Draft report Mercury Sources and Regulations, 1999 Update

Draft November 1, 1999

ACKNOWLEDGMENTS

A Note on Methodology and Sources

This paper updates an original report written by Ross & Associates in 1993, entitled Virtual Elimination Pilot Project: Mercury Sources and Regulations. The analytical framework and organization remain largely the same, with a few notable changes. First, this paper adds a section on the global mercury reservoir as a source of mercury deposition, to incorporate new knowledge derived from scientific research published since 1993 on the behavior of mercury in the environment, especially the cycling of mercury from the oceans to the atmosphere, and its retention, chemical transformation, and long-range transport. A corresponding section on international regulations has also been included.

Second, the original paper's focus on the regulations and data sources for Great Lakes States has been broadened to capture a national picture of States' activities. In part, this is made possible by several other EPA publications and documents, whose contents have been liberally employed in this paper. Foremost is the 1997 Mercury Study Report to Congress, an exhaustive review of every environmental aspect of mercury. This 9-volume report has numerous charts and diagrams, and extensive references for those interested in detailed information on mercury. EPA's Mercury National Action Plan, the United States Status Report on Mercury, and the Mercury Products Study by John Gilkeson of the Minnesota Pollution Control Agency were also extremely helpful. Other references include a 1997 report done by the Swedish National Chemicals Inspectorate (KEMI), Mercury in Products - a source of transboundary pollutant transport. For a full list of sources see Appendix G, Bibliography.

Finally, this paper does not distinguish between different types of mercury in its discussion of sources. The scientific literature emphasizes the significant behavioral differences among elemental mercury, ionic mercury, and organic and inorganic mercury compounds, in terms of accumulation in the aquatic food chain, atmospheric and oceanic residence times (the former greatly influencing long-range transport), and rates and forms of deposition. However, available source data do not specify the forms of mercury emitted from sources. Current scientific research will improve understanding of this issue in the years to come.

Binational Toxics Strategy - 
Mercury Sources and Regulations, 1999 Update

Draft November 1, 1999

I. Introduction

Mercury enters our lives more frequently than we may imagine. It may be in the fluorescent lights in our office, in old cans of latex paint, in our batteries, in our dental fillings, and numerous other sources. In the United States manufacturers used an estimated 381 tons of mercury in 1997, in products or in manufacturing processes.

A naturally-occurring element, mercury's value in numerous industrial processes was discovered centuries ago. Over time, however, we have discovered that mercury is a potent neurotoxin, particularly in the organic, methylmercury, form, capable of impairing neurological development in fetuses and young children and damaging the central nervous system of adults. People are most likely to be exposed to harmful quantities of mercury through consumption of fish contaminated with methylmercury. Exposure to elemental mercury vapor in indoor air can also cause serious harm.(1)

Fish consumption advisories throughout Great Lakes water bodies testify to the health risks caused by mercury present in the Great Lakes ecosystem. Mercury contamination is the most frequent basis for fish advisories issued by States or Tribes, represented in 60 percent of all water bodies with advisories. Thirty-nine states have issued fish consumption advisories in one or more water bodies, and ten States have issued statewide mercury advisories.(2 & 3)

The Great Lakes Binational Toxics Strategy, signed by Canada and the United States in April 1997, is an effort to reduce mercury and other persistent toxic substances in the Great Lakes. The Strategy sets a goal of virtual elimination of mercury from the Great Lakes Basin, with a U.S. challenge of 50 percent reductions nationwide in the use and release of mercury by 2006, and a Canadian challenge of 90 percent reduction in release of mercury in the Great Lakes basin by 2000. It creates a four-step process for each pollutant it addresses. Step one is information gathering about sources and uses; step two is analysis of current regulations, initiatives and programs which manage or control the pollutant; step three is identification of cost-effective options to achieve further reductions, and step four is implementation of actions towards the goal of virtual elimination. This report documents steps one and two, relating to sources and regulations of mercury in the United States.

Mercury in the Environment

When released to the environment inorganic mercury can be converted to methylmercury. Most environmental releases of mercury are inorganic, either in the elemental or ionic form. Most emissions of ionic mercury deposit within the region of the source, while elemental mercury enters a global atmospheric reservoir where it can remain for approximately one year, potentially traveling long distances.(4) In the environment, these forms of mercury can be converted to methylmercury, which can bioaccumulate and can reach dangerous levels in fish at the top of the aquatic food chain.

