Health effects of DIMP
Contents
Introduction
Diisopropyl methylphosphonate is a colorless liquid at normal temperatures. It is also known as methyl-,bis-(1-methyl-ethyl)ester, phosphonic acid, and methyl-diisopropyl ester. Diisopropyl methylphosphonate, or DIMP, is a chemical by-product resulting from the manufacture and detoxification of GB (also called Sarin), a nerve gas that the Army produced from 1953 to 1957. A chemical by-product is a chemical that is formed while making another substance. You might find diisopropyl methylphosphonate in places where GB has been produced, stored, or used, for example, the Rocky Mountain Arsenal (RMA) outside of Denver, Colorado. The RMA is where GB was produced for loading into chemical warfare munitions. Production of GB was discontinued in 1957, and it is not likely that GB, or diisopropyl methylphosphonate, will be produced in the United States in the future because of signing of a chemical treaty that bans not only the use but also the production and stockpiling of poison gases. Diisopropyl methylphosphonate is a colorless liquid. A small amount (0.1%, or 1g of DIMP in 1,000 mililiter (mL) of water) of it dissolves in water (Health effects of DIMP) , but some scientists have found it to be more soluble (8%). Once it is dissolved, little, if any, evaporates into the air.
Pathways for DIMP in the environment
Diisopropyl methylphosphonate was released into the environment at the RMA between 1953 and 1957. While most discharged diisopropyl methylphosphonate entered the groundwater at the RMA, some also entered the surface water and soils. It is unlikely that diisopropyl methylphosphonate escaped to the air because it does not evaporate easily. Diisopropyl methylphosphonate does not break down in the environment very quickly and can remain in water and soil for years. The flow of water during irrigation can carry diisopropyl methylphosphonate through the soil. Plants can take up diisopropyl methylphosphonate and store or accumulate it in leaves and DIMP may enter the food chain when animals eat these plants. However, because DIMP is rapidly changed to isopropyl methylphosphonic acid (IMPA) by animals that eat it, it is unlikely that DIMP will be present further up the food chain. Human exposure may also occur by consumption of home-grown fruits and vegetables irrigated by DIMP-contaminated water.
Exposure to DIMP
Exposure of the general population to diisopropyl methylphosphonate is expected to be rare and even then in small amounts. Only people living near a site where DIMP is found (such as RMA) may be exposed to this substance.
Drinking or showering with water containing diisopropyl methylphosphonate, or eating vegetables irrigated with it are the most likely ways that a person can be exposed to it. Water contaminated with DIMP has been found only at or near the RMA. In 1974 diisopropyl methylphosphonate was first measured in the groundwater at RMA. The reported amounts ranged from 0.5 parts per billion (ppb) to 44,000 ppb (1 ppb is equivalent to one part by weight of diisopropyl methylphosphonate in a billion parts by volume of water or soil). In 1989, soil samples from some areas in the RMA were reported to contain approximately 50 ppb to 240 ppb of diisopropyl methylphosphonate. During the most recent comprehensive groundwater sampling at RMA in 1995, diisopropyl methylphosphonate concentrations in groundwater were reported to range from less than 0.110 ppb to 965 ppb. It is possible that exposure to diisopropyl methylphosphonate might occur by eating plants that absorbed it from water or soil.
Pathways for DIMP in the body
Exposure of the general population to diisopropyl methylphosphonate is expected to be rare and even then in small amounts. Only people living near a site where DIMP is found (such as RMA) may be exposed to this substance.
Drinking or showering with water containing diisopropyl methylphosphonate, or eating vegetables irrigated with it are the most likely ways that a person can be exposed to it. Water contaminated with DIMP has been found only at or near the RMA. In 1974 diisopropyl methylphosphonate was first measured in the groundwater at RMA. The reported amounts ranged from 0.5 parts per billion (ppb) to 44,000 ppb (1 ppb is equivalent to one part by weight of diisopropyl methylphosphonate in a billion parts by volume of water or soil). In 1989, soil samples from some areas in the RMA were reported to contain approximately 50 ppb to 240 ppb of diisopropyl methylphosphonate. During the most recent comprehensive groundwater sampling at RMA in 1995, diisopropyl methylphosphonate concentrations in groundwater were reported to range from less than 0.110 ppb to 965 ppb. It is possible that exposure to diisopropyl methylphosphonate might occur by eating plants that absorbed it from water or soil.
Health effects of DIMP
Scientists use many tests to protect the public from the harmful effects of toxic chemicals and to find ways to treat people who have been harmed.
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).
Little is known about the human health effects of diisopropyl methylphosphonate. Skin rashes and other signs of irritation have been reported in some people who handled dead animals near a pond containing diisopropyl methylphosphonate and other chemicals, but it is not known which substances caused these effects.
Drinking large amounts of diisopropyl methylphosphonate kills animals. The amount needed to cause death in humans is not known for sure. Animal studies have shown no evidence that drinking or eating diisopropyl methylphosphonate causes fertility problems or birth defects. Animal studies have shown that eating diisopropyl methylphosphonate can affect some liver enzymes (indicating a response by the liver). However, test animals showed no liver disease. While most animal studies have shown only minimal toxic effects below a certain level of exposure, there is some evidence that diisopropyl methylphosphonate can cause effects on the blood and nervous systems at high levels. Overall, however, it is not a very toxic chemical.
Medical tests for exposure to DIMP
Once inside the body, diisopropyl methylphosphonate is rapidly converted to isopropyl methylphosphonic acid (IMPA), which is rapidly cleared from the blood. Laboratory tests can determine the amount of IMPA in the blood or urine. However, because IMPA leaves the body rapidly, these tests are useful only for recent exposure. It is helpful for your doctor to know whether there are other chemicals to which you have been exposed.
Further Reading
- The Agency for Toxic Substances and Disease Registry
- Interagency Coordinating Committee on the Validation of Alternative Methods
- European Centre for the Validation of Alternative Methods
- Institute for Laboratory Animal Research
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