1 

# memorandum

s 

## Environment and Resources

55 Wheeler Street, Cambridge, MA  Tel: 617 492

- 7100  www.abtassociates.com

Date September 26, 2011

To Tom Born, U.S. EPA/OW/OST

From Emily Giovanni , Elena Besedin

, Molly Cohen, David Mitchell

Subject Literature Review of the Impacts of Mercury from Dental Amalgam in Wastewater

This memo summarizes dental mercury discharges, impacts, and potential benefits of reductions resulting from the installation of mercury separators in dental offices in support of EPA’s associate d rulemaking. It complements and expands on the previous Detailed Study (U.S. EPA, 2008).



### 1 Introduction

Mercury is a well

- known environmental toxicant ubiquitously distributed at low levels in most terrestrial and aquatic ecosystems. Humans and wildlife ar e exposed to mercury primarily via the consumption of fish from mercury

- contaminated waterbodies, although other exposure pathways exist (such as through accidental inhalation at the workplace). When exposed to mercury, humans can experience a wide range

o f health effects, including damage to the brain, kidneys, heart, and especially nervous system. These impacts are particularly harmful for children, who can experience profound and permanent developmental and neurological delays as a result of exposure in

- utero

. Similar neurological effects as well as adverse impacts on reproduction have been documented in many wildlife species.

Because m ercury is extremely toxic even at very low concentrations dangerous levels in United States water bodies are increasingl y being detected (Scarmoutzos and Boyd, 2003). As of 200 8

, 50 states, 1 territory, and 3 tribes had issued mercury advisories, with 16.8 million lake acres and 1.3 million river miles under advisories (U.S. EPA, 2009 a ). Today, mercury can be detected in vi rtually every area of t he world, including the remote Polar R egions and other areas without emission sources of their own, as well as the upper reaches of the atmosp here (Scarmoutzos and Boyd, 2003).

S everal major sources of anthropogenic mercury emissions have been identified and are increasingly regulated, including power

- plant emissions, industrial and manufacturing activities, household products, agricultural applications, and waste disposal . As larger sources are increasingly regulated and controlled, regulatory attention has focused on identifying and reducing smaller sources (U.S. EPA, 2006). This has been concurrent with advances in the analytical measurement of mercury at increasingly refined detection limits and adoption of increasingly stringent e mission restrictions and water quality standards ( Stone, 2004; U.S. EPA, 2006).

Publicly owned treatment works (POTWs) are a known source of dilute amounts of anthrop ogenic mercury to surface waters

. To reduce mercury discharges to surface waters, some st ates have begun implement ing discharge limitations for POTWs in the past 15 years (CDPHE, 2004). Thus, m any POTWs have begun to work to identify and reduce discharges of mercury ent erin g their treatment systems. R ecen t research suggests that dental offices are a primary source category of mercury entering POTWs ( Larry
Walker Associates , 2002; NACWA, 2006; Vandeven and McGinnis, 2005; U.S. EPA, 2008).

However, a detailed assessment of environmental impacts of mercury discharges from dental offices is compli cated due to the difficulty of establishing definitive estimates of several factors, including:2

 The exact amount discharged by dental offices,

 The amount that POTWs are capable of removing

,  The extent of methylation in the environment,

 The uptake of mercur y from the environment to fish,

 Fish consumption rates, particularly by species,

 Effects of mercury to infants, children, and adults

. Additionally, the presence of natural ly

- occurring mercury throughout the environment can further complicate attribution o f mercury contaminations to particular sources. Given the increased sensitivity of detection technology, a major challenge to scientists and regulators is to develop an appropriate background or baseline level against which to establish discharge goa ls (Sc armoutzos and Boyd, 2003), especially given the relative dearth of historical data. Further, estimating the share of mercury emissions attributable to any individual source is complicated by the fact that reported emissions are frequently based on widely d ivergent methodologies and assumptions. For example, some use direct measurement while others use emission factors (Scarmoutzos and Boyd, 2003). However, there are a variety of scholarly, governmental, industry, and other literature sources that characteri ze mercury in dental wastewater discharges and its effects.

Given available information, t his literature review summarizes mercury discharges from dental offices,

the pollutant’s fate and transport, potential human health and wildlife effects

, and the redu ction potential

from dental offices

. This literature review will be used as a basis for qualitative assessment of benefits of

the Effluent Limitations Guidelines (ELGs) for mercury

- containing wastes from dentist offices. The

literature review is divided in to sections that include overviews of mercury forms, discharges from dental

offices

, effectiveness of the POTW treatment and discharges to surface waters, impacts to human health and wildlife, reduction potential and examples of existing state and municipa l separator requirement programs, and the potential value of benefits associated with mercury discharge reduction s . The final section provides a list of literature sources, and the appendices provide supplemental information.



### 2 Overview of Dental Amalgam Dis charges

Dental amalgam has been used as the primary restorative component (i.e. fillings) in dentistry for over 150 years (WDNR, 1997). It i s an alloy consisting of 50% mercury, plus powdered silver, tin, zinc, and

copper (Vandeven and McGinnis, 2005; Quic ksilver Caucus, 2008a). Previously, dentists mixed their

own amalgam from bulk liquid mercury and metal powders, but now it comes as ready

- to

- use capsules varying in size from 100 to 1,000 milligrams of mercury (IMERC, 2010).

Dental amalgam contributes to mercury pollution in United States water bodies through two pathway s:

 Air deposition. A ssuming that the average person has 7 filli ngs, about 3 tons of mercury is released from crematoria each yea r , eventually being deposited domestically or internationall y (Scarmoutzos and Boyd, 2003).

 Indirect discharge to surface waters via POTWs . T he primary route by which dental amalgam reaches surface waters is wastewater discharge from dental offices to publicly

- owned treatment works ( POTWs ) . Between 36% and 50% of all mercury reaching POTWs is attributable to dental office amalgam discharge, far exceeding all other commercial or residential facilities (Vandeven and McGinnis, 2005; U.S. EPA, 2006). One Colorado study found that dental clinics contribute 9.26 pounds o f mercury to the Littleton

- Englewood Wastewater Treatment Plant each y ear, or 62% of the total (CDPHE, 2004).3

This section 1) characterizes the different forms of mercury, 2) briefly summarizes a pass

- through analysis previously conducted by EPA to estimat e the current annual discharge rates from dental offices

in the United States and 3 ) characterizes the share of total anthropogenic mercury emissions that are

attributable t o various sources including dental offices

.

2.1 Forms of Mercury

Particulate and diss olved m ercury can take many forms, most commonly elemental, ionic/oxidized, inorganic, or organic (also known as methylmercury; ATSDR, 1999).

 Elemental mercury is the pure form of the metal, which is rarely found in nature. It is the

substance used in den tal amalgam, as well as other commercial products such as thermometers and electrical switches. Elemental mercury is volatile, displaying appreciable vapor pressure (Scarmoutzos and Boyd, 2003). As such, it is susceptible to absorption through the human

re spiratory tract. It is lipid soluble, and so it can cross the blood

- brain barrier causing neurological effects, and it can cross the placenta, facilitating impacts to infants and children exposed in

- utero after maternal exposure

. 1 Elemental mercury is prim arily of concern when it is inhaled due to its ability to a bsorb into the bloodstream; when it is ingested, less than 0.01% of it is absorbed into the digestive tract. Elemental mercury is a liquid under ambient conditions (Scarmoutzos and Boyd, 2003). How ever, when it is combined with other metals, elemental mercury dissolves and stabilizes, forming amalgam. Ionic mercury is elemental mercury that has

been oxidized.

 Inorganic mercury is elemental mercury combined with other elements such as chlorine or su lfur. Common species are mercuric chloride, mercuric acetate, mercuric sulfide, and others. This type of mercury is usually made up of white powders or crystals, although mercuric sulfide is red and is sometime used as a dying agent (including for tattoos) . Inorganic mercury is found primarily in batteries, some disinfectants, home health remedies, or skin

- bleaching creams (U.S. EPA, 2007). Inorganic mercury has low lipid solubility, and, on its own, is not as serious a health concern as elemental or organi c mercury.

 Organic mercury, or methylmercury, is mercury combined with carbon. This form is primarily produced from other forms of mercury by anaerobic bacteria in the aquatic environment (usually

in water body sediments). Methylmercury is the primary conc ern associated with mercury discharges to the environment. It is highly lipid

- soluble, and it primarily resides within fatty tissues in the body so it is eliminated from the body slowly (Scarmoutzos and Boyd, 2003).

Mercury discharged from dental offices primarily remains in elemental, amalgamated form throughout wastewater conveyance and treatment (Vandeven and McGinnis, 2005), during which it is typically co

mingled with other sanitary wastes. However, once it reaches surface waters, it can be transforme d into methylmercury which is the primary health and ecological concern associated with mercury discharges.

Exhibit 2

- 1 summarizes forms of mercury, their primary sources, and the relevant physical characteristics.

1 Discussed further in Section 4.24



### Exhibit 2

- 1. Forms of Mercury

Form Speci es Primary Sources/Load Solubility Physical State Water Lipid

Elemental Mercury Hg0 Vapor from dental amalgam;
Incineration of dental and medical waste; air emissions; vast majority of mercury in atmosphere (95

- 97%) Low High Heavy, mobile, liquid met al

Oxidized or
Ionic Mercury HgII Produced via oxidation of elemental mercury or demethylation of MeHg; Water emissions; May be dissolved in

POTW effluent High Low Crystals, granules, or powder

Inorganic Mercury Cl

- Hg

- Cl

Hg

- S Used in a variety of produ cts

(fungicides, insecticides); combination of ionic mercury with sulfur, oxygen and chlorine Low

Medium 1 Low Powders or

crystals

– mostly
white but can be
red or black

Methyl

mercury CH 3

- Hg + Few anthropogenic sources, aside
from indirect via met h y

lation of inorganic and ionic mercury; Stored
in macroinvertebrates and fish and mammal tissue; most common form of organic mercury Low High White powder or crystalline solids

1. Water and lipid solubility depend on the compound in question. Mercuric chloride, one of the most common inorganic mercury compounds, is soluble in water.

2.2 Dental Amalgam Use and Waste
Given the availability of new alternatives, improved dental hygiene, and concerns about the health implications of mercury, use of mercury amalgam by de ntists has decreased since the 1980s. For example, the American Dental Association (ADA) estimates that the number of restorations in 1999 was 71 million, down from 99.5 million in 1990 (Vandeven and McGinnis, 2005). Nonetheless, dentistry remains

one of t he largest mercury consuming industries in the United States, largely because amalgam is less expensive than other types of restorative materials such as resin composite, glass ionomer, resin ionomer, porcelain, and gold alloy ( Vandeven and McGinnis, 2005; Quicksilver Caucus, 2008a). Dental amalgam is the largest remaining dissipative uses of mercury, since many other dispersing uses of mercury 2 have

been decreased or el iminated (Swain, et al., 2007).

