Bromomethane (also called methyl bromide) is a colorless gas without much smell. Some bromomethane is formed in the ocean, probably by algae or kelp. However, most is made by humans to kill various pests (for example, rats, insects, or fungi) that might be present in homes, foods, or soil. Some bromomethane is also used to make other chemicals.
Bromomethane is usually stored in sealed containers to keep it from evaporating. If leaking containers of bromomethane are put in a waste site, most of the bromomethane will probably escape into the air. Small amounts might leak into the soil or pass through the soil and dissolve in underground water. Bromomethane has been found in underground water at two hazardous waste sites on the NPL.
Bromomethane breaks down in the environment to other chemicals. In air, it usually takes about 11 months for half the bromomethane that was released to disappear. In underground water, it usually takes about 1 month for half the bromomethane to break down.
Exposure to bromomethane
Because bromomethane is a gas, you are most likely to be exposed by breathing it in air. In most places around the world, levels in air are usually less than 0.025 parts of bromomethane per billion parts of air (ppb). Some cities have higher levels (up to about 1–2 ppb) because of releases from chemical factories and automobile exhausts. You will probably not be exposed to high levels unless you are near a place where bromomethane is being used for fumigation. Workers who fumigate homes or fields may be exposed to very high levels if proper safety precautions are not followed. Because bromomethane evaporates so quickly, it is usually not found in food, surface water, or soil.
Pathways for bromomethane in the body
If bromomethane is present at a waste site, you are most likely to be exposed to it by breathing the vapors in contaminated air. You might also be exposed by drinking water from contaminated wells, although this is less likely. If you breathe in bromomethane, about half of it will pass through your lungs and enter your blood. Studies in animals suggest that if you swallow bromomethane in water, nearly all of it will pass through your stomach or intestines and enter your body. Bromomethane that enters your body either from your lungs or stomach is quickly spread throughout your body by your blood. Most bromomethane in your body is broken down into other chemicals, and these chemicals leave your body in the urine or in the air you breathe out. This usually begins happening within minutes, and is usually nearly complete within several days. We do not know how much bromomethane can enter your body through the skin, but the amount is probably small.
Health effects of bromomethane
If you breathe bromomethane, you may develop a headache and begin to feel weak and nauseated several hours later. If you breathe a large amount, fluid may build up in your lungs and it may be hard to breathe. You may have muscle tremors, and sometimes even seizures. Your kidneys may also be injured, and urine production may slow or stop. In severe cases, these effects can lead to death. In less serious cases, most of these effects usually disappear after several weeks, but some of the effects may never go away.
You should know that one way to learn whether a chemical will harm people is to determine how the body absorbs, uses, and releases the chemical. For some chemicals, animal testing may be necessary. Animal testing may also help identify such health effects as cancer or birth defects. Without laboratory animals, scientists would lose a basic method for getting information needed to make wise decisions that protect public health. Scientists have the responsibility to treat research animals with care and compassion. Scientists must comply with strict animal care guidelines because laws today protect the welfare of research animals.
Additionally, there are vigorous national and international efforts to develop alternatives to animal testing. The efforts focus on both in vitro and in silico approaches and methods. For example, the National Toxicology Program (NTP) at the National Institute of Environmental Health Sciences (NIEHS) created the NTP Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM) in 1998. The role of NICEATM is to serve the needs of high quality, credible science by facilitating development and validation—and regulatory and public acceptance—of innovative, revised test methods that reduce, refine, and replace the use of animals in testing while strengthening protection of human health, animal health and welfare, and the environment. In Europe, similar efforts at developing alternatives to animal based testing are taking place under the aegis of the European Centre for the Validation of Alternative Methods (ECVAM).
Studies in animals suggest that if you swallow bromomethane, you might experience stomach irritation but would probably not experience lung, kidney, or brain injury. Bromomethane that gets on your skin can cause itching, redness, and blisters.
Studies in animals also suggest that bromomethane does not cause birth defects and does not interfere with normal reproduction except at high exposure levels. Animals that breathed bromomethane for 2 years did not develop cancer. Animals that swallowed bromomethane for 25 weeks had changes in their stomachs that could have been an early sign of cancer, but we do not know if swallowing bromomethane for a longer time would cause cancer. Both the International Agency for Research on Cancer and the EPA have determined that bromomethane is not classifiable as to its carcinogenicity in humans.
Medical tests for exposure to bromomethane
Several tests are available to tell whether you have been exposed to bromomethane, but each has limitations. The most direct test measures bromomethane in your blood or in the air you breathe out. However, this test is not usually used because most bromomethane does not stay in the body very long and special measuring equipment is needed. More often, the main breakdown product of bromomethane (bromide) is measured in blood samples. Bromide is normally present in the blood of all people, but the levels of bromide increase when people are exposed to bromomethane. The amount of increase depends on the level of exposure. Tests for bromide are only useful if done within 1-2 days following exposure, and are not very helpful in predicting if exposed persons will have health effects or how serious the effects will be, because not all people respond to bromomethane the same way.
Disclaimer: This article is taken wholly from, or contains information that was originally published by, the Agency for Toxic Substances and Disease Registry. Topic editors and authors for the Encyclopedia of Earth may have edited its content or added new information. The use of information from the Agency for Toxic Substances and Disease Registry should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.