Health effects of hexachlorocyclopentadiene (HCCPD)
Contents
Introduction
HCCPD is a light, lemon-yellow liquid that has a sharp, musty odor. It easily turns from a liquid to a vapor when exposed to air. The vapor looks like a blue haze. This chemical is also called percyclopentadiene, hexachloropentadiene, and hex. Some of its former trade names, still listed in chemical reference documents, are C-56, Graphlox, and HRS 1655. HCCPD is a manufactured chemical and does not occur naturally in the environment. It is made by adding chlorine (Health effects of hexachlorocyclopentadiene (HCCPD)) to cyclopentadiene, or by removing chlorine from octachlorocyclopentane. HCCPD is used to make a group of related pesticides (aldrin, chlordane, dieldrin, endosulfan, endrin, heptachlor, isodrin, mirex, and pentac). Only two of these pesticides, endosulfan and pentac, are currently registered for use in the United States. Thus, your exposure to these compounds is expected to be limited. Endosulfan and pentac are the only two of these pesticides that you can buy in a store. HCCPD is also used to make flame retardants, resins that won't burn, shock-proof plastics, esters, ketones, fluorocarbons, and dyes.
Most of the HCCPD in the environment results from releases during its production and disposal. Releases can also occur as a result of the manufacture, use, and disposal of pesticides made from HCCPD. Most people can smell HCCPD in the air at 30 parts HCCPD per billion (ppb) parts of air. Most people can smell it in water when it is present at 1.4 ppb. The amount of HCCPD that you can taste in water has not been measured and the taste has not been described.
Pathways for HCCPD in the environment
HCCPD can be released to the air as a vapor during its production and use. However, it does not remain in the air very long since it is usually broken down to other substances by sunlight and by reaction with other chemicals in the air. Half of the HCCPD released to the air is removed in less than one day.
When HCCPD is mixed with water at room temperature, only 2.1 milligrams will dissolve in a liter of water (2 parts per million or 2 ppm). In a stream or small river, the HCCPD near the surface will evaporate to the air. Sunlight on the water will cause HCCPD to change quickly into other chemicals. About half of the HCCPD in the water will be changed to other chemicals by the light in only four minutes.
The HCCPD that gets into soil binds to decaying plant and animal matter. If the soil is sandy, the HCCPD can move through the soil and reach the water that is under the ground. When soil that contains HCCPD also contains solvents like gasoline, paint thinners, and acetone, these liquids will help carry the HCCPD through the soil to lakes, rivers, or wells. Bacteria can change HCCPD in the soil to other chemicals, but scientists do not know the nature of these compounds. About half of the HCCPD in the soil will be changed to other chemicals by bacteria in 1–2 weeks.
HCCPD has been known to build up in fish, but only in very small amounts. We do not know if HCCPD accumulates in plants, milk, or animals used for food.
Exposure to HCCPD
If you live near a hazardous waste site where HCCPD or HCCPD-derived pesticides were disposed, you might be exposed to HCCPD in the air. In one survey, levels ranging from 0.032 to 0.053 ppb were measured in air near a hazardous waste site. HCCPD has not been reported in outdoor air in city, suburban, and rural areas. In most areas, the concentration of HCCPD in the air should be low because this chemical is not widely used.
HCCPD is not commonly found in surface water. In one survey, it was found in less than 0.1% of 854 water samples from various sources. The median concentration of HCCPD was less than 10 ppb in water. HCCPD in not often found in drinking water, so exposure by this route is unlikely. However, it may be formed during chlorination of water containing humic acid.
HCCPD may be present in soils that have recently been treated with the pesticides, endosulfan or pentac, because it is sometimes found as an impurity in these pesticides. The soils near a landfill where these pesticides (including those no longer used, such as aldrin, chlordane, dieldrin, endrin, heptachlor, and isodrin) or waste HCCPD were disposed might also contain HCCPD, but, since it binds to organic matter in soils, it is less likely to be free to affect you.
It is highly unlikely that you will be exposed to HCCPD in the foods you eat, although you could be exposed to very small amounts if you catch and eat fish that lived in HCCPD-contaminated water.
The highest exposures to HCCPD are likely to occur in people who are involved in the production or use of HCCPD, who handle pesticides made from it, or who treat wastes that contain it. These people can be exposed by breathing air contaminated with HCCPD, or by skin and eye contact with the vapors or liquid.
Air concentrations ranging from 270 to 970 ppb were reported at a waste water treatment plant after large amounts of the compound were dumped into a city sewage system. Traces of HCCPD were present in waste water at another treatment plant near an industrial facility that used it as a reactant for making pesticides.