Vandeven and McGinnis (2005) estimate that there were ov er 120,000 private dentists in the United States in 2001, with 76% using dental amalgam . A n estimated 31.3 million tons of waste amalgam is generated by United States dentists annually (30.5 tons of suspended solid mercury and 0.8 tons of dissolved mercury )

. 3

Not all of the waste amalgam is discharged to receiving sewer systems. Currently, all dentists in the United States use some mechanisms to capture dental amalgam, including chair

- side traps and vacuum
filters. About 80% use vacuum filters combined with chair

- side traps, with an overall capture efficiency of 81%, while most others use chair

- side traps only, with an overall capture efficiency of 68% (Vandeven and McGinnis, 2005). As summarized in Appendix A, 11 states and several municipalities require th at
dental offices also use dental amalgam separators, which remove a higher percentage of amalgam

2 Including fungicides, paper manufacturing, and skin

- lightening soaps

3 For placement s, assumes that the average mercury per filling is 450 mg, 25% of it is not used, and that 9% of amalgam from placements is discharged as waste; for removals, assumes that the average removal generates 300 mg of amalgam. For a more detailed description, se e the Detailed Study (U.S. EPA, 2008)5

particles (usually over 96%) using sedimentation, filtration, centrif ugation, and/or ion exchange (McManus and Fan, 2003; CDPHE, 2004)

. However, there are no commercially available separators that remove all dental mercury from the waste stream. Specifically, dissolved mercury or molecularly dispersed mercury species can pass through
separators and other mechanisms because it is too fine to settle out with oth er particles (Scarmoutzos and Boyd, 2003). Additionally, surfactants and disinfectants commonly discharged in the dental wastestream can increase mercury dissolution, causing a larger share of it to pass through traps, filters, and/or separators to be disc harged to POTWs. T he amalgam that is not capture d by in

- house control technologies

flow s out of the dental facility to POTWs (Vandeven and McGinnis, 2005 ).

2.3 Dental Amalgam Share of Total Mercury Loading

Overall, 60% to 70% of mercury contaminating United St ates waters is attributable to anthropogenic

s ources , while the remaining 30% to 40% is from natural sources such as volcanoes , geologic or mineral deposits, and volatilization from the oceans (Scarmoutzos and Boyd, 2003 ; Trasande, et al., 2005 )

. Exhibit 2

- 2 shows the approximate anthropogenic shares of mercury in the environment attributable to different sources as of 1994 and 1995 (the date of the most recent comprehensive data set; as cited in Scarmoutzos and Boyd, 2003). 4 The c ombustion of coal and other fossil fuels is the largest source of mercury emissions (Trasande, et al., 2005 ; Swain et al., 2007) .C ombined incineration of municipal and

medi cal waste is the second largest (Mohapatra, et al., 2007).

Based on th ese data, den tal offices appear to represent a relatively small share of total anthropogenic mercury in the environment (less than 1%). However, some of the dental amalgam discharged to POTWs
is settled out with biosolids during wastewater treatment

. 5 In some cases (ab out 2 2 % of the time), these

biosolids are incinerated or otherwise volatilized into the atmosphere. Because of this, as Scarmoutzos and Boyd (2003) point out, dental mercury emissions also contribute to municipal and medical waste incineration categories. As such, they account for a larger share of total mercury in the environment

– possibly up to 4% to 19%

– and they are responsible fo r discharges directly to water bodies, as well as atmospheric emissions that will eventually be deposited. Dental offices a lso represent a unique source in that they are numerous and very diffuse across the nation, further complicating efforts to curtail emissions (compared with less numerous sources such as coal burning utility plants).



### Exhibit 2

- 2 . United S tates Annual Anthropogenic Mercury Discharges by Source

Source Discharge Medium

(air/water) Amount

(tons per year) Percentage of Total

Coal Burning Utility

Plants Air 52.0 33.7%

Boilers Air 32.1 20.8%

Commercial Air 28.8 18.6%

Residential Ai r 3.3 2.1% Municipal Waste
Combustors Air 29.6 19.2%

Medical Waste

Incinerators Air 16 10.4%

Hazardous Waste
Combustors Air 7.1 4.6%

4 Although it is the most recent comprehensive data available, the data shown in Exhibit 2.2 suggests a lower contribution by dental offices than most updated estimates from and by the dental industry.

5 Treatment of b iosolids is discussed in more detail in Section 3.2

.6



### Exhibit 2

- 2 . United S tates Annual Anthropogenic Mercury Discharges by Source

Source Discharge Medium

(air/water) Amount

(tons per year) Percentage of Total

Chlor

- Alkali Industry Air 6.5 4.2%

Portland Cement Air 4.4 2.8% Lamp Breakage Water 3.1 2.0% Pulp and Paper Industry Air 1.7 1.1%

General Laboratories Water 1.4 0.9%

Dental Offices Water 0.6 0.4%

Total

-- 154.5 100% Adapted from Scarmoutzos and Boyd (2003); based on EPA data from 1994 and 1995

.
With regard to air emissions

, mercury can have long atmospheric residen ce, eventually being deposited far from the emission source. As such, only about 33% of anthropogenic air emissions released in the United States are deposited domestically; the rest enters the global mercury pool (Trasande, et al., 2005 ) ; with anthropogen ic emissions from the United States accounting for about 3% of the total global mercury pool (U.S. EPA, 2006). Likewise, much of the mercury deposited domestically was emitted internationally and came from the global mercury pool. 6 This global

- scale interm ixing ad d s complexity to any effort to track emissions attributable to any particular domestic source, including dental amalgam.



### 3 POTW Treatment

, Pass

- Through, and Discharges to Surface Waters

Once dental am algam is discharged with wastewater, it enters sewer systems or septic tanks. This section

describe s the waste treatment methods (e.g., primary, secondary and tertiary treatment) and removal efficiencies typically associated with POTWs, how much mercury is likely to be discharged as effluent to

receiv ing waters , and how mercury is converted to methylmercury once it reaches surface waters

.

3.1 Treatment at POTWs and Surface Water Discharges

Once wastewater from dental facilities reaches one of 17,345 POTWs in the United States , it undergoes
one or several t reatment processes. Preliminary treatment consists of passing the wastewater through filtering bars or screens to remove larg e pieces of debris or trash, and the primary treatment consists of sedimentation tanks, where solid materials (including some amalg am particles) settle to the bottom of the

ta n k. The solid materials are usually called sludge or biosolids , and are pumped out of the tank, often for further treatment. Secondary treatment of the wastewater consists of “activated sludge process,” or

aerati on, in whi ch bacteria consume the remaining organic materials in the wastewater. In some cases, the water then goes through disinfection (usually via chlorine, sometimes UV) before it is discharged to the receiving waterbody. POTWs have a 9 5 % capture rate for mercury ( Larry Walker Associates , 2002) , with most of the capture occurring during preliminary treatment, when particulate mercury settles out with

other solids.

Previously, one of the greatest difficulties associated with enforcement of stringent li mi tations on mercury discharges, including those from POTWs, was that monitoring technology was not advanced enough to detect mercury at or below the designated water quality criteria. With regard to trace metals, it proved particularly challenging to preclu de sample contamination during collection, transport, and analysis (U.S. EPA, 2002 ). However, m ethod 1631E , approved by EPA in 1999, is designed specifically to preclude contamination, 7 allowing regulators to produce reliable results even at the lowest wat er quality

6 For example, EPA (2006) estimates that only 17% of mercury deposited in the United States originated domestically or in Canada; the remaining 83% came from international so urces.

7 Via oxidation, purge and trap, and cold

- vapor atomic fluorescence spectrometry (CVAFS).7

certification levels published by EPA (between 0.5 ng/L and 100 ng/L; Hanlon, 2007; U.S. GAO, 2008)

. Currently, about 6% of POTWs have permits with mercury limitations, and another 10% have monitoring requirements (Larry Walker Associates, 2002)

.
The Great Lakes , which have particularly stringent mercury criterion for wildlife at 1.3 ng/L and human health at 3.1 ng/L

, provide an example (U.S. GAO, 2008)

. Canada and the United States jointly developed

t he Great Lakes Water Quality Agreement of 197 2 and the Great Lakes Bi national Toxics Strategy of
1996 and 1997 with the goal of the virtual elimination of persistent toxic chemicals includi ng mercury in

the Great Lakes ( U.S. EPA, 2000 ). However, p rior to the deployment of test method 1631E , EPA was n ot able to detect mercury at the level of the established water quality criteri on (U.S. GAO, 2008 ). T he approval and use of the new method thereby facilitated the identification of exceedances in pursuit of the
United States’ commitments

. Thereafter , the n umber of permits for discharges to Great Lakes waterbodies with mercury limitations increased from 185 in 2 005 to 292 in 2007

. 8

Permits for POTWs discharging to other water bodies are often based on the Great Lakes I nitiative

criterion . However, many of them are having difficulty meeting their discharge requirements , since

dissolved mercury can pass through standard POTW treatment s (i.e. it is not settled out during sedimentation as with most of the particulate mercury) and enter surface waters

. In order to address mercury discharges, POTWs are primarily relying on source control in an effort to meet stringent permit

limitations for discharges to surface waters (for example, see U.S. EPA, 2004).

3.2 POTW Sludge Disposal and Potential Discharges

Much of the me rcury that is captured by POTW treatment s is settled out along with biosolids during the sedimentation phase (Mohapatra, et al., 2007). However, the mercury content in biosolids is typically very low. For example, data from Pennsylvania shows that the mean and 95 th percentile concentrations of mercury in sewage sludge is well below standards for metals allowable for land

- applied biosolids (NRC, 2002). However, the fate and transport of mercury settled out with biosolids depends on the treatments and disposa l methods employed by the particular POTWs.

Many POTWs treat sludge in digesters, or heated oxygen

- free tanks, where anaerobic bacteria consume organic material (NY C DEP, nd.). Although the evidence is mixed, s ome research suggests that mercury

can be conve rted to methylmercury within sludge digesters, especially in summer months ( Pavlogeorgatos, et al., 2006; Gbondo

- Tugbawa, et al., 2010). After digestion, s ludge can then be de

watered to reduce its volume, creating biosolids that are disposed of via one of several potential methods, including land application, composting, incinerating, or landfilling. If the sludge is particularly high in mercury (or other toxics) municipalities may require disposing of it as hazardous waste, which is very expensive (Stone, 2004).

EPA has a longstanding policy of promoting the beneficial uses of biosolids, including composting (whereby biosolids are mixed with a bulking agent and decompose) or land application ( U.S. EPA , 1999; NYCDEP, nd.; NRC, 2002; Mohapatra, et al., 2007)

. Currently about 60% of the 5.6 million tons of biosludge generated annually in the United States is used for land application and is applied to about 0.1% of all agricultural lands in the United States ( U.S. EPA, 1999; NRC, 2002). In additio n to agricult ural application, s ludge is applied to forests, reclamation sites, or public sites such as golf courses and parks.

B iosolids used a s fertilizer have stringent standards for nine inorganic chemicals including mercury (U.S. EPA, 1999; 2010) , and so higher me rcury levels may preclude this beneficial use. However, mercury disposed of via land application is well below the threshold (U.S. EPA, 2009b).