Mercury does not degrade and is not destroyed by combustion. Although the global mercury cycle is imperfectly understood, scientists have reached consensus on important aspects of the behavior of mercury in the environment. Mercury cycles extensively between soils, the atmosphere, and surface waters. Scientists believe that atmospheric deposition of mercury emitted into the air by combustion, incineration, or manufacturing processes, contributes a large portion of the mercury found in waters and soils. In Minnesota, researchers estimated that in 1995, direct industrial discharges of mercury to surface water contributed only 1 to 2 percent of the mercury load to surface waters, while atmospheric deposition was responsible for 98 percent.(5) Mercury also has a long retention time in sediments and soils, and so may continue to be released from such depositions to surface waters and the atmosphere for long periods of time, possibly hundreds of years.(6)

Mercury emissions come from natural sources including marine and aquatic environments, as well as volcanic and geothermal activity. However, recent studies suggest that anthropogenic sources contribute the majority of mercury releases, and that the total atmospheric mercury burden has increased by a factor of between 2 and 5 since the beginning of the industrial age. Human activity has thus increased the amount of mercury circulating globally, the global mercury reservoir. Approximately one-third of total current global mercury emissions are thought to cycle from the oceans to the atmosphere and back, but it is believed that much less than 50 percent of the oceanic emission is from mercury originally mobilized by natural sources.(7) Recycling of mercury at the earth's surface, especially from the oceans, extends the influence and active lifetime of anthropogenic mercury releases. One study conservatively estimates that if all anthropogenic emissions ceased, it would take 15 years for mercury reservoirs in the oceans and the atmosphere to return to pre-industrial conditions. Others have estimated it could take much longer.(8)

Like global climate change and acid rain, therefore, mercury is a long-term, international concern that has disparate regional impacts. Mercury vapor in the atmosphere disperses widely, and can travel thousands of miles. However, in general, atmospheric deposition is higher in areas closer to emissions sources, and in those with greater annual precipitation. The 1997 Mercury Report to Congress (MRC) predicts the highest deposition rates in the United States to occur in the Great Lakes Basin, the Ohio River Valley, the Northeast and scattered areas in the South, with the Miami and Tampa areas experiencing the greatest mercury deposition.

The MRC used pollution fate and transport modeling to assess whether mercury deposition within the United States can be attributed primarily to anthropogenic U.S. sources, or to natural and foreign sources. The MRC estimated that, in 1995, of the total global annual input of 5,500 tons of mercury to the atmosphere from all sources, natural and anthropogenic, U.S. anthropogenic emissions contributed about 3 percent, or 158 tons. Of these, about one-third (~ 52 tons) are deposited in the lower 48 States, while the remaining two-thirds (~107 tons) diffuse beyond U.S. borders into the global reservoir.(9) The U.S. also receives mercury deposition from the global reservoir, calculated at about 35 tons in 1995.(10) Thus, U.S. anthropogenic emissions account for an estimated 60 percent of deposition in the United States, with remaining 40 percent attributed to the global reservoir. It is likely that reductions in emissions from incinerators since 1995 have reduced the share of mercury deposition in the United States attributable to U.S. sources.

The MRC estimates contain considerable uncertainty. Most importantly, there are uncertainties in the emissions inventory used for this modeling, including the mass of emissions from many sources, including natural sources. Moreover, the species of mercury emitted by most sources is highly uncertain; this issue is significant because ionic mercury emissions are expected to contribute substantially more deposition in the United States would an equal amount of elemental mercury emissions. Elemental mercury emissions have a greater impact on the global mercury pool.

Another means of assessing the relative contribution of U.S. sources to deposition in the United States makes use of actual environmental measurements. This approach compares levels of (and changes in) mercury deposition in remote areas, primarily influenced by deposition from the global pool of mercury, with deposition in areas closer to major sources of mercury emissions. One such study, using comparison of sediment cores from lakes in Minnesota and Alaska, concluded that roughly 40 percent of mercury deposition in the upper Midwest is attributable to U.S. anthropogenic sources, with the remainder divided approximately equally between natural emissions and global anthropogenic sources. This study noted that the importance of U.S. anthropogenic sources is likely declining, while global anthropogenic sources are contributing increasing amounts of mercury deposition.(11)

Reducing Mercury

At the state, federal, and international levels, numerous efforts are underway to curtail mercury releases into the environment. To understand what options are available to reduce mercury use and release we must first answer three basic questions:

(1) What are the sources of the mercury (supplying mercury and releasing mercury) into the environment?

(2) What products contain mercury?

(3) What regulations and non-regulatory measures currently influence mercury use and release?

The objective of this background paper is to provide a context for understanding the full range of mercury sources and existing regulations that affect mercury use and release. From this information, we will be able to understand the extent to which existing regulations encourage a reduction in mercury use and release, and identify other opportunities--including regulatory and non-regulatory programs--that might hasten the pace of reductions.

Table 1 provides an overview of the material covered in this background section.

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II. What Are the Sources of Mercury?

Mercury enters the atmosphere through the mobilization or release of geologically bound mercury by natural processes and human activities. Mercury is also re-emitted to the atmosphere by biological and geological processes drawing on a pool of mercury that was deposited to the earth's surface after initial mobilization by either human or natural activities.(12) This report focuses on anthropogenic sources of mercury.

This report divides U.S. anthropogenic mercury sources into two broad groups, based on these two different roles of mercury: is mercury intentionally used or is it incidentally released? In addition to U.S. anthropogenic sources, the Great Lakes receive mercury deposition as the result of inputs from the global reservoir of atmospheric mercury emitted by natural sources and global anthropogenic sources. Table 2 details the categories of mercury sources used in this report.

Intentional Use: When mercury is used intentionally as an input in production processes or consumer products, three distinct but inter-related types of activities contribute to mercury releases. Activities in this category include:

(1) Production or supply of mercury;

(2) Use of mercury as part of a manufacturing process or within a product; and

(3) Disposal of mercury-containing wastes.

