the mercury in dental 
amalgam can methylate when stored in a holding tank (see M.E. Stone, et.al), so some 
fraction of the mercury in dental amalgam waste must be bioavailable.  See General 
Comment 3 for approach to address bioavailability of mercury from dental amalgam. 
Section 10, Paragraph 2: 
More work and explanation is needed on the “default bioavailability factor”. The report 
states that this 50% figure “was chosen based on best scientific judgment”. (McGroddy and 
Chapman 1997 is cited in the context of limited data on amalgam).  A 50% figure appearing 
in Attachment 1: Supporting Calculations, shows that this 50% was an “assumption” based 
on “Hg dissolution rates from Okabe 1987 and Marek 1990”.  These two citations don’t 
appear to be listed with the other references. 
If a wastewater treatment plant incinerates its sludge, and operates with a wet scrubber 
system, mercury from amalgam may be carried back to the headworks of the treatment plant. 
Therefore, mercury that came into the plant as amalgam may be discharged to a receiving 
water as mercury (not amalgam).  See General Comment 3 for approach to address 
bioavailability of mercury from dental amalgam. 
Section 10, Paragraph 2: 
It is stated that “EPA and state regulatory agencies assume for simplicity that all of the total 
mercury that enters the environment may be converted to methylmercury.”  The reason is not 
for “simplicity”, but rather to be “protective, conservative, and recognizing the potential for 
long-term breakdown of materials”. See General Comment 3 for approach to address 
bioavailability of mercury from dental amalgam. 
Section 10, Paragraph 4: 
A “leachate collection system” is mentioned, without commenting on how leachate is 
managed.  Leachate may be trucked or piped to wastewater treatment plants. AMSA Comments on ADA Scientific Assessment 
December 17, 2002 
Page 17 
Section 10, Paragraphs 4 and 5: 
Apparently, the report assumes that there will be no release of mercury from sludge, even 
though the third paragraph mentions the “general lack of data on the long-term 
environmental behavior of amalgamated mercury.”  This warrants additional discussion. 
Section 10, Paragraph 5: 
What is the following comment based on: “Mercury is known to be in utility ash…and is 
expected to be present in the ash from the incineration of sludge”?  The report assumes that 
100% is released, which is probably appropriate.  The comment about “expected to be 
present in ash” should either be deleted or data for mercury in ash should be provided. 
MCES data showed zero (Balogh and Liang 1995). 
Section 11, Paragraph 1:  
“Figure 1 and the following summarizes….  Bioavailable mercury from dental facilities in 
POTW effluent entering surface waters – up to 0.27 tons….  Mercury from dental facilities 
in incinerated POTW biosolids that is converted to elemental mercury and may be converted 
into methylmercury – 0.77 tons….  Mercury from dental facilities that may be converted into 
methylmercury (from incineration of sludge and direct discharge in POTW effluent) – up to 
1.04 tons.” 
As discussed above, there is insufficient information to make conclusions about 
bioavailability.  See General Comment 3 for approach to address bioavailability of mercury 
from dental amalgam.  This passage should be modified to read, “Figure 1 and the following 
summarizes.… Mercury from dental facilities in incinerated POTW biosolids – 0.77 tons… 
Total mercury entering the environment from dental facility wastewater – 1.3 tons.” 
Section 11, Paragraph 3 and Table 2:  
“Table 2 compares the estimated bioavailable mercury discharges associated with dental 
facilities with that from other domestic sources.  Figure 2 graphically represents these data.  
These comparison data are from EPA’s 1997 Mercury Study Report to Congress and 
represent data from the early to mid-1990s.” 
Table 2 and the accompanying discussion are misleading.  A comparison is made between 
mercury discharged by dental facilities in the United States and mercury air emissions from 
various industrial sectors in the United States.  However, as is clearly presented in the 
Mercury Study Report to Congress from which the data were taken, only about one-third of 
the air emissions of mercury in the United States are actually deposited in the United States.  
The purported objective of the report is to “Estimate the influence of dental amalgam 
discharges on the levels of methylmercury in the environment,” (Section 1, Paragraph 4).  To 
determine the influence of dental amalgam discharges on the environment, one needs to 
compare mercury loadings that are occurring in the same part of the environment.  If the 
scope of the report was global mercury discharges from dental facilities it would make sense 
to ignore the effect of transport of mercury out of the area of interest.  However, comparing AMSA Comments on ADA Scientific Assessment 
December 17, 2002 
Page 18 
the discharge of mercury from U.S. dental facilities with overall U.S. air emissions of 
mercury, when two-thirds of that mercury is deposited out of the U.S., is misleading.   
The amount of U.S. air emissions of mercury estimated to be deposited within the U.S. is 52 
tons.  An additional 35 tons of mercury is deposited in the U.S. from the global reservoir of 
mercury, for a total deposition of roughly 87 tons (per the Mercury Study Report to 
Congress).  Any comparison of mercury reaching the environment from dental facility 
wastewater in the U.S. should be compared to the actual loading of mercury deposited in the 
U.S. from air emissions, which is 87 tons (based on mid-1990s data). 
Additionally, Table 2 neglects to mention the air emissions from dental preparations, as 
presented in the Mercury Study Report to Congress.  Per the Mercury Study Report to 
Congress, 0.7 tons per year of mercury enter the air from dental preparations.  If the term, 
“Dental-Related” is to be used in Table 2, it should encompass all dental-related mercury 
emissions, including air emissions and mercury in human waste from amalgam fillings.  A 
more appropriate term would be “Dental Facility Wastewater.”   
Finally, while the report has been modified to state that the data in Table 2 are from the early 
to mid-1990s, it is misleading to compare these data with 1999 dental facility wastewater 
discharges.  Air emissions of mercury have declined significantly since the early to mid-
1990s due to imposition of stringent air emission regulations on several sectors including 
municipal waste combustors and medical waste incinerators.  In order for the report to be 
accurate, these reductions must either be taken into account or the dental facility wastewater 
discharges must be taken from the early to mid-1990s.  While it is difficult to find actual 
data, the Mercury Study Report to Congress itself indicates that there will be at least a 90% 
reduction in mercury emissions from municipal waste combustors and medical waste 
incinerators. 
Therefore, Section 11, paragraph 3 and Table 2 should be amended to read as follows: 
“Table 2 lists air emissions from domestic sources of mercury.  These comparison data are 
from EPA’s 1997 Mercury Study Report to Congress.” 
Table 2.  Summary of Mercury Emissions Sources Located in the U.S. 
Source Estimated Mercury Releases (tons Hg/yr) 
Coal Utility Boilers 51.6 
Commercial/Industry Boilers 28.4 
Hazardous Waste Combustors 7.1 
Chlor-alkali Manufacturing 7.1 
Portland Cement Manufacturing 4.8 
Municipal Waste Combustors 3.0
11
Medical Waste Incinerators 1.6
12
                                                          
