1 ATTACHMENT 1

Introduction

This attachment is a discussion of E NVIRON’s limited update of the scientific assessment (“SA”) published in 2005 1 , including estimates of inputs to surface water from two potential emissions sources not prev iously addressed: medical incinerators and landfills. A sensitivity analysis is presen ted showing how varying levels of compliance with ADA’s 2004 Best Management Practices (“ BMPs”) and use of amalgam separators affects the amount of mercury discharged to surface water. Absolute costs and costeffectiveness associated with the various levels of BMP co mpliance and separator use are

also estimated and discussed.

Mercury fate

The primary purposes of this update are to 1) refine the analysis by including more recent data and study results; and 2) to account for potential mercury emissions from two sources that were previously not discussed, but that may receive mercury amalgam waste

—medical incinerators and landfills. In our earlier assessment, we did not specifically state the ultimate disposal location of amalga m collected in chair-side traps (“traps”) and vacuum pump filters (“filters”). However, amalgam captured in these two devices comprises the large majority of amalgam rem oved from dental wastewater, and thus the fate of this mercury should be assessed. In 2004 ADA published BMPs that emphasized recycling of amalgam collected from all sources in dental offices, such as scrap amalgam and particulate amalgam ca ught in traps and filters 2 . We assess here the fate of mercury that is handled in two ways that are not in accordance with BMPs (i .e., disposal of waste amalgam in regular trash, which is ultimately disposed in landfills, and disposal in biohazard bags, which are incinerated).

1 Vandeven, J.A. and McGinnis S.L. 2005. An assessment of mercury in the form of amalgam in dental wastewater in the United States. Water, Air, and Soil Pollut. 164: 349–366 (“2005 Vandeven/McGinnis Article”). 2 ADA. Best Management Practices For Amalgam Waste. 2004. Chicago, IL2 This assessment relies heavily on results from our previous assessment and on the results from recent assessments by EPA and others. We have incorporated new data where applicable to further refine our assessment. Our general approach is the same as that taken in our previous SA—we used statisti cs from the literature where possible, and made estimates to the extent necessary. Inhe rent in this process was the necessity to make several assumptions, which are discussed below.

Amount of mercury discharged from dental offices

We assumed that a total of 31.25 tons of mercury are discha rged annually from dental offices. This is the amount of mercury wh ich ERG estimated to be discharged, based primarily on results from our previous SA and also on updated stat istics regarding the

number of dentists 3 . We assumed this discharge am ount for ease of comparison with ERG’s study, though current data suggest that the actual am ount is slightly lower— probably closer to our previous estimate of 29.7 tons or perhaps even lower. The

additional amount of 1.55 tons is due almost entirely to the greater number of dentists actively practicing 4

.

It is important to note, however, that though we believe the number of active dentists did indeed increase as ERG stated, the number of removals per dentist has likely decreased

from our earlier estimate of 710 and 440 remova ls per general dentis t and specialist per year, respectively. A lower removal rate is likely because amalgam placements have been decreasing for several years, including estimated d ecreases of 29% from 1990 to

1999 5 , 30% from 1990 to 1996 6 , and 20.5% from 1999 to 2005 7 . Based on an amalgam

3 Memorandum from Derek Singer, ERG, to Jan Matuszko, EPA, Subject: Dental Amalgam Separators: Summary of Removal Efficiencies, Current Use and Cost Effectiveness (DCN 04851) (September 26, 2007). 4 ADA. 2007. Survey and Economic Research on Dentistry, Frequently Asked Questions: How many dentists are there in the U.S.? http://www .ada.org/ada/prod/survey/faq.asp#howmany. 5 Berthold, M. 2002. Restoratives: Trend data shows shift in use of materials. Am. Dental Assoc. News 33(11) 10-11. 6 Sznopek, J. and Goonan, T. 2000. The materials flow of mercury in the economies of the United States and the World. United States Geological Su rvey Circular 1197. Denver, Colorado. 7 ADA, Economic Impact of Regulating Amalgam, Public Health Reports. Se ptember–October 2007 /Volume 122. at 657, 659-660. http://www.ada.org/prof/resour ces/topics/amalgam_ economic_impact.pdf3 lifetime of approximately 8-9 years 8 , the number of amalgam restorations in place and available for removal is likely lower, due to the lower number of placements in 1999 as compared with 1990. Further, recent data from a municipal study show that removal rates are substantially lower, approxima tely 169 removals per dentist per year 9

. Nevertheless, we have used ERG’s estimate of 31.25 total tons of mercury discharged

from dental offices so as to facilitate comparisons between ERG’s estimates and our own.

