Mixtures of Pesticides Detected in Crab Embryos Completed

By Environmental Health Program May 31, 2011

Scientist Collecting Sand Crabs From an Urban Estuary

Richmond, California

The Shore Crab Collected From a Rocky Cover

Bodega Bay, California

Crab embryos from two Northern California salt marshes accumulate mixtures of currently used as well as discontinued pesticides, according to a study published by U.S. Geological Survey (USGS) and University of California scientists in the journal Environmental Toxicology and Chemistry.

The scientists detected pyrethroid and organophosphate insecticides as well as 20 other pesticides, including DDT, in crab embryos using newly developed techniques at the USGS Toxic Substances Hydrology Program's Pesticide Research Laboratory. The highest concentrations of pyrethroids and organophosphate insecticides were detected in embryo samples collected adjacent to a suburban housing development reflecting the use of these pesticides by homeowners and their subsequent pathways into the environment. Samples from both salt marshes indicate that DDE, the major breakdown product of the legacy insecticide DDT, was the most frequently detected pesticide and was found at the highest concentrations. Although banned over 30 years ago in the United States, DDT as well as its degradates are highly persistent and have been detected worldwide in many types of aquatic organisms. Detections of pyrethroid, organophosphate, and other pesticides in crab embryos indicate these organisms are exposed to a mixture of these compounds during early, sensitive life stages. These results also indicate that exposure pathways are derived from complex combinations of older pesticides that linger in the environment for decades as well as newer pesticides that are more likely attributed to recent runoff and other shorter term hydrologic events.

Scientists use invertebrates, like shore crabs, as early warning signs or sentinels for assessing the health and productivity of ecosystems. So like the proverbial canary in the coal mine, scientists can use crab embryos to test for the accumulation of contaminants in aquatic organisms. In this case the scientists were also testing a newly developed analytical method to measure the concentrations of pesticides in the embryos.

Scientist collecting sand crabs from an urban estuary near Richmond, California — USGS scientist collecting sand crabs from an urban estuary near Richmond, California. Crabs utilize these rocky intertidal areas as feeding and breeding grounds.

These findings on pesticide exposures from the early-life stages of a sentinel species can help decision and policy makers, as well as scientists, prioritize and assess the potential impacts of pesticides on the overall health of the environment. Funding for this work was provided by the USGS Toxic Substances Hydrology Program, USGS Priority Ecosystems Program, and U.S. Environmental Protection Agency Star Grant Program (R82867601).