Certain agricultural chemicals used in California's Central Valley may be present in water and sediment in high enough levels to cause potential reproductive harm to waterfowl and shorebirds, a team of UC Davis researchers has found. The farm chemicals have estrogenic qualities that, when ingested by wildlife, can disrupt the endocrine system, causing reproductive problems and abnormalities in developing embryos. The researchers, led by Michael Johnson, an associate research engineer in the UC Davis civil and environmental engineering department, sought to learn whether widespread exposure of wildlife to the chemicals was possible as a result of normal agricultural activities. Previous laboratory research has shown that estrogens affect the reproduction of wildlife. But investigations of estrogenic compounds in nature have been limited so far to studies of the feminization of alligators and gulls, and to deformities in Great Lakes birds -- where high levels of contaminants were released in specific areas. Sampling water and sediment found in agricultural drains in one California county high in fruit and nut production, the researchers found the presence of moderately weak to moderately strong estrogen-receptor binding chemicals. Water samples contained slightly higher levels of the chemicals than did sediment. Waterfowl and shorebirds use the agricultural drains during fall migration through the Central Valley. The researchers say that the chemicals move from fields to the drain canals during the summer by infiltrating the soil and moving through shallow groundwater or through drain tile systems. Though the results are preliminary, "it appears that endocrine disrupters do occur in the environment where wildlife could come into contact with them," Johnson said. Project results were recently published in the Bulletin of Environmental Contamination and Toxicology.