By Ferris Jabr for Scientific American:
Chemicals derived from flowers may sound harmless, but new research raises concerns about compounds synthesized from chrysanthemums that are used in virtually every household pesticide.
For at least a decade, pyrethroids have been the insecticide of choice for consumers, replacing organophosphate pesticides, which are far more toxic to people and wildlife. But evidence is mounting that the switch to less-toxic pyrethroids has brought its own set of new ecological and human health risks.
About 70 percent of people in the United States have been exposed to pyrethroids, with children facing the highest exposure, according to a study published this month. Although the human health threats are unknown, animal studies have found evidence of damage to neurological, immune and reproductive systems.
In addition, pyrethroids are flowing off yards and gardens, contaminating some streams and rivers at concentrations that can kill small creatures vital to the survival of fish and other aquatic life. Both California and the U.S. Environmental Protection Agency are reevaluating the chemicals because of safety concerns.
“Pyrethroids are obviously a safer alternative to organophosphates, but just because they are safer doesn’t mean they are safe,” said Dana Boyd Barr, a research professor of environmental health at Emory University’s Rollins School of Public Health in Atlanta, Georgia. Barr authored a study that for the first time has measured pyrethroid exposure in the U.S. population.
Pyrethroids are found in more than 3,500 products used inside homes and on crops, yards, and gardens – including lice shampoos, indoor foggers, flea sprays for pets and pesticides to fight ants, wasps, mosquitoes, aphids and spiders. Consumers can identify pyrethroids in products by checking labels for compounds that end in “thrin,” such as bifenthrin, permethrin and cypermethrin.
The compounds are synthetic versions of naturally occurring insecticides called pyrethrins harvested from chrysanthemum flowers. Chemists alter the structure of the pyrethrin molecule to make it more stable in sunlight and to increase its toxicity. The chemicals kill insects by interfering with basic nerve cell functioning. Insects and other invertebrates are highly susceptible to them, while birds and mammals are better able to counteract their effects…
[continues on Scientific American]