8 EPA estimated that it would take at least two 5

- year permit cycles to completely implement the stricter permit limitations associated with the improved monit oring (U.S. GAO, 2008).8

Landfilling is another common disposal method (U.S. EPA, 1999) . NYDEC (2006) indicates that 26% of

biosolids in New York are landfilled by 50% of the state ’ s POTWs. This represents an increas e from 17%
in 1998 . This may be due to multiple factors, including that the number of landfills accepting biosolids has increased over the same time period, and that tipping fee s make the option attractive to communities (NYDEC, 2006).

Beneficial disposal methods and landfilling can r esult in the risk of erosion and runoff of mercury contained in the sludge to local waterbodies (NRC, 2002). W atershed characteristics such as the s ize and topography can affect mercury loading via runoff (Munthe et al., 2007)

. Very large watersheds may be less responsive to loading reductions because of reduced yield per unit area but larger overall yields , and

forest disturbances can increase loadin gs (Munthe et al., 2007). In addition to concerns about runoff, there is some evidence that sunlight and heat can cause mercury to volatize from the soil into the atmospheric pool (NRC, 2002).

Incineration is another common disposal method of biosolids. Th is process reduces biosolids to residue that consists of ash taking up about 20% of the original volume (U.S. EPA, 1999). U.S. EPA (1999) estimates that about 22% of biosolids are incinerated nationally

. There is no method that can feasibly

remove trace me rcury from the biosolids in advance of the incineration process (WERF, 2009 ), and as such this method may result in the discharge of mercury to the atmosphere (CDPHE, 2004)

. Vandeven and McGinnis (2005) estimate that about 1 ton of dental amalgam is incine rated in sewer sludge incinerators. Of this amount, 0.2 tons are emitted to the atmosphere , with 0.1 tons being atmospherically deposited within the United States and ultimately reach ing domestic surface water

.
The Water Environment Research Foundation (W ERF, 2009) summarizes actions by incinerators to remove mercury from atmospheric emissions , which vary depending on the operation and the physical properties of the merc ury species present . Elemental mercury, which is the predominant form from dental amalg am, is difficult to capture, and presents the greatest challenge to control strategies because it is

water insoluble. This property makes wet scrubbing ineffective at controlling elemental mercury, and it is also resistant to electrostatic precipitation (W ERF, 2009). This challenge is compounded by the fact that other types of mercury can be converted to elemental mercury by the high temperatures in incinerators.

Other types of mercury can be partially removed by wet scrubbing processes, and further reduc tion s have been demonstrated via the use of fabric filters and wet electrostatic precipitators. To date, only two biosolid incinerators have installed mercury

- specific control systems call activated carbon fixed

- bed polishing systems: 1) Ypsilanti , Michiga n, which reports that the systems removes over 99% of mercury from exhaust gas, and 2) St. Paul, Minnesota, which reports 94% efficiency with that system, and an additional 4% from a wet electrostatic precipitator.

Although it depends on the particular spe cies, most types of mercury are highly soluble (Lindberg, et al., 2007). Because of this, once it enters the atmospheric pool

, it has a long residency and can often be deposited far distances away from the original discharge point, including places tha t ha ve few sources of

emissions such as the Arctic (Hylander and Goodsite, 2006). However, there is also evidence that mercury can be deposited relatively close to the emission source. In Seattle, deposition decreased significantly coincident with decreased em issions from local incineration sources (Lindberg, et al., 2007).

3.3 Methylation in Surface Waters
Methylmercury exposure via fish consumption is the primary health and ecological concern associated with mercury pollution. However, all types of mercury disch arges can contribute to this exposure pathway, since mercury can be transformed into methylmercury by bacteria present in the sediments of9

wate r bodies. 9 M icroorganisms and decomposers in the top layers of sediments and soils (such as bacteria and fungi) w ill, as a by

- product of natural sulfate

- reduction metabolism, convert elemental or other inorganic forms of mercury to methylmercury (USGS, 1997; WDNR, 1997; ATSDR, 1999; Chin, et al., 2000; U.S. EPA, 2005a; Mohapat ra, et al., 2007) . Once mercury is conver ted to methylmercury, it can enter the food chain through ingestion by bacteria and phytoplankton which are consumed by invertebrate grazers, with subsequent transfer to smaller forage fish and eventually to larger game fish and piscivorous

waterfowl and w ildlife (USGS, 1997).

Many water body

- specific factors such as carbon sources and sulfur species present can affect the rate and degree of methylation (WDNR, 1997; U.S. EPA, 2006; Munthe, et al., 2007). The biological cycle of mercury is delicately balance d, and small changes in input rates and the chemical form of mercury may result in increased methylation rates in sensitive systems (Eisler, 1987). Waters that are already impaired have higher potential for anaerobic methylation. For example, higher concen trations of dissolved organic carbon (DOC) and lower pH levels are likely to increase the mobility of mercury in the aquatic ecosystem (USGS, 1997; WDNR, 1997). Also, increased water sulfate levels are likely to increase methylation (WDNR, 1997). Munthe, e t al. (2007) state that anoxic conditions (especially in wetlands), warm,

shallow

- organic rich lake sediments, and increased decomposition due to flooding are conditions that favor methylation

. According to Chan, et al. (2003) and Scheuhammer, et al. (2007 ) ecosystems that are especially vulnerable to methylation are low alkalinity, low pH surface waters with high organic carbon concentrations or large upstream or adjacent wetlands, dark

- water lakes and streams, and waters with adjoining or upstream terrest rial areas subject to flooding. According to the authors, piscivorous wildlife species living in inland freshwater habitats have higher mercury exposure rates than the same species living in nearby estuarine or marine habitats. Also, human activities can i ncrease rates of methylation. For example, flooding of soils to create reservoirs increases the decomposition of vegetation, increasing the dissolution of organic carbon, which causes increased release of mercury that is bound to organic material (Chan, et al., 2003). Eisler (1987) found close correlations between mercury content of zooplankton and suspended particulate matter and sediment and fish muscle, suggesting that suspended matter and zooplankton are a pathway between sediments and fish.



### 4 Environment al Impacts

The two main categories of concern with respect to mercury in the environment are human health effects (most commonly attributed to the consumption of mercury

- contaminated fish) and wildlife effects. There have been several incidences of high ex posures and poisonings demonstrating that high methylmercury exposures can cause acute, immediate, and in some cases severe symptoms among both humans and

wildlife.

One of the most well

- known and well

- studied incidences contributing to the current knowled ge regarding effects from mercury exposures via fish consumption occurred in Minamata Bay, Japan . This incident

was caused by a chemical plant that released mercury directly into the bay for several years . Among infants and children, effects included cereb ral palsy, mental deficiency, primitive reflexes, limb deformities, altered physical growth, sensory impairments, dysarthria, hyperkinesias, delays reaching developmental milestones, increased incidents of stillborn male infants (Mergler, et al., 2007; U.S . EPA, 2005a; 2005b; Mohapatra, et al., 2007; CDC, 2009). Among adults, effects included paresthesia , ataxia, dysarthria, hearing impairment, progressive constriction of the visual field, sensory disturbance, tremors,

9 Methylation can also occur aerobically in certain environments (such as soils), but primarily it occurs anaerobically in surf ace water sediments.10

difficulty walking, irritability, deat h (Carrington, et al., 2004; Mergler, et al., 2007; U.S. EPA, 2005b; CDC, 2009)

In addition to human health impacts, a wide v ariety of animals were affected by this incident . A bnormal mercury content was found among many fish and shellfish, as well as necr opsied cats who had

succumbed to what was known as Minamata d isease. Among others, observed wildlife effects in

Minamata included poisoned cats, dogs, rats, waterfowl, and pigs, who behaved erratically (such as walking in circles) and died, flying crows an d grebes that suddenly fell into the sea and drowned, and a large number of dead fish that were found flo ating on the surface of the sea (Eisler, 1987).

However, although the Minamata Bay incident and other s significantly contributed to the current

knowled ge concerning the effects of methylmercury on human health and wildlife, exposures attributable to dental mercury discharges are likely to be subtler and cause human health and wildlife effects more consistent with chronic, low

- level exposure. These levels of exposure can also cause cognitive and developmental effects in populations with moderate fish consumption patterns. This section will explore the relatively extensive body of literature addressing these topics, touching on exposure pathways, mercury be havior within organisms, levels of exposure considered to be harmful and specific effects on

human health and wildlife.

4.1 Bioac cumulation
Mercury concentrations in most surface waters are well below the drinking water maximum concentration limit of 2 ppb (AT SDR, 1999 ; Scarmoutzos and Boyd, 2003 ). However, concentrations of mercury in fish are generally on the order of a million times the concentration in the water, due to bioaccumulation ( U.S. EPA, 2005 a ; 2006). Methylmercury is highly lipid

- soluble , meaning that organisms (including wildlife and humans) sequester mercury in body tissues much faster than they lose it ( USGS, 1997; WDNR, 1997 ; Scarmoutzos and Boyd, 2003 ) . Organisms at the lowest trophic levels such as phyto plankton and bacteria absorb mercury fr om the aquatic environment through a combination of passive diffusion and facilitated
transport (Chin, et al., 2000 ; U.S. EPA, 2005b ). These organisms are consumed by organisms at intermediate trophic levels (e.g

. , zooplankton, young

- of

- year fish) which ar e, in turn, consumed by higher trophic level organisms. This process is biomagnification, or the incremental increase in the concentration of a contaminant at each level of the food chain, since each link is progressively more concentrated (USGS, 1997).

Du e to this bioaccumulation and biomagnification , organisms at the highest trophic levels (such as predatory fish, piscivorous mammals or birds, and humans) reach the highest concentrations of mercury (WDNR, 1997) . This accumulation can be profound, with bio magnifications of 100,000 times from algae to top predators having been documented (Chin

, et al., 2000). Because of this

, a dditions of relatively small amounts of mercury that reach methylation zones can lead to disproportionate effects at higher

levels of the food chain (Munthe, et al., 2007). Although bioaccumulation also occurs in terrestrial environments, it is much more pronounced in aquatic ecosystems, possibly because aquatic chains generally have more trophic levels.

Because of the complex pathways by which mercury loading , methylation, and bioaccumulation occur

, there is a wide range of ecosystem response rates, from months to decades (Munthe, et al., 2007). Oftentimes, there is a long lag between emissions and effects, making identification and qua ntification of damages difficult (Hylander and Goodsite, 2006). The timing and magnitude of changes in mercury impacts from increased or decreased loading depends on case

- specific factors such as timing and extent of loading, the chemical form of mercury, ecosystem characteristics, and the role of the terrestrial environment in delivering atmospherically deposited mercury to waterbodies (Munthe, et al., 2007).11

4.2 Human Health Effects
Bioavailability (i.e. the fraction of mercury that is absorbed into the blood stream and it able to exert toxic effects) depends in part on the type of mercury, since each type has a different route of entry, absorption rate into circulatory system, biostability, and capacity for biotransformation. For example, while

elemental merc ury is easily absorbed into the circulatory system upon inhalation, it is not easily absorbed when it is ingested (with less than 0.01% being absorbed in the gastrointestinal tract ). Methylmercury, in contrast, is readily absorbed upon ingestion, with an a bsorption rate of 95% (Sca rmoutzos and Boyd,

2003 ). Methylmercury also has a longer half

- life (i.e. the time it takes for the body to eliminate half the body burden) than elemental mercury

, at 70 to 80 days rather than 58. Additionally, mercury can change forms inside the body. Once it reaches the brain, methylmercury is slowly transformed chemically to mercuric mercury and is thereafter trapped in the brain.