Capture efficiency of chair-side traps and filters We assumed that chair-side traps and f ilters capture 78% of mercury in amalgam discharged in dental office wastewater, in accordance with our previous SA. ERG assumed the same chair-side trap and filter capture efficiencies as we did in the SA (i.e., 68% efficiency for chair-side traps alone and 81% efficien cy for chair-side traps and filters), though they calculated the amount of mercury not ca ptured from the two sources separately. Though their calculation method va ried slightly from our previous method, the results were not significantly different fr om ours for that portion of the flow with chair-side traps alone or chair-side traps and filters.

Capture efficiency of amalgam separators For purposes of this calculation, we assume d that amalgam separators capture 99.2% of particles exhibiting a size dist ribution of that presented in ISO11143, which is the median efficiency of separato rs as presented by ERG 10 . However, there is an important but subtle difference between the results presen ted by ERG and results from our current analysis. ERG has overestimated the incremental capture efficiency of amalgam separators downstream of chair-side traps and filters.

8 Ibid. 9 Barron, T. 2005. Mercury source analysis for 2004. Internal Review Draft. Prepared for San Francisco PUC. July. http://sfwater.org/Files/Reports/Hg_Tech_M emo_1d.pdf. The report showed 184 removals per dentist among those that actively remove amalgams and 169 removals per dentist if all dentists are considered. 10 Memorandum from Derek Singer, ERG, to Jan Matuszko, EPA, Subject: Dental Amalgam Separators: Summary of Removal Efficiencies, Current Use and Cost Effectiveness (DCN 04851) (September 26, 2007).4 As stated earlier, the effective capture effici ency of chair-side trap s and filters is 78%, which is weighted by the efficiencies of each and their respective usage rates. These devices capture the largest amalgam partic les in dental wastew ater, resulting in a downstream particle size dist ribution that no longer matc hes that of ISO11143, but is weighted more toward smaller particles. Give n that separators opera te using one or more of centrifugation, sedimentation, and filtration to remove amalgam particles, the smallest are the most difficult to capture. Once the chair-side traps and filters remove the largest particles, the remaining distribution consis ts of smaller, more difficult to capture, particles. Therefore, the efficiency of sepa rators downstream of traps and filters will be slightly lower than the efficiency in captu ring particles from the ISO11143 distribution. In this case, the total efficiency of a tr ap+filter+separator tr ain is 99.2%—the same efficiency as a separator alone . The incremental efficiency, E I , is calculated using the following equation: 99.2% = 78% + 22% × E I . Using this equati on, we calculated the incremental efficiency to be approximately 96.4% 11 . ERG overestimated efficiency by assuming that 99.2% of amalgam particles not captured by traps and filters are captured by separators.

Another way to look at the numbers is to calc ulate the efficiency of separators regardless of whether traps or filters are upstream. ERG stated that of 31.25 tons of mercury discharged from dental facilities, 26.21 are currently captured and that installation of separators would result in capture of an a dditional 4.93 tons, for a total of 31.14 tons per year. However, if the overall efficiency of any system that includes separators is 99.2%,

the maximum amount that can be removed is 31.25 tons × 99.2% = 31.0 tons, not 31.14, as ERG has stated. Though the difference is sm all, it is significant, especially when considering the cost per ton removed.

11 Note that in our previous SA, we estimated the incr emental efficiency of separators downstream of chairside traps and filters to be 95%, based on results from studies by MCES and MDA (Metropolitan Council Environmental Services and Minnesota Dental Association. 2001. Evaluation of Amalgam Removal Equipment and Dental Clinic Loadings to the Sanita ry Sewer. Minneapolis-St. Paul, Minnesota) and ADA (Fan, P.L., Batchu, H., Gasparac, W., Sandrik, J., an d Meyer, D. 2002. Laboratory evaluation of amalgam separators. J. ADA. Vol 113, 577–584). Thus the current study assumes a slightly higher incremental efficiency than we previously used.5 Assuming that 100% of dental offices install separators with a median efficiency of 99.2%, 0.25 tons of the initial 31.25 will not be captured and will be discharged to surface waters. Therefore, the amount of mercury discharged in POTW effluent even if all dental offices had separators would not drop significantly from the 0.3 tons of dental mercury that Vandeven and McGinnis estimated is currently being discharged from

