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Manganese

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Introduction

Manganese is a naturally occurring substance found in many types of rock. Pure manganese is a silver-colored metal, somewhat like iron in its physical and chemical properties. Manganese does not occur in the environment as the pure metal. Rather, it occurs combined with other chemicals such as oxygen, sulfur, and chlorine. These compounds are solids that do not evaporate. However, small dust particles of the solid material can become suspended in air. Some manganese compounds can dissolve in water, and low levels of these compounds are normally present in lakes, streams, and the ocean.

Rocks containing 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, as an ingredient in some ceramics, pesticides, and fertilizers, and in dietary supplements.

Fate & Transport

Manganese can change from one compound to another (either by natural processes or by man's activities), but it does not break down or disappear in the environment.

Exposure Pathways

Because manganese is a natural component in the environment, you are always exposed to low levels of it in water, air, soil, and food. In drinking water, levels are usually about 0.004 parts manganese per million parts of water (ppm). In air, levels are usually about 0.02 micrograms manganese per cubic meter of air (ug/m3). Levels in soil usually range from 40 to 900 ppm. Manganese is also a normal component of living things, including both plants and animals, so manganese is present in foods. For nearly all people, food is the main source of manganese, and usual daily intakes range from about 2,000 to 9,000 ug/day. The exact amount you take in depends on your diet.

You are most likely to be exposed to higher-than-normal levels of manganese 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. In these factories, you would be exposed to manganese mainly by breathing in manganese dust. If you live near such a factory, you could also be exposed to higher-than-average levels of manganese dust in the outside air, although the amounts would be much lower than in the factory. You might be exposed to higher-than-average levels if you live near a coal or oil-burning factory, or close to a major highway, because manganese is released into air when fossil fuels are burned. If manganese compounds from a factory or a waste site get into water, you could be exposed to higher-than-average levels by drinking the water.

Metabolism

If you live near a hazardous waste site, you could be exposed to manganese in soil or water, or to manganese-containing dust particles in air. If you get manganese-contaminated soil or water on your skin, very little will enter your body. If you swallow manganese in water or in soil, most of the manganese is excreted in the feces. However, about 3-5 percent is usually taken up and kept in the body. If you breathe air containing manganese dust, many of the dust particles will be trapped in your lungs. Some of the manganese in these particles may then dissolve in the lungs and enter the blood. The exact amount that does this is not known. Particles that do not dissolve will be carried in a sticky layer of mucus out of the lungs to the throat, where they will be swallowed into the stomach.

Because manganese is a regular part of the human body, the body normally controls the amount that is taken up and kept. For example, if large amounts are eaten in the diet, the amount that is taken up in the body becomes smaller. If too much does enter the body, the excess is usually removed in the feces. Therefore, the total amount of manganese in the body usually tends to stay about the same, even when exposure rates are higher or lower than usual. However, if too much manganese is taken in, the body may not be able to adjust for the added amount.

Health Effects

Eating a small amount of manganese each day is important in maintaining your health. The amount of manganese in a normal diet (about 2,000-9,000 ug/day) seems to be enough to meet your daily need, and no cases of illness from eating too little manganese have been reported in humans. In animals, eating too little manganese can interfere with normal growth, bone formation, and reproduction.

Too much manganese, however, can cause serious illness. Although there are some differences between different kinds of manganese, most manganese compounds seem to cause the same effects. Manganese miners or steel workers exposed to high levels of manganese dust in air may have mental and emotional disturbances, and their body movements may become slow and clumsy. This combination of symptoms is a disease called manganism. Workers usually do not develop symptoms of manganism unless they have been exposed for many months or years. Manganism occurs because too much manganese injures a part of the brain that helps control body movements. Some of the symptoms of manganism can be reduced by medical treatment, but the brain injury is permanent.

It is not certain whether eating or drinking too much manganese can cause manganism or not. In one report, humans who drank water containing high levels of manganese developed symptoms similar to those seen in manganese miners or steel workers, but it is not certain if the effects were caused by manganese alone. In another report, people who drank water with above average levels of manganese seemed to have a slightly higher frequency of symptoms such as weakness, stiff muscles, and trembling of the hands. However, these symptoms are not specific for manganese, and might have been caused by other factors. Studies in animals have shown that very high levels of manganese in food or water can cause changes in the brain. This information suggests that high levels of manganese in food or water might cause brain injury, but it does not appear that this is of concern to people exposed to the normal amounts of manganese in food, water, or air. The chances of harm from exposure near a waste site can only be evaluated on a site-by-site basis.

Breathing too much manganese dust can also cause irritation of the lungs. Sometimes this makes breathing difficult and it can also increase the chances of getting a lung infection, such as pneumonia. However, this can happen from breathing in many different kinds of dust particles, not just those that contain manganese.

A common effect in men who are exposed to high levels of manganese dust in air is impotence. As a result, men exposed to high levels may not be able to father children. Studies in animals show that too much manganese may also injure the testes. Much less is known about the effects of too much manganese in women. Studies in animals suggest that females may not be as sensitive to manganese as males, but this is not certain.

There is not much information on whether manganese can cause birth defects. One study in humans suggests that high exposures to manganese in the environment might increase the chances of birth defects, but other factors besides manganese might have been responsible. One study in animals shows that exposure of pregnant females to high levels of manganese in air can lead to changes in behavior of the offspring. Since there are so few studies on this, more research is needed to determine the importance of these observations.

No studies have been done to determine if breathing manganese dust causes cancer. Some studies in animals suggest that eating high amounts of manganese might increase the chances of getting cancer. However, only a few animals in these studies got cancer, and it was difficult to tell if the tumors were really caused by the excess manganese. Thus, there is little evidence to suggest that cancer is a major concern for people exposed to manganese in the environment or near waste sites. The EPA has determined that manganese is not classifiable as to human carcinogenicity.

There is no information on any human or animal health effects from skin contact with manganese.

Information excerpted from:

Toxicological Profile for Manganese July 1992

Agency for Toxic Substances and Disease Registry
U.S. Dept. of Health and Human Services