Public Health Statement for

Hexachlorocyclohexane

CAS#
g-HCH 581-89-9
a-HCH 319-84-6

July 1999

This public health statement tells you about hexachlorocyclohexane and the effects of exposure. 

The Environmental Protection Agency (EPA) identifies the most serious hazardous waste sites in the nation.  These sites make up the National Priorities List (NPL) and are the sites targeted for long-term federal cleanup activities.  Hexachlorocyclohexane has been found in at least 144 of the 1,467 current or former NPL sites.  However, the total number of NPL sites evaluated for this substance is not known.  As more sites are evaluated, the sites at which hexachlorocyclohexane is found may increase. This information is important because exposure to this substance may harm you and because these sites may be sources of exposure.

When a substance is released from a large area, such as an industrial plant, or from a container, such as a drum or bottle, it enters the environment.  This release does not always lead to exposure.  You are exposed to a substance only when you come in contact with it.  You may be exposed by breathing, eating, or drinking the substance or by skin contact.

If you are exposed to hexachlorocyclohexane, many factors determine whether you'll be harmed.  These factors include the dose (how much), the duration (how long), and how you come in contact with it.  You must also consider the other chemicals you're exposed to and your age, sex, diet, family traits, lifestyle, and state of health.

1.1 What is hexachlorocyclohexane?

Hexachlorocyclohexane (HCH), also known as benzene hexachloride (BHC), is a synthetic chemical that exists in eight chemical forms called isomers.  The different isomers are named according to the position of the hydrogen atoms in the structure of the chemical.  One of these forms, gamma-HCH (or g-HCH, commonly called lindane), is produced and used as an insecticide on fruit, vegetables, and forest crops.  It is also used in the United States and in many other countries as a topical treatment for head and body lice and scabies, a contagious skin disease caused by mites.  It is a white solid whose vapor may evaporate into the air.  The vapor is colorless and has a slight musty odor when it is present at 12 or more parts HCH per million parts air (ppm).  g-HCH has not been produced in the United States since 1976.  However, imported g-HCH is available in the United States for insecticide use as a dust, powder, liquid, or concentrate.  It is also available as a lotion, cream, or shampoo to control scabies and head lice. 

Technical-grade HCH, a mixture of several chemical forms of HCH, was also once used as an insecticide in the United States and typically contained about 10–15% g-HCH as well as the alpha (a), beta (b), delta (d), and epsilon (e) forms of HCH.  Virtually all of the insecticidal properties reside in the gamma isomer.  Technical-grade HCH has not been produced in the United States since 1983.  In addition, isomers of HCH other than g-HCH may not be made or used commercially in the United States.

The scope of this profile includes information on technical-grade HCH, as well as the alpha (a), beta (b), gamma (g), and delta (d) isomers.  Available information on the epsilon (e) isomer is limited and is not included in this profile. 

1.2 What happens to hexachlorocyclohexane when it enters the environment?

Although technical-grade HCH is no longer used as an insecticide in the United States, a-, b-, g-, and d-HCH have been found in the soil and surface water at hazardous waste sites.  In air, the different forms of HCH can be present as a vapor or attached to small particles such as soil and dust; the particles may be removed from the air by rain.  g-HCH can remain in the air for as long as 17 weeks depending on moisture in the air and temperature.  In soil, sediments, and water, it is broken down to less toxic substances by algae, fungi, and bacteria.  In general, HCH isomers are broken down quickly in water; in natural water samples, g-HCH does not remain for much longer than 30 days.  g-HCH is not generally found in drinking water.  The length of time that HCH isomers remain in soil is not known. 

1.3 How might I be exposed to hexachlorocyclohexane?

Humans can be exposed to a-, b-, g-, and d-HCH in workplace air; in the air surrounding factories where HCH is used; or by eating plants, meat, milk, or water that contain forms of HCH.  According to the National Occupational Exposure Survey from 1981–1983, about 15,000 workers were exposed to HCH.  At spill and dump sites, HCH isomers can enter the air from contaminated soil and from plants grown in contaminated soil.  They can also be washed from the soil and plants into surface water.  Typically, people are not exposed to the a, b, and d forms of HCH separately, but to g-HCH only or to technical-grade HCH, which contains a mixture of the isomers.  People are exposed to g-HCH (lindane) when it is applied to the skin as a lotion or shampoo to control lice and scabies.  The most severe exposures to lindane have occurred in workers who make lindane or in other workplaces such as fertilizer manufacturing sites.

