sunday times: lingering pesticides and chemicals

April 24, 2005

in Environmental issues, Science

My friend P. sent me this article regarding a recent, as yet unpublished, study that found traces of DDT and similar organochlorines in North American non-migratory songbirds. This is surprising on two levels. The first is pretty obvious: DDT has been banned in the U.S. for over 30 years.

Study author R. Given Harper of Illinois Wesleyan University expected to find higher levels of pesticides in migratory songbirds, which winter in Latin America, where pesticides that are banned or restricted in the U.S. are still being used . Thus the other surprise was that the resident birds had two to ten times higher levels of DDT than did the migratory birds, and 17 types of organochlorines were found in resident birds versus only one to five types in the migratory birds.

This certainly seems counterintuitive. Where is the DDT coming from? But this excerpt from The Birder’s Handbook (Ehrlich, Dobkin, Wheye, 1988) may hint at an answer:

“…DDT has been shown to be present as a contaminant in the widely used toxin dicofol (a key ingredient in, among others, the pesticide Kelthane). Dicofol is a chemical formed by adding single oxygen atoms to DDT molecules. Unhappily, not all the DDT gets oxygenated, so that sometimes dicofol is contaminated with as much as 15 percent DDT. Overall, the 2.5 million pounds of dicofol used annually in pesticides contain about 250 thousand pounds of DDT.”

More information on the impact of pesticides on birds, including those compounds still used commonly in the U.S.:

UPDATE APR 30: Lake Apopka, Florida’s third largest lake, is an unfortunate poster child for the long lasting effects of pesticide contamination.  The lake is in an agricultural setting, and restoration efforts included flooding surrounding farms to restore marshes.  Hundreds of birds began to die as pesticides (mainly dieldrin, DDT and toxaphene) in the soils were reintroduced into the food chain (there was a big problem with alligators as well).

It takes a big dose of these pesticides to kill bird outright.  Imagine what the sub-lethal effects of such massive contamination might be! Apparently little or nothing has been done to study such chemically-induced impairments such as behavioral changes.  But the last few years eggs have been tested for contaminent levels.  Over the last three years, 30% of bird eggs had DDT related contamination, despite remediation efforts.

You can read more about Lake Apopka at the Friends of Lake Apopka web site.

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