These activities, especially waste disposal, release mercury into the environment. Because the quantity of mercury used directly influences a significant amount of the mercury ultimately released into the environment, several leverage points are potentially available to reduce mercury releases. The price and supply of mercury, the feasibility of recycling, the availability of alternative inputs or processes, and the structure of existing regulations all contribute to a company's decision to use mercury in their production processes or products.

Incidental Release: Incidentally released mercury comes from three categories of sources:

(1) Energy Production where the fuel source (primarily coal) contains mercury;

(2) Mobile sources where the fuel source (primarily diesel) contains mercury; and

(3) Manufacturing processes where the raw materials contain trace amounts of mercury

These activities, particularly coal combustion, contribute a large portion of overall mercury air emissions. In many countries, copper, lead and zinc smelting are also large mercury emitters. However, because these processes do not rely on mercury, their mercury emissions are not influenced by the costs associated with using mercury. They are affected only by regulatory costs associated with releasing mercury. Therefore, the opportunities for reducing mercury releases from these sources will differ from those for sources that rely on mercury for some aspect of their business.

Table 2:  Sources of Mercury

The source categories used throughout this report are, for the most part, consistent with sources identified in recently released reports that track mercury use and emissions, specifically the U.S. Geological Survey Minerals Yearbook and the Mineral Commodity Summary (formerly the Bureau of Mines Mineral Industry Surveys), the USEPA 1997 Mercury Study Report to Congress, and the USEPA 1990 Emissions Inventory of Forty Potential §112(k) Pollutants under the Clean Air Act Amendments of 1990 (§112(n)(1)(B)). By using similar source categories, we can combine information on mercury use and emissions trends at a national level with an overview of existing regulations.

Influx from the Global Mercury Reservoir: According to the MRC, a computer simulation of long-range transport of mercury suggests that 35 tons of mercury from the global reservoir is deposited in the continental United States annually.(13) While some of the mercury in the global reservoir has been mobilized by natural processes, human activity is responsible for several-fold increases in the total atmospheric mercury burden over the last two hundred years. These increases have raised atmospheric deposition rates, even in areas far from mercury sources, and make mercury emissions an international policy issue.

According to the MRC computer simulation, U.S. sources add roughly three times more mercury to the global reservoir annually than is deposited from the global reservoir to the continental United States. Other nations will therefore look to reduce U.S. emissions. Over the last decade, however, the United States has both drastically reduced the use of mercury in products and manufacturing processes, and passed regulations that will limit mercury emissions from waste combustion (see Table 14: Actual and Projected Mercury Emissions). The United States has an interest in encouraging other nations to make similar reductions. Domestic regulation of mercury releases will therefore reduce U.S. mercury levels more effectively if it helps encourage international efforts to control mercury releases abroad.

Appendix A includes a detailed "use tree" of mercury sources.

A. U.S. Anthropogenic Mercury Emissions Inventory

Estimated anthropogenic mercury emissions in the United States during 1994/95 were 149 tons per year, a 25 percent reduction from 1990 estimated emissions. Table 3 summarizes mercury emissions in 1990 and 1994/95, based primarily on two mercury emissions inventories prepared by USEPA--the 1990 inventory, published in 1999 under Section 112k of the Clean Air Act, and the 1994/1995 inventory, which was published in 1997 in the Mercury Report to Congress. The figures reported here reflect some adjustments to the inventories as published by USEPA.(14)

Source sectors are listed in order of 1994/95 emissions mass. Coal-fired utility boilers are the largest source category, accounting for approximately one-quarter of emissions in 1990 and one-third of emissions in 1994/95. Medical waste incinerators drop from approximately one-quarter of 1990 emissions to one-tenth of the 1994/95 emissions, while municipal waste combustors are approximately one-fifth of emissions in both 1990 and 1994/95.
   

There are significant uncertainties in many of the emissions estimates. For instance, emissions from the most significant emissions source within the chlorine production sector, the chlor-alkali mercury cell room, are not directly measured but rather are based on emission factors developed during the 1970s. Mobile source emissions estimates were developed recently, but are based on a small number of emissions tests.

In general, few categories in the 112k and MRC inventories in have estimates developed from a true "bottom-up" basis, that is, estimates developed specifically for individual sources and then summed to obtain a national total. Instead, both reports adopt "top-down" emissions estimate techniques. For example, the MRC used an emission factor-based approach to develop both facility-specific and nationwide emissions estimates. This approach requires an estimate of the ratio of the mass of mercury emitted to a measure of source activity, such as total heat input for fossil fuel combustion. Using this ratio, called the "emission factor," and an estimate of the annual nationwide activity level for each source, the report generates a national emissions estimate for that source activity. Emission factors reflect the 'typical control' achieved by the air pollution control measures applied across the population of sources within a source category. The emission factor-based approach does not generate exact emission estimates. Uncertainties are introduced in the estimation of emission factors, control efficiencies, and the activity level measures.(15)

Moreover, at least two potentially significant sources are missing from the 112k and Report to Congress inventoriesBuse of iron and steel scrap and solid waste processing and transport. Using emission estimates developed for these categories in Section II, 3, B, would make total emissions for 1995 176 tons, a 27 percent decrease from 1990 [see Table 4]. These estimates are highly uncertain.