POTWs. The lack of a decrease in POTW effluent mercury concentrations after separator installations has been documented in the literature. Despite this lack of evidence demonstrating a decrease in effluent concentration after se parator installation, NACWA (formerly AMSA) reported that one st udy from POTWs in the City of Wichita, Kansas preliminarily showed 29% reduction in effluent mercury concentrations when separators were installed 12 . Though several other studies c ontradict this conclusion, we have included in our sensitivity analysis a scenario in which effluent mercury concentrations decrease by 30%.

Capture efficiency of POTWs As stated in the previous SA, approximate ly 95% of mercury entering a POTW will be removed and not discharged with effluent. The high efficiency of POTWs in removing mercury from wastewater is supported by resu lts from a number of studies showing that mercury capture efficiencies for POTWs ranging from 95% to 99%. A 2002 AMSA study included a review of 15 POTWs ranging in capacity from 4 million gallons per day (MGD) to 375 MGD 13 . AMSA found the average mercury capture efficiency to be 95%. Balogh and Liang (1995) 14 and Balogh and Johnson (1998) 15 found capture efficiencies for three POTWs to be 96%, 98%, and 99%.

The high effectiveness of POTWs in capturing amalgam makes scientific sense as well. Amalgam particles are much dens er than water and thus sett led out and are removed with

12 The anecdotal decrease in effluent concentrations was relayed by personal communication from C. Hornback to ENVIRON. 13 Association of Metropolitan Sewerage Agencies (A MSA). 2002. Mercury Source Control and Pollution Prevention Program. Washington, D.C. 14 Balogh, S. and L. Liang. 1995. Mercury pathways in municipal wastewater treatment plants. Water, Air, Soil Pollut. 80:1181–1190. 15 Balogh, S. and Johnson, L. 1998. Mercury mass ba lances at two small wastewater treatment plants. Metropolitan Council Environmental Services (MCES), Minneapolis-St. Paul, Minnesota.6 other particulates entering POTWs. The de nsity of amalgam particles is approximately 11 g/cm 3 , depending upon the particular composition. For example, amalgam can be composed of tin, copper, silver and mercur y, with densities of approximately 7.3 g/cm 3

, 9 g/cm 3 , 10 g/cm 3 , and 13.5 g/cm 3 , respectively . The compos ition of one amalgam type is 30% silver, 50% mercury, 5% copper and 15% tin, resulting in an amalgam with a density of approximately 11 g/cm 3 . Amalgams with other compositions would have

similar densities.

Based on the above analyses, it is reasonabl e to conservatively estimate that POTWs remove 95% of influent mercury. As the proc esses used to remove particles in a POTW are similar to those in separators, the smallest particles that escape capture in separator will likely not be captured in a POTW. For this reason we have assumed that for wastewater treated with separators, the mercur y not captured will also not be captured in POTWs. In other words, for the portion of flow from facilities w ith separators, POTWs will not capture any additional mercury, and for the portion of flow from facilities without separators, the ca pture efficiency is 95%.

Implementation of BMPs As stated earlier, a primary focus of this upda te is to assess the fate of mercury captured in chair-side traps and vacuum pump filters—in particular that portion which is not recycled. In 2004 ADA published BMPs for amal gam waste in an effort to reduce the amount of mercury entering th e environment. These BMPs provide guidance regarding proper use and storage of mercury and proper disposal of amalgam waste. The BMPs state that amalgam waste should always be recycled and should not be placed in biohazard containers, in fectious waste containers (red bags ) or regular garbage. In the current analysis, mercury collected in chai r-side traps and filt ers that was handled according to BMPs was assumed to be recycled and not enter the environment, including surface waters. Mercury not handled according to BMPs was assumed to either be sent to

medical incinerators or to landfills. The amount of mercury emitted from either one was

estimated based on emission rates from the literature.7 Emissions from medical incinerators ADA’s 2004 BMPs specifically state that am algam waste should not be disposed in biohazard containers, in fectious waste containers (red bags ). This is primarily because this type of waste is typically incine rated, thus converting mercury from a bound (amalgamated) form into a volatile, mobile fo rm. We assumed that 96% of mercury from amalgam waste sent to a medical inci nerator was captured by pollution control equipment, based current regulations re garding emissions from medical waste

incinerators 16 . Mercury captured in medical incinerator polluti on control equipment was assumed to be handled according to applic able regulations and not released to the

environment. We assumed that all dental o ffices with amalgam separators would recycle mercury captured in separators.

