Warning on Neurotoxic Pesticides

By | June 8, 2015

imidacloprid-chemical-structureA controversial decision by the US Environmental Protection Agency (EPA) to allow water borne use of a neurotoxic pesticide has ignited debate on the safety of using pesticides directly on aquatic ecosystems.

The pesticide in question is imidacloprid, a chemical used extensively for pest control on millions of acres of farmland and cropland, along with golf courses and residential lawns.

Imidacloprid is also the “active ingredient” in several dog and cat flea control products such as Bayer Advantage.

Imidacloprid works by blocking neurotransmission in invertebrates (think bugs and insects), effectively paralyzing them. It has also been implicated as a factor (but not the only factor) in the ongoing collapse of bee colonies in North America over the past 10 years.

The EPA’s decision in favor of using imidacloprid on water surfaces was in response to a request from a group of oyster farmers in Willapa Bay, Washington state, who have been battling infestations of burrowing shrimp for decades. In sufficient amounts, imidacloprid will probably kill the unwanted shrimp, allowing a bigger harvest of oysters.

A Risky Gamble Avoided, For Now

The issue at hand is, what are the long term effects on the aquatic food chain when imidacloprid is introduced directly into the water, including the effect on salmon and other fish?

Salmon RiverUnfortunately, no one knows the answer to this question.

Imidacloprid dissolves easily in water, and can hang around for more than a year in deeper water with little sunlight. It’s reasonable to assume that fish feeding on algae will ingest unknown amounts of the chemical.

It appears the EPA, along with the Washington state Department of Ecology, were willing to take a gamble that there wouldn’t be any negative “upstream” effects on the regional aquatic ecosystem from imidacloprid use.

However, the Washington state Department of Ecology abruptly reversed course less than two weeks before the pesticide spraying was to begin, and cancelled the permit. It appears that a combination of public pressure and safety concerns encouraged this reversal.

There will be future pressure to increase yields from aquatic farming. We believe the best approach is to clearly understand the benefits and risks of any method (chemical or otherwise), before proceeding.