11
 Based on 29.6 tons Hg/yr emissions in the early to mid-1990s and a 90% reduction since then to new U.S. EPA 
emissions guidelines that have since been implemented. AMSA Comments on ADA Scientific Assessment 
December 17, 2002 
Page 19 
Geothermal Power Production 1.4 
Other 12.0 
Total (from all sources) 117 
Source: USEPA. 1997. Mercury Study Report to Congress.  EPA-452/R-97-003 
“The Mercury Study Report to Congress further indicates that only approximately one-third 
of U.S. anthropogenic mercury emissions are deposited within the lower 48 United States.  
Additionally, another 35 tons of mercury is deposited in the U.S. from mercury in the global 
atmosphere.  Therefore, the total amount of mercury deposited from air emissions in the U.S. 
is 74 tons per year (35 tons/yr + 117 tons/yr*0.3333) (1999 estimate; reductions in air 
emissions from mid-1990s to 1999 were taken into consideration).  For comparison, the 
amount of mercury entering the environmental from dental facility wastewater discharges is 
1.3 tons/yr.” 
Section 11, Paragraph 4:  
“As indicated in Table 2, dental-related mercury that may be considered bioavailable 
represents less than 0.7% of the total bioavailable mercury released in the U.S.” 
As discussed above, it is misleading to compare dental facility wastewater discharges of 
mercury to air emissions of mercury in the U.S.  This sentence should read, “As indicated 
above, the mass of mercury entering the environment from dental facility wastewater is 1.7% 
of the mass of mercury deposited in the U.S. due to air emissions.  Mercury from dental 
facility wastewater may represent a higher loading of mercury to surface waters, as not all 
mercury deposited in the U.S. from air emissions will reach surface water bodies.” 
Section 12, Paragraph 1:  
“The estimates of dental-related mercury discharges presented above assume that all of the 
general dentists…” 
“Dental-related” mercury discharges would include amalgam in human waste from fillings.  
Additionally, the calculations were based only on private general dentists, not all general 
dentists.  See comment on Section 3.  The calculations should be based on the total number 
of general practice dentists (in this instance, those performing amalgam procedures), not only 
private general practice dentists. 
Section 12, Paragraph 3:  
“The decreased BMP and use and capture efficiencies considered in this scenario result in a 
2.52-ton increase in the amount of mercury discharged to POTWs from dental facilities 
nationwide.” 
                                                                                                                                                                                          
12
 Based on 16.0 tons Hg/yr emissions in the early to mid-1990s and a 90% reduction since then to new U.S. EPA 
emissions guidelines that have since been implemented. AMSA Comments on ADA Scientific Assessment 
December 17, 2002 
Page 20 
The correct amount of mercury discharged to POTWs from dental facilities nationwide under 
Scenario 1 is 9.90 tons/year
13
.  As the discharge under the baseline scenario is 6.34 tons/year, 
the increase is 3.56 tons/year. 
Section 12, Paragraph 5:  
The comment “increases only marginally to 1.85 tons” should be reworded.  If the base value 
is 1.04 tons with proper management, an increase to 1.85 tons is not “only marginally”. 
  
Section 12, Paragraph 6:  
“The results of Scenarios 1 and 2 indicate that the sensitivity of our analysis to any variations 
in the rate and manner in which BMPs are implemented in the dental industry is extremely 
limited…” 
In the report, the results of Scenario 2 indicate a 78% increase in environmental releases of 
mercury due to lack of proper BMP usage.  Corrected numbers reveal a doubling in 
environmental releases due to lack of proper BMP usage. “Extremely limited” is an 
inappropriate term to describe such a large impact.  Rather, the sensitivity analysis indicates 
that the amount of mercury released to the environment from dental facility wastewater is 
strongly dependent upon the use of BMPs.  Looking at the situation in reverse, if only 50% 
of dentists are currently fully compliant with BMPs (as depicted in Scenario 2), then 
encouraging dentists to fully implement BMPs could result in a substantial reduction of 
mercury releases to the environmental from dental facility wastewater.   
Section 13: 
In AMSA’s telephone comments on the first draft, we emphasized that the draft 
misinterpreted the results reported by MCES, and recommended that the correct 
interpretation of that data shows an average capture of 89% amalgam passing vacuum filters, 
and about 94% of amalgam passing chair-side traps, for an average result of 92.5%.  In the 
new draft, while acknowledging the existence of these empirical data, the author has chosen 
to rely on an entirely abstract calculation based on the theoretical possibility that a separator 
could pass the ISO 11143 test with a 95% capture efficiency, but only attain an 
“incremental” efficiency of 60-74% of the amalgam particles passing a vacuum filter.  The 
problem with the use of this “scenario” is that there is no evidence that any currently 
available separator actually performs in this fashion. 
The ADA has published the results of ISO testing of all of the amalgam separators that were 
available on the U.S. market at the time of their test.
14
  The average results were greater than 
99% removal, and no unit tested less than 97%.   The difference between >99% and the 
report’s theoretical 95%, is significant.  The report assumes that its “straw-man” will allow 
                                                          