As in our previous assessment, we assume d that 33% of mercury emitted from medical

incinerators would enter United States surface waters, based on a 1997 USEPA

estimate 17 . The resulting amounts of mercury en tering surface wate rs are shown in

Table 1 and are discussed further below.

Emissions from landfills and land-applied biosolids We estimated the amount of mercury that w ould be disposed in solid waste landfills assuming various levels of compliance with 2004 BMPs, which advise dentists not to dispose any amalgam waste in regular garbage. Total annual mercury emissions in the

U.S. have been estimated at <0.1 tons per year in 1994–1995 and 0.2 tons per year in

1996 18 . The total mercury directed to landfills or collected as hazardous waste was estimated to be 295 metric tons (330 U.S. tons) in 1996 19 . Therefore, we conservatively estimated the emission rate to be 0.2 tons emitted/330 tons disposed = 0.0606%. In other words, 0.0606% of mercury from dental offices that is disposed in landfills is emitted to

16 Proposed regulations requiring that hospital/medica l/infectious waste incinera tors (HWIMI) capture 96% of mercury emissions were published in Federal Register, Volume 72, No. 24, February 6, 2007. 17 United State Environmental Protection Agency. 1997. Mercury study report to Congress. EPA-452/R-97- 003. 18 United Nations Environment Programme (UNEP). 2002. Global Mercury Assessment. Geneva, Switzerland. At page 98. December. This document cites to http://www.chem.unep.ch/mercury/Repor t/Final%20Assessment%20report.htm 19 Ibid. page 99.8 the air. As with other emissions to air, we assume that 33% of total mercury emissions

from landfills reach U. S. surface water.

Based on EPA statements, we further assume d that mercury in land-applied biosolids would be bound as amalgam and wo uld not be available for leaching to surface water or

volatilization to the atmos phere in significant amounts 20,21

.

Emissions from incinerated biosolids We assumed that capture of mercury in from sewage sludge incinerator (SSI) emissions to be the same as presented in the previous SA, i.e., 79% capture efficiency, based on

AP-42 emission factors 22 . As in the 2005 SA, we assumed that 33% of mercury emitted from SSIs to the atmosphere is deposited in U.S. surface waters 23

.

Estimated costs

A fundamental issue related to a regulation regarding mandato ry installation of amalgam separators is the cost with implementing su ch a regulation. This section discusses our methods for estimating costs of implemen tation of BMPs and use of separators.

To estimate costs incurred by dentists in implementing BMPs, ENVIRON obtained estimates for recycling waste that include s amalgam (e.g., scrap amalgam, traps and filters with amalgam, etc). ENVIRON spoke with several mercury recyclers, separator

manufacturers and distributors to ask if they recycle amalgam waste or have estimates of the cost associated with recycling. Various methods for recycling amalgam waste exist. Some recyclers sell a recycling service in which the recycler will send the dentist an

20 ADA Prior Comments, EPA-OW-2006-0771 at 54-55; 204-208; 213-215. 21 EPA’s Road Map, Addressing Mercury Rel eases at 28 (July 2006), available at

< http://epa.gov/mercury/pdfs/I_HgReleases.pdf >. The mercury in amalgam is bound into the mixture and the mercury in the amalgam in biosolids is less likely to be released into the air. The study cited by EPA in the administrative record is limited and measured mercury from all sources, not just mercury from amalgam and, therefore, was not a measure of the lik elihood of mercury in amalgam being released from soil. 22 United States Environmental Protection Agency. 1995 . Compilation of air pollutant emission factors, AP-42, Fifth edition, Volume I: Stationary Point and Area Sources. Washington, D.C. 23 United State Environmental Protection Agency. 1997. Mercury study report to Congress. EPA-452/R-97- 003.9 empty bucket to contain amalgam waste and a return shipping label. The dentist then fills the bucket with amalgam waste and ships it back to the recycler. ENVIRON asked if the recyclers were able to estimate a representa tive amount of time dentists take to fill a certain size (e.g., one gallon) recycling bucket. They reported that the times vary widely from as short as one month to as long as a year. Costs per buck et generally ranged from just under $100 per bucket to over $300, depending upon the se rvice and on the size of

the bucket. Based on our conversations with these manufacturers and distributors, we estimated that a conservative (low) cost to be approximately $150 per year.

