Health effects of hexachlorobutadiene
Contents
Introduction
Hexachlorobutadiene, also known as HCBD, perchlorobutadiene, or Dolen-Pur, is a colorless liquid. It does not evaporate or burn easily. Hexachlorobutadiene has a turpentine-like odor. Most people will begin to smell a mild to pungent odor if the compound is present in air at 1 part hexachlorobutadiene per million parts of air (ppm). It is not known how it tastes or at what level people can taste it. Hexachlorobutadiene does not occur naturally in the environment. It is formed during the processing of other chemicals such as tetrachloroethylene, trichloroethylene, and carbon tetrachloride. Hexachlorobutadiene is an intermediate in the manufacture of rubber compounds and lubricants. It is used as a fluid for gyroscopes, a heat transfer liquid, or a hydraulic fluid. Outside of the United States it is used to kill soil pests. (Health effects of hexachlorobutadiene)
Pathways for hexachlorobutadiene in the environment
Hexachlorobutadiene is released to the environment in air, water, and soil, mainly as a result of its disposal following industrial use. Most of the hexachlorobutadiene wastes are destroyed by burning; some are released to the air in this process. It is not known what happens to hexachlorobutadiene after it enters the air. Based on the information we have on similar compounds, it may be broken down by sunlight and react with gases in the atmosphere. It is not known what chemicals are formed by these reactions or if the compounds formed are harmful. Based on the properties of similar compounds, one-half of the hexachlorobutadiene in the air is expected to be broken down to other chemicals within 60 days.
Hexachlorobutadiene may be released to water during disposal of factory waste. It is not known what happens to it in water or how long it remains there. Hexachlorobutadiene that is present in water may pass into the air or soil in small amounts. Small amounts of hexachlorobutadiene may be released to soil as a result of disposal of industrial wastes containing it. It is not known what happens to hexachlorobutadiene after it contacts soil. Because hexachlorobutadiene binds to most soils, it is expected to remain there for some time. The hexachlorobutadiene present in sandy soils may move through the soil to underground water. However, no information was found on how much reaches the underground water or how long it stays in the water. Hexachlorobutadiene can build up in fish and shellfish, where waters are contaminated. It is not known if hexachlorobutadiene builds up in plants.
Exposure to hexachlorobutadiene
You may be exposed to hexachlorobutadiene by breathing contaminated air, eating contaminated food, drinking contaminated water, or by direct skin contact with this chemical. People working in the industrial facilities where hexachlorobutadiene is formed or used may be exposed. Concentrations found in outside air were 2–3 parts hexachlorobutadiene per trillion parts of air (ppt). Levels were much higher in or near industrial facilities where hexachlorobutadiene is formed or used. One survey detected air concentrations ranging from 22 to 43,000 ppt in a production facility. No information is available on how many workers are potentially exposed to hexachlorobutadiene.
Although hexachlorobutadiene is not very soluble in water, small amounts may be found in some public drinking water (less than 1 part hexachlorobutadiene per billion parts water [ppb]). It may also be found in underground water near hazardous waste sites. Hexachlorobutadiene has no agricultural or food chemical uses in the United States.
Levels ranging from 0.1 to 4.7 milligrams per kilogram have been found in fish and shellfish because the compound is present in some surface water.
Exposure at waste sites is most likely to occur from the landfill disposal of waste by-products originating from chlorinated hydrocarbon manufacture.
Pathways for hexachlorobutadiene in the body
Hexachlorobutadiene may enter your body through the lungs when you breathe air contaminated with it. It also may enter your body if you drink water or eat food contaminated with hexachlorobutadiene. With the exception of fish and shellfish, however, hexachlorobutadiene has not been found in food. The amount of hexachlorobutadiene that enters your body by these routes depends on how much of the chemical you eat or drink.
What happens to hexachlorobutadiene when you breathe vapors of the compound is not known, but it most likely moves across your lungs into your bloodstream. In animal studies, most of the hexachlorobutadiene is changed by the body into more toxic compounds. It is not known how rapidly hexachlorobutadiene and its breakdown products are removed from your body through your urine and feces. Some is expected to remain in your body fat for long periods.
Health effects of hexachlorobutadiene
In one study of workers at a solvent production plant who breathed hexachlorobutadiene for long periods, the compound was shown to affect the function of the liver. Because the workers were also exposed to other solvents (carbon tetrachloride and perchloroethylene), it is not certain if this effect was caused by hexachlorobutadiene alone. Studies in mice showed that brief exposure to high concentrations of hexachlorobutadiene irritate the nose. The effects of breathing low levels of hexachlorobutadiene are not known.
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).
Ingestion of hexachlorobutadiene damaged the kidneys of rats and mice and, to a lesser extent, the liver of rats. These effects occurred after both short- and long-term exposures at very low dose levels. Young rats were affected more than adult rats. The kidneys of female rats appeared to be affected more than those of males. On the other hand, the liver of male rats was affected, but the liver of female rats was not. It is not clear if the differences between the sexes might be seen in humans. Kidney, brain, and liver damage were also seen in rabbits after contact of their skin with the compound for a short period.
Hexachlorobutadiene decreased fetal body weight in rats, but did not affect fetal development or impair their ability to produce offspring. The lungs, heart, brain, blood, muscles, and skeleton in rats or mice were not damaged after short- or long-term exposure.
Studies in rats indicate that hexachlorobutadiene may increase the risk of kidney cancer if exposures occur for long periods. The International Agency for Research on Cancer (IARC) has determined that hexachlorobutadiene is not classifiable as to its carcinogenicity in humans, but indicated that there was limited evidence that hexachlorobutadiene was carcinogenic in rats. EPA has determined that hexachlorobutadiene is a possible human carcinogen.
Medical tests for exposure to hexachlorobutadiene
Exposure to hexachlorobutadiene can be determined by measuring the chemical or its breakdown products in blood, urine, or fat. These tests are not usually performed in most doctors' offices because special equipment is needed. Samples can be collected and sent to special laboratories to determine if you were exposed to hexachlorobutadiene. These tests cannot determine how much of the chemical you were exposed to or if adverse health effects will occur as a result of the exposure.
Further Reading
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