The inventory can be divided between emissions related to intentional use of mercury and emissions related to use of fuels or materials that contain trace amounts of mercury.(16) Taking just those sources that account for more than one ton of mercury emissions per year in 1994/95, sources that result from intentional mercury use are: municipal waste combustors, medical waste incinerators, chlorine production, hazardous waste incineration, sewage sludge incineration, land breakage, and general laboratory activities. Emissions from these sources added to 63.4 tons annually in 1994/95. If the estimates for use of steel scrap and solid waste processing and transport are added, emissions related to deliberate use add to 91.4 tons per year. Incidental release sources greater than one ton in 1994/95 are: coal-fired utility boilers, non-road and on-road mobile sources, Portland cement production, industrial boilers, pulp and paper production, animal cremation (though these emissions may be partly the result of deliberate use as well), petroleum refineries, geothermal power, distillate oil combustion for residential heating, and commercial/institutional heating. These sources added to 79.1 tons annually in 1994/95.

The source categories that emit the most mercury nationally are likely the biggest emitters in the Great Lakes region as well, with some differences. The Great Lakes States account for 29 percent of U.S. population, but 36 percent of estimated mercury emissions from electric utilities,(17) likely as the result of greater coal use by Midwestern utilities than the national average. Two mercury cell chlor-alkali facilities in the Great Lakes basin account for 19 percent of chlorine production capacity among the 12 mercury cell facilities nationwide. Some sources that are not significant in the national inventory are important in the Great Lakes Region; for instance, the only taconite production in the United States occurs in Minnesota and Michigan, and accounts for roughly half a ton of estimated mercury emissions annually.

This section provides a brief overview of the three stages of the mercury life cycle that contribute to mercury releases as a result of intentional mercury use: 1) production; 2) use; and 3) disposal. Most releases come during the disposal stage, but the production and use stages provide potential intervention points to influence the amount of mercury ultimately released in the disposal stage.

The mercury available for use in the United States comes from five main sources: 1) Primary mercury production; 2) Secondary mercury production (mercury recovery); 3) Mercury compound production; 4) Government stocks; and 5) Imports. Table 8 illustrates the relative contributions of these sources to the United States mercury supply.

Primary Mercury Production. Virgin mercury is mined from mercury ore or produced as a by-product of gold mining. In the United States, mercury is produced only as a by-product of gold mining. The last mercury ore mine, the McDermitt Mine in Nevada, closed in 1990. No by-product mercury mines are located in the Great Lakes States. Primary mercury production continues in other countries including Spain, China, and the former Soviet Union.

Secondary Mercury Production. Mercury is recovered from discarded products and industrial wastes such as chlor-alkali wastes, dental amalgams, fluorescent light tubes, electronic devices, batteries, and other instruments such as thermometers. There are two basic categories of secondary mercury production: recovery of liquid mercury from dismantled equipment and mercury recovery from scrap products using extractive processes.(18) Liquid extraction involves draining the liquid mercury from dismantled equipment. Recyclers use thermal or chemical processes to extract mercury from scrap. Most commonly, the mercury is vaporized in a retort and collected by condensation. Condensed mercury is then distilled to remove impurities. Triple-distilling yields the highest purity mercury.

Recovery of liquid mercury accounts for most secondary production. One mercury recycler, Bethlehem Apparatus Company, estimated that mercury recovered using extractive processes accounted for 15 to 20 percent of the total mercury reported as recycled from industrial scrap in 1995. Secondary production reached a high of 534 tons (122 percent of industrial demand) in 1995, but has since fallen. Table 6 below shows the trends in U.S. mercury consumption and secondary mercury production.

 

Three facilities, all located in Great Lakes states, produce the bulk of secondary mercury in the United States. D.F. Goldsmith Chemical and Metal in (Evanston, IL) specializes in distilling 99 percent or greater flowable mercury, and Bethlehem Apparatus (Hellertown, PA) and Mercury Refining Company (Albany, NY) retort and distill a wide variety of mercury wastes and scrap material. However, they do not accept certain types of Resource Conservation and Recovery Act (RCRA) wastes. Currently, eleven plants in the U.S. recycle mercury from fluorescent lights, using physical separation to recover mercury. Six of these facilities opened in 1993.

Secondary mercury production released an estimated 0.4 tons of mercury in 1995.

Mercury Compound Production. Mercury compounds are used in a wide variety of pharmaceuticals and other products. Commonly used mercury compounds include mercuric oxide (cathode material in batteries), mercuric chloride (pharmaceuticals), phenylmercuric acetate (used in paints and pharmaceuticals), mercuric sulfide (used in red pigment and pharmaceuticals), and thimerosal (a preservative used in medicines and contact lens solution). One mercury compound manufacturer is currently located in Great Lakes states:

Government Stocks. The United States government maintains a supply of mercury as part of the National Defense Stockpile, established at the end of World War I to maintain adequate supplies of materials deemed critical to national defense. The Defense Logistics Agency (DLA), a unit of the Department of Defense, manages the stockpile. DLA periodically evaluates the quantity of mercury and other materials needed in the stockpile, and may sell any "excess" material on the open market. Mercury is stored and sold in flasks, which contain 75.9 pounds of mercury. Regulations governing the sale of excess mercury are described in Section III ("Regulations").