We assumed that the annual cost of owni ng and operating an amalgam separator to be $770.85, based on recent work by ERG. This cost is in general agreement with results from our conversations with amalgam separa tor manufacturers and distributors. Using the annual cost of $770.85 for ownership and operation of an amalgam separator and $150 per year for implementation of BMPs, we calculated the cost of implementing various scenarios, ranging from 65% complia nce with BMPs and dental offices with separators installed to 100% compliance with BMPs and all dental offices with separators

installed.

In addition to estimating absolute costs asso ciated with complying with BMPs and using separators, we estimated the cost per ton of mercury prevented from entering surface waters for the two scenarios of effectively 0% reduction in effluent mercury and 30% reduction in effluent mercury. The results of this analysis are summarized in Table 1 and

discussed further below.

Results

Estimated amounts of merc ury entering surface water Table 1 summarizes the amounts of mercury th at would reach surface waters in the U.S.

under the various scenarios. Several observa tions are worth highli ghting. First, it is important to note the very small quantities of mercury that are being considered in this analysis. Even in the worst case scenario in the table (65% impl ementation of BMPs and 0% of facilities with separato rs), the amount of mercury rele ased to surface waters is10 relatively small (0.532 tons, compared with a total of 31.25 tons disc harged from dental offices).

Second, the results from the present analysis are in agreement with those of our earlier SA. For example, in the case of 100% sepa rator installation, 0.25 t ons of mercury reach surface waters, which is similar in magnitude to the 0.3 tons estimated in the earlier SA. Also, for the case with 100% compliance with BMPs (i.e., no mercury captured in traps and filters reaches surface water), the result converges to 0.419 tons, similar to the value of 0.4 tons estimated previously.

Third, the amount of mercury that is prev ented from entering surface waters after installation of separato rs is very small. In the extr eme case where 35% of those without separators are out of complia nce with BMPs and send their amalgam waste to medical incinerator, 0.282 tons of mercury are prevente d from entering surface waters if 100% of dentist offices have separators.

Estimated costs of implementation of BMPs and use of separators Our estimates of the costs associated with implementing BMPs and installing and maintaining amalgam separators are summarized in Table 1. At the low end, assuming no separators are installed and 65% of dental offices are complying with BMPs, the total cost is approximately $9.8M. At the other ex treme, where 100% of dental offices are complying with BMPs and also have separators installed, the total cost is approximately $92.9M. Using ERG’s estimate of $770.85 per de ntal office and 100,843 dental offices, the total cost would be approximately $77.7M . Adding the cost of implementing BMPs

at all dental offices would result in $92.9M, which matches our result.

However, our current estimate of the cost of separator use per ton of mercury captured varies significantly from ERG’ s. ERG calculated the cost of capturing amalgam to be approximately $11M per ton, based on total cost of $54.4M to remove approximately 4.93 tons of mercury. We estimate that th e cost would range from $319M to $461M per ton. ERG’s analysis falls shor t in at least two ways.11 First, ERG overestimated the effectiveness of separators by assuming that the efficiency of separators in capturing particles passing through chair-side traps and/or filters is the same as the efficiency in capturing particles fr om the entire size range of particles in the

ISO11143 distribution. This is an incorrect assump tion. ERG stated that only 0.1 tons would be discharged to surface waters. Ho wever, even if 99.2% efficiency can be achieved, the smallest amount of mercury that can be discharg ed to surface water is 0.25 tons, even if all dental offices installed a nd used separators. Thus, the greatest amount removed would be 4.79 tons, not 4.93 tons. This works out to approximately $11.4M per

ton.