1.4 How can hexachlorocyclohexane enter and leave my body?

g-HCH and the other isomers of HCH can enter your body when you eat food or drink water contaminated with HCH.  Inhaling air contaminated with g-HCH or other isomers of HCH can also lead to entry of these chemicals into the lungs.  g-HCH can be absorbed through the skin when it is used as a lotion to control scabies or body lice.  In general, HCH isomers and the products formed from them in the body can be temporarily stored in body fat.  Among the HCH isomers, b-HCH leaves the body the most slowly.  a-HCH, d-HCH, and g-HCH, and the products formed from them in the body, are more rapidly excreted in the urine; small amounts leave in the feces and expired air.  HCH breaks down in the body to many other substances; these include various chlorophenols, some of which have toxic properties. 

1.5 How can hexachlorocyclohexane affect my health?

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.

One way to see if a chemical will hurt people is to learn how the chemical is absorbed, used, and released by the body; for some chemicals, animal testing may be necessary.  Animal testing may also be used to identify health effects such as cancer or birth defects.  Without laboratory animals, scientists would lose a basic method to get information needed to make wise decisions to protect public health.  Scientists have the responsibility to treat research animals with care and compassion.  Laws today protect the welfare of research animals, and scientists must comply with strict animal care guidelines.

In humans, the effects of breathing toxic amounts of g-HCH and/or a-, b-, and d-HCH can result in blood disorders, dizziness, headaches, and possible changes in the levels of sex hormones in the blood.  These effects have occurred in workers exposed to HCH vapors during pesticide manufacturing.  People who have swallowed large amounts have had seizures; some have died.  A few people, who have used very large amounts of g-HCH or used it frequently on their skin, have developed blood disorders or seizures.  However, no cause-and-effect relationship between exposure to g-HCH and blood disorders in humans has been established.  Animals that have been fed g- and a-HCH have had convulsions, and animals fed b-HCH have become comatose.  All isomers can produce liver and kidney effects.  Reduced ability to fight infection was reported in animals fed g-HCH, and injury to the ovaries and testes was reported in animals given g-HCH or b-HCH.  HCH isomers are changed by the body into other chemical products, some of which may be responsible for the harmful effects.  Long-term oral administration of a-HCH, b-HCH, g-HCH, or technical-grade HCH to laboratory rodents has been reported to result in liver cancer.  The Department of Health and Human Services (DHHS) has determined that HCH may reasonably be anticipated to cause cancer in humans.

1.6 How can hexachlorocyclohexane affect children?

This section discusses potential health effects from exposures during the period from conception to maturity at 18 years of age in humans.

The most likely source of exposure for children is from the use of shampoos and lotions containing g-HCH for the treatment of lice.  HCH has also been found as a residue in food products; b-HCH isomer accumulates in animal tissue.  In the body, a-, d-, and g-HCH are rapidly broken down and excreted.  Although HCH is a restricted use pesticide in the U.S., children could be exposed from eating foods grown in areas where HCH is still used or misused as a pesticide.  HCH has also been detected in breast milk and this is a possible exposure pathway for infants and children.

Limited information is available on the specific health effects resulting from HCH exposure in children.  Health effects observed in adults should also be of potential concern in children.  Children can experience convulsions from exposure to g-HCH.  Accidentally eating enough g-HCH can kill a child.  It is not known for sure whether children are more susceptible than adults to health effects from exposure g-HCH.  However, a study performed on rabbits showed that young animals had higher death rates and greater sensitivity than adults when g-HCH was applied to skin.

We do not know whether HCH causes birth defects in humans.  Technical grade and g-HCH do not cause significant birth defects in animals.  Animals fed g-HCH during pregnancy had an increased number of fetuses with extra ribs, a normal variation.  HCH has been shown to cross the placenta in pregnant women.  HCH is likely to be stored in fat.  It has been measured in skin lipids and breast milk.  In studies on rats, HCH has been shown to pass from the mother to newborns in the dam's milk and causes neurological and hormonal effects.  The male offspring of female rats that had been fed HCH during lactation demonstrated a 50% reduction in testosterone levels and reduced testicular weight in adolescence and adulthood.

1.7 How can families reduce the risk of exposure to hexachlorocyclohexane?

If your doctor finds that you have been exposed to significant amounts of HCH, ask if children may also be exposed.  When necessary your doctor may need to ask your state department of public health to investigate.