Because elemental mercury is not easily absorbed in the circulatory system

, it is considered a safe dental filling material. Although some mercury from fillings is ingested, the elemental form of it readily passes through the digestive system to be excreted (Scarmoutzos and Boyd, 2003)

. T he average person receives much higher exposure to mercury from ea ting fish due to the process of bioaccumulation. In this way, methylmercury, which is readily absorbed through the digestive system, represents a more serious health threat than elemental mercury with regard to dental use of mercury (Scarmoutzos and Boyd, 2003).

The human health eff

ects associated with methyl mercury have been relatively well

- documented via in

depth studies of high exposures as well as population

- level studi es of relatively lower, but more chronic

exposures. Multiple episodes of disease amon g numerous exposed populations that are widely separated geographically provide a basis for high confidence in the association of methylmercury exposure and adverse health effects (U.S. EPA, 1997). The primary exposure route is fish consumption. Birds and

mammals can also be a dietary source, but they tend to store methylmercury in feathers and fur where it is less easily digestible, while fish accumulate it in tissue. Since methylmercury binds to proteins and amino acids, it cannot be removed by cooking or cleaning since the muscle is retained (Mergler, et al., 2007).

Once it is ingested, mercury passes to the liver and quickly enters the bloodstream to go to other parts of the body (ATSDR, 1999; Goldman and Shannon, 2001; Rice and Hammit, 2005; U.S. EPA, 2 005a). It combines with amino acids, so it can easily cross the blood

- brain barrier (WDNR, 1997; Goldman and Shannon, 2001). Methylmercury causes a wide range of effects, but target organs are the brain, liver, and kidneys (Chin, et al., 2000; Rice and Ham mit, 2005). It has a strong affinity for sulfur and as such can affect cell metabolism by interfering with membrane and enzyme functions of individual cells (Chin, et al., 2000).

There are several measures of mercury exposure. Hair and blood concentration s (including cord blood) are valid biomarkers, but convey different information about exposure (Mergler, et al., 2007). For example, hair analysis is best for examining dynamic changes in exposure, while blood concentration presents a more immediate and fu ll picture of current exposure. EPA sets a reference dose 10 (RfD) based

on blood concentrations. Currently, this is set at 0.0001 mg/kg by weight/day (U.S. EPA, 2005a), and is

associated with a national ambient water quality criteria for human health protec tion of 0.3 parts per million. However, this criterion is not a bright line; rather, it is intended as a broad frame of reference for evaluating methylmercury levels (U.S. EPA, 2005a).

Exposures among women of childbearing age are of particular importance in establishing RfDs, since infants exposed in

- utero are especially vulnerable to the effects. Because of this vulnerability, EPA has set a benchmark dose level (BMDL) for cord blood mercury of 58 ug/L, although effects have been

10 an estimate (with uncertainty spanning perhaps an order of magnitude) of a daily o ral exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime12

documented at significant ly smaller exposures (Trasande, et al., 2005 ). The National Health and Nutrition Examination Survey (NHANES) reported blood concentrations and mercury intake from fish and shellfish among this population segment. The results of the survey indicate that 6% of women of childbearing age have blood concentrations above the RfD, with higher concentrations among women who reported eating 3 or more servings of fish during the previous 3 months (U.S. EPA, 2005a). Women

who eat fish or shellfish at least twice per w eek had 7 times higher b lood concentrations of mercury (Mahaffey, et al., 2004).

4.2.1 Fish Consumption
Consumption of fish, particularly predatory fish, is the largest source of human mercury exposure (WDNR, 1997; Stone, 2004; U.S. EPA, 2005b), accounting for 87% of exposures (Mahaffey, et al., 2004). As such, patterns of human exposure to methylmercury are largely determined by global distribution of fisheries, trade in fish, and fish consumption (Swain, et al., 2007), and blood mercury

levels increase with hi gher levels of consumption (Rice and Hammit, 2005; CDC, 2009).

In the United States, b etween 70% and 90% of the population consume s seafood from the commercial market (Rice and Hammit, 2005). According to Goldman and Shannon (2001), the top ten commercial

fish species

– canned tuna, shrimp, p ollock, salmon, cod, catfish, clams, flatfish, crabs, and scallops

– represent 85% of the seafood market and contain an average mercury concentration of 0.1 ug/g. Half the harvest of developing nations (including tuna and other piscivorous species) is exported to the United States or other industrialized nations (Swain, et al., 2007). In the United States, 42% of edible fish sold are imported (Trasande, et al., 2005 ), and most fish consumed are ocean species (U.S. EPA, 2006). As discussed above, however, s ome of the imported and ocean fish are contaminated by United States contributions to the global mercury pool (Trasande, et al., 2005 ).

In recent years, fish consumption advisories for United States water bodies and fo r entire states have sharply increased (Stone, 2004). In 2008, 16.8 million lake acres and 1.3 million river miles were impaired for mercury, representing increases of 19% and 42% respectively from 2006 levels (U.S. EPA, 2009). This represents a total of 3 ,361 total impairments, up from 3,080 in 2006. There are several explanations for this upward trend , including that:

 S tates are increasingly issuing advisories to increase awareness of human health risk of mercury exposure from fish consumption (U.S. EPA, 2009 a ).

 States such as Idaho, Oregon, and Wyoming have issued new statewide advisories, driving the increased acreage and mileage

.  Increased frequency and sensitivity of monitoring are facilitating faster and more accurate identification of mercury conce ntrations that may pose a threat, suggesting that the mercury impairments themselves are not increasing as rapidly as our abilities to detect them and distribute the necessary information.

Attributing mercury concentrations in water bodies or fish tissue t o any particular source of mercury discharges is extremely difficult

. First, some mercury is naturally occurring in the environment, and it can be deposited to water bodies via volcanoes, mineral deposits, or other sources . As such, it is difficult to

esta blish a baseline concentration against which to measure anthropogenic contributions. This challenge is complicated by the fact that adequately sensitive detection methods to identify potentially harmful concentrations have only recently been approved and d eployed. Because of this, there is little historical data for establishing past concentrations and discharges.

Additionally, anthropogenic emissions can be deposited locally or very distantly from the original source, depending on site

- specific circumstan ces and atmospheric conditions. Mercury in any particular water body may have originated locally, regionally, or internationally. There is also a temporal factor13

contributing additional complexity to attribution. Once mercury reaches surface waters through atmospheric deposition, runoff from surrounding land areas, or direct discharges, it can be stored for a long time (on the scale of years) before it is methylated and/or taken up in to the aquatic food chain. Afte r it enters the food chain, methylmercury f rom one source can be combined with mercury from multiple sources through bioaccumulation. Because of these and other factors, attributing mercury content in fish tissue to any particular source is virtually impossible.

4.2.2 Infant and Child Health Effects

Infa nts and children can be affected by mercury when they are exposed in

- utero after maternal fish consumption. Because mercury disturbs cell divisions and neural migrations

, they are particularly

suscep tible to the effects of mercury. Effects can be documente d in children at intake levels 5 to 10 times lower than adults (WDNR, 1997). In the incidences of high exposures, asymptomatic mothers bore children who were severely affected, further suggesting that developing fetuses are more vulnerable to the

effects o f mercury than adults (Rice and Hammit, 2005; U.S. EPA, 2005b). Fetal mercury levels are at
least equal to or higher than maternal levels (Goldman and Shannon, 2001), with some estimates placing the average cord blood mercury concentration 70% higher than the maternal blood concentration (Trasande, et al., 2005 ; Mergler, et al., 2007) . Also, mercury can be transferred to breast milk, extending infant exposure post

- birth (Goldman and Shannon, 2001).

There have been three major epidemiological studies docume nting the effects of methylmercury on children exposed in

- utero : Seychelles (Davidson, et al., 1997), Faroe Islands (Grandjean, et al., 1997)

, and New Zealand (Kjellstrom, et al., 1989)

. In 2000, the National Research Council (NRC) was commissioned by EPA to review available information on methylmercury effects ; in its final report, t he NRC summarized and evaluated these epidemiological studies (NRC, 2000). Although the Seychelles study was unable to establish a statistically significant relationship betwee n mercury and childhood developmental test performance, the Faroe Islands and New Zealand studies did, and the Faroe Islands study is generally considered to be the most reliable with regard to the effects of methylmercury on children exposed in

- utero . Bas ed on the weight of evidence of these three studies, NRC (2000) concluded that low doses of mercury in

- utero will likely lead to subtle but measurable neurological effects in

children.

At low exposures (those likely to be associated with methylmercury exp osure in

- utero from maternal fish consumption), documented effects on infants and children include abnormal cognitive performance, delays in the development of la nguage, memory, attention, visual

- spatial and motor functions, overall decrease in IQ, and ele vated blood pressure (WDNR, 1997; Jakus, et al., 2002; Trasande, et al., 2005 ; Carrington, et al., 2004; Mergler, et al., 2007; CDC, 2009). Also, the effects of prenatal mercury exposure may not become apparent until years after birth (WDNR, 1997; Jakus, e t al., 2002; Mergler, et al., 2007). For example, Mergler, et al. (2007) did a study of 9

- year

- olds and found that adverse effects on higher

order cognitive functions were not apparent until the child reached a higher level of maturity.

4.2.3 Adult Health Effect s Adult health impacts from mercury consumption are less studied (Mergler, et al., 2007) , but there is still a considerable body of evidence consistently documenting negative cognitive, neurologi cal, and cardiovascular effects (U.S. EPA, 1997; WDNR, 1997). Effects of overt poisoning hav e been documented

from high

- exposure incidences , and several studies have documented the effects of lower, chronic exposures consistent with current fish consumption patterns in the United States (and those more likely to

res ult from dental amalgam discharges)

. Effects from low exposures (consistent with methylmercury exposure from fish consumption) include visual defects such as loss of peripheral vision and chromatic and contrast sensitivity, loss of manual dexterity, hand

- eye coordination, and grip strength, ataxia, paresthesia , hearing loss, tremors, coma,14

death, cerebellar changes, atrophy, focal cortical lesions, motor impairment, reproductive impairment, and renal toxicity (Rowe, et al., 1996; WDNR, 1997; Jakus, et al., 2002; U.S. EPA, 2005a; 2005b; Mergler, et al., 2007; CDC, 2009). In addition, some studies have suggested a link between methylmercury exposure and increased risk for cardiovascular disease, coronary heart disease, and acute myocardial infarction (AMI), e specially among men (WDNR, 1997; U.S. EPA, 2005a; 2005b; Mergler, et al., 2007; CDC, 2009). As EPA (2005b) notes, these results are particularly noteworthy since fish consumption has traditionally been considered to be protective of cardiovascular health.

