March 4th, 2009
By Barbara Kessler
Green Right Now
What happens when salmon are given a pesticide cocktail? The effects can be more pronounced than the damage done from exposure a single pesticide, according to a study just released in the Environmental Health Perspectives journal.
In an attempt to replicate real world pesticide exposures, researchers from NOAA Fisheries Service and Washington State University studied how coho salmon reacted to five common pesticides, individually and in various combinations.
They found that almost every pesticide pairing resulted in a chemical reaction in the brain – a reduction of an enzyme – that could lead to the accumulation of acetylcholine, which would affect the salmon’s behavior and jeopardize its ability to survive.
Need we mention here that salmon are already facing a host of difficulties from warming rivers inhospitable to breeding behavior to industrial pollution and overfishing?
The pesticides were tested at various levels (including some considered safe), for a total of 30 different combinations – 20 of the 30 produced stronger reactions than the chemicals could be expected to produce on their own. The outcomes led the researchers to conclude that it was the synergy of the chemicals being combined that increased the toxicity.
Three of the 30 combinations killed the fish outright within 24 hours.
The chemicals tested included those commonly used in agriculture in California and the Pacific Northwest – diazinon, malathion, chlorpyrifos, carbaryl and carbofuran – and found in runoff and streams.
The final conclusion, according to a synopsis on the journal website: “In light of the current findings, mixtures that have been considered relatively safe may pose more of a hazard to wildlife than was previously thought.”
Or, as co-author NOAA zoologist Nathaniel Scholz told the AP: “We need to design new research that takes into effect the real-world situation where pesticides almost always coincide with other pesticides.”
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