Healthy Milk, Healthy Baby
Chemical Pollution and Mother's Milk
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Toxaphene is a persistent chlorinated insecticide that is a mixture of more than 670 chemicals called polychlorinated terpenes. Toxaphene is a chemical of international concern because it is persistent in the environment and because it tends to travel long distances in the air and water.1
Toxaphene has been used mainly as an agricultural insecticide on cotton, but has also been used on cereal grains, fruits, nuts and vegetables. In addition, it has been used to control ticks and mites in livestock, and to kill unwanted fish species in lakes.2 Toxaphene became the most widely used insecticide in the United States in the mid-1970s after DDT was banned, but has since been banned for general use.
Toxaphene in the Body
Toxaphene enters the environment as a result of its use on agricultural crops, against fish species in lakes and during disposal. Once in the environment, toxaphene is quite persistent. It does not dissolve easily in water and binds very strongly to soil and sediment. Depending on the type of soil and the climate, toxaphene can persist in soil for as long as 12 years.
Toxaphene is often used as an indicator of organochlorine levels in aquatic ecosystems because it is ubiquitous in water and is consistently measured in great quantities in fish.
Human beings can be exposed to toxaphene in several ways. The most significant exposure route is the consumption of contaminated fish and shellfish.3 Other possible routes include breathing air near a hazardous waste site where toxaphene was disposed or drinking water contaminated with the chemical.4
Once consumed by humans, some toxaphene leaves the body in a few days through the feces and urine, but some remains, stored in body fat, including breast milk.
Controlling Exposure: Bans and Restrictions
As of 2003, toxaphene had been banned or restricted in 25 countries, and made illegal for import in 35 countries.5
Toxaphene is still allowed in the United States for emergency agricultural situations, decided on a case-by-case basis by the EPA. It is commonly used in Puerto Rico and the Virgin Islands to control insects on banana and pineapple crops.6
Toxaphene has appeared in parts of the world where it was never used, the result of a phenomenon called "global distillation," in which the chemical evaporates and moves on global air currents to eventually precipitate in rain or snow.
Assessing the Extent of Toxaphene 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. In the case of toxaphene, agencies have established a number of benchmarks, mostly related to fish consumption. No benchmarks have been established relating to potential toxaphene exposure through breast milk.
The U.S. EPA and many state environmental agencies in the United States have established fish consumption advisories related to toxaphene contamination. These advisories recommend reduced, or no, intake of certain fish species. The advisories recommending reduced fish consumption are based on an acceptable daily intake (ADI) level for toxaphene. The EPA's ADI for toxaphene is 0.2 micrograms per kilogram, twice the level established in Germany. Some advisories recommend low or discontinued intake of fish by sensitive populations -- children and pregnant women, for example. The EPA has set a maximum contaminant level (MCL) of 3 parts per billion for toxaphene in drinking water.
Breast Milk Monitoring Studies Measuring Toxaphene
Very little data has been gathered on toxaphene levels in breast milk, perhaps because of the lack of sensitive and accurate analytical techniques. Only a few studies have recorded toxaphene in breast milk, and most of these have found it at low levels.7 However, one study comparing toxaphene levels in northern and southern Canada found breast milk contamination levels in indigenous women from northern Canada's Keewatin District that were more than 11 times higher than those found in a national survey of women across southern Canada. Figure 1 shows this data.
This difference may even be somewhat downwardly biased, since sampling for the national survey was completed in 1992, while the samples from Keewatin women were obtained in 1997. Toxaphene concentrations may have been lower in 1997 than in 1992, since Canada phased toxaphene out in the 1970s, and breast milk pollutant concentrations have been shown to decrease over time with no new exposures.8 More data on toxaphene concentrations in Canadian food sources and the environment, and on the role of regional dietary habits, would be necessary to identify the exact cause of this discrepancy, but researchers suggest that toxaphene contamination in northern Canada may be a result of aerial transport and bioaccumulation in northern aquatic life.9
Despite this overall lack of data, toxaphene remains a chemical of concern and is scheduled for international ban subject to the Stockholm Convention. Its potential for bioaccumulation and the high incidence of fish contamination make it worthy of international concern.
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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; Jensen, A.A. and S.A. Slorach, Chemical Contaminants in Human Milk , Boca Raton Ann Arbor Boston: CRC Press, Inc. (1991).
last revised 3.25.05