4.3 Wildlife Effects

There is also consistent evi dence across a number of sources that wild populations of fish, birds, and mammals in many regions of North America consume diets with methylmercury concentrations that are likely to be toxic (Mergler, et al., 2 007). Although they may be significant, there is less evidence pertaining to effects on reptiles, amphibians, aquatic invertebrates

, and vegetation (U.S. EPA, 2005b ; Scheuhammer, et al., 2007 )

. This section summarizes and discuss es the available body of li terature addressing the effects of mercury on wildlife

. As described above, methylmercury accumulates in fish tissue, with accumulation patterns di ffering among fish species and higher concentrations at the top trophic levels of the aquatic food chain (WDN R, 1997; U.S. EPA, 2005b; Mergler, et al., 2007). P redatory fish such as tuna, marlin, swordfish, walleye, and northern pike can have concentrations as high as multiple parts per million (Mahaffey, et al., 2004). Signs of acute mercury poisoning among fish include flaring of gill covers, increased frequency of respiratory movement, loss of equilibrium, and sluggish movement, and signs of chronic exposure include emaciation, brain lesions, cataracts, diminished response to change in light intensity, inabilit y to capture food, abnormal motor coordination, and various erratic behaviors (Eisler, 1987; U.S. EPA, 2005b). However, overt effects on fish occur only at very high mercury concentrations. Most fish have no symptoms at concentrations ten times those toler able for humans (WDNR, 1997).

As with humans, effects of mercury exposure among fish

- eating mammals and birds can be serious, often resulting in neurological impacts. Mercury can penetrate the blood

- brain barrier and ca u se brain lesions, spinal cord degene ration, and dysfunction of the central nervous system (Chan, et al., 2003). Eisler (1987) notes that methylmercury primarily affects the central nervous system, particularly the sensory, visual, and auditory areas that are associated with coordination, irr eversibly damaging the cells of the central nervous system. For animals with diets containing mercury concentrations higher than 1 mg/kg (primarily fish diets) , effects may be as serious as neurotoxicity, mental derangement, coma, and death (Eisler, 1987; Scheuhammer, et al., 2007).

Birds ca n be killed by mercury exposure , especially fish

- eating birds (Eisler, 1987; USGS, 1999)

. However, major die

- offs caused by merc ury have rarely been reported (USGS, 1999), and the dose of methylmercury needed to cause s evere acute poisoning is higher than what is usually found in the environment (Chan, et al., 2003) , or what is likely to result from dental amalgam discharges . Rather, the

effect is an insidious and scattered pattern of mortality (USGS, 1999). In most case s, exposures lead to emaciation syndrome and a variety of sublethal effects that may act together to cause eventual death (Eisler, 1987, Chan, et al., 2003)

. Chan, et al. (2003) found that birds exposed to lower levels of methylmercury were less likely to hunt, seek shade, walk, peck, or fly, while other activities such as preening increased. Other s ublethal effects can include incoordination, ruffled feathers, droopy eyelids, falling, slowness, calmness, withdrawal, hyporeactivity, hypoactivity, weakness, tremors, delayed righting time, exaggerated wing response, failure to properly place feet, verti go, anorexia, paralysis,

convuls ions, abnormal vocalizations, and adverse effects on growth, development, reproduction, hatching, blood and tissue chemistry, me tabolism, and behavior ( Eisler, 1987; WDNR, 1997 ; USGS, 1999 ; Chan, et al., 2003 ).15

Methylmercury exposure can also have serious impacts on reproduction among wildlife at exposures lower than 1/5 the level needed to cause neurological symptoms (Chan, et al ., 2003). As with humans, embryos and newborns are most at risk, since mercury affects cell division. These effects are particularly well documented among loons; the reproductive success of loons with high levels of methylmercury is

about half that of unaf

fected loons (WDNR, 1997), and decreased reproductive success of loons breeding in lakes has been documented in areas that were affected by mercury accumulation from a chlor

- alkali plant ’s discharges (Chan, et al., 2003; U.S. EPA, 2005b).



### 5 Reduction Potent ial and Municipal/State Programs

Due to mercury reductions in other sectors and industries, dental offices are now the largest source of mercury in wastewater influent to POTWs (Chin, et al., 2000; Quicksilver Caucus, 2008 a ). From a regulatory standpoint, they represent a unique source because each office sends a relatively very small amount of mercury to POTWs and they are very geographically diffuse. However, collectively they represent a substantial contribution of mercury because they far outnumber any other significant source.

The dental community is aware of the mercury issue and has taken measures to reduce the amount going

off

- site. Most dentists currently use chair

- side traps and in some cases vacuum filters to prevent their wastewater systems from plugging as a result of amalgam waste. These mechanisms reduce amalgam discharge to some extent; however, much of the amalgam waste passes through them and into the wastewater being discharged to POTWs.

Beyond the capture rates associated with typical ch air side traps and filters, t h e amalgam separator is designed specifically to remove dental amalgam from wastewater and minimize the amount of mercury discharged to POTWs and ultimately receiving waters. Separators use a variety of methods to remove

mercur y particles (along with other solids) from wastewater, including (McManus and Fan, 2003):

 sedimentation, in which tanks or baffles reduce the speed of wastewater flow to allow particles to settle out (removes 90% of particles in a couple of hours),

 filtrat ion, which can remove particles and sometimes dissolved mercury,

 centrifugation, which spin s water, drawing particles to the sides of the unit, and/or

 ion exchange, which use s chemicals that bind with mercury, drawing it to the bottom.

According to Quicks ilver Caucus (2008 a ), properly installed and maintained separators are the most effective means of reducing amalgam discharges from dental offices

. The International Organization for Standardization (ISO) provides standardized metrics and test methods for amalgam separators (ISO 11143). This is the most commonly

- used metric for evaluating separators, and it requires that 95% of amalgam particles by weight be removed from the waste stream. 11 Most available separators achieve higher capture rates. For example, EPA previously reported that properly installed and maintained separators typically remove 95% to 99.99% of particles (U.S. EPA, 2005c). As a n additional benefit, installation of amalgam separators would also decrease discharges of silver and other metal s to POTWs (NACWA, 2006).

The Association of Metropolitan Sewerage Agencies (AMSA) commissioned a study (Larry Walker Associates, 2002) to determine whether various source control programs (including separator requirements) could meaningfully reduce mercu ry in POTW influent and help them to achieve discharge

standards. They assessed the current influent rates from several POTWs, and found that discharges from dental offices and human waste associated with dental amalgam were t he t wo prim ary sources of

11 60% of particles between 0.5 millimeters and 3.15 mm, 10% of particles 0.1 mm to 0.5 mm, and 30 % of particles 0.1 mm or

smaller.16

merc ury. They identified source control strategies and estimated potential reductions for them based on predicted effectiveness (including participa tion rates and other factors) and the estimated load. Seven plants were used as detailed case studies (including 3 in Ohio, 2 in California, 1 in M aine, and 1 in Minnesota). I n each of the cases, dentists were the greatest contributors to mercury loads, accounting for an average of 35% of mercury flowing into POTWs . The source control outcome modeling also indicated that dental offices (and hospitals) have the greatest potential for achieving measurable reductions.

Despite this potential, it is difficult to make predictions about mercury fluxes at the local level, given the current knowledge on mercury cycles, althou gh it is possible to gain an understanding of fluxes on the global, co ntinental, and regional scales (U.S. EPA, 2005a). As such, it may be difficult to accurately predict mercury reductions in waterbodies due to local installation of separators. However, t here is some evidence of reductions attributable to separators. So me dentists have already installe d separators , either voluntarily or to comply with state or local requirements, and there is a relatively robust literature addressing their effectiveness at reducing the amount of amalgam going off

- site in wastewater. Many states and municipalities (as well as almost all European countries) already have programs requiring

installation of separators in dental offices . These state and municipal programs are sum marized in Appendix A

. Although some separator programs are relatively new (for example, Cleveland’s Northeast Ohio Region

Sewer District is implementing a separator requirement in which all offices must install a se parator before November, 2011), s ome pr ograms have demonstrated measurable reductions after implementing separator

req uirements. For example, Massachusetts and King County programs have realized 50% reductions of mercury discharges to POTWs (Quicksilver Caucus, 2008 b ). Stone (2004) and others d ocument case
studies of separator effectiveness in Toronto, Minneapolis/St. Paul, Duluth, Great Lakes (in Illinois), and

Denmark.

 Toronto: all dental offices were required to install sepa rators by 2002. Since then, there has been

an estimated a 58% reduct ion of mercury in POTW sludge, with only 800 out of 1100 facilities participating . Full compliance was expected to result in a nearly 80% reduction in monthly mercury concentrations in sludge. Mohapatra et al. (2007) similarly documented a significant

decr ease in mercury levels following Toronto’s bylaws, with a 40% to 68% decrease in the amount going into sewers within 8 months of implementation.

 Minneapolis/St. Paul: MCES did a study of amalgam separators at 24 community dental offices. They found mercury reductions between 29% and 44% in POTW sludge after s eparator installation. Mercury in dental wastewater was reduced by 91% to 99%.

 Duluth: 35 regional dental facilities installed separators, and influent to POTWs from these

facilities decreased from 0.18 pounds per day in 1993 to less than 0.02 pounds in 2002.

 Great Lakes: installation of separators on naval base dental facilities was associated with a 52% decrease in mercury levels in POTW influent , an d exceedances of POTW mercury d ischarge

limitations d ecreased from 54 per year to 3.

 Denmark: mercury in wastewater was decreased from 57 grams per dentist per year to 8 grams when separators were installed ( RPA, 2002), and overa ll POTWs influent reductions of 80% were observed (Larry Walker Associates, 2002 ).



### 6 Benefits of Reducing Dental Mercury Discharges

Reductions of dental mercury discharged by POTWs into receiving waters are expected to result in

human healt h and ecological benefits. The economic value of these benefits will be largely dependent on

the t ypes of illnesses and environmental impacts, exposure thresholds associated with those effe cts

, the monetary value of these effects, and the reduction potential compared with a baseline l evel of discharge

.17

The fate and transport of mercury in the environme nt (including methylation and bioaccumulation) will

also be an important factor an important factor of reduction impacts, since they determine the timing and medium of human and wildlife exposures.

S everal factors complicate analyse s of the economic benef its associated with reducing mercury discharges from dental offices. For example, the health benefits associated with reductions may be delayed since exposure can result from long

- ago discharges that have been stored in water body sediments for years

befor e being methylated and entering the trophic web

. Dental wastewater lines may also serve as reservoirs of previously discharge mercury that leak over time (Stone, 2004). According to USGS (1997), modeled scenarios predict that if mercury emissions were decr eased by 5%, it would take 8 years before changes in fish concentrations would be observed. Additionally, there is need to track benefits at a wide variety of geographic scales, from local to global , and there are uncertainties regarding mercury fate in th e environment and the human body (Swain, et al., 2007).

Despite these and other uncertainties, s everal studies have shown that decreased point source loading of mercury to waterbodies decreases mercury concentrations in fish (Munthe, et al., 2007). This w ill almost certainly lead to some economic benefits associate d with the health and wildlife e ffects discussed above. Several studies have attempted to quantify the economic benefits associated with the reduction of mercury

emissions from other sectors. To some extent, their methods and findings may also pertain to reductions

from the dental sector.

