Chlordane

Exposure to chlordane occurs from its past use as a pesticide. The acute (short-term) effects of chlordane in humans consist of gastrointestinal distress and neurological symptoms, such as tremors and convulsions. Chronic (long-term) inhalation exposure of humans to chlordane results in effects on the nervous system. An occupational study reported an association between chlordane exposure and non-Hodgkins’s lymphoma, while other human studies did not show an association between chlordane exposure and leukemia or multiple myeloma. Animal studies have reported liver cancer in mice and male rats exposed to chlordane via ingestion.

Uses

Chlordane was used as a pesticide in the United States from 1948 to 1988. In 1988, all approved uses of chlordane in the United States were canceled.

From 1983 to 1988, chlordane’s only approved use was to control termites in homes. The pesticide was applied underground around the foundation of homes.

Before 1978, chlordane was also used as a pesticide on agricultural crops, lawns, and gardens and as a fumigating agent. In 1978, EPA canceled the use of chlordane on food crops and phased out other above-ground uses over the following 5 years.

Sources and Potential Exposure

Before 1988, exposure to chlordane may have occurred in the workplace; persons involved in the manufacture, formulation, or application of chlordane, such as farmers, lawn-care workers, and pest-control workers may have been exposed.

Studies on chlordane levels in indoor air reported levels ranging from < 1 to 610,000 nanograms per cubic meter (ng/m3).

Currently, exposure to chlordane appears to be highest for those persons living in homes that were treated for termites with chlordane. Chlordane may be found in the air in these homes for many years after treatment.

Additional exposure to chlordane may occur from digging in soil around the foundation of homes where chlordane was applied. Mean residue levels in soil around 30 homes treated with chlordane ranged from 22 to 2,540 parts per million (ppm).

Exposure to chlordane may also occur from eating chlordane-contaminated food. Chlordane remains in the food supply today because much of the farmland in the United States was treated with chlordane in the 1960s and 1970s, and it remains in the soil for over 20 years.

Chlordane has been listed as a pollutant of concern to EPA’s Great Waters Program due to its persistence in the environment, potential to bioaccumulate, and toxicity to humans and the environment.

Assessing Personal Exposure

Levels of chlordane and its breakdown products in blood and fat can be measured and used as an indication of chlordane exposure.

Health Hazard Information

Acute Effects:

Neurological effects, such as headache, dizziness, irritability, and convulsions, and effects on the blood have been seen from acute chlordane exposure in animals and humans.

Chlordane is considered to have high acute toxicity based on short-term animal tests in rats.

Chronic Effects (Noncancer):

Chronic exposure of humans to chlordane by inhalation results primarily in effects on the nervous system.

Animal studies have reported effects on the liver, kidney, blood, thyroid, and respiratory and nervous systems from chronic exposure to chlordane via inhalation.

The Reference Concentration (RfC) for chlordane is 0.0007 milligrams per cubic meter (mg/m3) based on liver effects in rats. The RfC is an estimate (with uncertainty spanning perhaps an order of magnitude) of a daily inhalation exposure to the human population (including sensitive subgroups) that is likely to be without appreciable risk of deleterious noncancer effects during a lifetime. It is not a direct estimator of risk but rather a reference point to gauge the potential effects. At exposures increasingly greater than the RfC, the potential for adverse health effects increases. Lifetime exposure above the RfC does not imply that an adverse health effect would necessarily occur.

EPA has low confidence in the RfC based on: (1) medium confidence in the principal study because it had relatively large group sizes in which histopathological analyses on the known animal target tissue, the liver, were thoroughly performed, and (2) low confidence in the database because hepatic toxicity was consistent across routes of exposure; however, recent evidence indicates that neurotoxicity, a known human endpoint in acute exposures, may be a relevant endpoint in chronic human exposures, and no chronic animal studies have examined neurotoxicity. Studies on pre- and post-natal animals indicating chlordane mimicry of sex steroids raise reproductive concerns, and no multigenerational reproductive studies, by any route, existing.

The Reference Dose (RfD) for chlordane is 0.0005 milligrams per kilogram body weight per day (mg/kg/d) based on liver necrosis in mice.

EPA has medium confidence in the RfD based on: (1) medium confidence in the principal study because it had large group sizes in which histopathological analyses on the known animal target tissue, the liver, were thoroughly performed, and (2) medium confidence in the database because hepatic toxicity was consistent across routes of exposure; however, recent evidence indicates that neurotoxicity, a known human endpoint in acute exposures, may be a relevant endpoint in chronic human exposures, and no chronic animal studies have examined neurotoxicity. No multigenerational reproductive studies have been performed by any route. The wide array of special studies and numerous chronic studies with consistent results are judged adequate information to rate the overall confidence in the database as medium.

Reproductive/Developmental Effects:

A study of women living in homes repeatedly treated for termites with chlordane revealed an increased incidence of ovarian and uterine disease, compared with a reference population. However, it is not possible to state whether these effects were solely due to chlordane or to other chemicals as well.

An animal study reported biochemical and behavioral laterations mimicking male sex steroids, while another study reported alterations in reproductive behavior, both in male rats exposed to chlordane.

Cancer Risk:

An occupational study investigating men with non-Hodgkin’s lymphoma found that the odds of chlordane use as an insecticide were significantly greater among cases than among controls.

Two other epidemiological studies did not find an association between chlordane exposure and leukemia or multiple myeloma.

Animal studies have reported liver cancer in mice and male rats exposed to chlordane via ingestion.

Chlordane is a thick, liquid man-made chemical whose color ranges from colorless to amber.