13
 Fax from Ann Heil of the Los Angeles County Sanitation Districts (LACSD) to Jay Vandeven, ENVIRON, 
November 12, 2002 
14
   “Laboratory Evaluation of Amalgam Separators,” P.L. Fan, Hanu Batchu, et al, JADA, Vol. 133, 577-599 
(May, 2002) AMSA Comments on ADA Scientific Assessment 
December 17, 2002 
Page 21 
5% of amalgam to pass through, out of the 12% that pass through a vacuum filter, resulting 
in an “incremental efficiency” of approximately 60%.   If, however, one uses the average 
result from the ADA test, and assumes that only 1% will pass through, the “incremental 
efficiency” turns out to be 92%.  Moreover, the “incremental efficiency” would be even 
higher if the ADA’s average result were not rounded down to 99%.  In fact, there is no 
empirical evidence that the units tested by ADA would be any less effective on a smaller 
sized-particle mix than they are on the ISO formula.   
The authors advance no justification for basing its analysis on a purely hypothetical 
possibility, while disregarding actual empirical results achieved in the testing of real devices.  
There are reasons to be concerned about the correlation between the ISO test and actual in 
situ performance, and these questions are the subject of on-going research.   For purposes of 
creating a model based on currently available data, the results reported by MCES are far 
more defensible than the theoretical construction used in the report.  The authors should 
discard the 60% to 74% theory, except perhaps for use in the sensitivity analysis.  Its lead 
results should be based on 92% removal.   (Note that the MCES study accounted for all 
mercury discharged through the system, including dissolved portions that are not measured 
in the ISO formula). 
Using 95% as the high-end scenario would be inappropriate as the analysis is based on an 
arbitrary assumption.  A better approach would be to use 99% as the high-end, based on an 
assumption that municipalities and regulatory agencies will use that as a Best Available 
Technology standard. 
Section 13, Paragraph 4: 
The report should note that clinics (at least in some service areas) are switching away from 
vacuum systems that use a vacuum filter, resulting in more waste discharged to the sewer.  In 
such a situation, if a separator is installed, it will achieve a higher percent removal. 
The report states that “Many studies have indicated that chair-side traps capture as much as 
75% of amalgam particles and that vacuum filters capture as much as 50%.”  Please provide 
citations for this information. 
The authors may have been using WEF 1999 for the vacuum filter 50% figure, which may 
have been in error (too high of a percentage).  Further discussion on this topic is needed. 
If an ISO tested separator needs to pass 95%, it will be designed to remove more than 95%. 
The low end of the range (60%) is calculated out only by assuming chair-side traps and 
vacuum filters remove more and more – thereby acting as a two-stage “separator” anyway. 
Section 14: 
The report states that the capture efficiencies in conjunction with chair-side and filter traps 
were as low as 13%.  It appears that the report’s efficiency value is based on the total amount AMSA Comments on ADA Scientific Assessment 
December 17, 2002 
Page 22 
of amalgam passing through the system and removed by the separator.  However, to figure 
the efficiency of the separator, the amount entering the separator post chair-side and vacuum 
filter should be compared with the amount exiting the separator.  This will produce a much 
more realistic picture of the efficiency of the product.   
It should also be noted that the chair-side and vacuum filters may not be removing any 
additional amounts of amalgam since they have been in use for a long period of time.  With 
recent attention given to BMPs, it is likely that the dental offices have increased maintenance 
activities on these apparatuses, resulting in slight decreases of mercury contaminated 
discharges, but not at levels sufficient enough to realize significant decreases of mercury 
loadings received at POTWs.  The City of Wichita (Wichita, Kansas) implemented a dental 
mercury BMP program in September 2000, which involved increased maintenance activities 
for the removal of particles at the chair-side traps and cleaning the vacuum filter.  The City 
did not see any measurable decreases at the POTW headworks until after January, 2002, 
three months after installation of amalgams separators was required.   
HEADWORKS MERCURY LOADINGS
0
0.05
0.1
0.15
0.2
0.25
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
MONTH
1999
2000
2001
2002
MAHL
 Dental Amalgam 
BMP program 
initiated October 
2001
Section 14, Paragraph 1:  
Change reference to “Section 6” to “Section 7,” as the capture efficiency of BMPs is 
discussed in Section 7. 
Section 14, Paragraph 1:  
At minimum, change “77.8%” to “78%,” due to a lack of certainty in the numbers used to 
calculate the figure.   AMSA Comments on ADA Scientific Assessment 
December 17, 2002 
Page 23 
Section 14, Paragraph 2:  
Change the term “dental-related” in the first and second sentences to “dental facility.”  The 
term “dental-related” in reference to wastewater discharges would include mercury loadings 
from human waste due to the presence of amalgam fillings in residents.  
Section 14, Paragraph 2 
The numbers in Figure 5 are incorrect.  The purpose of Figure 5 is to examine the flow of 
mercury in dental wastewater nationwide with amalgam separators operating at 60% capture 
efficiency after implementation of dental BMPs (total system efficiency of 95%).  However, 
the removal efficiency of vacuum filters was incorrectly accounted for in the calculations for 
Figure 5.  AMSA has examined Figure 5 and amended the calculations below.  However, we 
feel the underlying approach used may be inappropriate and warrants further discussion. 
The value of 60% was established by assuming that the chair-side traps and vacuum filters 
remove 88% of mercury, more than the 81% mentioned in Section 13.  When the efficiency 
of the chair-side traps and vacuum filters increases to 88%, more mercury is removed by the 
chair-side traps and vacuum filters, and less mercury is removed by the amalgam separators.  
This means that in Figure 5, the amount passing through the vacuum system after the chairside traps and vacuum filters in not 6.34 tons, but rather a lesser amount. 
The basis for the Figure 5 numbers is given in Section 13, paragraph 4, which states that, 
“Many studies have indicated that chair-side traps capture as much as 75% of amalgam 
particles and that vacuum filters capture as much as 50%.  Applying these percentages, the 
combined capture of the chair-side trap and vacuum filter approaches 88%… the actual 
incremental efficiency of the separator would be about 60%.”  This means that an 
incremental efficiency of 60% for the separator is only applicable when the combined chairside trap and vacuum filter efficiency is taken to be at least 88% or so.  In drawing up Figure 
5, the author should use a combined chair-side trap and vacuum filter removal efficiency of 
