Boy, we make it hard on the fish!  Researchers from NOAA and WSU conducted a study that was published Monday in the journal, Environmental Health Perspectives.  The authors concluded that some pesticides work together in a deadly synergy, becoming more harmful than the sum of the parts would indicate.  The finding is very important since currently, the EPA tests pesticides one at a time to see how much is needed to kill fish.  

Jeff Barnard, AP Environmental Writer, quotes one of the authors, Nathaniael Scholtz, a research zoologist at NOAA's Northwest Fisheries Science Center.  "We need to design new research that takes into effect the real-world situation where pesticides almost always coincide with other pesticides."

NOAA and the EPA are evaluating pesticides under terms of an agreement reached in a lawsuit brought by Northwest Coalition for Alternatives to Pesticides, among others.  "Last year, NOAA Fisheries issued findings under the Endangered Species Act that diazinon, malathion and chlorpyrifos jeopardize the survival of all 28 species of Pacific salmon listed as threatened or endangered in the West.  The three chemicals, found by the U.S. Geological survey to contaminate rivers throughout the West, interfere with salmon's sense of smell, making it harder to avoid predators, locate food and even find their native spawning streams and reproduce. At higher concentrations, they kill fish outright."

An additional 34 pesticides must be tested under terms of the settlement.  In the study, fish brains were analyzed for levels of the enzyme acetylcholinesterase, "which allows impulses to move between neurons in the brain".  According to Scholz, "Earlier research found that lower levels of the enzyme affected the ability of fish to feed and swim, which would affect their ability to survive".

In addition, the researchers believe it is possible that combinations of chemicals suppress another enzyme, which assists the body to rid itself of toxins.  "Another new avenue for research will be how pesticides combine with other water quality problems, such as warm water, to harm salmon, Scholz said."