Chlordane [factsheet]

CHLORDANE

Please Note: The main sources of information for this fact sheet are EPA's Integrated Risk Information System (IRIS), which contains information on oral chronic toxicity of chlordane and the RfD, and the carcinogenic effects of chlordane including the unit cancer risk for inhalation exposure, and the Agency for Toxic Substances and Disease Registry's (ATSDR's) Toxicological Profile for Chlordane. Other secondary sources include the Hazardous Substances Data Bank (HSDB), a database of summaries of peer-reviewed literature, and the Registry of Toxic Effects of Chemical Substances (RTECS), a database of toxic effects that are not peer reviewed.

Environmental/Occupational 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. (1)

* 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; indoor air in treated homes contains an average of 0.002 mg/m³of chlordane. (1)

* Additional exposure to chlordane may occur from digging in soil around the foundation of homes where chlordane was applied. (1)

* 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. (1)

* 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 (2).

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. (1)

Health Hazard Information

Acute Effects:

* Acute inhalation and oral exposure to high levels of chlordane in humans results in gastrointestinal upset and neurological symptoms, such as tremors and convulsions. (1,3)

* Chlordane is considered to have high acute toxicity based on short-term animal tests such as the LD₅₀ test in rats. (4)

Chronic Effects (Noncancer):

* Chronic exposure of humans to chlordane by inhalation results in effects on the nervous, respiratory, and cardiovascular systems and on the liver, blood, and lung. Gastrointestinal symptoms have also been observed. (1,5,6)

* Animal studies have reported effects on the liver, kidney, blood, thyroid, and respiratory and nervous systems from chronic exposure to chlordane via inhalation. (1,5,6)

* The RfD for chlordane is 0.00006 mg/kg/d based on liver hypertrophy in rats. (7)

* EPA has medium confidence in the critical study on which the RfD was based since it is of adequate quality; low confidence in the database because of (1) the lack of an adequate reproduction study and adequate chronic study in a second mammalian species and (2) inadequate sensitive endpoints studied in existing studies, particularly since chlordane is known to bioaccumulate over a chronic duration; and, consequently, low confidence in the RfD.

* The RfC for chlordane is under review by EPA. (7)

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. (1)

* Developmental studies have reported reduced fertility in rats fed chlordane, neurological effects in the offspring of mice treated with chlordane (although exposure could have come from nursing), but no evidence of malformations or fetal toxicity in rats. (1)

Cancer Risk:

* Human studies on chlordane exposure and cancer are inconclusive. There are three studies on workers exposed via inhalation to chlordane. One study reported a marginal increase in bladder cancer; however, the sample size was very small. The other two studies did not show an association between chlordane exposure and cancer. (1,7)

* Animal studies have reported liver cancer in mice and male rats exposed to chlordane via ingestion. (1,7)

* EPA considers chlordane to be a probable human carcinogen (cancer-causing agent) and has classified it as a Group B2 carcinogen. (7)

* EPA uses mathematical models, based on animal studies, to estimate the probability of a person developing cancer from breathing air containing a specified concentration of a chemical. EPA calculated an inhalation unit risk estimate of 3.7 H 10^-4 (m g/m³)^-1. EPA estimates that, if an individual were to breathe air containing chlordane at 0.003 Fg/m³* over his or her entire lifetime, that person would theoretically have no more than a one-in-a-million increased chance of developing cancer as a direct result of breathing air containing this chemical. Similarly, EPA estimates that breathing air containing 0.03 Fg/m³ would result in not greater than a one-in-a-hundred thousand increased chance of developing cancer, and air containing 0.3 Fg/m³ would result in not greater than a one-in-ten thousand increased chance of developing cancer. (7)

* EPA's Office of Air Quality Planning and Standards, for a hazard ranking under Section 112(g) of the Clean Air Act Amendments, has ranked chlordane in the nonthreshold category. The 1/ED₁₀ value is 11 per (mg/kg)/d and this would place it in the medium category under Superfund's ranking for carcinogenic hazard. (3,4)

