Mercury
8.8 Regulatory standards8.7.2 Organic mercury
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higher exposure concentrations resulting in a shorter latency period. The exact bio- logical mechanisms underlying this latency period are unclear. Some researchers have suggested that latency not only reflects the time to reach accumulation of MeHg in the brain, but also reflects achievement of a threshold wherein enough tissue is destroyed so that the capacity of the central nervous system to compen- sate for the damage is overwhelmed. Observation of long latencies following ces- sation of MeHg administration in animals and humans, however, may also derive from long-term demethylation of MeHg to inorganic mercury in the brain.
There are numerous sources of metallic mercury in the home and workplace. The best advice is to dispose properly of any product with mercury and above all avoid exposure, especially inhalation, particularly for young children. In the past few years, many industries have worked to reduce the use of mercury in products. In addi- tion, some states have also restricted the use of mercury or have developed pro- grams to aid in the recycling and recovery of mercury. The average household fever thermometer contains about 3 grams of mercury, which does not seem like much, until it is multiplied by the 105 million households in the United States. Even if only half of the households had a mercury thermometer, the total amount of mer- cury is very large. Additional sources of atmospheric mercury include coal-fueled electric generation facilities, hospital waste, fluorescent light bulbs, dental surgeries, and even crematoriums. Efforts are being made on a number of fronts to mandate reduction in mercury released into the atmosphere and in general reduce the use of mercury. As individuals, we must also work to ensure mercury products are properly recycled and take action to reduce atmospheric mercury.
If a mercury spill occurs, it is very important to ventilate the area and notuse a vacuum cleaner to clean up the mercury. A vacuum cleaner will only warm and dis- perse the mercury in the room. Collect all the mercury and place in a sealed con- tainer and take it to an appropriate disposal site. If it is a large spill, professionals must be called. Table 8.2 lists some of the more common sources of metallic mercury.
The primary concern with organic mercury is methyl mercury in fish. Children and women of childbearing age should be cautious about consuming fish known to accumulate mercury such as tuna, shark, swordfish, and pike. Local fish consump- tion advisories should be followed.
The liquid silver inorganic mercury evaporates into the atmosphere. When inhaled, mercury crosses easily into the blood and then to the brain, thus the primary 8.8.1 Inorganic mercury
8.8 Regulatory standards
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Table 8.2 Common sources of metallic mercury Switches in gas furnaces, heaters, etc.
Major household appliances (tilt switches in freezers, dryers, etc.) Irons (tilt switches)
Automobile switches
Bilge pumps, sump pumps, etc. (float switches) Dental amalgam
Measuring devices and laboratory equipment, such as barometers, manometers, etc.
Medical equipment and supplies Fluorescent lights
Batteries Computers Novelty items Film pack batteries
hazard concern is from inhalation. Metallic mercury is poorly absorbed after oral ingestion, thus this is much less hazardous than inhalation. Below are some of the advisories on mercury vapor inhalation.
n ATSDR – minimal risk level (MRL) – 0.2 µg/m3
n OSHA – permissible exposure limits (PEL)-TWA – 0.05 mg/m3
n ACGIH – threshold limit value (TLV)-TWA – 0.05 mg/m3
The primary human exposure to methyl mercury is from consumption of contam- inated fish. The most sensitive population is the developing fetus or infant due to the effects of methyl mercury on the nervous system (neurotoxic) and developmental effects. Exposure limits and fish consumption advisories are directed at pregnant women, women of childbearing age, and children. All agencies also recognize that fish con- sumption has many nutritional benefits and is an important part of many people’s diet.
Nevertheless, the widespread distribution of mercury and subsequent bioaccumula- tion of methyl mercury requires that many agencies have developed recommenda- tion for levels of mercury in fish. Below is a list of some of these recommendations, but it is very important to consult the local fish consumption advisories.
n FDA – 1 ppm in commercially harvested fish (i.e. tuna fish)
n FDA – action level – 0.47 µg/ kg per day
n ATSDR – minimal risk levels (MRLs) – 0.30 µg/ kg per day
n Washington State – total daily intake – 0.035–0.08 µg/ kg per day
n EPA – Reference Dose (RfD) – 0.1 µg/ kg per day
(In 1997 the EPA estimated that 7% of the women of childbearing age in the United States exceed the established RfD of 0.1 µg/ kg per day.)
n 41 states have issued over 2000 fish consumption advisories related to mercury
8.8.2 Organic methyl mercury
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Recommendation from the State of Washington (US)
n Women of childbearing age should limit the amount of canned tuna they eat to about one can per week (six ounces.) A woman who weighs less than 135 pounds should eat less than one can of tuna per week.
n Children under six should eat less than one half a can of tuna (three ounces) per week. Specific weekly limits for children under six range from one ounce for a twenty pound child, to three ounces for a child weighing about sixty pounds.