Second, and more importantly, ERG did not c onsider the effectiv eness of POTWs in reducing mercury discharge to surface waters, but rather assumed that installing separators would decrease the amount of mercury released to surface waters by full 4.93 tons. In reality, only 0.419 tons would ultima tely reach surface water with no separators installed, and only approximately 0.169 tons fr om biosolids incineration emissions and POTW effluent would actually be prevented from entering surface waters by installing separators. According to our current cal culations, an additional 0.118 tons would be captured if the remaining 70% of dental offi ces currently without separators installed them. Based on total costs of approximat ely $54.4M for 70% of dentists to install separators 24 , the estimated cost would be $461M per ton captured.

Comparison with previous results In our previous SA, we estimat ed the annual cost for all 95,0 66 dental offices to install and operate separators to range from $76M to $114M and the cost per ton to range from $380M to $1.14B. At the low end, we used as a basis the scenario in which 30% of 0.3 tons (i.e., 0.1 tons) in effluent would be prevented from entering surface water. The net reduction, including 0.1 tons from incinerated biosolids, was 0.2 tons. Therefore, the low cost per ton was calculated to be $76M/0.2 ton = $380M/ton.

24 Memorandum from Derek Singer, ERG, to Jan Matuszko, EPA, Subject: Dental Amalgam Separators: Summary of Removal Efficiencies, Current Use and Cost Effectiveness (DCN 04851) (September 26, 2007).12 At the high cost end, we estimated that onl y 0.1 tons of mercury would be prevented by installing separators. Using the higher annual cost value of $1200, 95,066 dental offices and 0.1 tons, the resulting cost per ton preven ted from entering surface water is $1.14B.

The differences between our previous study results and the pres ent results are due primarily to two factors. Firs t, the higher end cost used pr eviously is higher than the baseline cost used here ($1200 as opposed to $770.85). Second, the higher incremental capture efficiency used here (96.4% currently as opposed to 95% pr eviously) results in greater mercury capture, which results in lowe r cost per ton for a given absolute cost.