88%, not 78%.  A simple assumption of 88% removal across the chair-side traps and vacuum 
filters results in 3.43 tons per year of mercury entering amalgam separators (28.6*(1 – 0.88) 
= 3.43), not 6.34 tons per year as indicated in Figure 5.  Applying a 60% capture efficiency 
to the amalgam separators results in 1.37 tons per year of mercury exiting the separators 
(3.43*(1 – 0.6) = 1.37 tons/year), for a capture of 3.43 – 1.37 = 2.06 tons per year in the 
amalgam separators. 
Note that the 3.43 tons per year figure of mercury entering the separators is only applicable if 
it is assumed that all dentists employ 50% efficient vacuum filters.  If 20% of dentists do not 
have vacuum filters, as assumed in the baseline scenario depicted in Figure 1, this number 
would change.  Assuming that 28.6 tons/year of mercury from dentists, 80% of this or 22.88 
tons/year would be generated at dental facilities that have vacuum filters and the remainder, 
5.72 tons/year, would be generated at dental facilities that do not have vacuum filters.  All of 
the mercury would pass through 75% efficient chair-side traps, resulting in 5.72 tons/year of 
mercury leaving the traps at dental facilities with vacuum filters and 1.43 tons/year of AMSA Comments on ADA Scientific Assessment 
December 17, 2002 
Page 24 
mercury leaving the traps at dental facilities without vacuum filters.  The dental facilities 
with vacuum traps would remove an additional 50% of this mercury, for a discharge to 
amalgam separators from these facilities of 2.86 tons/year.  At the facilities without vacuum 
filters, the full 1.43 tons/year leaving the chair-side traps would enter amalgam separators.  
Applying an amalgam separator removal efficiency of 60% to facilities with vacuum filters 
results in a discharge of 2.86*(1 - 0.6) = 1.14 tons/year of mercury discharged from the 
amalgam separators at these facilities.  At the facilities without vacuum separators, it is not 
appropriate to apply an amalgam separator efficiency of 60%.  The amalgam separator 
efficiency of 60% should only be used when the combination of chair-side trap removal and 
vacuum filter removal together is about 88%.  This allows an amalgam separator efficiency 
of 60% to result in an overall (trap + filter + separator) removal efficiency of 95%.  In the 
case of facilities with 75% efficient chair-side traps and no vacuum filters, 80% is the 
appropriate removal efficiency to use for the amalgam separator to obtain an overall removal 
efficiency of 95%.   ((100% – 75%)*(100% – x) = 100% – 95%; x = 80%)  Applying the 
80% removal efficiency to the 1.43 tons/year of mercury entering amalgam separators at 
facilities without vacuum filters results in the discharge to POTWs of 0.29 tons/year from 
these facilities.  The total discharge to POTWs from facilities with and without separators is 
then 1.14 + 0.29 = 1.43 tons/year.  The amount of mercury removed in the separators is 
(2.86-1.14) + (1.43-0.29) = 2.86 tons/year.  These calculations are graphically depicted in 
Attachment A. 
Numbers in Section 14, paragraphs 2, 3, 4, and 5 should also be corrected, based on the 
above calculations. 
Section 14, Paragraph 3:  
Change the term “dental-related” in the last sentence to “dental facility,” for reasons 
discussed above. 
Section 14, Paragraph 3:  
“As discussed above, we have conservatively assumed that approximately half of this dentalrelated mercury, or about 0.18 tons, will potentially be bioavailable over long durations in 
the environment.” 
Delete this sentence.  See General Comment 3 for approach to address bioavailability of 
mercury from dental amalgam. 
Section 14, Paragraph 3:  
“… by about 0.17 tons (0.53 tons – 0.36 tons), corresponding to a reduction of potentially 
bioavailable mercury in the discharge of about 0.09 tons.” 
Change calculations and discussion to address total mercury only.  See General Comment 3 
for approach to address bioavailability of mercury from dental amalgam. 
   AMSA Comments on ADA Scientific Assessment 
December 17, 2002 
Page 25 
Section 14, Paragraph 4:  
Change the term “dental-related” in the first sentence to “dental facility,” for reasons 
discussed above. 
Section 14, Paragraph 4:  
Delete the phrases, “and converted to bioavailable mercury,” and “potentially bioavailable,” 
in the second and third sentences, respectively, for reasons discussed above. 
Section 14, Paragraph 5:  
Delete the terms “bioavailable” and “potentially bioavailable” in this paragraph for the 
reasons discussed above. 
Section 14, Paragraph 6: 
Change the term “dental-related” in the first, second, third, fourth, and fifth sentences to 
“dental facility,” for reasons discussed above. 
Section 14, Paragraph 6:  
“Conservatively assuming that approximately half of this dental-related mercury will 
potentially be bioavailable over long durations in the environment, the use of amalgam 
separators results in a reduction of bioavailable mercury discharges in POTW effluent of 
0.24 tons (assuming a 95% additional separator capture efficiency).” 
Delete this sentence due to lack of evidence to support the hypothesis that only half of 
dental-related mercury is potentially bioavailable over long durations.  See General 
Comment 3 for approach to address bioavailability of mercury from dental amalgam. 
Section 14, Paragraph 7:  
Change the term “dental-related” in the first, second, and third sentences to “dental facility,” 
for reasons discussed above. 
Section 14, Paragraph 7:  
Change calculations and discussion to address total mercury only.   See General Comment 3 
for approach to address bioavailability of mercury from dental amalgam. 
Section 14, Paragraph 8:  
“Combining the reductions of bioavailable dental-related mercury from POTWs to receiving 
waters (0.24 tons) with… incineration of biosolids (0.73 tons)…by about 0.97 tons.” 
Remove references to bioavailable mercury and “dental-related” wastewater and correct 
calculation to address total mercury only.  See General Comment 3 for approach to address 
bioavailability of mercury from dental amalgam. AMSA Comments on ADA Scientific Assessment 
December 17, 2002 
Page 26 
Section 15, Title: 
“Cost-Benefit and Cost-Effectiveness Analysis” 
This title should be changed to “Cost-Effectiveness Analysis,” as the section does not 
address any of the benefits of dental amalgam removal.  To conduct a cost-benefit analysis, 
potential benefits resulting from the use of the amalgam separators would have to be 
discussed.  As part of the cost effectiveness analysis, ADA should compare the cost per 
pound for a POTW to remove mercury from wastewater of $21 million to the cost per pound 
for dentists to remove amalgam via separators. 
Section 15: 
The cost estimates relied on by the authors are inconsistent with available information, 
including, for example, the estimates given in the ADA’s report on its ISO testing of 
commercially available separators, which shows that among the units achieving >99% 
removal there are three available for $500 or less.
15
   