See: http://www.doh.wa.gov/fish/ FishAdvMercury.htm
Mercury is a potent toxicant and a global environmental pollutant. There is over- whelming data that demonstrate that low levels of exposure to methyl mercury or mercury vapor damage the nervous system, particularly the sensitive developing ner- vous system. Mercury vapor travels around the globe in the atmosphere. Once on the ground or in the water, it is converted to methyl mercury and accumulates in the food supply, contaminating fish, a main source of protein for many people. There needs to be a global effort to reduce human release of mercury into the environ- ment. The production, sale, and use of mercury must be restricted in recognition of the health effects of mercury. Mercury use in consumer products, such as ther- mostats, thermometers, and jewelry should be eliminated and replaced with already well-established and cost-effective alternatives. Coal contains low levels of mer- cury that are released as the coal is burned. The discharge from coal-fired electric generating facilities can be greatly reduced with current technology. Finally there must be ongoing monitoring of mercury contamination in fish and appropriate advisories issued to protect sensitive populations. This will involve education of the consumer about limiting the consumption of fish that accumulate mercury.
Summary of recommendations on mercury
n Reduce global environmental release
n Restrict global production and sale and use
n Clean up contaminated sites
n Reduce mercury emission from coal-fired electric power facilities
n Reduce or eliminate use in consumer products (cars, thermometers, ther- mostats, jewelry)
n Advise women of childbearing age on fish consumption
n Monitor mercury levels in fish 8.9 Recommendation and conclusions
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n A Small Dose of Mercury presentation material. Online. Available HTTP:
<http://www.crcpress.com /e_products/> and follow the links to downloads and then the catalog number TF1691.
Web site contains presentation material related to health effects of mercury.
n United Nations Environment Program’s Global Mercury Assessment. Online.
Available HTTP: <http://www.chem.unep.ch/mercury/> (accessed: 5 April 2003).
This program aims to develop a global assessment of mercury and its compounds, including an outline of options for addressing any significant global adverse impacts of mercury.
n World Health Organization – Mercury. Online. Available HTTP: <http://
www.who.int/pcs/cicad/full_text/cicad50.pdf (accessed: 5 April 2003).
Document on the health effects of organic and inorganic mercury.
n Health Canada – Mercury. Online. Available HTTP:
<http://www.hc-sc.gc.ca/english/iyh/environment/mercury.html>
(accessed: 9 April 2003).
Health Canada provides information on the health effects and environmental distribution of mercury.
n US Food and Drug Administration (FDA) – Advisory on Methyl Mercury and Fish. Online. Available HTTP: <http://www.cfsan.fda.gov/~lrd/tphgfish.html>
(accessed: 5 April 2003).
Site has recent FDA consumer information on methyl mercury.
n US Environmental Protection Agency (EPA):
1. EPA – Main site on Mercury. Online. Available HTTP: <http://
www.epa.gov/mercury/> (accessed: 5 April 2003).
2. EPA Advice on Eating Non Commercial Fish – Advice for Women and Children. Online. Available HTTP: <http://www.epa.gov/waterscience/
fishadvice/advice.html> (accessed: 5 April 2003).
3. EPA Fact Sheet: Fish Caught by Family and Friends – Advice for Women and Children. Online. Available HTTP: <http://www.epa.gov/waterscience/
fishadvice/factsheet.html> (accessed: 5 April 2003).
4. EPA (1997). Mercury Study Report to Congress. Office of Air Quality Planning and Standards and Office of Research and Development.
EPA-452-R-97 –003 through –010 (Volumes I–VIII0. Online. Available HTTP: <http://www.epa.gov/oar/mercury.html> (accessed: 5 April 2003).