 Hagen , et al. (1999) conducted a study of the economic benefits of reduced mercury emissions in Minnesota. They administered a mail survey and presented respond ents with four options for a 50% reduction in emissions: 1) in Minnesota, 2) in the Midwest, 3) in the United States, and 4) in the world. They found an annual household willingness

- to

- pay (WTP) was $118.91, $212 million

statew ide or $0.12 per person per d ay for reductions in the Midwest.

 Jakus, et al. (2002) evaluated the economic and health effects of mercury advisories on the Maryland portion of the Chesapeake Bay, specifically with regard to striped bass, which is of primary concern in that area. They e stimated the welfare loss to recreational anglers, the welfare loss to consumers and producers of commercial striped bass, and the health benefits to recreational anglers from avoided consumption. They found that the annual welfare loss to recreational ang lers over all Maryland saltwater fishing days was $8.83 million (in 2000 dollars), and that the annual consumer and producer surplus losses from commercial fish consumption
advi sory were $215,800 and $304,500 respectively. Using an estimated value of a sta tistical life of $3.11 million, they calculated that the value of health damages associated with male mortality (between the ages of 40 and 59 only) from mercury consumption were approximately $14 million annually. They also evaluated the economic impacts of IQ losses due to prenatal exposure to

mercury from fish consumption. However, the authors did not find a significant IQ loss based on consumption of striped bass from Maryland’s portion of the Bay.

 Trasande, et al. ( 2005 ) estimated the economic impact o f anthropogenic mercury exposure in the United States 2000 birth cohort, and calculated the fraction of the cost that may be attributed to

emissions from the electric sector. They utilize the “environmentally attributable fraction” (EAF), which is the port ion of disease that would be eliminated if environmental risk factors were

reduced to their lowest feasible level. They evaluated the cost per case based on lifetime lost productivity of affected infants, which they consider to be very conservative (versus other methods such as willingness to pay) . According to their results, the loss of IQ from exposure to methylmercury of anthropogenic origin is $8.7 billion annually (in 2000 dollars), with a range between $2.2 billion and $13.9 billion with conservative assumptions. With less conservative assumptions, their estimates range up to $43.8 billion annually. Restricting the analysis to effects attributable only to United States anthropogenic sources results in a loss of IQ worth $3.1 billion18

annually, or up to $15.8 billion. This analysis includes consideration only for IQ loss from

exposure in

- utero , not for other possible effects such as ca rdiovascular impacts in adults.

 U.S. EPA (2005b) conducted an economic analysis of regulations to reduce mercury emissions from power plants in the United States under the Clean Air Mercury Rule, using a model that provides information about changes in fish tissue mercury concentrations based on changes in air deposition. The authors assume that imported fish (accounting for 35% of consumer demand) is not likely to be substantially affected, but that methylmercury from domestic freshwater

recreational and commercial fish is likely to be reduced, that about 16% of the U.S. population partic ipates in recreational fishing, that a nnual demand for fishing product is 42 .1 pounds per person, that 88% of people eat fish or shellfish at least once per month, that 26% of fish tissue samples contain higher than 0.3 ppm mercury, that 5% of samples have concentrations above 1 ppm, and that there is an IQ decrease of 0.13 points for every ppm increase in maternal hair mercury concentration. The st udy quantifies the change in IQ among children exposed in

- utero as a result of the regulation, but states that restricting the analysis to this endp oint is likely to

underestimate the benefits. They foun d that a child of a typical fre shwater fisher lost 0.06 to 0.07 IQ points due to me rcury exposure during 2001, that the child of subsistence farmers lost 0.331 points , and that each IQ point was worth about $8,800.

 Rice and Hammit (2005) assign ed economic values to two mercury

- related health effects: cognitive abilities and cardiovascular events. Their model assumes that changes in the q uantity of mercury deposited le d to linear and proportional changes in fish methylmercury concentrations

, that one lost IQ po int wa s worth $16,500 (2000 doll ars), and that children born to mothers above EPA’s RfD lose an estimated average 0.77 IQ points . Based on a cost

- of

- illness approach, they

found that the total cost of IQ losses per annual birth cohort was about $19.9 million, with 359,000 children born to mothers with mercury levels above EPA’s reference dose , affecting their year of schooling, workforce participation, and wages. The authors also estimate d that the

l ifetime cost of a myocardial infarction is between $37,030 and $83,290 depending on the age

and sex of the affected individual.

 Hylander and Goodsite (2006) quantified remediation costs and compared them with preventative measures and potential health eff ects in the Arctic , where they state that about 3⁄4 of children are born with unsafe mercury concentrations, even though that region has few or no mercury
emission sources of its own. Their analysis was restricted to the cost of remediation at 6 sites, the

c ost of preventing and controlling emissions, food damage costs, and loss of IQ in Greenland. They based their IQ valuation analysis on Trasande, et al. ( 2005 ) and studies of mercury concentrations in mothers and newborns in Greenland in 1998 and 1999. They estimate that the cost of IQ loss due to mercury toxicity in Greenland is about $59.1 million every year, and note that effects are more intense with a higher proportion of deficiencies, but with a lower overall population compared with the United States.

Each of these studies could contribute to a full economic analysis of the benefits associated with potential reductions of mercury discharges from the dental studies. For example, Hagen et al. (1999) provide

estimates for WTP for reducing mercury emission s. The results of this study could be used to develop a benefit transfer approach to valuing reductions in mercury emissions from crematoria. Likewise, Jakus, et al. (2002) and Rice and Hammit (2005) provide economic values for some of the more well

- docume nted health effects of methylmercury, which could be used in a more detailed analysis of health benefits from reduced mercury discharges

. Trasande, et al. ( 2005 ) is the most relevant and easily applicable to estimating the benefits associated with

reduced discharges of mercury from the dental sector. The authors calculate d the entire economic cost of IQ loss among children resulting from mercury exposure in

- utero , and then calculate d the fraction19

attributable to the electric sector. This approach may also lend some insight into the potential IQ

- related benefits of reductions from the dental sector, if the environmentally

- attributable fraction (EAF) approach were transferred across sectors. Under conservative assumptions, Trasande, et al. (2005) estimated th at
United States anthropogenic mercury emissions result in $ 3.1 billion loss in IQ annually (in 2000 dollars). Applying the EAF of emissions from dental offices of 0.4% (from Exhibit 2

- 2 ) results in a total annual cost of $ 12.4 million from IQ losses assoc iated with methylmercury exposure in

- utero from dental offices alone (in 2000 dollars). This could represent potential benefits from reduction of mercury discharges from

dental offices.

However, there are many uncertainties associated with this estimate. F or example, the 0.4% EAF used is based on data from 1994 and 1995, and as such is likely to be outdated and not directly pertinent to today’s share of discharges, especially given that many of the larger sources shown in Exhibit 2

- 2 have implemented contro ls since then. This may result in an underestimate o f potential IQ

- related benefits if the actual EAF for dental amalgam is higher. This estimate also does not consider other health

- related benefits such as reduced cardiovascular disease or neurological im pacts among adults. Additionally, implementation of a separator requirement (or equivalent) will not result in a total elimination of discharges from dental offices, and as mentioned above it is unclear where and when benefits would

occur.

In addition to reduced mercury impacts to human health and wildlife, reduction of mercury in dental

wastewater could have additional benefits such as reduced treatment costs an d permit exceedances for

POTWs. For example, after Massachusetts began requiring installation o f amalgam separators in January 2006, loadings of mercury to the Deer Island Treatment Plant decreased significantly (Rex, 2006). Massachusetts Water Resource Authority data show that daily influent loading decreased from 0.55 lb/day in 2002 to 0.43 lb/day in 2006, and effluent loadings decreased from 0.1 lb/day to less than 0.05 lb/day during the same period.

The Security Sanitation District (District) in El Paso, Colorado is another example (Garcia, 2009). That treatment plant was issued a discharge permi t for mercury in 2003, limiting effluent concentrations to 0.044 ug/L until 2006

, and to 0.011 ug/L thereafter. In 2006 , the District began to systematically violate the permit . As such, the Colorado Department of Public Health and the Environment issued a Notice of Violation and Cease and Desist order to the District, ordering it to research and address sources of mercury. Since dental offices were the primary source of mercury to the District, they were required to install separators by September 2006 and initiate specific maintenance, recordkeeping, and other best management practices in 2007. Since 2008, the District has consistently been compliant with the standards, and the installation of separators by contributing dentists was clearly a significant f actor in that

success.20



### 7 Sources

Agency for Toxic Substances and Disease Registry (ATSDR), Department of Health and Human Services. 1999. Toxicological Profile for Mercury.

American Dental Association (ADA). 2007 a . Best Management Practices for Amalgam Was te.

American Dental Association (ADA). 2007b. Comments of the American Dental Association Concerning the Environmental Protection Agency Dental Office Scoping Study. Letter to Environmental Protection Agency from W. J. Walsh, December 21.

Carrington, C.D., B. Montwill, and P.M. Bolger. 2004. An Intervention Analysis for the Reduction of Exposure to Methylmercury from the Consumption of Seafood by Women of Child

- bearing Age. Regulatory T oxicology and Pharmacology 40: 272

- 280.

Center for Disease Control (CDC ), Department of Health and Human Services. 2009. Fourth National Report on Human Exposure to Environmental Chemicals.

Chan, HM, AM Scheuhammer, A Ferran, C Loupelle, J Holloway, and S Weech. 2003. Impacts of Mercury on Freshwater Fish

- Eating Wildlife and Humans. Human and Ecological Risk Assessment 9(4):

1

- 17.

Chin, G., J. Chong, A. Kluczewska, A. Lau, S. Gorjy, and M. Tennant. 2000. The Environmental Effects of Dental Amalgam. Australian Dental Journal 45: 246

- 249.

City of Boulder. 2007. City of Boulder Dental Wastewater Mercury Reduction

-- Program Overview.

Attachment 1

-- Council WIP. February 1, 2007.

City of San Jose. 2010. Environmental Services: Dental Amalgam Program Frequently Asked Questions. Updated 8 December 2010. Accessed 2 March 2011. http://www.sanjoseca.gov/esd/wastewater/dental

amalgam

- program

- faqs.asp

Colorado Department of Public Health and Environment (CDPHE). 2004. Pueblo Dental Mercury

Pollutio n Prevention Project Final Report. Tetra Tech EM, Inc.

Connecticut Department of Environmental Protection (CT DEP). 2006. Best Management Practices for Dental Amalgam. Updated 15 December 2006. Accessed 2 March 2011. http://www.ct.gov/dep/cwp/view.asp?a=2708&q=323996&depNav_GID=1638

Davidson, P.W., G.J. Myers, C. Cox, C. Axtell, C. Shamlaye, J. Sloane

- Reeves, E. Cernichiari, L. Needham, A. Choi, Y. Wang, M. Berlin, and T.W. Clarkson. 1998. Effects of Prenatal Methylmercury Exposure from Fish Consumption on Neurodevelopment Outcomes at 66 Months of Age in the Seychelles Child Development Study. Journal of American Medical Association 280: 701

- 707.