The authors state that they took the average cost from the products for which they obtained 
cost information for.  In modeling foreseeable costs in a greatly expanded market, it is 
debatable whether the average of current vendor quotes is a reasonable basis for assumed 
costs.  Although several factors would affect prices in an expanding market, it would be 
reasonable to expect that vendors could take advantage of economies of scale, and that 
buyers would generally gravitate toward lower prices.   Dominance of sales by products in 
the lower range of the current price scale represents, at a minimum, a highly likely scenario 
for future costs.   Thus, the report’s analysis is not credible without an estimate of the overall 
cost if the average purchase fell at $500, rather than the $1,000 to $2,000 figure used in the 
report.  
Section 15: 
The report uses a headcount of 133,092 dentists to determine the high-end number of 
separators needed.  Elsewhere in the report, 122,312 dentists was used to determine loadings.  
As outlined above, AMSA believes the total number of general practice dentists for the 
loading determinations should be 133,092.  The number of separators needed would not be 
based on this number, but rather on the number of clinics, as it is expected that clinics will 
only need one separator for all on-site dentists.  AMSA believes 100,000 may be an accurate 
estimate for the number of separators needed nationwide.    
Section 15: 
AMSA suggests that ADA use the following figures for the reports cost estimates:  Initial 
cost of the units is between $50 and $1895, with an average purchase price of $770.  
Installation costs average $179 (ranging from included with initial to $400).  Operation and 
maintenance (O&M) costs average $366 ($50 - $780) as opposed to $700 - $1,000 (all costs 
                                                          