Conclusions

We performed a limited update of our previous assessment by 1) using more recent data and 2) estimating emissions from medical incinerators and landfills that may receive amalgam waste. Results were summarized as a sensitivity analysis for various scenarios in Table 1. In addition, we estimated the absolute cost of implementing 2004 BMPs and installing and using amalgam separators. Fi nally, we calculated the cost per ton of preventing mercury from entering surface wa ters by installing and using amalgam separators. Those costs range d from $319M to $461M per ton.Percent compliance with pre-2007 BMPs (1) 65% 65% 80% 80% 90% 90% 100% 100%Destination of non-recycled mercury Medical incinerator Landfill Medical incinerator Landfill Medical incinerator Landfill NANABaseline estimate of mercury reaching surface waters (2)0% of dental facilities using separators0.531 0.420 0.483 0.420 0.451 0.419 0.419 0.41930% of dental facilities using separators0.447 0.369 0.413 0.369 0.391 0.368 0.368 0.36850% of dental facilities using separators0.391 0.335 0.367 0.335 0.350 0.335 0.334 0.33475% of dental facilities using separators0.320 0.293 0.308 0.292 0.300 0.292 0.292 0.29290% of dental facilities using separators0.278 0.267 0.273 0.267 0.270 0.267 0.267 0.267100% of dental facilities using separators0.250 0.250 0.250 0.250 0.250 0.250 0.250 0.250"30% effluent mercury reduction" scenario (3)0% of dental facilities using separators0.531 0.420 0.483 0.420 0.451 0.419 0.419 0.41930% of dental facilities using separators0.424 0.347 0.391 0.346 0.368 0.346 0.346 0.34650% of dental facilities using separators0.353 0.298 0.329 0.297 0.313 0.297 0.297 0.29775% of dental facilities using separators0.264 0.236 0.252 0.236 0.244 0.236 0.236 0.23690% of dental facilities using separators0.211 0.200 0.206 0.199 0.203 0.199 0.199 0.199100% of dental facilities using separators0.175 0.175 0.175 0.175 0.175 0.175 0.175 0.175Baseline costs of implementation (4)0% of dental facilities using separators$9,832,193 $9,832,193 $12,101,160 $12,101,160 $13,613,805 $13,613,805 $15,126,450 $15,126,45030% of dental facilities using separators$34,740,918 $34,740,918 $36,329,195 $36,329,195 $37,388,046 $37,388,046 $38,446,898 $38,446,89850% of dental facilities using separators$51,346,735 $51,346,735 $52,481,218 $52,481,218 $53,237,541 $53,237,541 $53,993,863 $53,993,86375% of dental facilities using separators$72,104,006 $72,104,006 $72,671,247 $72,671,247 $73,049,409 $73,049,409 $73,427,570 $73,427,57090% of dental facilities using separators$84,558,368 $84,558,368 $84,785,265 $84,785,265 $84,936,529 $84,936,529 $85,087,794 $85,087,794100% of dental facilities using separators$92,861,277 $92,861,277 $92,861,277 $92,861,277 $92,861,277 $92,861,277 $92,861,277 $92,861,277Cost effectiveness baseline scenario (total cost per tons removed by separators) (5)0% of dental facilities using separatorsNA NA NA NA NA NA NA NA30% of dental facilities using separators$295,087,979 $487,076,408 $346,449,196 $475,806,776 $394,397,282 $468,239,592 $460,628,692 $460,628,69250% of dental facilities using separators$295,087,979 $487,076,408 $346,449,196 $475,806,776 $394,397,282 $468,239,592 $460,628,692 $460,628,69275% of dental facilities using separators$295,087,979 $487,076,408 $346,449,196 $475,806,776 $394,397,282 $468,239,592 $460,628,692 $460,628,69290% of dental facilities using separators$295,087,979 $487,076,408 $346,449,196 $475,806,776 $394,397,282 $468,239,592 $460,628,692 $460,628,692100% of dental facilities using separators$295,087,979 $487,076,408 $346,449,196 $475,806,776 $394,397,282 $468,239,592 $460,628,692 $460,628,692Cost effectiveness - "30% effluent mercury reduction" scenario (total cost per tons removed by separators) (6)0% of dental facilities using separatorsNA NA NA NA NA NA NA NA30% of dental facilities using separators$232,985,219 $338,253,352 $262,116,168 $329,992,739 $287,198,126 $324,458,188 $318,901,501 $318,901,50150% of dental facilities using separators$232,985,219 $338,253,352 $262,116,168 $329,992,739 $287,198,126 $324,458,188 $318,901,501 $318,901,50175% of dental facilities using separators$232,985,219 $338,253,352 $262,116,168 $329,992,739 $287,198,126 $324,458,188 $318,901,501 $318,901,50190% of dental facilities using separators$232,985,219 $338,253,352 $262,116,168 $329,992,739 $287,198,126 $324,458,188 $318,901,501 $318,901,501100% of dental facilities using separators$232,985,219 $338,253,352 $262,116,168 $329,992,739 $287,198,126 $324,458,188 $318,901,501 $318,901,501Notes:6. Cost effectiveness for the "30% effluent mercury reduction" scenario was calculated the same way it was in the baseline scenario, except that the cost was divided by the estimated amount of mercury preventedfrom entering surface water assuming an additional 30% reduction in effluent concentrations.4. This baseline cost estimate assumes $770.85/year for separators and $150/year for BMPs for 100,843 dental offices (ERG, 2007) that use amalgam. $770.85 is the estimated annual cost for owning andoperating an amalgam separator, as calculated by ERG, 2007. The cost includes $1,200 capital cost, spread over 10 years at 7%interest plus $600 annual operation and maintenance.5. Cost effectiveness was calculated by taking the cost of the dental community owning and operating separators and dividing itby the estimated amount of mercury prevented from entering surface water. Forexample, the baseline cost for the scenario with 30% separators and 65% BMP compliance is (30%)(100,843)($770.85+$150)+(100%-30%)(100,843)(65%)($150) = $34,740,918.Table 1Annual amount of mercury entering surface water and costsassociated with varying levels of compliance with 2004 ADA BMPs and use of amalgam separators(tons; assuming 31.25 tons discharged in dental wastewater)1. We assumed that 100% of dental offices with separators installed were in compliance with BMPs. The "Percent compliance withBMPs" refers to the percentage of dental offices that are in compliance withBMPs, yet do not have a separator installed. For example, where 100% of dental offices have separators installed, 100% are also in compliance with BMPs.2. The baseline assessment scenario is the same as that in our previous SA. This assumes that POTWs capture 0% of that portionof mercury entering separators but which is not captured.3. This scenario is the same as the baseline, except that it includes an assumption that mercury entering separators but is notcaptured is actually reduced by 30%, compared to the baseline scenario. This is inaccordance with a scenario presented in our earlier SA.