At the end of April 1994, DLA held 127,000 flasks (4,819 tons) of mercury in the stockpile. With a current stockpile goal of zero for mercury, all of this material is considered excess. After selling its entire 1994 mercury allocation (10,000 flasks), DLA suspended future mercury sales in July 1994 until the environmental implications of these sales are addressed.

The Department of Defense (DOD) recently completed an Environmental Assessment on the sale of its currently managed mercury stockpile. Based on the National Environmental Policy Act and the results of this assessment, DOD will now conduct an Environmental Impact Statement (EIS) on the disposition of the stockpile. Because EIS process is comprehensive, a final EIS may take several years to complete. In the meantime, DOD has begun a complete review of the five facilities across the U.S. currently storing its mercury, and is inspecting all the mercury containing flasks to ensure proper and safe storage.

The Department of Energy (DOE) is storing approximately 145 tons of mercury. DOE has identified 5 tons of mercury-contaminated wastes currently awaiting disposal as part of an ongoing inventory of such wastes. DOE's Mixed Waste Focus Area-Mercury Working Group, in conjunction with EPA, has initiated studies of the direct treatability and disposal of high mercury-inorganic subcategory wastes that contain radioactive materials resulting from nuclear weapons production. These treatability studies include the evaluation of technologies such as alternative oxidation technologies, stabilization using specialized amendments, amalgamation technologies, sulfur polymer cement stabilization, and mercury solubilization and removal.

Imports. The United States imported 180 tons of mercury in 1997, the most recent year for which data are available. Estimated 1998 imports are 220 tons. From 1994 to 1997, 37 percent of U.S. imports came from Russia, 25 percent from Canada, 13 percent from Kyrgyzstan, and 10 percent from Spain. Mercury compounds are also imported. Section III, B, 1 "Mercury in Commerce" discusses mercury imports and relevant tariffs in more detail.

Mercury is used in industries worldwide because of its distinctive properties. It conducts electricity, acts as a biocide, is useful in the measurement of temperature and pressure, and forms alloys with almost all other metals. With these and other properties, mercury plays an important role in several industrial sectors.

Table 9 shows the trends in domestic mercury use since 1980, and the relative amounts of mercury used in the following industrial categories: Chemical and Allied Products; Electrical and Electronic Uses; and Instruments and Related Products.

Mercury use in the United States declined 79 percent between 1980 and 1995, from 2231 tons per year to 480 tons per year. From 1995 to 1997 mercury use declined a further 21 percent to 381 tons per year. The most significant changes in reported mercury consumption are the dramatic reduction in mercury used in paints, and especially in batteries. In addition, there have been significant reductions in the 1980s and 1990s in use of mercury in laboratories, wiring devices and switches, and measuring and control instruments.

Public pressure has also driven manufacturers to seek alternatives to non-essential mercury in their products. For example, public outcry against mercury switches contained in children's light-up sneakers caused the manufacturer to change to a non-mercury switch that accomplishes the same purpose. The manufacturer now provides a toll-free number for customers to request a postage-paid mailer and return the shoes for proper mercury disposal.

Table 9: U.S. Industrial Consumption of Refined Mercury Metal, by Use* (tons)
Sources: US Bureau of Mines, Mineral Industry Surveys, July 1994, US Geological Survey, Minerals Yearbook 1998

2.a. Use of mercury in manufacturing processes (chlorine and caustic soda manufacture)

The largest user of mercury in the United States, and perhaps globally, is the chlor-alkali industry, which produces chlorine, caustic soda and hydrogen gas. Mercury emissions from this sector were estimated at 10 tons in 1990, falling to seven tons in 1995, reflecting closure of several mercury cell chlor-alkali facilities.

The mercury cell production process, responsible for less than 15 percent of U.S. chlorine production capacity, relies on a mercury as a cathode in the electrolytic separation of salt. Within the mercury cell, a long, shallow, covered trench, a thin layer of mercury flows under a layer of brine; caustic soda adheres to the mercury, while chlorine migrates to electrodes above. The mercury is subsequently separated from the caustic soda and added back to the process. Mercury is lost from the process through evaporation of mercury that spills or leaks; moreover, opening of the mercury cells for maintenance is potentially a significant source of mercury emissions. Emissions from the mercury cell room are in the nature of an area source, and are not routinely measured. Other sources of mercury within a chlor-alkali plant are measured, and include the hydrogen and end box ventilation streams. In addition, caustic soda produced from this process contains traces of mercury.

