M

Manganese

CASRN 7440-39-3

Physical Properties

Manganese is a naturally occurring substance found in many types of rock. Pure manganese is a silver-colored metal. However, it does not occur in the environment as a pure metal but is combined with other elements in compounds. Some of the common inorganic compounds containing manganese are: manganese chloride, manganese sulfate, manganese acetate, manganese oxide, manganese dioxide, potassium permanganate, manganese phosphate, and manganese silicate.

Uses

Rocks with high levels of manganese compounds are mined and used to produce manganese metal. This manganese metal is mixed with iron to make various types of steel. Some manganese compounds are used in the production of batteries, in dietary supplements, and as ingredients in some ceramics, pesticides, and fertilizers. Manganese is also a component of an automobile fuel additive. Manganese is an essential trace element and is necessary for good health. The human body typically contains small quantities of manganese, and under normal circumstances, the body controls these amounts so that neither too little nor too much is present.

Sources of Exposure in Iowa

Manganese is present in soil at levels that average almost 1,500 milligram per kilogram (mg/kg) or 1,500 parts per million (ppm). Manganese is also a normal part of living things, including both plants and animals, so it is present in foods. For nearly all people, food is the main source of manganese, and usual daily intakes range from about 1 to 10 mg/day. A person is most likely to be exposed to higher-than-usual levels of manganese or manganese containing chemicals if you work in a factory where manganese metal is produced from manganese ores or where manganese compounds are used to make steel or other products. A person might also be exposed to higher-than-usual levels if you live near a coal- or oil-burning factory because manganese is released into the air when these fossil fuels are burned.

Health Effects from Large Acute Exposures

Exposure to high levels of manganese dust in the air may cause mental and emotional disturbances, and body movements may become slow and clumsy. This combination of symptoms is called “manganism” and would normally only develop if the exposure to high levels of manganese occurred over the course of many months or years.

Health Effects from Smaller Chronic Exposures

Chronic exposure to lower levels of manganese has been linked to deficits in the ability to perform rapid hand movements and some loss of coordination and balance, along with an increase in reporting mild symptoms such as forgetfulness, anxiety, or insomnia. What is still unknown is the lowest level at which adverse neurological effects can occur after long-term exposures to manganese. There is not enough information to classify manganese as carcinogenic.

Protection from Exposure

Individuals who work in an industry that may be exposed to elevated levels of manganese dust should wear respiratory protection when necessary.

Mercury

CASRN 7439-97-6

Physical Properties

Elemental (metallic) mercury is the pure form; it is not combined with other elements. Mercury occurs naturally in the environment and exists in several forms: elemental mercury; inorganic mercury or mercury salts; and organic mercury, most commonly as methylmercury. Methylmercury is the subject of another fact sheet. Elemental mercury is a heavy silver liquid at room temperature, and has a very high vapor pressure (volatizes easily). Elemental mercury vapors are colorless and odorless. People who have breathed mercury vapors have reported a metallic taste.

Uses

Elemental mercury is used in thermometers, barometers, batteries, and electrical switches. It is used in the production of chlorine gas and caustic soda and in extracting gold from ore or articles containing gold. Silver-colored dental fillings (dental amalgams) typically contain about 50 percent elemental mercury. Elemental mercury is still used in some herbal or religious remedies in Latin America and Asia, and in rituals or spiritual practices in some Latin American and Caribbean religions such as Voodoo, Santeria, and Espiritismo. Other chemicals containing mercury are still used as antibacterials. These products include mercurochrome, which contains 2%, and thimerosal and phenylmercuric nitrate, which are used in small amounts as preservatives in some prescription and over-the-counter medicines.

Sources of Exposure in Iowa

Because mercury occurs naturally in the environment, everyone is exposed to very low levels of mercury in air, water, and food. Spills of elemental mercury from broken thermometers, barometers, or damaged electrical switches may result in exposure to mercury vapors from indoor air. A small spill of elemental mercury in an enclosed room can produce high levels of mercury in the air. A potential source of exposure to metallic mercury for the general population is mercury released from dental amalgam fillings. Exposure to very small amounts of mercury, such as from dental amalgam fillings, does not necessarily pose a health risk. Those who use mercury in herbal remedies or rituals will be exposed to mercury from contaminated indoor air.

