In addition to these reports, numerous scientific studies and experiments vindicate DDT.
U.S. Fish and Wildlife Service biologists fed large doses of DDT to captive bald eagles for 112 days and concluded that “DDT residues encountered by eagles in the environment would not adversely affect eagles or their eggs,” according to a 1966 report published in the “Transcripts of 31st North America Wildlife Conference.”
The USFWS examined every bald eagle found dead in the U.S. between 1961-1977 (266 birds) and reported no adverse effects caused by DDT or its residues.
One of the most notorious DDT “factoids” is that it thinned bird egg shells. But a 1970 study published in Pesticides Monitoring Journal reported that DDT residues in bird egg shells were not correlated with thinning. Numerous other feeding studies on caged birds indicate that DDT isn’t associated with egg shell thinning.
In the few studies claiming to implicate DDT as the cause of thinning, the birds were fed diets that were either low in calcium, included other known egg shell-thinning substances, or that contained levels of DDT far in excess of levels that would be found in the environment – and even then, the massive doses produced much less thinning than what had been found in egg shells in the wild.
So what causes thin bird egg shells? The potential culprits are many. Some that have been reported in the scientific literature include: oil; lead; mercury; stress from noise, fear, excitement or disease; age; bird size (larger birds produce thicker shells); dehydration; temperature; decreased light; human and predator intrusion; restraint and nutrient deficiencies.
Most of this evidence was available to the Environmental Protection Agency administrative judge who presided over the 1971-1972 hearings about whether DDT should be banned. No doubt it’s why he ruled that, “The use of DDT under the regulations involved here does not have a deleterious effect on freshwater fish, estuarine organisms, wild birds or other wildlife.”
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