Mercury regulation in the United States
Methylmercury can accumulate in living organisms and reach high levels in fish and marine mammals via a process called biomagnification (i.e. concentrations increase in the food chain).
The Earth's surface soils, water bodies and bottom sediments are thought to be the primary biospheric sinks for mercury.
[4][5] The largest emissions of mercury to the global atmosphere occur from combustion of fossil fuels; mainly coal in utility, industrial, and residential boilers.
The general population is primarily exposed to methylmercury through the diet (especially fish) and to elemental mercury vapors due to dental amalgams.
Other sources are significant such as water consumption, some of the cereals choices, some specific vegetables as well as a variety of red and white meat.
Moreover, a variety of fish, milk, meat and wheat accompagned of selenium, zinc, magnesium, and vitamins C, E and B allow an alteration of the mercury metabolism.
In fact, some populations are affected by a lack of appetite others have seen a reduction of their food or fluid intake as well as a significant weight loss.
Impacts on cognitive thinking, memory, attention, language, and fine motor and visual spatial skills have been seen in children exposed to methylmercury in the womb.
For methylmercury, the US Environmental Protection Agency (US EPA) has estimated a safe daily intake level of 0.1 μg/kg body weight per day.
The American Conference of Governmental Industrial Hygienists (ACGIH) recommends that metallic mercury exposures be limited to an average of 0.025 mg/m3 over an 8-hour workday.
[22] While much is generally known about mercury bioaccumulation and biomagnification, the process is extremely complex and involves complicated biogeochemical cycling and ecological interactions.
The two main pathways by which terrestrial plants can be exposed to mercury are uptake from soils into the roots and absorption directly from the air.
[24] Inorganic mercury released into the atmosphere is converted to methylmercury by the action of microbes that live in aquatic systems including lakes, rivers, wetlands, sediments, soils and the open ocean.
The primary piece of federal legislation governing the airborne release of mercury in the United States is the Clean Air Act.
[32] However, as of early 2011, no federal limits of mercury from coal and oil-fired electric utility steam generating units (EGUs) were on the books.
[33] This push gained further impetus in 2005, when the EPA released a report titled The Nata Inventory Modified for the Toxics Rule 2005 Base Year,[34] which linked 2/3's of the total amount of mercury released in 1990 to three source categories: stationary power plants, municipal waste combustors, and medical waste incinerators.
Additionally, according to the report the two latter categories saw 96% and 98% reductions of total mercury release, respectively, between the 15-year period between 1990 and 2005 while power plant emissions fell by only 10%.
In its place, the EPA issued a rule to permanently cap and reduce mercury emissions from stationary power facilities.
[36] In December 2008, the D.C. Court of Appeals vacated the CAMR on the grounds that it illegally exempts utilities from the list of regulated source categories under the MACT standards.
[46] NPDES permits include technology-based effluent limitations, which are based on the performance of control and treatment technologies.
[58][47]: 5-44–5-49 Mercury (and other metals) that are discharged to POTWs are frequently typically removed within the treatment system and end up in the sewage plant's sludge.
The ADA study and other research supported EPA's 2014 estimate that dental offices—over 100,000 nationwide—were annually sending 4.4 tons of mercury to POTWs.
[66][67] Resource Conservation and Recovery Act (RCRA) regulations outline specific classification and disposal requirements for products and wastes that contain mercury.
[40] On February 23, 2011, following ten years of litigation, the EPA released scaled-back air emission rules for industrial boilers and solid waste incinerators.
[40] Since 1979 the Convention on Long-range Transboundary Air Pollution has addressed some of the major environmental problems of the UNECE region through scientific collaboration and policy negotiation.
The Convention has been extended by eight protocols that identify specific measures to be taken by Parties to cut their emissions of air pollutants.
[76] Most of the priorities for action to reduce risk from mercury have been defined within partnerships: Artisanal and small-scale gold mining (ASGM) is a complex global development issue.
[79] Transition success has been demonstrated in thermometers, switches and relays, batteries other than button cells, thermostats, HID auto discharge lamps, and sphygmomanometers.
Policies designed to decrease the production, use and trade of mercury must be accompanied by access to viable, safe and secure long term storage.
It provides a standardized methodology and accompanying database enabling the development of consistent national and regional mercury inventories.