15
   “Laboratory Evaluation of Amalgam Separators,” P.L. Fan, Hanu Batchu, et al, JADA, Vol. 133, 577-599 
(May, 2002). AMSA Comments on ADA Scientific Assessment 
December 17, 2002 
Page 27 
are King County, Washington estimates based on information from 14 vendors and are 
consistent with other cost estimates reviewed).   
Section 15, Paragraph 1:  
“In this section, we estimate the industry-wide costs for an incremental reduction in 
methylmercury related to dental amalgam discharges.” 
The reference to methylmercury should be changed to reference total mercury, and the scope 
of the sentence should be made clear.  The sentence should read, “In this section, we estimate 
the industry-wide costs for an incremental reduction in mercury related to dental facility 
amalgam discharges.” 
Section 15, Paragraph 1:  
“The incremental bioavailable mercury reduction attained from using amalgam separators at 
these efficiencies ranges from 0.57 to 0.97 tons.” 
References to bioavailable mercury should be removed and the numbers should be corrected 
accordingly.  See General Comment 3 for approach to address bioavailability of mercury 
from dental amalgam.     
Section 15, Paragraph 2:  
“… requiring separators at 110,910 to 133,092 individual locations.” 
Many dentists share office space with other dentists, and amalgam separators are available to 
treat the discharge from multiple dental chairs simultaneously.  Therefore, it is unlikely that 
each dentist will require an individual separator.  No explanation is given in the report for the 
110,910 number.  See comment above regarding number of dentists and number of required 
separators.  
Section 15, Paragraph 2:  
Regarding “costs not considered”, it is unlikely that many POTWs would require sampling. 
POTWs would structure a program to operate as inexpensively as is possible for both the 
POTW itself and the dental community. 
One set of costs not considered in this report are health costs associated with additional 
mercury releases to the environment.  Fish consumption advisories can result in costs to 
administer the consumption advisory program.  There may be lost revenues if there is less 
sport or commercial fishing. 
One key point to consider regarding costs is that if a clinic operates with a vacuum filter, 
then installs an amalgam separator in place of the vacuum filter, the new cost will be 
partially offset if the vacuum filter is no longer needed, or if the vacuum filter is left in place 
downstream of the separator (as a back-up to protect the vacuum pump). AMSA Comments on ADA Scientific Assessment 
December 17, 2002 
Page 28 
The report should also note that BMPs are not cost free.  For example, there are costs 
associated with replacement filters for vacuum systems.  At least some separators would 
allow the dentist to forego the cost of filter replacement, and would probably extend the life 
of the vacuum system.  The incremental cost of the separator would therefore be less, 
perhaps significantly less, than its total purchase and O&M cost.   
If a clinic is properly managing waste vacuum filters, the cost savings could be significant if 
such filters are no longer purchased or shipped out for recycling or processing. 
Section 15, Paragraph 3 
As discussed above, we recommend that cost calculations be based upon 100,000 separators.   
As also discussed above, we recommend that the capital cost of each unit should be the 
average purchase cost plus the average installation, or $949 ($770 + $179), and O&M costs 
should be taken as $366 per year.  Therefore, the industry-wide capital cost is estimated to be 
$94.9 million (100,000*$949).  The annual industry-wide O&M cost is estimated to be $36.6 
million (100,000*$366).  If it is assumed that each separator has a ten-year useful life and 
that the capital cost is spread evenly over the ten years, the combined annual industry-wide 
cost is estimated to be $46.1 million ($94.9 million/10 + $36.6 million). 
Section 15, Paragraph 4 
To determine the cost per pound of mercury removed in amalgam separators, the report only 
looks at reductions in bioavailable mercury.  As discussed extensively throughout these 
comments, references to bioavailable mercury should be removed.  See General Comment 3 
for our recommended approach to address bioavailability of mercury from dental amalgam.  
Additionally, the report does not consider reductions of mercury to grit or land applied 
biosolids as actual reductions in mercury released to the environment.  We recommend that 
all mercury removed by amalgam separators, whether it ends up in incinerated biosolids, 
land-applied biosolids, surface waters, or grit to be considered in determining the cost 
effectiveness of amalgam separators.  Therefore, the amounts of mercury removed by 
amalgam separators should be taken as 2.86 tons/year for separators having an incremental 
removal efficiency of 60%, and 6.02 tons/year for separators having an incremental removal 
efficiency of 95%.  Accordingly we estimate the cost to remove mercury in dental 
wastewater using amalgam separators ranges from $3830 to $8060 per pound (($46.1 
million/6.02 tons per year)(1 ton/2000 pounds) = $3830/pound; ($46.1 million/2.86 tons per 
year)(1 ton/2000 pounds) = $8060/pound), or about $8 to $18 per gram. 
Section 15, Paragraph 5 
“The use of amalgam separators will not be cost effective in reducing environmental levels 
of methylmercury.” 
The calculations in these comments indicate that the use of amalgam separators is highly cost 
effective in preventing releases of mercury to the environment, particularly when compared AMSA Comments on ADA Scientific Assessment 
December 17, 2002 
Page 29 
to the costs to remove mercury at POTWs of approximately $21 million per pound or 
$46,000 per gram. 
Section 15, Paragraph 5 
“The difference in the quantity of bioavailable mercury released to the environment from the 
use of BMPs and an amalgam separator – at most 0.97 tons – is relatively small compared to 
the total amount of bioavailable releases.” 
Delete references to bioavailable mercury in this paragraph, per General Comment 3.  
Additionally, the amount of mercury removed via amalgam separators alone – up to 6.02 
tons per year – constitutes a large portion of the mercury loadings to POTWs in the United 
States.  Therefore, installation of amalgam separators at dental facilities nationwide is likely 
to have a significant impact on levels of mercury in wastewater reaching POTWs.  As 
POTWs do not destroy mercury, but rather transfer it to effluent, grit, and biosolids, a 
significant reduction in the amount of mercury entering POTWs will result in a significant 
reduction in the amount of mercury released from POTWs.  We agree that the total amount 
of mercury released from POTWs is small compared to other releases of mercury in the 
United States, but POTWs must still meet regulatory requirements for their releases, 
particularly to surface water bodies. 
Section 16: 
For the reasons discussed above, the cost figures are too high.  AMSA does not know what 
the long-term maintenance and disposal costs for separators will be, but we believe that 
market forces will drive prices downward.   
These costs break down even further when taken to the individual patient level.  The authors 
state that dentists nationally performed 66 million amalgam placements in 1999.   It would 
appear that a national effort to install amalgam separators would be likely to cost the average 
dental patient less than $1.  
Section 16: 
ADA estimated the cost for the entire dental community to remove mercury at the source of 
the discharge to be $45,000 - $139,000 per pound.  The costs would be escalated well 
beyond that figure if POTWs have to treat to remove mercury in order to meet water quality 
standards or biosolids disposal criteria.  This is directly due to the increased flows POTWs 
must treat as compared to the discharge volumes leaving a dental facility.  The report should 
reflect this information.    
Section 16, Paragraph 1:  
“… levels of methylmercury in the environment.” 
Change to, “… levels of mercury in the environment.” AMSA Comments on ADA Scientific Assessment 
December 17, 2002 
Page 30 
Section 16, Paragraph 1:  
“… the amount of dental-related mercury in the wastewater.” 
Change to, “the amount of mercury from dental facilities in the wastewater,” since mercury 
in wastewater from human waste containing amalgam is not discussed. 
Section 16, Paragraph 1:  
“The large majority of the mercury removed by these processes has a low bioavailability and 
is managed in a manner (e.g., recycling, landfilling) that would not significantly contribute to 
methylmercury levels in surface waters. 
References to bioavailable mercury should be removed.  See General Comment 3 for 
approach to address bioavailability of mercury from dental amalgam.     
Section 16, Paragraph 1:  
“As a result, only about 1 ton of the mercury used in dental amalgam nationwide is 
ultimately converted to a bioavailable form that could potentially be methylated in the 
environment.” 
  
