Pesticides harm salmon. As headlines go, this isn't terribly shocking, considering the backlash against insecticides that began in 1962 with Rachel Carson's publication of "Silent Spring."

Pesticides harm salmon. As headlines go, this isn't terribly shocking, considering the backlash against insecticides that began in 1962 with Rachel Carson's publication of "Silent Spring."

And yet it hasn't been possible to emphatically state as fact that agricultural chemicals play a role in the decline of endangered salmon runs in the Pacific Northwest.

This ignorance is now fading, thanks to a National Marine Fisheries Service study that was forced by an environmental lawsuit in Seattle. The Seattle Post-Intelligencer reported draft findings of the study last week.

NMFS scientists uncovered "overwhelming evidence" that three of the first pesticides it tested harm salmon's ability to swim, find food, reproduce and escape predators.

One of the three, Malathion, has long been commonly used by homeowners to control lawn weeds, in addition to widespread application by farmers and orchardists on more than 100 crops. Diazinon is used on 50 crops and Chloripyrifos on about three dozen, besides being applied to control mosquitoes and fire ants.

Like most such chemical studies, this one exposed the salmon to far greater concentrations for a longer period than they would ever likely see in the wild. Agricultural interests argue that natural exposures tend to consist of brief pulses in the water, which rapidly dissipate. Hopefully, they are correct.

But NMFS asserts that even at much lower levels, these chemicals affect young salmon in ways certain to negatively impact their ability to prosper, or even survive. Together with dams, adverse ocean conditions and other challenges, it seems these chemicals may contribute to generalized population declines.

These three pesticides have been characterized as the nastiest of farm products still widely used, but NMFS is also about to turn its attention to 34 newer compounds to see what they do to salmon.

It would be nice if curtailing pesticide use were a silver bullet for salmon problems, but unfortunately the situation is far more complex. Modern agriculture, aquaculture and forestry are all highly dependent on man-made chemicals. In our area, for example, cranberry and oyster growers both have historically relied upon spraying to control weevils, mud shrimp and other pests.

With enough time and thought, options can be developed. Cranberry farms have been committed for the past decade to Integrated Pest Management, weaning themselves away from Chlorpyrifos and Diazinon. Growers of other produce can achieve similar results.

The Bush administration is currently seeking to limit how much attention the U.S. Environmental Protection Agency has to give studies like this one when it licenses pesticides. It should be obvious, however, that it is better to make decisions based upon complete information. As in this case, the answers may not be welcome or the responses convenient, but we can't keep sweeping the damage caused by pesticides under the rug.