While this industry is the largest U.S. mercury user, the fate of much of this mercury is uncertain. Reported releases of mercury from the chlor-alkali sector account for a small percentage of mercury purchased by this sector.(19) Purchases of mercury by this industry either increase the inventory of mercury within chlor-alkali plants, or replace losses of mercury to the air, water, solid wastes or products. Unfortunately, only one chlor-alkali plant (Vulcan Chemical, in Port Edwards, Wisconsin) conducts a mass balance for mercury, so the amounts lost to the environment versus added to inventory cannot be determined. To improve this situation, the Chlorine Institute has developed a guidance on conducting a mercury mass balance, and several plants are planning to begin doing mass balances. In addition, the Chlorine Institute and Olin Corporation are working with USEPA on a project to better characterize emissions from the mercury cell room, the major area of uncertainty about environmental releases from this industry.

As of 1999, twelve mercury-cell chlor-alkali plants remain in the United States, two in the Great Lakes. On a per-facility basis, chlor-alkali plants are the largest emitters of mercury. For more information about this sector, see the Chlor-Alkali Commitment under Section IV "Non-Regulatory and Voluntary Approaches to Mercury Reduction". Table 10 lists U.S. Mercury-Cell Chlor-Alkali Production Facilities.

2.b. Use of mercury in products.

Mercury use in products can lead to emissions in the production process, as well as during the use and disposal of the product. Manufacture of mercury-containing instruments caused an estimated 0.5 tons of emissions in 1995, and preparation and use of dental materials an estimated 0.7 tons. Several states regulate mercury-containing products directly by limiting or prohibiting mercury content in certain products, and restricting disposal options. Both state and federal content and regulations have had a direct impact on the quantity of mercury consumed in industrial activities. These are discussed in more detail in Section III "Regulations". Disposal of mercury-containing products is covered in Section II, 3, B, "Waste Disposal and Recycling".

• Paint Manufacturing: Until the early 1990s, the mercury compound phenylmercuric acetate was used to control mildew in latex paints. However, EPA curtailed this use, eliminating mercury in interior latex paints in 1990 and exterior paints in 1991. Mercury emissions from volatilized paint and demolition waste may continue from paints manufactured before the ban. Minnesota Pollution Control Agency estimates that latex paint volatilization caused 500 pounds of emissions annually in Minnesota in 1990; by 1995, estimated emissions dropped to 10 pounds.

• Batteries: In 1988, battery manufacturing alone consumed almost 25 percent of the total mercury use in the United States. Since then, as manufacturers have found alternatives to mercury in alkaline batteries, and both the Congress and the States have begun limiting mercury content in batteries, the amount of mercury used in batteries has declined by over 95 percent. The battery industry has eliminated the use of mercury in alkaline batteries, except for button cells.

• Electric Lamps: More than half a billion mercury-containing lamps, including fluorescent, mercury vapor, metal halide, and high-pressure sodium lamps, are produced each year. From 1989 to 1995, the average mercury content of fluorescent bulbs fell roughly 53 percent, from 48.2 mg to 22.8 mg. Additional reductions are expected; Philips Lighting announced in 1995 that it would be selling 4-foot fluorescent lamps with less than 10mg of mercury. At the same time, sales of fluorescent lamps increased between 3 and 5 percent a year. Emissions of mercury resulting from the breakage of these lamps is estimated to be 1.5 tons per year. In 1993, 98 percent of these bulbs were treated as municipal solid waste, while the remaining 2 percent were recycled. In July 1999, EPA added mercury-containing lamps to the Universal Waste Rule to facilitate their collection and recycling, by reducing the regulatory burden associated with these activities.(20)

• Wiring Devices and Switches: Mercury's ability to conduct electricity makes it useful for wiring devices and switches, although substitutes exist. In addition to home thermostats and silent wall switches, relays and switches containing mercury have various industrial uses in high-voltage applications, telecommunications switching equipment, alarms, and semi-conductors. Mercury is also used in automobiles for a variety of switches, but the prominent use (85 percent of mercury in U.S. autos) is in hood switches.(21)

• Measuring and Control Instruments: Mercury's mechanical properties as a high-density/low friction metal fluid make it useful for a wide variety of measuring and control instruments, although, as with wiring devices and switches, substitutes for mercury exist. Mercury has been widely used in a variety of temperature measurement and sensing devices such as medical and laboratory thermometers, flame sensors, and thermostat sensors. Many instruments that measure and control pressure and flowrate also contain mercury including manometers, barometers, air flow measurement devices, and pressure safety devices.

• Dental Equipment: Mercury is used frequently in dental amalgam tooth fillings; amalgam is a mixture of roughly equal parts metallic mercury and an alloy of silver, tin, copper and zinc. Dental preparation and use cause an estimated 0.7 tons of air emissions annually. In addition, dental offices are an important source of mercury in sewage. Substitutes for mercury amalgam in dental restoration are available; these substitutes are preferred in some applications, but the majority of dentists prefer to use amalgam for restoration of posterior teeth.

Table 10 lists the primary products that contain mercury in each of the source categories discussed in this section. In addition, Appendix A includes a detailed mercury use tree.