References to bioavailable mercury should be removed.  Additionally, make it clear that 
dental amalgam in human waste was not considered.  See General Comment 3 for approach 
to address bioavailability of mercury from dental amalgam. 
Section 16, Paragraph 1:  
Correct the last two sentences to reflect total mercury instead of bioavailable mercury and 
use revised cost figures as discussed above.  

 

Dental Advertising Services

Since 2004 MercuryFreeDentists.com has been connecting holistic dentists and biological dentists with internet visitors who are searching for safe amalgam removal and other dental services.  Now we offer two other services to help you get more traffic directly to your website.  Click on the title's below to learn more about our dental advertising services.

Pay-Per-Click Campaign Management

Starting as soon as tomorrow you can have more traffic going directly to your website from text or banner ads.  Google manages the ad placement and you only pay when somebody clicks (visits your site.)  Learn more about how it works, why you need us to manage your campaign, and our Lower Cost Guarantee.

 

Performance Based SEO (Search Engine Optimization)

No doubt you get spammed by, and are skeptical of, the many claims to put your website at the top of Google yet you realize how beneficial it would be to have your website show up on page 1 for applicable search terms.  That is why we developed our PERFORMANCE based SEO service with ZERO RISK to you.  Besides a small setup fee which also covers a website analysis you don’t pay for anything until your chosen keywords show up on page 1 or 2 of Google.  Learn more about how we can increase organic traffic to your website with our Zero Risk Guarantee.

 

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Since 2004 Mercury Free Dentists.com has had a search engine friendly directory.  Listings include an unlimited description which can include hyperlinks, images and HTMl as well as interactive Google map and visitor counter.  Your listing is indexed by Google and other search engines allowing visitors who search your name in Google to go straight to your directory listing.   Learn more about why your practice should be listed in our directory as well as our page 1 of Google Directory Guarantee that ensures your listing will be on page 1 of Google when someone types in your name in Google.  

 

 

 

Search Engine Optimization (SEO) Services For YOUR Website

Mercury Free Dentists.com is dedicated to bringing our dentists more patients through online resources. Assuming you have a great website, THE BEST online resource for recruiting new patients through your site is search engines. Of course to harness this resource you need to be listed on the first page of Google, Yahoo and Bing! You probably receive a few spam e-mails per week promising to put your website at the top of Google. Whether you have been suckered by these spammers or not, you know it is not that easy and not every website can be on Google’s 1st page. BUT, SEARCH ENGINE OPTIMIZATION DOES WORK and it IS possible to be on page 1 of Google. Mercury Free Dentists has dominated the top 5 positions of Google for the last 10 years for appropriate keywords (search terms - biological dentist, holistic dentist, and of course mercury free dentist as well as many others).

Now we are offering this valuable service of search engine optimization to our dentists! Here is why it is a win-win with ZERO RISK to you:
- Low setup fee. This includes an initial evaluation of your website’s condition from the search engine’s perspective.
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- If we are unable to get at least one of your keywords onto page 1 of Google in 12 months you will get a FULL REFUND of your setup fee. That’s right! That’s ZERO RISK!

 

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FAQ

What if I don’t already have Google Analytics or if changes need to be made to my site?

Google Analytics is a free service offered by Google. Your webmaster should be able to easily add it and any other optimization changes that we suggest to your site. If you don’t have a webmaster who actively manages your site, we can make changes for an hourly charge after you give us access to your site.

How do I know what keywords to choose? Can I choose ANY keyword?

You will suggest keywords specific to your geographic location and services offered that you would like your site (or specific pages of your site) to be ranked well on. We will analyze these keywords and expand the list to show similar keywords and provide a report detailing monthly search volume for those keywords. If a keyword is not relevant to your website or if the search volume is too low we may reject keywords which will not produce a win-win experience. (If you are ranked #1 position for a keyword that only 10 people search per month it does not help you and you will not continue to use our service).

How many keywords can be optimized?

The initial setup fee covers 5 keywords. Additional keywords can be optimized but will require $100 per 5 keywords to start the optimization work.

How long does it take before I see results?

Real / significant results take 3 – 6 months. Google is somewhat of a black box and their algorithm for ranking websites continues to evolve / change.   Nevertheless, we have seen good success and believe we can help you increase web traffic and get new patients.

How long of a contract is required?

Because it takes 3-6 months to see real results we require a 6 month contract. After 6 months it becomes a month to month agreement where you can cancel at anytime. But remember, you won’t pay any monthly fees unless your keywords are ranked on page 1 or 2 of Google!

How much is the initial setup fee?

$350. This includes a complete website analysis and initial work on 5 keywords (after keyword analysis and discussion). Access to your Google Analytics and Webmaster tools is also required.

How much traffic can I expect?

When we do the keyword analysis we will provide monthly search estimates for the search terms provided / suggested.  If your website is the # 1 result you can expect to get clicked on ~ 55% of the time that term is searched, # 2 result can expect a ~ 15% click rate, # 3 ~ 10% click rate … down to ~3% click rate for # 10. We will carefully help you select keywords which have the most searches AND are the most relevant to your practice.

 

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Do you need more traffic to your website?

Who doesn't right?  If you are wondering how to put your ads on the top or the side of Google to show up when local people search for dentists, or if you already have an Adwords campaign but the costs are too high and the results too low, then you have come to the right place.   We manage pay-per-click campaigns for dentists who need new patients.  Google has made its billions by connecting site visitors who need a product or service to advertisers like you.  But how do you get started and should a dentist or dental office manager be spending hours just to learn the basics of pay per click advertising and wasting valuable marketing dollars on simple mistakes?