Health Effects from Large Acute Exposures

Less than 0.01% of swallowed metallic mercury (from a broken oral thermometer, for example), enters the body through the stomach and intestines. Even when a larger dose of metal mercury is swallowed, very little enters the body. If mercury vapors are breathed, however, about 80% enters bloodstream directly from the lungs, then rapidly travels to other parts of the body, including the brain and kidneys. Permanent damage to the brain has been shown from exposure to sufficiently high levels of metallic mercury. Metallic mercury vapors may affect many areas of the brain and their associated functions, resulting in a variety of symptoms. These include personality changes (irritability, shyness, nervousness), tremors, changes in vision (constriction or narrowing of the visual field), deafness, muscle incoordination, loss of sensation, and memory difficulties.

Health Effects from Smaller, Chronic Exposures

Longer-term occupational exposure to metallic mercury is associated with the development of kidney disease, resulting in excess protein in urine. Exposure to mercury vapor has also given rise to skin irritation. Studies have failed to show a correlation between elemental mercury vapor exposure and cancer.

Protection from Exposure

Special care should be taken in cleaning up a mercury spill, to avoid inhaling elemental mercury. A vacuum cleaner or a broom should never be used to clean up a mercury spill. 

Methylmercury

CASRN 22967-92-6

Physical Properties

Organic mercury (organomercurials) is formed when a mercury atom bonds to a carbon atom via a covalent bond. Methylmercury is considered the most toxic of the organomercurials. Methylmercury exists as a positive ion and is soluble in water. Methylmercury is formed by microorganisms in water that convert inorganic mercury to organic mercury. Methylmercury can bio-accumulate in organisms in the natural environment.

Uses

Organic mercury has been used as a fungicide in the treatment of seeds, and in exterior paints. It has been used as preservative for timber, and as a disinfectant.

Sources of Exposure in Iowa

The main source of exposure to methylmercury is the food people eat, mainly fish. Both marine and freshwater fish can contain methylmercury. Most of the mercury in fish is believed to originate from the atmosphere, contributed by both natural and manmade sources (such as coal-fired power plants). Bacteria in streams, lakes and oceans cause chemical changes that transform the inorganic mercury in the water into methylmercury. Fish absorb the methylmercury as they feed in the waters. Methylmercury accumulates in the muscle tissue of some fish more than others, depending on what they eat, how long they live, and how high they are in the food chain. A person’s exposure to methylmercury will depend on the methylmercury content of the fish’s tissue, and the amount of fish the person eats.

Health Effects from Large Acute Exposures

Methylmercury is more easily absorbed through the gastrointestinal tract than metallic mercury. Exposure to large amounts of methylmercury is rare, but has happened in the case of surface water pollution by mercury effluent in Japan in 1956 and 1964, and from eating contaminated grain in Iraq in 1956 and 1960. These examples of exposure to high concentrations of mercury produced the following symptoms: memory loss, depression, stumbling gait, numbness and sensation of “pins and needles” in extremities, tremor of hands, face, or legs.

Health Effects from Smaller, Chronic Exposures

Longer-term exposure to methylmercury results from eating fish regularly. For most people, eating fish regularly will not result in exposure to very high levels of methylmercury. Most of the concern about mercury in fish is related to potential adverse neurodevelopment outcomes (intelligence, motor skills, behavior) in children of mothers who ate large amounts of fish before and during pregnancy. Current research seems to indicate that the health benefits of including fish in the diet most likely outweigh the risks of methylmercury exposure. Methylmercury is classified as a possible human carcinogen.

Protection from Exposure

Since most methylmercury exposure results from eating fish, the Iowa Departments of Public Health and Natural Resources have developed a program to advise Iowa residents about fish species with high levels of methylmercury and other environmental contaminants. Information on the fish contaminant advisory program is included in the list of internet links below.