Heptachlor (C.A.S. 76-44-8) is a man-made compound that was commonly used by exterminators and homeowners to control and kill termites, and by farmers to kill insects in seed grains and on crops. Heptachlor epoxide is an oxidation product of heptachlor formed by many plants and animals, including people, after exposure to heptachlor. Heptachlor is present as an impurity in the pesticide chlordane.

Since late 1978, most uses of heptachlor have been phased out; the chemical is no longer available to the general public. As of April 1988, heptachlor can no longer be used for the underground control of termites.

Chemical properties:

Heptachlor is a crystalline solid when it is pure, and a waxy solid as a technical-grade product. Heptachlor epoxide is a solid. Heptachlor is soluble in water; heptachlor epoxide is insoluble. As a pure compound, heptachlor is a light tan solid that smells some-thing like camphor. Synonyms for heptachlor are: 1,4,5,6,7,8,8-heptachloro-3a,4,7,7a-tetrahydro-4,7-methanoindene; heptachlorodi- cyclopentadiene.

Synonyms for heptachlor epoxide are 1,4,5,6,7,8,8-heptachloro- 2,3-epoxy-2,3,3a,7,7a-hexahydro-4,7-methanoindene; epoxyheptachlor.

• Chemical Name: Heptachlor
• Regulatory Name: 1,4,5,6,7,8,8-Heptachloro-3A,4,7,7A-TETRAHDRO-4,7-ETHANO-1H-INDENE HEPTACHLOR
• Formula: (C₁₀H₅C_l7)
• DOT Label: Poison
• CAS: 76-44-8
• STCC: 4960630
• CHRIS: HTC
• UN Number: 2761

Health effects:

Heptachlor and heptachlor epoxide are clearly toxic to animals and humans. How they affect human health depends on the amount and extent of exposure. Most heptachlor and heptachlor epoxide are absorbed readily through the gastrointestinal tract, but inhalation and skin contact are also potential routes of exposure.

Long-term exposure to heptachlor or heptachlor epoxide may affect the liver. There is evidence that heptachlor and heptachlor epoxide are associated with infertility and improper development of offspring.

There is little information available regarding human health effects from brief exposures to high levels of heptachlor. Although there are reports of acute and chronic toxicity in humans because of exposure to heptachlor, with symptoms including tremors, convulsions, kidney damage, respiratory collapse, and death, details of such episodes are not well documented.

A Federal Drug Administration study of estimated dietary intake of heptachlor epoxide by geographic region indicates that toddlers and infants from the north central region of the United States are at greater risk of heptachlor epoxide exposure than those in other sections of the country.

A possibly significant area of exposure risk involves people, especially military personnel, whose homes have been treated with heptachlor for termite control. People whose homes have been treated may continue to be exposed to this chemical through the air over long periods of time.

• IDHL: 35MG/M3; Not applicable for Heptachlor, a potential human carcinogen. (NIOSH, 1997)
• TLV TWA: 0.05 MG/M3 Skin, Suspected human Carcinogen (©ACGIH, 1999)
• NIOSH REL: Ca TWA 0.5 mg/m3 [skin]
• OSHA PEL: TWA 0.5 mg/m3 [skin]

Economics:

The only U.S. manufacturer of Heptachlor is Velsicol Chemical Corp, Rosemont, IL.

No information is available about importation of heptachlor or heptachlor epoxide.

Regulation:

The Occupational Safety and Health Administration (OSHA) has established permissible exposure limits for heptachlor.

Cancellation of most uses of heptachlor was announced in 1978. Uses that were cancelled and their cancellation dates are:

• Field corn treatment - August 1, 1980
• Seed treatment (barley, oats, wheat, and rye corn) - September 1, 1982;
• (sorghum) - July 1, 1983
• Citrus, Florida - December 31, 1979
• Pineapples - December 31, 1982
• Narcissus bulbs - December 31, 1980

Heptachlor and heptachlor epoxide are not regulated by EPA under the Clean Air Act. Heptachlor is regulated as a hazardous substance under Section 311 of the Clean Water Act. Heptachlor and heptachlor epoxide are listed under Section 307 of the Federal Water Pollution Control Act as toxic pollutants.

Heptachlor and heptachlor epoxide are regulated as hazardous substances under Superfund. EPA in 1981 initiated a Label Improvement Program to reduce the potential risk for pesticide application of heptachlor.

Under the Emergency Planning and Community Right-to-Know Act of 1986, releases of more than one pound of heptachlor into the air, water, or land must be reported annually and entered into the National Toxic Release Inventory (TRI) data base.

See EPA's Toxic Release Inventory.

Notations:

The NIOSH recommended exposure limits (RELs) are time-weighted average (TWA) concentrations for up to a 10-hour workday during a 40-hour workweek. A short-term exposure limit (STEL) is designated by "ST" preceding the value; unless noted otherwise, the STEL is a 15-minute TWA exposure that should not be exceeded at any time during a workday. A ceiling REL is designated by "C" preceding the value. Any substance that NIOSH considers to be a potential occupational carcinogen is designated by the notation "Ca."

The OSHA permissible exposure limits (PEL) are found in Tables Z-1, Z-2, and Z-3 of the OSHA General Industry Air Contaminants Standard (29 CFR 1910.1000). Unless noted otherwise, PEL are TWA concentrations that must not be exceeded during any 8-hour workshift of a 40-hour workweek. A STEL is designated by "ST" preceding the value and is measured over a 15-minute period unless noted otherwise. OSHA ceiling concentrations (designated by "C" preceding the value) must not be exceeded during any part of the workday; if instantaneous monitoring is not feasible, the ceiling must be assessed as a 15-minute TWA exposure. In addition, there are a number of substances from Table Z-2 (e.g., beryllium, ethylene dibromide, etc.) that have PEL ceiling values that must not be exceeded except for specified excursions. For example, a "5-minute maximum peak in any 2 hours" means that a 5-minute exposure above the ceiling value, but never above the maximum peak, is allowed in any 2 hours during an 8-hour workday.

Information Sources:

• CAMEO®, U.S. Environmental Protection Agency, National Oceanic and Atmospheric Administration, www.epa.gov/ceppo.
• Chemical Manufacturers Association, 1300 Wilson Blvd., Arlington, VA 22209: (703) 741-5000 or Chemical Referral Library, (800) 262-8200.
• National Institute of Environmental Health Sciences, Clearinghouse on Environmental Health Effects, 100 Capitola Drive, #108, Durham, NC 27713; (800) 643-4794; fax (919) 361-9408.
• TOXNET, National Library of Medicine, National Institutes of Health; www.toxnet.nlm.nih.gov
• U.S. Environmental Protection Agency, 401 M St., SW, Washington, DC 20460; Right to Know Hotline (800) 535-0202.
• U.S. Department of Labor, Occupational Health and Safety Administration, Washington, DC, www.osha.gov
• OSHA PEL: Z-1 Table: www.osha-slc.gov/OshStd_data/1910_1000_TABLE_Z-1.html
• OSHA PEL: Z-2 Table: www.osha-slc.gov/OshStd_data/1910_1000_TABLE_Z-2.html