There are two primary pathways through which families can be exposed to HCH.  g-HCH, also known as lindane, is used in shampoos and lotions for the treatment of lice.  It is normally safe if used as directed, but is often misused.  If you use shampoos or lotions containing g-HCH, follow the directions carefully.  Products containing g-HCH (lindane) should never be used on infants.  Shampoos or lotions that contain lindane should be stored out of the reach of young children to prevent accidental poisonings.  You may expose your child to lindane if you use lindane to treat lice on your child's head.  There are alternatives that do not involve the use of lindane.

g-HCH is a restricted use pesticide.  Its allowed use around the home is limited to structural treatments, animal shampoos, and animal flea dusts.  Your children may be exposed to HCH if an unqualified person applies pesticides containing it around your home.  In some cases, the improper use of pesticides banned for use in homes has turned homes into hazardous waste sites.  Make sure that any person you hire is licensed and certified to apply pesticides.  Your state licenses each person who is qualified to apply pesticides according to EPA standards and further certifies each person who is qualified to apply "restricted use" pesticides.  Ask to see the license and certification.  Also ask for the brand name of the pesticide, a Material Safety Data Sheet (MSDS), the name of the product's active ingredients, and the EPA registration number.  This information can be  important if you or your family react to the product.

1.8 Is there a medical test to determine whether I have been exposed to hexachlorocyclohexane?

HCH isomers can be measured in the blood, urine, and semen of exposed persons.  Samples of these fluids can be collected in a doctor's office and sent to a laboratory that has the special equipment needed to measure the levels of HCH.  Although the amount of HCH isomers in blood, urine, or semen can be measured, it is usually not possible to determine the environmental levels to which the person was exposed or to predict the health effects that are likely to occur from specific concentrations.  The products of HCH that are formed in the body and then found in the urine have also been measured to find out whether a person was exposed to HCH.  However, this method cannot yet be used to determine exposure to HCH alone because other environmental chemicals produce the same end products. 

1.9 What recommendations has the federal government made to protect human health?

The federal government develops regulations and recommendations to protect public health.  Regulations can be enforced by law.  Federal agencies that develop regulations for toxic substances include the Environmental Protection Agency (EPA), the Occupational Safety and Health Administration (OSHA), and the Food and Drug Administration (FDA).  Recommendations provide valuable guidelines to protect public health but cannot be enforced by law.  Federal organizations that develop recommendations for toxic substances include the Agency for Toxic Substances and Disease Registry (ATSDR) and the National Institute for Occupational Safety and Health (NIOSH).

Regulations and recommendations can be expressed in not-to-exceed levels in air, water, soil, or food that are usually based on levels that affect animals, then they are adjusted to help protect people.  Sometimes these not-to-exceed levels differ among federal organizations because of different exposure times (an 8-hour workday or a 24-hour day), the use of different animal studies, or other factors.

Recommendations and regulations are also periodically updated as more information becomes available.  For the most current information, check with the federal agency or organization that provides it.  Some regulations and recommendations for HCH include the following:

g-HCH is categorized by EPA as a restricted use pesticide.  It can only be used by certified applicators.  EPA has also recommended guidelines on how much HCH can be present in drinking water for specific periods of time without producing health effects.  EPA advises that children should not have more than 1.2 milligrams per liter of water (mg/L) in 10 days or more than 0.033 mg/L per day for long-term (7 years) exposure.  For long-term exposure in adults, EPA recommends that there should not be more than 0.12 mg/L in drinking water.  The EPA has classified a-HCH and technical-grade HCH as probable human carcinogens.  b-HCH has been classified as a possible human carcinogen, while d-HCH has been designated as not classifiable for human cancer.  IARC has classified HCH as a possible human carcinogen.  EPA has classified HCH as a hazardous waste that must meet certain disposal requirements.

OSHA regulates levels of g-HCH in the workplace.  The maximum allowable amount in workroom air during an 8-hour workday in a 40-hour workweek is 0.5 mg per cubic meter of air.

1.10 Where can I get more information?

If you have any more questions or concerns, please contact your community or state health or environmental quality department or

 Agency for Toxic Substances and Disease Registry
 Division of Toxicology
 1600 Clifton Road NE, Mailstop E-29
 Atlanta, GA 30333

 * Information line and technical assistance

 Phone: 888-422-8737 
 FAX: (404)498-0057

ATSDR can also tell you the location of occupational and environmental health clinics.  These clinics specialize in recognizing, evaluating, and treating illnesses resulting from exposure to hazardous substances. 

 * To order toxicological profiles, contact 

 National Technical Information Service
 5285 Port Royal Road
 Springfield, VA 22161
 Phone: 800-553-6847 or 703-605-6000

 

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References

Agency for Toxic Substances and Disease Registry (ATSDR). 1999. Toxicological profile for hexachlorocyclohexane. Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service. 

http://www.atsdr.cdc.gov/toxprofiles/phs43.html