ERTH 308 Lecture 16: Mercury in the Environment PDF

ERTH 308: Lecture 16 Mercury in the Environment Learning Objectives 1) Name several ways that mercury can get into the atmosphere or waterways. 2) State 3 different forms of mercury, and explain how methylmercury is formed. 3) Define the term biomagnification and sta...

ERTH 308: Lecture 16 Mercury in the Environment Learning Objectives 1) Name several ways that mercury can get into the atmosphere or waterways. 2) State 3 different forms of mercury, and explain how methylmercury is formed. 3) Define the term biomagnification and state how this happens in aquatic animals. Name several fish that have high and low levels of mercury. 4) State several health effects of mercury poisoning. 5) Describe the case studies of mercury poisoning in Iraq, Japan, and Ontario. 6) State the composition of dental amalgam, its use, and its positive and negative aspects. How Does Mercury Get into the Environment? Mercury is a chemical element that can be found in small concentrations in many rocks and is the main component of the mineral cinnabar (HgS). Natural background levels can be detected in soils, air, and water around the world. Mercury is present in gases emitted by volcanoes. Mining and industrial applications for the metal have increased significantly since the industrial revolution. Base metal smelting and gold mining both create mercury vapor, which is a potential hazard. Mercury mines pose an environmental concern. Cinnabar https://www.dakotamatrix.com/images/products/cinnabar31980c.jpg How Does Mercury Get into the Environment? In 1990, three industry sectors made up approximately two-thirds of total U.S. mercury emissions: medical waste incinerators, municipal waste combustors, and coal-fired power plants. The first two of these sectors have been subject to emissions standards for years and as a result have reduced their mercury emissions Sources of Mercury Emissions in the U.S. 1990 Emissions Industrial 2005 Emissions Percent tons per year Category (tpy) Reduction (tpy) Power Plants 59 53 10% Municipal Waste 57 2 96% Combustors Medical Waste 51 1 98% Incinerators https://www.epa.gov/mats/cleaner-power-plants  How Does Mercury Get into the Environment? Coal- and oil-fired power plants emit harmful pollutants, including mercury, metallic toxins, and acid gases. In 2011 the U.S. EPA introduced legislation to: prevent 90 percent of the mercury in coal burned in power plants from being emitted to the air reduce 88 percent of acid gas emissions from power plants reduce 41 percent of sulfur dioxide emissions from power plants https://www.epa.gov/mats/cleaner-power-plants  Mercury in Aquatic Species Mercury is converted to methylmercury by bacteria in sediments. Methylmercury biomagnifies in aquatic animals, and the concentrations can increase by a million fold in animals at the top of the food chain. Methylmercury is 100% absorbed through the gastro- intestinal tract and distributed through the body Methylmercury formula [H3CHg]+. It is the major source of organic mercury for all humans. https://en.wikipedia.org/wiki/Methylmercury http://en.wikipedia.org/wiki/File:MercuryFoodChain-01.png  YouTube: Mercury-contaminated Fish | Consumer Reports (1:44) http://www.maine.gov/dhhs/eohp/fish/hgposter.htm http://www.kyenvironmentalfoundation.org/uploads/1/8/5/9/18595042/9813206_orig.png  Health Effects of Mercury As a reproductive toxin and a potent neurotoxin, mercury affects the brain and the central nervous system. Pregnant women, women of childbearing age, and small children are at greatest risk. Mercury can cross the placenta and cause irreparable neurological damage to the fetus. In March 2001 a study by the CDC found that 1 in 10 women in the U.S. have mercury levels high enough to cause neurological damage in their children - about 400,000 babies a year. http://pubs.usgs.gov/fs/1995/fs216-95/images/f5.png  Case Study: 1971 Iraq poison grain disaster https://en.wikipedia.org/wiki/1971_Iraq_poison_grain_disaster The 1971 Iraq poison grain disaster was a mass methylmercury poisoning incident that began in late 1971. Grain treated with a methylmercury fungicide and never intended for human consumption was imported into Iraq as seed grain from Mexico and the United States. Due to a number of factors, including foreign-language labelling and late distribution within the growing cycle, this toxic grain was consumed as food by Iraqi residents in rural areas. People suffered from paresthesia (numbness of skin), ataxia (lack of coordination of muscle movements) and vision loss. The recorded death toll was 459 people. By Source, Fair use, https://en.wikipedia.org/w/index.php?curid =27670253  Case Study: Minamata, Japan https://en.wikipedia.org/wiki/Minamata_disease Minamata disease is a neurological syndrome caused by severe mercury poisoning. Symptoms include ataxia, numbness in the hands and feet, general muscle weakness, loss of peripheral vision, and damage to hearing and speech. It was caused by the release of methylmercury in the industrial wastewater from the Chisso Corporation's chemical factory, which continued from 1932 to 1968. This highly toxic chemical accumulated in shellfish and fish in Minamata Bay, which, when eaten by the Protestors at the gates local population, resulted in mercury poisoning. of the Chisso factory As of March 2001, 2,265 victims had been (A. M. Smith) officially recognised (1,784 of whom had died). YouTube: The 'Dancing Cat' Disaster of Japan | Minamata Explained (5:24)  Case Study: First Nations people in Ontario https://en.wikipedia.org/wiki/Ontario_Minamata_disease Ontario Minamata disease is a neurological syndrome caused by severe mercury poisoning. It severely affected two First Nation communities (Grassy Narrows and Whitedog) in Northwestern Ontario following consumption of local fish contaminated with mercury, and one First Nation in Southern Ontario due to illegal disposal of industrial chemical waste. In the 1960’s and 1970’s, Dryden Chemical Company dumped over 9,000 kg of mercury into the Wabigoon-English river system. This mercury was transformed to methylmercury by bacteria in the river. Japanese researchers found more than 90 per cent of the populations show signs of poisoning. 