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Chemical Pollution and Mother's Milk

Chemicals: Mirex

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Mirex is an extremely stable and persistent organochlorine insecticide. It has been used primarily to control insect pests. Best known for its use against the fire ant in the southeastern United States, it has also been used in other countries against termites, ants and other agricultural pests. Mirex has also been used industrially as a fire retardant.1

Mirex in the Body

Mirex enters the environment as a result of its use in pest control and in the disposal of industrial wastes. Once it enters the environment, mirex tends to bind to soil and other particles and does not break down easily. It does not dissolve in water and is very persistent in soil. Once it has entered soil and underwater sediments, mirex begins to bioaccumulate in living organisms, including fish, cattle and other animals that have eaten contaminated food products.

Humans can be exposed to mirex by breathing, touching or eating dust or soil particles near hazardous waste sites that contain mirex; and by eating contaminated fish and other animal products.2

Controlling Exposure: Bans and Restrictions

Mirex began to be restricted in the mid-1970s. In the United States, the EPA canceled mirex's registration in 1976, and manufacture of the pesticide was stopped in 1978.3 As of 2003, mirex had been banned or restricted in 6 countries,4 and targeted as a chemical of concern in the EPA's examination of industrial pollution in the Great Lakes.5

Assessing the Extent of Mirex Exposure: Limits and Benchmarks

Most chemicals that are either in widespread use or that have caused widespread contamination are subject to national and international benchmark levels, established to protect public health. The U.S. Environmental Protection Agency (EPA) set a tolerable daily intake level (TDI) for mirex of 200 picograms per kilogram of body weight per day. No breast milk monitoring data has shown infant exposure at or near this level.6

The U.S. Food and Drug Administration has also established a fish contamination "safety level" because of the incidence of mirex-contaminated fish. This level is 100 picograms per kilogram of body weight in fish.7 A picogram is one-trillionth of a gram.

Breast Milk Monitoring Studies Measuring Mirex

Very few studies looking at mirex levels in breast milk have been conducted. The few that exist were done in Canada and the United States. Those studies that have been done detected mirex in extremely small trace amounts.8 Scientists have also conducted studies looking at the relationship between fish consumption and breast milk and blood-serum levels of mirex. Although blood-serum levels of mirex appear to be correlated with fish consumption, these studies have not shown mirex levels in breast milk to be a concern.9

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Chlordane | DDT | Dieldrin, Aldrin and Endrin | Hexachlorobenzene | Hexachlorocyclohexane | Heptachlor | Mirex | Nitro Musks | Toxaphene | Dioxins and Furans | PBDEs | PCBs | Solvents | Lead, Mercury, Cadmium and Other Metals


1. Fisher, B.E., "Most Unwanted," Environmental Health Perspectives Journal 107(1) (1999): pp. A18-21.

2. ATSDR, ToxFAQs for Mirex and Chlordane, 1996.

3. Ibid; Environmental Defense, "Mirex Cancellation Announced," Environmental Defense Newsletter 7(5) (1976).

4. Pesticide Action Network, Pesticides Database,

5. Service, E.N., Great Lakes Toxic Mining Zones Watered Down, Environmental News Service (1999).

6. ATSDR, ToxFAQs for Mirex and Chlordane (1996).

7. Ibid.

8. Jensen, A.A. and S.A. Slorach, Chemical Contaminants in Human Milk, Boca Raton Ann Arbor Boston: CRC Press, Inc. (1991).

9. Kearney, J.P., et al." Blood PCB, p,p'-DDE, and Mirex in Great Lakes Fish and Waterfowl Consumers in Two Ontario Communities," Environmental Research 80 (1990): pp. S138-149; Kostyniak, P.J., et al. "Relation of Lake Ontario Fish Consumption, Lifetime Lactation, and Parity to Breast Milk Polychlorobiphenyl and Pesticide Concentrations," Environmental Research Section A 80 (1999): pp. S166-S174.

last revised 3.25.05

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