Why you need us to manage your campaign!

Perry Marshall is an internet marketing guru and the authority on Google Adwords.  In his book "The Ultimate Guide to Google Adwords"  Perry explains 

Badly organized ads and keywords will cripple your Google campaigns and cost you a ton of money.  Properly organized campaigns get results from the beginning and are easy to adjust and optimize.  Overtime this makes a huge difference.

How does it work?

You give us a list of keywords that you would like your ads to be connected with.  We create two ads that highlight your services / specialties and when a visitor searches Google for the keywords listed your ads will appear.  You don't have to pay anything unless the visitor clicks on your ad.  Every week we will create one new ad and drop the ad with lower performance.  Over time this optimizes your ads to have the best performance for your keywords and in your geographic region.  Cost per click comes down so your traffic count goes up with the same budget.  

What controls do I have?  I don't want to pay for clicks from visitors all around the globe.

Of course you don't.  Google has made a science out of connecting people with the information and advertisers that best meets their needs.  That is how they became and have stayed the biggest search engine in the world.  Google allows you to specify geographic location.

What if I want to only run ads during office hours?

You can do that.  Google allows you to specify hours and days of the week.  

How much does it cost?  

In our experience costs per click can range from as little as $0.03 on Facebook to as much as $ or $2 on Google.  The less you know the more it costs.  These sites use a form of auction such that advertisers who are willing to pay more for a certain keyword get to the top of the list.  But, since they only get paid when a visitor CLICKS on your ad they give preferential treatment to ads which have higher click through rates (CTR) and better landing pages(the page the visitor 1st sees when he clicks your ad).  

Costs per click depend on many factors but here are a few:

Keyword Competition - If you want your advertisement to be at the top of the list and shown every time you have to pay more OR have a better click through rate and landing page than your competition (which costs a lot less).

Quality Score - Google ranks your landing page on how relative it is to what people are searching for (keywords) and how relative it is to the text in your ad.  If a visitor searches "exercise," your ad reads "Learn how to be healthy" and your landing page is about amalgam fillings but never mentions the word "exercise" or "learn" then your quality score will be low and you will have to bid higher in order to get your ad shown.

CTR - Google would rather show your ad and charge you $0.10 per click if it gets clicked on 50% of the time then show someone else's ad and charge them $1.00 if it gets clicked on 0.05% of the time.  Writing good ads and choosing the right keywords makes Google your friend and lowers cost significantly.  

What about management fees?

We charge a small percentage of the total amount spent to manage your campaign.  Because a properly managed campaign can result in savings of 50% or more per click, our services actually save you money compared to the cost if you manage the ads yourself.   In fact, if you currently have an Adwords campaign running that you are managing in house we guarantee that we can lower the cost per click and take our commission out of the difference.

What if I have a small budget?

Both Google and Facebook allow you to set a daily budget.  Because costs per click come down over time as we hone your ads and keywords we recommend starting with a small budget for the first month ($5 - $10 / day) and then raising it..  Your final budget might be determined by your local population and keywords chosen.  

What kind of tracking do I have after the click?

If you have a Google Analytics account already set up on your website you can see the following statistics specifically for those coming from your pay per click campaign:

Bounce rate - how many used the back button to go back to Google

Time on the site - How long they stayed and how many pages they looked at

It is difficult to know how many people picked up the phone and made a phone call or scheduled an appointment unless a specific offer is made on the landing page (i.e. 50% off first visit with coupon code PPC50).

We are happy to work with you to create a unique page and special offers to help you measure the effectiveness of your campaign.

 

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Mercury Levels in Body Fluids After Amalgam Removal 

 
Dr. Boyd Haley, professor of Chemistry/Biochemistry emeritus at the University of Kentucky, recently gave a lecture at a dental convention. His lecture was titled, the Toxicity of Mercury and its Relationship to Neurological Illness and Oxidation Stress.  
In a series of short articles I would like to summarize and simplify what he presented. He rightfully stated that without degrees in chemistry, most of us would not understand all that he presented. We did understand most of the conclusions following the scientific articles and it is my hope that you will also understand and benefit.
 
A pro-amalgam spokesperson recently stated that it is “estimated” that only 0.03 mcg. (Micrograms) Of mercury is given off in a single day. On that basis, he said, it would take several hundred amalgams to provide a toxic dose.
 
First, why would someone representing a science-based organization, have to estimate something as toxic as mercury is to humans? A recent study, funded by the International Academy of Oral Medicine and Toxicology, shows that different types of amalgam emits more mercury than others and that a single spill (very small amalgam) emits between 4.0 and 20.0 mcg of mercury a day at room temperature and without abrasion (it would have been much greater at body temperature, or after chewing or brushing). 4.0 to 20.0 mcg/day is about 133 to 666 times more than was estimated by this “scientist.” This is a sad example of perverting or ignoring science to support erroneous claims.
 
A study done inStockholm, Sweden published in 1997 byL. Bjorkman,et.al. evaluated the mercury concentration in saliva and feces before and after removal of dental amalgam fillings. Ten subjects had all their mercury fillings removed at one appointment. 
 
Before removal the mercury concentration in their feces was more than ten times higher than the samples from an amalgam free reference group of ten individuals. A considerable increase of mercury concentration in feces two days after removal was followed by a significant decrease.  The decrease continued until checked at 60 days after removal when it was just slightly higher than the non amalgam reference group figure.
 
In saliva, there was an exponential decline in the mercury concentration during the first two weeks after removal.  It was concluded that, 1) amalgam fillings are significant sources of mercury in saliva and feces, and, 2) the uptake of amalgam mercury in the GI tract in conjunction with proper removal of amalgam fillings appears to be low.
   

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