National Marine Fisheries Service concurs, pesticides acting together harm salmon

National Marine Fisheries Service concurs, pesticides acting together harm salmon

 
As noted in a prior post, researchers have found that various pesticides act synergistically to harm salmon. The report by scientists of the Northwest Fisheries Science Center evaluated the effects of 5 of the most extensively used pesticides in the Pacific Northwest and California-diazinon, malathion, chlorpyrifos, carbaryl, and carbofuran-on the brains of juvenile coho salmon.
 
As noted previously, nearly every pairing of the five pesticides inhibited activity of an important brain enzyme, acetylcholinesterase, after the salmon were exposed over a 96-hour period. This enzyme plays a critical role in several neurological pathways, and at reduced levels can diminish fish survival and even cause death.
 
Researchers expected that the harmful effects of pesticide combinations would simply add up as they accumulated. As noted in a prior post, for some combinations, they found that the toxic effects of reduced brain enzyme levels were much greater than predicted if each chemical was acting in isolation of the other. This synergy made those particular pesticide combinations more harmful than the sum of their parts. As the doses of individual pesticides increased, the synergistic effects were almost uniformly more pronounced. For some chemical combinations, the data suggest synergistic effects are possible at concentrations below the lowest levels used in the study. No salmon died when exposed to an individual pesticide, yet many died outright when exposed to combinations. The most deadly pairing was diazinon and malathion.
 
The report, which has now been blessed, can be found at http://www.ehponline.org/docs/2008/0800096/abstract.html.
 
As a result, the National Marine Fisheries Service has asked EPA to restrict the use of three pesticides (carbaryl, carbofuran and methomyl) that are seen as posing the greatest threat to the survival of more than a dozen threatened or endangered species of Pacific salmon and steelhead on the West Coast.