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Chlordane and Heptachlor

Chlordane and heptachlor are pesticides that were used in agriculture in the United States from the 1950's until the 1980's. Chlordane was used in homes and for termite control. Heptachlor was used as a soil and seed treatment and for termite control. Since 1992, the use of heptachlor has been limited to treatment of fire ants near utility equipment. Both pesticides can remain in treated soils, in agricultural runoff water, and near factories where they were manufactured. Chlordane and heptachlor can be found in the air and dust of buildings long after treatment for termites or insects was performed.

People are usually exposed to these chemicals by eating foods high in fat, such as meat, fish, and dairy products. Pregnant women may pass these chemicals to the fetus, and after birth, chlordane and heptachlor may be passed to infants through breast milk. Chlordane and heptachlor are converted in the body into chemicals called metabolites. These chemicals leave the body slowly over a period of months to years.

The human health effects from low environmental exposures to these chemicals are unknown. Short-term large exposures to either chlordane or heptachlor can cause seizures and injure the liver. Both chlordane and heptachlor are considered possible cancer-causing chemicals in humans.

Dichlorodiphenyltrichloroethane (DDT)

Dichlorodiphenyltrichloroethane (DDT) is an insecticide used in agriculture. The United States banned the use of DDT in 1972, but some countries still use the chemical. DDT has also been used in the past for the treatment of lice. It is still in use outside the United States for the control of mosquitoes that spread malaria. DDT and its related chemicals persist for a long time in the environment and in animal tissues.

People are most likely to be exposed to DDT from foods, including meat, fish, and dairy products. DDT can be absorbed by eating, breathing, or touching products contaminated with DDT. In the body, DDT is converted into several breakdown products called metabolites, including the metabolite dichlorodiphenyldichloroethene (DDE). DDT and DDE are stored in the body's fatty tissues. In pregnant women, DDT and DDE can be passed to the fetus. Both chemicals are found in breast milk, resulting in exposure to nursing infants.

Human health effects from DDT at low environmental doses are unknown. Following exposure to high doses, human symptoms can include vomiting, tremors or shakiness, and seizures. Laboratory animal studies showed effects on the liver and reproduction. DDT is considered a possible human carcinogen.

Organophosphorus Insecticides: Dialkyl Phosphate Metabolites

Organophosphorus insecticides are chemicals used to kill many types of insects. These chemicals account for a large share of all insecticides used in the United States, including those used on food crops. Most home uses of organophosphorus insecticides have been phased out in the United States. Certain organophosphorus insecticides (e.g., malathion, naled) are also used for mosquito control in the United States.

People are exposed to organophosphorus insecticides by eating foods treated with these chemicals. Exposure can also occur from hand-to-mouth contact with surfaces contaminated with the insecticides. Less common exposures include breathing in the insecticides or absorbing them through the skin. Farm workers, gardeners, florists, pesticide applicators, and manufacturers of these insecticides may have greater exposure than the general population. Once they enter the body, about 75% of the organophosphorus insecticides in use in the U.S. are converted to breakdown products called dialkyl phosphate metabolites. These metabolites are not considered toxic, but indicate an exposure to organophosphate insecticides.

A sudden exposure to large amounts of organophosphorus insecticides may lead to health problems such as nausea, vomiting, irregular or slow heartbeat, difficulty breathing or tightness in the chest, salivation, weakness, paralysis, and seizures. When people are exposed over a long period of time to smaller amounts of these pesticides, they may feel tired or weak, irritable, depressed, or forgetful.


Arcury TA, Grzywacz JG, Chen H, Vallejos QM, Galván L, Whalley LE, Isom S, Barr DB, Quandt SA. Variation across the agricultural season in organophosphorus pesticide urinary metabolite levels for Latino farmworkers in eastern North Carolina: project design and descriptive results. Am J Ind Med. 2009 Jul;52(7):539-50.

Arcury TA, Grzywacz JG, Isom S, Whalley LE, Vallejos QM, Chen H, Galván L, Barr DB, Quandt SA. Seasonal variation in the measurement of urinary pesticide metabolites among Latino farmworkers in eastern North Carolina. Int J Occup Environ Health. 2009 Oct-Dec;15(4):339-50.

Harley KG, Marks AR, Bradman A, Barr DB, Eskenazi B. DDT exposure, work in agriculture, and time to pregnancy among farmworkers in California. J Occup Environ Med. 2008 Dec;50(12):1335-42.

Hemakanthi De Alwis GK, Needham LL, Barr DB. Determination of dialkyl phosphate metabolites of organophosphorus pesticides in human urine by automated solid-phase extraction, derivatization, and gas chromatography-mass spectrometry. J Anal Toxicol. 2008;32(9):721-7.

LaKind J.S., Berlin C.M., Sjödin A., Turner W.E., Wang R., Needham L.L., Paul I.M., Stokes J.L., Naiman D.Q., Patterson D.G. 2009. Do human milk concentrations of persistent organic chemicals really decline during lactation? Chemical concentrations during lactation and milk/serum partitioning. Environ Health Perspect 2009 117: 1625-1631.

Meeker JD, Barr DB, Hauser R. Pyrethroid insecticide metabolites are associated with serum hormone levels in adult men. Reprod Toxicol. 2009 Apr;27(2):155-60.

Naeher LP, Barr DB, Rithmire N, Edwards J, Holmes AK, Needham LL, Rubin CS. Pesticide exposure resulting from treatment of lice infestation in school-aged children in Georgia. Environ Int. 2009 Feb;35(2):358-62.

Panuwet P, Prapamontol T, Chantara S, Thavornyuthikarn P, Bravo R, Restrepo P, Walker RD, Williams BL, Needham LL, Barr DB. Urinary paranitrophenol, a metabolite of methyl parathion, in Thai farmer and child populations. Arch Environ Contam Toxicol. 2009 Oct;57(3):623-9.

Purdue MP, Engel LS, Langseth H, Needham LL, Andersen A, Barr DB, Blair A, Rothman N, McGlynn KA. Prediagnostic serum concentrations of organochlorine compounds and risk of testicular germ cell tumors. Environ Health Perspect. 2009 Oct;117(10):1514-9.

Smith JN, Campbell JA, Busby-Hjerpe AL, Lee S, Poet TS, Barr DB, Timchalk C. Comparative chlorpyrifos pharmacokinetics via multiple routes of exposure and vehicles of administration in the adult rat. Toxicology. 2009 Jun 30;261(1-2):47-58.

Whyatt RM, Garfinkel R, Hoepner LA, Andrews H, Holmes D, Williams MK, Reyes A, Diaz D, Perera FP, Camann DE, Barr DB. A biomarker validation study of prenatal chlorpyrifos exposure within an inner-city cohort during pregnancy. Environ Health Perspect. 2009 Apr;117(4):559-67. Epub 2008 Dec 5.

Winnik B, Barr DB, Thiruchelvam M, Montesano MA, Richfield EK, Buckley B. Quantification of Paraquat, MPTP, and MPP+ in brain tissue using microwave-assisted solvent extraction (MASE) and high-performance liquid chromatography-mass spectrometry. Anal Bioanal Chem. 2009 Sep;395(1):195-201. The U.S. Government's Official Web PortalDepartment of Health and Human Services
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