New DDT Report Confirms Data Supporting 1972 Ban, Finds Situation Improving
[EPA press release - August 11, 1975]
Residues of the pesticide DDT in the food supply, human tissues and in the environment have declined in recent years especially since the chemical was banned for major uses by EPA in 1972.
This information is included in a new report to Congress on the subject by the Environmental Protection Agency.
The report, titled "DDT--A Review of Scientific and Economic Aspects of the Decision to Ban Its Use as a Pesticide," cites studies showing that human dietary intake of DDT in the U.S. has declined from 13.8 milligrams per day in 1970 to 1.88 mg/day in 1973. Residues in human fatty tissues have declined from nearly 8.0 parts per million (ppm) in 1971 to 5.9 ppm in 1973 based on large scale samplings of more than 1,000 people, according to the report. EPA said that health and environmental risks may be associated with even these lower levels but that the decline is encouraging.
Most uses of DDT, including all food applications, were banned by EPA three years ago because of unreasonable adverse effects on man and the environment. The new report was prepared at the request of the House Appropriations Committee.
In general, the report confirms EPA's 1972 findings. It also shows that risks are declining since the ban, that alternative pesticides are available and that economic impacts have been nominal, well within the range of those projected in 1972.
According to the report, the ban has contribute to the decline of DDT levels in fish. For example, one Federal study of Lake Michigan lake trout showed DDT levels decreased from 19.19 ppm in 1970 to 9.96 ppm in 1973. DDT levels in coho salmon declined from 11.82 ppm in 1969 to 4.48 million in 1973.
Residues of the pesticide have declined in some birds, e.g. songbirds and ospreys, but are still high enough to adversely effect other birds, especially birds of prey.
As for the economic impact of the ban, the report concludes that for most crops, including cotton which in the past accounted for 80 percent of DDT use, production has been maintained. However, costs have increased in some cases.
The report says that nationally the cost of switching to alternative pesticides has cost cotton farmers slightly more than $1.00 per acre per year. In the southeastern U.S., however, this figure increases to an additional $6.00 per acre per year. For the consumer, the cost of buying cotton goods produced with other pesticides increased 2.2 cents per person per year.
In reviewing studies conducted since the ban, the report concludes that DDT should still be considered a potential human cancer agent based on the results of animal studies. In addition, the report confirms that DDT is stored in human fatty tissue, wildlife and fish; DDT is toxic to fish and birds and interferes with the reproduction of some species; DDT persists in soil and water for years.
A number of alternative pesticides were available to substitute for DDT at the time of the ban. Since, the others have been identified. Together, these substitutes include methyl parathion, parathion, malathion, guthion, azodrin, crotoxyphos, methomyl, diazinon, methoxychlor and others. In most cases, they have been effective in controlling pests and economical to use, according to the report. Regarding cotton, the report cites preliminary testing indicating that a combination of chemical and non-chemical controls, e.g. "field checking" for insects and support for natural predators, may be the most effective and economical means to control the boll-weevil and other cotton pests.
The Agency has attempted to administer the ban with flexibility, paying special attention to emergency use situations. For example, uses of DDT were granted by EPA in 1974 to safeguard timber in the northwestern U.S. from the tussock moth and to control the pea leaf weevil on the dry pea crop in Idaho and Washington. This past fall, in a separate action, substantial amounts of Maine timber were saved from spruce budworm damage by EPA's rapid registration of two DDT substitutes.