Dube, A. Undated. Best Manage ment Practices (BMP’s) Includes Amalgam Separators What is the reality? National Sales Manager Solmete X, a division of Layne Christensen

. East Bay Municipal Utility District (EBMUD). Undated. East Bay Municipal Utility District's Dental Mercury Permit Pro gram. Available electronically at: http://www.ebmud.com/sites/default/files/pdfs/dental

- newsletter.pdf

Eisler, Ron. 1987. Mercury Hazards to Fish, Wildlife and Invertebra tes: A Synoptic Review. U.S. Fish and Wildlife Services. Biological Report 85(1.10) Contaminant Hazard Reviews. April 1987, Report No.

10.

Foley, F. 2010. RE: New Requirement Installation of a Dental Amalgam Separator. Letter Dated September 24, 2010. Sup erintendent of Environmental Services, Northeast Ohio Regional Sewer District. Available electronically at: http://www.drna.com/NEORSD_Separator_Program.pdf21

Garcia, A. 2009. EPA Audit Follow Up Report, Re: Follow

- up to Audit Performed at Security San. Dist. On March 10, 2008, Mercury Control

– Security Sanitation District.

Gbondo

- Tugbawa, S.S., J.A. McAlear, C.T. Driscoll, and C.W. Sharpe. 2010. Total and Methylmercury

Transformations and Ma ss Loadings within a Wastewater Treatment Plant and the Impact of the Effluent Discharge to an Alkaline Hypereutrophic Lake. Water Research 44: 2863

- 2875.

Goldman, L.R. and M.W. Shannon. 2001. Technical Report: Mercury in the Environment: Implications

for Pediatricians. American Academy of Pediatrics.

Grandjean, P., P. Weihe, R.F. White, F. Debes, S. Araki, K. Yokoyama, K. Murata, N. Sørensen, R. Dahl, and P.J. Jørgensen. 1997. Cognitive deficit in 7

- year

- old children with prenatal exposure to methylmercury . Neurotoxicol. Teratol. 19(6):417

- 428.

Hagen, D.A., J.W. Vincent, and P.G. Welle. 1999. Economic Benefits of Reducing Mercury Deposition in Minnesota. Minnesota Pollution Control Agency and the Legislative Commission on Minnesota

Resources.

Hanlon, J.A. 2 007. Analytical Methods for Mercury in National Pollutant Discharge Elimination System (NPDES) Permits. Memorandum to Water Division Directors, Regions 1

– 10.

House Oversight and Government Reform Committee Subcommittee on Domestic Policy Hearing. 2010.

T estimony by Al Dube, National Sales Manager of SolmeteX. 10 June 2010. Available electronically at http://mercurypolicy.org/wp

- content/uploads/2010/05/sometex

- testimo ny.pdf

Hylander, L.D. and M.E. Goodsite. 2006. Environmental Costs of Mercury Pollution. Science of the Total

Environment 368: 352

- 370.

Interstate Mercury Education and Reduction Clearinghouse (IMERC). 2010. IMERC Fact Sheet: Mercury Use in Dental Amalga m.
Jakus, P., M. McGuinness, and A. Krupnick. 2002. The Benefits and Costs of Fish Consumption Advisories for Mercury. Resources for the Future Discussion Paper 02

- 55.

Kjellström, T., P. Kennedy, S. Wallis, A. Stewart, L. Friberg, B. Lind, T. Wutherspoon, and C. Mantell. 1989. Physical and Mental Development of Children with Prenatal Exposure to Mercury from Fish. National Swedish Environmental Protection Board Report No. 3642. As cited in NRC (2000) and Jakus, et al. (2002).

King County Department of Natu r al Resources and Parks (KC DNRP). 2005. Fact Sheet : Discharging Dental Wastewater into the King County Sewer System. Industrial Waste Program. March 2005. Available electronically at: http://your.kingcounty.gov/dnrp/library/wastewater/iw/dentalfact.pdf

King County Industrial Waste Program (KCIW). Undated. Mercury levels in King County biosolids. Updated February 28, 2011. Accessed 1 March 2011. Available electronically a t: http://www.kingcounty.gov/environment/wastewater/IndustrialWaste/GettingDischargeApproval/Dental/ Mercury.aspx

Larry Walker As sociates. 2002. Mercury Source Control and Pollution Prevention Program Evaluation: Final Report. Association of Metropolitan Sewerage Agencies (AMSA).

Lindberg, S., R. Bullock, R. Ebinghaus, D. Engstrom, X. Feng, W. Fitzgerald, N. Pirrone, E. Prestbo, and C. Seigneur. 2007. A Synthesis of Progress and Uncertainties in Attributing the Sources of Mercury in Deposition. AMBIO: A Journal of the Human Environment 36: 19

- 33.

Louisiana Department of Environmental Quality (LDEQ). 2007. Mercury Minimization Program Guide for Permits Under the Louisiana Pollution Discharge Elimination System.22

Mahaffey, K.R., R.P. Clickner, and C.C. Bodurow. 2004. Blood Organic Mercury and Dietary Mercury Intake: National Health and Nutrition Examination Survey, 1999 and 2000. Enviro nmental Health Perspectives 112: 562

- 570.

McManus, K.R. and P.L. Fan. 2003. Purchasing, Installing, and Operating Dental Amalgam Separators:

Practical Issues. Journal of the American Dental Association 134: 1054

- 1065.

Mergler, D., H.A. Anderson, L.H.M. Ch an, K.R. Mahaffey, M. Murray, M. Sakamoto, and A.H. Stern. 2007. Methylmercury Exposure and Health Effects in Humans: A Worldwide Concern. AMBIO: A

Journal of the Human Environment 36: 3

- 11.

Milwaukee Metropolitan Sewage District (MMSD) and University of W isconsin Extension . 200 6

. Amalgam Management at Dental Offices. Accessed 2 March 2011. http://v3.mmsd.com/AssetsClient/Documents/rules/section_11.214.pdf

Mohapatra, S.P., I. Nikolova, A. Mitchell. 2007. Managing Mercury in the Great Lakes: An Analytical Review of Abatement Policies. Journal of Environmental Management 83: 80

- 92.

Munthe, J., R.A. bodily, B.A. Branfireun, C.T. Criscoll, C.C. Gilmour, R. Harris, M. Horvat, M. Lucotte, and O. Malm. 2007. Recovery of Mercury

- Contaminated Fisheries. AMBIO: A Journal of the Human

Environment 36: 33

- 44.

National Association of Clean Water Agencies (NACWA). 2006. Controlling Mercury in Wastewater Discharges from Dental Clinics: White Paper.

National Association of Clean Water Agencies (NACWA). Undated. Mercury Control Program Case Studies. Available electronically at: http://www.neorsd.org/I_Lib rary.php?a=download_file&LIBRARY_RECORD_ID=2492

National Res earch Council (NRC). 2002. Biosolids Applied to Land: Advancing Standards and Practices. July 2002. Division on Earth and Life Sciences.

National Research Council (NRC). 2000. Toxicological Eff ects of Methylmercury. Washington DC: National Academy Press.

New Hampshire Department of Environmental Services. Undated. New Hampshire Dental Legislation. Accessed 1 March 2011. Available electronically at: http://des.nh.gov/organization/commissioner/p2au/pps/ppdpp/legislation.htm

New Jersey Department of Environmental Protection (NJDEP) Mercury Workgroup. 2009. New Jersey Mercury Reduction Action Plan. Draft for Stakeholder Comment, November 5, 2009. Available electronically at: http://www.state.nj.us/dep/dsr/mercury/final

- hg

- plan11

- 5.pdf

New York City Department o f Environmental Protec tion (NYC DEP). Undated. New York City’s Wastewater Treatment System. Available electronically at: www.nyc.gov/html/dep/pdf/wwsystem.pdf

New York State Department of E nvironmental Conservation (N Y DEC). 2006. Biosolids Management in

New York State. Division of Solid & Hazardous Materials. February 2006. Available electronically at: http://www.dec.ny.gov/docs/materials_mi nerals_pdf/bioreprt.pdf

Oregon Dental Association (ODA). Undated. Amalgam Separator Law. Accessed 2 March 2011. http://www.oregondental.org/i4a/pages/index.cfm?pageid=3542

Pavlog eorgatos, G.D., N.S. Thomaidis, A.D. Nikolaou, and T.D. Lekkas. Determination of Methyl Mercury in a Pilot

- Scale Activated Sludge Wastewater Treatment Plant. Global NEST Journal 8: 61

- 67.

Quicksilver Caucus. 2008 a . Dental Mercury Amalgam Waste Management W hite Paper.

Quicksilver Caucus. 2008 b . Case Studies of Five Dental Mercury Amalgam Separator Programs.23

Rex, A. 2006. Summary of MWRA Mercury Monitoring Data. November 27.

Rhode Island and Providence Plantations Department of Environmental Management (RIDE M). 2006.

EarthWatch Rhode Island

– Topic: A Sweet Tooth for Mercury. July 23, 2006. Available electronically

at: http://www.dem.ri.gov/earthwatch/pdf/11.pdf

Rice, G. and J.K. Hammit. 2005. Econ omic Valuation of Human Health Benefits of Controlling Mercury

Emissions from U.S. Coal

- Fired Plants. Northeast States for Coordinated Air Use Management (NESCAUM).

Risk & Policy Analysts Limited (RPA). 2002. Risks to Health and the Environment Related to the Uses of Mercury Products: Final Report. Prepared for The European Commission, DG Enterprise.

Rowe, N.H., K.S. Sidhu, L. Chadzynski, and R.F. Babcock. 1996. Potential Public Health Risks Related to Mercury/Amalgam Discharge from Dental Offices. Journal of the Michigan Dental Ass n 78: 32

- 36.

Scarmoutzos, L.M. and O.E. Boyd. 2003. Environmental and Toxicological Concerns of Dental Amalgam and Mercury. MVS Solutions, Inc.

Scheuhammer, A.M., M.W. Meyer, M.B. Sandheinrich, and M.W. Murray. 2007. Effects of

En vironmental Methylmercury on the Health of Wild Birds, Mammals, and Fish. AMBIO: A Journal of

the Human Environment 36: 12

- 19.

Stern, A., J. Burger, M. Gochfield, and C. Weisel. 2001. Mercury and Methylmercury in the New Jersey Pregnant Population. Archive s of Environmental Health 56: 4

- 10.

Stone, M.E. 2004. The Effect of Amalgam Separators on Mercury Loading to Wastewater Treatment
Plants. Journal of the California Dental Association 32: 593

- 600.

Swain, E.B., P.M. Jakus, G. Rice, F. Lupi, P.A. Maxson, J.M. Pacyna, A. Penn, S.J. Spiegel, and M.M. Veiga. 2007. Socioeconomic Consequences of Mercury Use and Pollution. AMBIO: A Journal of the

Human Environment 36: 45

- 61.

Trasande, L., P.J. Landrigan, and C. Schechter. 2005 . Public Health and Economic Consequenc es of Methyl Mercury Toxicity to the Developing Brain. Environmental Health Perspectives 113: 590

- 596.