28% of adults in Grassy Narrows have attempted suicide, more than double the rate of other First Nations. https://www.cbc.ca/news/canada/thunder-bay/grassy-narrows-health-report-release-1.4675091 YouTube: How mercury exposure has affected Grassy Narrows residents (4:12)  Mercury and Dental Amalgam What is dental amalgam? Dental amalgam is a dental filling material used to fill cavities caused by tooth decay. It has been used for more than 150 years in hundreds of millions of patients around the world. Dental amalgam is a mixture of metals, consisting of liquid (elemental) mercury and a powdered alloy composed of silver, tin, and copper. Approximately 50% of dental amalgam is elemental mercury by weight. The chemical properties of elemental mercury allow it to react with and bind together the silver/copper/tin alloy particles to form an amalgam. Dental amalgam fillings are also known as “silver fillings” because of their silver-like appearance. Despite the name, "silver fillings" do contain elemental mercury. https://www.fda.gov/medicaldevices/productsandmedicalprocedures/de ntalproducts/dentalamalgam/ucm171094.htm  Mercury and Dental Amalgam How do dentists make dental amalgam? When placing dental amalgam, the dentist first drills the tooth to remove the decay and then shapes the tooth cavity for placement of the amalgam filling. Next, under appropriate safety conditions, the dentist mixes the powdered alloy with the liquid mercury to form an amalgam putty. (These components are provided to the dentist in a capsule as shown in the graphic.) This softened amalgam putty is placed and shaped in the prepared cavity, where it rapidly hardens into a solid filling. Is the mercury in dental amalgam the same as the mercury in some types of fish? No. There are several different chemical forms of mercury: 1) elemental mercury Hg 2) inorganic mercury (e.g. HgS, HgO, HgCl2) 3) organic mercury (e.g. methylmercury) – Hg combined with carbon The form of mercury associated with dental amalgam is elemental mercury, which can slowly release mercury vapor. The form of mercury found in fish is methylmercury, a type of organic mercury. Mercury vapor is mainly absorbed by the lungs. Methylmercury is mainly absorbed through the digestive tract. The body processes these forms of mercury differently and has different levels of tolerance for mercury vapor and methylmercury. https://www.fda.gov/medical-devices/dental-devices/dental-amalgam-fillings What should I know before getting a dental amalgam filling? Deciding what filling material to use to treat dental decay is a choice that must be made by you and your dentist. Benefits: Dental amalgam fillings are strong and long-lasting, so they are less likely to break than some other types of fillings. Dental amalgam is the least expensive type of filling material. Risks: Dental amalgam contains elemental mercury. It releases low levels of mercury in the form of a vapor that can be inhaled and absorbed by the lungs. High levels of mercury vapor exposure are associated with adverse effects in the brain Are dental amalgam fillings dangerous? The FDA in the U.S. has reviewed the best available scientific evidence to determine whether the low levels of mercury vapor associated with dental amalgam fillings are a cause for concern. Based on this evidence, FDA considers dental amalgam fillings safe for adults and children ages 6 and above. Clinical studies in adults and children ages 6 and above have found no link between dental amalgam fillings and health problems. If I am concerned about the mercury in dental amalgam, should I have my fillings removed? If your fillings are in good condition and there is no decay beneath the filling, FDA does not recommend that you have your amalgam fillings removed or replaced. Removing sound amalgam fillings results in unnecessary loss of healthy tooth structure, and exposes you to additional mercury vapor released during the removal process. Is dental amalgam used in Canada? Health Canada currently does not restrict dental amalgam. Scientific studies have not verified that dental amalgam is causing illness in the general population. It has been known for some time that amalgam fillings release minute amounts of mercury vapour, especially with chewing, and that this mercury can be absorbed, reach body organs, and cross the placenta. This is also true of mercury absorbed from natural sources, such as food. Health Canada estimates that for the average Canadian adult 20 to 59 years old the amount of mercury absorbed by the body from all sources is about nine millionths of a gram per day. Of this total dental amalgam is estimated to contribute about three millionths of a gram per day. Canadian Dental Association https://www.cda-adc.ca/en/oral_health/faqs/dental_amalgam_faqs.asp Health Canada https://www.canada.ca/en/health-canada/services/drugs-health- products/reports-publications/medical-devices/safety-dental-amalgam- health-canada-1996.html It is our conclusion that although amalgam contributes detectable amounts of mercury to the body, these levels do not approach those recognized to cause illness. However, surveys by the American Dental Association have shown that over half the population believes that dental amalgam could cause health problems. YouTube the term Mercury Dental Amalgam http://cdn.patch.com/users/11156/2013/04/T800x600/d5a1561e13045d64ad50 77525de51960.jpg