Incineration of wastes that contain mercury leads to substantial mercury emissions; mercury releases from other waste disposal pathways are less well characterized, but potentially substantial as well. The Mercury Report to Congress estimates that incineration of municipal waste, medical waste, hazardous wastes and sewage sludge accounted for one-third of mercury emissions, or 54 tons. Incinerator emissions have fallen substantially since 1990, when incinerators accounted for 99 tons of emissions, nearly half of the estimated total. A decline in the amount of mercury in discarded batteries probably accounts for most this decrease, along with other pollution prevention efforts and regulations on incinerators in some states.

According to the MRC, mercury emissions from municipal waste combustors (MWCs) will decline in the future for three reasons. First, EPA has issued New Source Performance Standards and guidelines for new and existing MWCs estimated to reduce mercury emissions by about 90 percent from the 1990 baseline. Second, the inlet concentration of mercury in the MWC waste stream is estimated to be half of what it was in 1990, as fewer mercury-containing components such as batteries, thermometers, thermostats, pigments, and paints are entering the municipal solid waste (MSW) stream. Third, some states, led by Florida, New Jersey and Minnesota, have enacted either MWC legislation requiring the use of activated carbon injection, mandatory recycling for or bans on the sale of certain mercury-containing products.(22)

Mercury emissions from wastes that are not incinerated, but rather landfilled or recycled, are less well characterized than emissions from incinerators. However, such emissions, from landfills, product breakage, processing, storage and transportation of wastes, and from recycling of metal scrap, could be substantial. The Swedish National Chemicals Inspectorate estimates that 18 percent, or 72 tons, of mercury emissions in Europe are attributable to mercury use in products. Of the emissions attributable to products, 47 tons (66 percent) result from incineration, but an additional 14.5 tons (20 percent) results from recycling of steel scrap; 9.2 tons (13 percent) is emitted by landfills, and 0.8 tons (1 percent) results from breakage of products during use. More than half of these estimated non-incineration emissions result from disposal or recycling of lighting and electrical equipment, with disposal of batteries and measuring and control devices responsible for the remainder.

Minnesota Pollution Control Agency (MPCA) has independently arrived at similar conclusions regarding the importance of non-incineration waste disposal and recycling as source of mercury to the environment. MPCA estimates that 2,031 pounds of emissions (44 percent of the total mercury emissions in Minnesota) resulted from purposeful use of mercury in 1995, down from 5,852 pounds (69 percent) in 1990. Most of these emissions occurred during waste disposal.(23) Of the 1995 emissions resulting from purposeful use of mercury, slightly more than half resulted from incineration. Incineration of municipal solid waste, medical waste, hazardous waste, sewage sludge, accounted for 1133 pounds of emissions. This total includes 270 pounds of emissions estimated from on-site household waste incineration, a source not calculated in national estimates and a source that will not be affected by regulation of incinerators. Unlike the Swedish study, MPCA attributed a negligible amount of emissions to landfills, but did estimate 432 pounds of emissions resulting from mercury volatilization during solid waste collection and processing. An additional estimated 166 pounds of emissions resulted from use of metal scrap at a single facility in Minnesota, 83 pounds resulted from fluorescent lamp breakage and 48 pounds resulted from spills and land dumping.(24)

MPCA's estimate of 432 pounds of emissions resulting from volatilization during solid waste collection and processing in 1995 represents a 67 percent reduction from estimated 1990 emissions from this category, based on reductions in the mercury content of solid waste. These estimates assume that five percent of mercury in solid waste is volatilized during collection, transportation and mechanical processing. Scaling MPCA's 1990 estimate for this category up to the national level would yield an estimate of approximately 32 tons of emissions annually.(25) Assuming that efforts to reduce the mercury content of solid waste have been three-quarters as successful nationwide as in Minnesota, 1995 emissions would be 16 tons.

Thus, even if incinerator emissions were eliminated, disposal and recycling of mercury-containing products would likely remain an important source of mercury releases. The various sources of mercury release resulting from waste disposal and recycling are described in greater detail below.

Municipal Solid Waste: Municipal solid wastes are contaminated by a variety of mercury-containing items. A 1992 EPA study found that household batteries were the primary source of mercury to the municipal solid waste stream. Discarded batteries contained an estimated 621 tons of mercury in 1989, more than 85 percent of the total. Another significant source, paint residues, contained an estimated 18 tons of mercury in 1989. Both of these sources, batteries and paints, have been significant reduced as the result of reductions in the mercury content of these products. Reductions in the mercury content of discarded batteries is likely to continue to decline. The remaining significant sources of mercury to municipal solid waste are mercury-containing lamps, fever thermometers, thermostats, and light switches.(26) A 1999 study by the Florida Department of Environmental Protection found that in 1995, batteries were still the largest source of mercury to the solid waste stream, followed by mercury devices (switches, thermometers, and thermostats) and lighting, with a total of 12 tons of mercury discarded in Florida. By 2000, however, mercury discards to municipal solid waste are projected to decline to less than six tons per year, with mercury devices accounting for more than half of the total remaining and batteries declining from more than seven tons of mercury in 1995 to less than two tons in 2000.(27)