Physical Properties

* Chlordane is a thick, liquid man-made chemical whose color ranges from colorless to amber. (1)

* Chlordane is not soluble in water and is either odorless or has a mild, irritating odor. The odor threshold for chlordane is not available. (1)

* The molecular formula for chlordane is C₁₀H₆Cl₈ and the molecular weight is 409.76 g/mol. (1)

* The vapor pressure for chlordane is 1x10^-5 mm Hg at 25 EC and the log octanol/water partition coefficient (Log K_ow) is 5.54. (1,3)

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. (1)

* 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. (1)

* 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 for the next 5 years. (1)

Health Data from Inhalation Exposure

Concentration (mg/m³)	Health numbers^a	Regulatory, advisory numbers^b	Reference
1000.0
_ _ _ _ 100.0		* OSHA IDLH (500 mg/m³)	1
_ _ _ _ 10.0
_ _ _ _ 1.0
_ _ _ _ 0.1		* OSHA PEL, ACGIH TLV and NIOSH REL (0.5 mg/m³)	1
_ _ _ _ 0.01
_ _ _ _ 0.001
_ _ _ _ 0.0001
_ _ _ _ 0.00001
_ _ _ _ 0.000001	* EPA Cancer Risk Level (1-in-a-million excess lifetime risk) = 3 H 10^-6 mg/m³ ^c		7

See notes on following page.

ACGIH TLVCAmerican Conference of Governmental and Industrial Hygienists' threshold limit value expressed as a time-weighted average; the concentration of a substance to which most workers can be exposed without adverse effects.

NIOSH RELCNational Institute of Occupational Safety and Health's recommended exposure limit; NIOSH-recommended exposure limit for an 8- or 10-h time-weighted-average exposure and/or ceiling.

OSHA IDLHCOccupational Safety and Health Administration's immediately dangerous to life and health; concentration representing the maximum level of a pollutant from which an individual could escape within 30 min without escape-impairing symptoms or irreversible health effects.

OSHA PELCOccupational Safety and Health Administration's permissible exposure limit expressed as a time-weighted average; the concentration of a substance to which most workers can be exposed without adverse effect averaged over a normal 8-h workday or a 40-h workweek.

^a Health numbers are toxicological numbers from animal testing or risk assessment values developed by EPA.

^b Regulatory numbers are values that have been incorporated in Government regulations, while advisory numbers are nonregulatory values provided by the Government or other groups as advice.

^c These cancer risk estimates were derived from oral data and converted to provide the estimated inhalation risk.

References

1. Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological Profile for Chlordane (Draft). U.S. Public Health Service, U.S. Department of Health and Human Services, Atlanta, GA. 1992.

2. U.S. Environmental Protection Agency. Deposition of Air Pollutants to the Great Waters. First Report to Congress. EPA-453/R-93-055. Office of Air Quality Planning and Standards, Research Triangle Park, NC. 1994.

3. U.S. Environmental Protection Agency. Handbook of RCRA Ground-Water Monitoring Constituents: Chemical and Physical Properties (Appendix IX to 40 CFR Part 254). Office of Solid Waste, Washington, DC. 1992.

4. U.S. Department of Health and Human Services. Registry of Toxic Effects of Chemical Substances (RTECS, online database). National Toxicology Information Program, National Library of Medicine, Bethesda, MD. 1993.

5. U.S. Department of Health and Human Services. Hazardous Substances Databank (HSDB, online database). National Toxicology Information Program, National Library of Medicine, Bethesda, MD. 1993.

6. U.S. Environmental Protection Agency. Updated Health Effects Assessment for Chlordane. Environmental Criteria and Assessment Office, Office of Health and Environmental Assessment, Office of Research and Development, Cincinnati, OH. 1988.

7. U.S. Environmental Protection Agency. Integrated Risk Information System (IRIS) on Chlordane. Environmental Criteria and Assessment Office, Office of Health and Environmental Assessment, Office of Research and Development, Cincinnati, OH. 1993.