5. EPA Integrated Risk Information System. Online. Available HTTP:
<http://www.epa.gov/iris/index.html>
8.10.3 North American agencies 8.10.2 European, Asian, and international agencies 8.10.1 Slide presentation 8.10 More information and references
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n US Agency for Toxic Substance Disease Registry (ATSDR) – Toxicology Profile Series on Mercury. Online. Available HTTP: <http://www.atsdr.cdc.gov/
toxprofiles/tp46.html> (accessed: 5 April 2003).
ATSDR produces toxicology profile documents on many compounds includ- ing mercury.
n US Agency for Toxic Substance Disease Registry (ATSDR) – Toxicology Pro- file Series on Mercury. Online. Available HTTP: <http://www.atsdr.cdc.gov/
mrls.html> (accessed: 5 April 2003).
ATSDR’s list of minimal risk levels.
n US Department of Labor – Occupational Safety & Health Administra- tion (OSHA). Online. Available HTTP: <http://www.osha.gov/> (accessed:
5 April 2003).
n US Geological Survey (USGS). Online. Available HTTP: <http://www.usgs.gov/>
(accessed: 5 April 2003).
Site has maps and supply information on mercury.
n US National Research Council (NRC) – Toxicological Effects of Methylmercury.
Online. Available HTTP: <http://www.nationalacademies.org/publications/>
(accessed: 5 April 2003).
The full NRC report on mercury can be read on the web.
n Washington State Department of Health – Fish Facts for Health Nutrition.
Online. Available HTTP: <http://www.doh.wa.gov/fish/> (accessed: 5 April 2003).
Site has information on Washington State’s advisory of fish consumption and mercury.
n The Mercury Policy Project (MPP). Online. Available HTTP: <http://
www.mercurypolicy.org/> (accessed: 5 April 2003).
“MPP works to raise awareness about the threat of mercury contamination and promote policies to eliminate mercury uses, reduce the export and trafficking of mercury, and significantly reduce mercury exposures at the local, national, and international levels.”
n American Conference of Governmental Industrial Hygienists (ACGIH®).
Online. Available HTTP: <http://www.acgih.org/home.htm> (accessed: 5 April 2003).
“ACGIH is a member-based organization and community of professionals that advances worker health and safety through education and the development and dissemination of scientific and technical knowledge.”
n Clarkson, T. (1998). Methylmercury and fish consumption: Weighing the risks.
Can Med Assoc J, 158, 1465 –1466.
n Clarkson, T. W. (2002). The three modern faces of mercury. Environ Health Perspect, 110 Suppl 1, 11–23.
8.10.5 References
8.10.4 Non-government organizations
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n Gilbert, S. G. and Grant-Webster, K. S. (1995). Neurobehavioral effects of developmental methylmercury exposure. Environ Health Perspect, 6, 135–142.
n Kales, S. N. and Goldman, R. H. (2002). Mercury exposure: current concepts, controversies, and a clinic’s experience. J Occup Environ Med, 44(2), 143 –154.
n Martin, D. M., DeRouen, T. A. and Leroux, B. G. (1997). Is mercury amal- gam safe for dental fillings? Washington Public Health, 15(Fall), 30 –32.
n MMWR. (1996a). Mercury exposure among residents of a building formerly used for industrial purposes – New Jersey, 1995. Morbidity Mortality Weekly Report, 45(20), 422– 424. Online. Available HTTP: <http://www.cdc.gov/
mmwr/preview/mmwrhtml/00041880.htm> (accessed: 5 July 2003).
n MMWR. (1996b). Mercury poisoning associated with beauty cream – Arizona, California, New Mexico and Texas, 1996. Morbidity Mortality Weekly Report, 45(29), 633 – 635. Online. Available HTTP: <http://www.cdc.gov/
mmwr/preview/mmwrhtml/00043182.htm> (accessed: 5 July 2003).
n Putman J. (1972). Quicksilver and slow death. National Geographic 142(4), 507–527.
n Zeitz, P., Orr, M. F. and Kaye, W. E. (2002). Public health consequences of mercury spills: Hazardous Substances Emergency Events Surveillance system, 1993 –1998. Environ Health Perspect, 110(2), 129 –132.