Pathways for HCCPD in the body
There is no information available to tell us what happens to HCCPD once it enters the human body. Based on studies in animals, if you are exposed to HCCPD through food or drinking water, most of the HCCPD you eat or drink will stay bound to the food or water and only a small amount will enter your bloodstream. Thereafter, most of the HCCPD (64–80%) will leave your body in your feces and the rest will leave in your urine.
Animal studies have shown that up to 95% of the HCCPD that is inhaled stays in your windpipe and lungs, and a small amount reaches your liver and kidneys. Inhaled HCCPD, therefore, causes more health effects in people and animals than HCCPD that is ingested.
If HCCPD touches your skin, it can enter your body. Based on studies in animals, when either pure HCCPD or a solution with 10% HCCPD in mineral oil comes in contact with your skin, a sore can form. The open sore will allow more HCCPD to enter your body.
Most of the HCCPD that enters your body is changed to other chemicals, but those chemicals have not been identified. A small amount of HCCPD remains unchanged.
Health effects of HCCPD
To protect the public from the harmful effects of toxic chemicals and to find ways to treat people who have been harmed, scientists use many tests.
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).
Information on the health effects of HCCPD on people is limited to one incident involving short-term exposure to HCCPD vapors (0.04–19.2 ppm). Exposure occurred at a waste water treatment plant as a result of an industrial release of HCCPD into the sewage system. This incident showed that the breathing passageways (nose, throat, lungs) in people are very sensitive to HCCPD. You may get a sore throat or have shortness of breath and chest discomfort if you breathe HCCPD at high levels. Your eyes may burn and turn red, and your skin may be irritated. Some people get headaches when they breathe high levels of HCCPD.
Your kidneys and liver may show signs that you have been exposed to HCCPD. Some people who were exposed to HCCPD had increased amounts of protein in their urine and increased levels of other compounds in their blood. These are signs that kidney and liver effects may have occurred after exposure to HCCPD. Other people who were exposed did not show these effects.
Bleeding, swelling, and fluid buildup occurred in the lungs of rats, mice, guinea pigs, and rabbits that inhaled small amounts of HCCPD vapors for two weeks under controlled conditions. Severe breathing difficulty was seen in animals exposed to large amounts of HCCPD for a short period of time, and all the animals died during or soon after exposure. In rats, some cells of the lung, windpipe, and nose contained yellow-colored or clear granules after exposure to a very low level (0.01 ppm) of HCCPD in air for a long time. In monkeys, higher levels (0.2 ppm) caused similar changes in those cells.
When rats and rabbits swallowed HCCPD dissolved in corn oil or peanut oil, cells in the lungs, liver, kidney, brain, and heart were harmed and a sore formed in the stomach lining. When the doses were high (261–1,950 milligrams per kilogram of body weight [mg/kg]), most of the animals died after only one dose. There was damage to stomach lining and kidney cells in mice given a low concentration of HCCPD in corn oil by mouth 5 days a week for several months. Because these mice were also exposed to another chemical, hexachlorobutadiene, it is not clear if the cell damage in the kidneys was caused by HCCPD alone.
No information is available on whether HCCPD affects the reproductive organs of people.
No information is available on whether HCCPD causes cancer in people. The Department of Health and Human Services (DHHS) has determined that HCCPD does not cause cancer in rats and mice under the conditions of the study conducted by the National Toxicology Program. The International Agency for Research on Cancer (IARC) has not evaluated HCCPD as a possible cancer-causing chemical. The EPA has determined that HCCPD is not classifiable as to its ability to cause cancer in people.
Health effects in children
This section discusses potential health effects from exposures during the period from conception to maturity at 18 years of age in humans.
Children are unlikely to be exposed to HCCPD. There is no information on the effects of exposure to HCCPD in children or in adults who were exposed as children. We do not know whether HCCPD causes birth defects in humans. Studies in animals indicate that exposure to HCCPD does not cause problems during development. HCCPD did not cause birth defects or impair the ability of mice and rabbits to produce offspring. We do not know whether HCCPD can cross the placenta or accumulate in breast milk.
Reducing risk of exposure to HCCPD
If your doctor finds that you have been exposed to significant amounts of HCCPD, he or she can advise you about the potential risk of exposure to the rest of your family. When necessary your doctor may need to ask your state public health department to investigate.
Medical tests for exposure to HCCPD
If you have been recently exposed to HCCPD, your blood and urine can be tested for its presence. Such tests are not routinely done in a doctor's office because special equipment is needed. Doctors often can collect blood or urine samples and send them to special laboratories to determine if you have been exposed to HCCPD; but these laboratories can't determine how much HCCPD you were exposed to, or whether your health will be affected. Exposure to HCCPD that occurred weeks or months before your test is not likely to be detected in either your blood or urine.
Further Reading
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