United States Environmental Protection Agency ( U.S. EPA). 2010. Introduction: Biosolids. Updated 13

October 2010.

United States Environmental Protection Agency (U.S. EPA). 2009 a . 2008 Biennial Listing of Fish Advisories. Office of Science and Technology, Fish Advisory Program. EPA

- 823

- F

- 09

- 007.

United States Environmental Protection Agency (U.S. EPA). 2009b. Targeted National Sewage Sludge Survey: Samplin g and Analysis Technical Report.

United States Environmental Protection Agency (U.S. EPA). 2008. Health Services Industry Detailed Study: Dental Amalgam. EPA

- 821

- R

- 08

- 014.

United States Environmental Protection Agency (U.S. EPA). 2007. Inorganic Mercury: T EACH Chemical Summary. U.S. EPA, Toxicity and Exposure Assessment for Children’s Health.

United States Environmental Protection Agency (U.S. EPA). 2006. EPA’s Roadmap for Mercury. EPA

HQ

- OPPT

- 2005

- 0013.

United States Environmental Protection Agency (U.S. E PA). 2005 a . Revision of December 2000 Regulatory Finding on the Emissions of Hazardous Air Pollutants From Electric Utility Steam Generating

Units and the Removal of Coal

- and Oil

- Fired Electric Utility Steam Generating Units From the Section 112(c) List; Final Rule. 40 CFR Part 63.24

United States Environmental Protection Agency (U.S. EPA). 2005b. Regulatory Impact Analysis of the Clean Air Mercury Rule: Final Report. Office of Air Quality Standards and Planning. EPA

- 452/R

- 05

- 003.

United States Environmental Protection Agency (U.S. EPA). 2005c. Region 8 Industrial Pretreatment Program. POTW Mercury Control Strategy. As cited in U.S. EPA (2008).

United States Environmental Protection Agency (U.S. EPA). 2004. Mercury Pollutant Minimization Program Guidance. Reg ion 5, NPDES Programs Branch.

United States Environmental Protection Agency (U.S. EPA). 2002. Method 1631, Revision E: Mercury in Water by Oxidation, Purge and Trap, and Cold Vapor Atomic Fluorescence Spectrometry. EPA

- 821

- R

02

- 019.

United States Environme ntal Protection Agency (U.S. EPA). 2000. Great Lakes Binational Toxics Strategy Draft Report for Mercury Reduction Options. Prepared by Ross & Associates Environmental Consulting.

United States Environmental Protection Agency (U.S. EPA). 1999. Biosolids Ge neration, Use, and Disposal in the United States. Solid Waste and Emergency Response. EPA 530

- R

- 99

- 009.

United States Environmental Protection Agency (U.S. EPA). 1997. Mercury Study Report to Congress.

Volume VII: Characterization of Human Health and Wildl ife Risks from Mercury Exposure in the United

States. EPA

- 452/R

- 97

- 009.

United States Geological Survey (USGS) , Department of the Interior . 1999. Field Manual of Wildlife

Disease

– General Field Procedures and Disease of Birds. Chapter 45: Mercury. Nationa l Wildlife Health Center, Biological Resources Division, Information and Technology Report 1999

- 001. Available electronically at: http://www.nwhc.usgs.gov/publications/field_ manual/chapter_45.pdf

United States Geological Survey (USGS), Department of the Interior. 1997. Mercury Contamination of Aquatic Ecosystems. Fact Sheet FS

- 216

- 95.

United States Government Accountability Office (U.S. GAO). 2008. Testimony before the Subco mmittee on Water Resources and Environment, Committee on Transportation and Infrastructure, House of Representatives: Great Lakes Initiative EPA and States Have Made Progress, but Much Remains to be Done If Water Quality Goals are to Be Achieved. Statement of David Maurer, Acting Director, Natural

Resources and Environment.

Vandeven, J.A. and S.L. McGinnis. 2005. An Assessment of Mercury in the Form of Amalgam in Dental Wastewater in the United States. Water, Air, and Soil Pollution 164: 349

- 366.

Vermont St atutes Online. 2005. Title 10: Conservation and Development, Chapter 164: Comprehensive Mercury Management. V.S.A. § 7110. Mercury

- added products used in dental procedures. Accessed 2

March 2011. http://www.leg.state.vt.us/statutes/fullsection.cfm?Title=10&Chapter=164&Section=07110

Washington State Department of Ecology. 2003. Memorandum of Understanding: Washington State Department of Ecology and Washin gton State Dental Association. August 1 2003. Available electronically at: http://www.ecy.wa.gov/mercury/documents/dental

- mou.pdf

Water Environment Research Foundation (WERF). 2009. M inimizing Me rcury Emissions in Biosolids

In cinerators. Final Report. 04

- CTS

- 7T.

Wisconsin Department of Natural Resources (WDNR). 1997. Wisconsin Mercury Sourcebook: A Guide to Help Your Community Identify and Reduce Releases of Elemental Mercury.25



### Append ix A : State and Municipal Dental Mercury Reduction Programs

Exhibit A

- 1 summarizes 11 state and 8 municipal programs aimed at reducing dental mercury discharges through separator requirements.



### Exhibit A

- 1

. State and Municipal Dental Mercury Reduction Programs

State or Municipality Regulation Date Requirements or

Additional Details Documented Reductions Notes Citation

Connecticut Sections 22a

- 616(d)

and 22a

- 622 CGS 10/23/2003 Requires dentists to
i mplement BMPs and
install separators ; CT DEP performs inspections CT DEP , 2006

Louisiana Act 126 of the

2006 Louisiana Legislature 2007 Requires installation of amalgam separators Pre

- 2007 ADA BMPs are required for 1,586
dentists in the state. All should be in compliance based on
Act 126. ADA, 2007b;

LDEQ, 2007

Maine CHAPTER 301

H.P. 514

- L.D. 697 5/15/2003 Any dental office, placing, removing, or repairing dental amalgam must install an amalgam separator by 2005 Maine DEP reviewed pre

and post

- amalgam separator requirement mercury levels in sewage sludge and did not find as significant as those
observed in a Boston study. Quicksilver Caucus, 2008 b

Massachusetts 310 CMR 73.00 3/1/2006 Implement BMPs and install separators which

opera te at 95% removal efficiency From 2004

- 2006, amalgam

separator use increased to >80%, and mercury levels in MWRA sludge decreased by about 48%. Voluntary program
than became mandatory in 2006 Quicksilver

Caucus, 2008 b

New Hampshire House Bill 1251 &

PART Env

- Ws 905 (RSA 485

- A:4) 5/28/2005 Implement BMPs and install separators which operate at 95% removal efficiency Allows recycling

-- 20.43 lbs recycled
2006

- 2007 NHDES

,

undated26



### Exhibit A

- 1

. State and Municipal Dental Mercury Reduction Programs

State or Municipality Regulation Date Requirements or
Additional Details Documented Reductions Notes Citation

New Jersey N.J.A.C. 7:14A

- 1 10/1/2007 Implement BMPs and install separators which operate at 95% removal efficiency (by 2009) No information on reductions, but dental
facilities contribute 35

- 45% of mercury entering NJ's treatment plants, and this rule is expected to result in ~2,550 lbs of mercury removed from the
environment ea ch year NJDEP Mercury Workgroup,
2009

New York 6 NYCRR Subpart

374

- 4 5/12/2006 Require recordkeeping and certified separators which operate at 99% removal efficiency -- Requires ~15,000
dentists to install separators by 2008 Quicksilver

Caucus, 2008 b

Oregon Senate Bill 704,

revised HB 3611 (679.520) 1/1/2008 Implement BMPs and install separators by 2011 No data available

-- recent regulation Estimate of 1,900

facilities impacted ODA, undated ; House Oversight Subcommittee,
2010

Rhode Island RI GLC Sec tion 1.

Chapter 23

- 24.9 2/26/2008 Implement BMPs and install separators which operate at 99% removal efficiency by 2008 -- RIDEM, 2006

Vermont 10 V.S.A. § 7110 2005 Implement BMPs and install separators which operate at 95% removal efficiency by 2007 -- Vermont Statutes Online,
2005

Washington WAC 173

- 303

-

071(3)(a)(ii)(D) (existing hazardous waste rule) MOU

- 2003 Implement BMPs and install amalgam separations which operate at 95% removal efficiency by 2005 Statewide fish tissue monitoring data showe d a drop of mercury levels in
monitored fish populations. Drop is too
small with too few data points to call it a trend ~2,600 dental offices in Washington state are impacted.
V oluntary memo of understanding became mandatory Quicksilver

Caucus, 2008 b ; Wash ington
State Department of Ecology, 200327



### Exhibit A

- 1

. State and Municipal Dental Mercury Reduction Programs

State or Municipality Regulation Date Requirements or
Additional Details Documented Reductions Notes Citation

Minneapolis/St. Paul, MN N/A 2003 Requires certified separators which operate at 99% removal efficiency The mercury level in the
influent has been reduced by approximately one half since the Program began. Voluntar y

-- but those without separators have to apply for permit, test and meet stringent limit Quicksilver

Caucus, 2008 b

King County,
WA King County

Code

— Title 28 Implement BMPs and install amalgam separations which operate at 95% removal efficiency (or perf orm BMPs and apply for permit) King County realized a

50% reduction in mercury
in biosolids after 95% of
its dentists installed amalgam separators and
followed BMPs Quicksilver Caucus, 2008 b ; KCIW, undated; KC
DNRP

Boulder, CO 11

- 1

- 3 and 11

-

3

- 24 3/ 12/2007 Implement BMPs and install amalgam separations which operate at 95% removal efficiency -- Over 90 dental offices
in the Boulder

- area impacted City of Boulder,

2007

Fort Collins, CO 3/1/2004 A ll dentists in the city must install amalgam

separa tor 30% reduction Dube, undated ; CDPHE, 2004

San Francisco,
CA Order No. 01

- 072 7/1/2001 Implement BMPs and install amalgam separations which operate at 95% removal efficiency Collection system sampling
found >90% reduction in total Hg, biosolids 25

- 32 %
reduction Studies have shown

that approximately 61% of the mercury entering WWTP is from dental practices. Dube, undated; City of San Jose, 2010

Cleveland, Ohio (Northeast Ohio Region Sewer District) Administrative

Order No. 8021 Develop, submit and
i mplement BMPs

, including separators with 99% efficiency by
November 2011 -- Includes 518 dental clinics and 14 hospitals Foley, 2010; NACWA,
undated

Eas t Bay Municipal Utility
District (EBMUD) , CA 40 CFR 403.12 (l) 11/1/2001 Implement BMPs and
install am algam separators Data indicate a 30% reduction of mercury loading to EBMUD’s wastewater treatment plant
as a result of these efforts Has removed over 1,200 lbs of waste NACWA, undated; EBMUD,
undated28



### Exhibit A

- 1

. State and Municipal Dental Mercury Reduction Programs

State or Municipality Regulation Date Requirements or
Additional Details Documented Reductions Notes Citation

Milwaukee, WI (Mi l waukee Metropolitan Sewage District) 11.214 1/26/2004 Implement BMPs and install amalgam separators by 2007 -- NACWA, undated; MMSD, 2004