The Cancer Assessment Review Committee of the U.S. Environmental Protection Agency (EPA) has issued its finding that pyrethrins, which are naturally occurring insecticides found in the flowers of chrysanthemum species grown in Africa and Australia, are unlikely to cause cancer in humans at doses to which people are likely to be exposed.

"This is an important conclusion and a positive finding," said David Carlson, Technical Chair of the Pyrethrin Steering Committee/Joint Venture. The group, which is a consortium of pyrethrin producers along with formulators of pyrethrin-based products sold in the U.S., operates under the auspices of the Consumer Specialty Products Association, Washington, D.C.

Pyrethrins have been used for centuries for insect control. In the U.S., they are used primarily for home, garden and pet care products. They are also used in municipal mosquito control programs, as well as in consumer products to control mosquitoes. These compounds are in high demand for organic farming because they degrade in sunlight in a few hours, leaving virtually no residues. Products used in commercial, industrial and institutional food handling establishments also include pyrethrins.

The EPA had relied on lifetime feeding studies in rats, a standard procedure for assessing potential human health effects, in an earlier evaluation. In these studies, rats are fed much higher doses than humans would ever likely ingest, even in high exposure situations. Based on these studies, the EPA concluded that there might be human health effects under specific, although unlikely, circumstances. It reversed this position, however, based on new scientific evidence showing that the mode of action by which pyrethrins affect rats is not applicable to humans at the dose levels at which humans would be exposed.

"We are gratified that the EPA used the best science available in its re-evaluation of pyrethrins," said Thomas G. Osimitz, Ph.D., consultant to the Pyrethrin Steering Committee/Joint Venture. "By carefully considering the mode of action of pyrethrins in rats and the implausibility of this mode of action operating in humans at relevant dose levels, the EPA has both protected public health and permitted the appropriate use of highly effective and environmentally favorable insecticides such as pyrethrins," he said.