Hyalella azteca are invertebrates that are widely used for sediment and water toxicity studies. Investigators have found that H. azteca collected from sites influenced by agricultural/urban runoff are as much as 2-times less sensitive to pyrethroid insecticides than lab-grown H. azteca. In contrast, the insecticide sensitivities of H. azteca collected from undeveloped sites beyond the influences of agricultural/urban runoff were similar to those of lab-grown populations.
The results suggest that standard compliance testing of ambient waters, stormwater, and agricultural runoff and sediments using lab-grown H. azteca populations may not accurately reflect the health of resident H. azteca and the environments in which they live.
"Although laboratory tests can predict effects in the field, care should be taken when using the lab data for 303(d) listing if alternative field data indicate that the organisms of concern are not affected by the constituent of concern, such as pyrethroids," said Stephen Clark, lead author of the Environmental Toxicology and Chemistry study.