Incineration of municipal solid waste accounted for 30 tons of mercury emissions in 1995, down from 42 tons in 1990. Mercury is less likely to reach the environment if it is landfilled than if it is incinerated, since incineration causes mercury to volatilize while landfilling can immobilize significant amounts of mercury. However, only about 15 percent of municipal solid waste is incinerated; most of the remainder is landfilled. The Mercury Report to Congress estimates that landfills emit 0.074 tons of mercury annually, based on measurements of mercury in landfill gas. However, a recent Oak Ridge National Laboratory (ORNL) study of landfills in Florida indicates that the working face of the landfill may be more important than landfill gas as a source of mercury emissions. While most of the mercury buried within the landfill may be immobilized, operations on the working face lead to emissions as mercury-containing devices break. Moreover, the study found that emissions of landfill gas may include highly toxic organic mercury, as the result of reactions that take place within the landfill.(28)

Disposal of mercury-containing wastes leads to mercury emissions from waste storage, transport and processing, as well as from landfills. The ORNL landfill study in Florida found that waste transfer stations, dumpsters, and garbage trucks are potentially also sources of mercury emissions. The Mercury Report to Congress estimates that breakage of mercury lamps (primarily during disposal) cause 1.5 tons of emissions annually, but no estimates are provided for other mercury containing products, such as thermometers and thermostats.

Medical Waste: Medical waste contains much higher concentrations of mercury than municipal solid wastes as the result of the disposal of thermometers and other mercury-containing medical devices, and the use of mercury in medicines and laboratory chemicals. Incineration of medical waste accounted for an estimated 16 tons of emissions in 1995, down from 50 tons in 1990. While most medical waste is incinerated, mercury emissions can occur during the transport and processing of waste prior to incineration. Ongoing efforts to implement pollution prevention at medical facilities, for instance through the American Hospital Association-USEPA Memorandum of Understanding, will help reduce both these sources of emissions.

Scrap Metal: Recycling of scrap metal leads to emissions from scrap processing and from metal production, if the scrap is contaminated by mercury devices contained in autos, appliances, and scrapped industrial equipment. The New Jersey Department of Environmental Protection estimates 719 lbs/year emissions from three sources (one electric arc steel furnace and two iron foundry cupolas), based on stack tests. Contamination of iron and steel scrap with mercury-containing devices is the most likely cause of these emissions. Assuming that mercury in scrap is the sole source of the emissions and that the New Jersey facilities are representative, an estimate of mercury emissions nationwide from iron and steel production can be derived. Depending on the New Jersey facility that this estimate is based on, emissions are between 7 tons and 18 tons annually, with a central estimate of about 12.5 tons. These estimates are strikingly similar to the Swedish National Chemical Inspectorate's estimate of 14 tons of annual emissions resulting from steel scrap in Europe. They are also in accord with a mass balance approach -- roughly 10 tons of mercury were used in autos annually, until recent years,(29) and more than one ton is used annually in white goods. Scrapped industrial equipment contains additional mercury. While additional testing is needed in order to develop a more certain emissions estimate, emissions at these levels would be a significant addition to the estimated 0.25 tons from "blast furnaces and steel mills" in the 1990 112k emissions inventory, based on Toxics Release Inventory reporting (the Report to Congress makes no estimate for this sector). The amount of mercury emitted from scrap metal smelting is likely to decline as U.S. automakers reduce the use of mercury switches in their vehicles (see Section IV, "Voluntary Initiatives and Non-Regulatory Approaches to Mercury Reduction" ). Additional reductions could be achieved by programs to remove mercury switches from existing autos.

Demolition Debris: Demolition debris is another potential source of mercury. Buildings are equipped with numerous mercury-containing devices, such as thermostats and fluorescent lamps. If these devices are not removed prior to demolition, emissions can result as these devices are broken. There are no estimates available of mercury emissions from this source.

Hazardous Wastes: USEPA has established six different categories of mercury-containing hazardous waste: D009 Wastes--Characteristic Mercury Wastes; K071 Wastes--Brine purification muds from the mercury cell process in chlorine production, where separately prepurified brine is not used; K106 Wastes--Wastewater treatment sludge from the mercury cell process in chlorine production; P065 Wastes--Mercury fulminate; P092 Wastes--Phenylmercury acetate; U151 Wastes--Mercury. These wastes are described in greater detail in Appendix H.

Disposal of these wastes depends on mercury content and the presence of hazardous organic wastes. Wastes with mercury content higher than 260 ppm must be roasted or retorted (yielding mercury for recycling), and if organics are present, they must be incinerated. Incineration of hazardous wastes at cement kilns, hazardous waste incinerators and lightweight aggregate kilns caused emissions of an estimated 6.6 tons of mercury in 1997. Retort units released an estimated 0.4 tons of mercury in 1995.

Water Releases: Mercury enters directly into water and wastewater from a number of small, diffuse sources. Landfills leach mercury which is carried by runoff into water systems. Homes, small laboratories, medical offices and clinics, and commercial/industrial sites dispose of mercury-containing products such as reagents, cleaning solutions, and medicines, and clean-up from small spills and broken products such as thermometers, directly down the drain. These discharges are not monitored, and usually end up in water treatment plants. Some of the mercury discharged to water treatment plants ends up in sewage sludge. Incineration of sewage sludge accou