An assay measuring the chemiluminescent response of hemocytes from the oyster Crassostea virginica was used to assess the effects of environmental pollutants on phagocytosis. In vivo and in vitro effects of heavy metals (copper, cadmium, zinc, and aluminum), pesticides (dieldrin and chlordane), and organic compounds (naphthalene and 2,4-dinitrophenol) on the chemiluminescent response of stimulated oyster hemocytes were tested. In most cases, exposure to a hlgh pollutant concentration resulted in a decreased chemiluminescent response. After in vivo treatment, the response of the hemocytes depended on the duration of exposure to the pollutant and pollutant concentration. Instances of both acclimation and cumulati\re toxlc~ty of pollutants were observed.

Abstract-Samples collected from urban streams in the cities of Sacramento and Stockton, California, USA, during the precipitation season were analyzed for diazinon and chlorpyrifos. Concentrations were determined with enzyme-linked immunosorbent assays specific for each pesticide. Two hundred thirty-one samples from the two cities were analyzed for diazinon; 85% exceeded California Department of Fish and Game water-quality criteria for this pesticide. Chlorpyrifos was measured in 90 of the samples collected from Sacramento and Stockton; 80% exceeded the California Department of Fish and Game criterion for this pesticide. Thirty-six of 47 samples (76.6%) tested for toxicity produced total mortality within 72 h with Ceriodaphnia dubia. Toxicity identification evaluations on selected samples confirmed that toxicity was primarily due to one or both of these pesticides. Uses of diazinon and chlorpyrifos in urban areas include dormant sprays on fruit trees, professional landscape and maintenance uses, and structural pest control. Pesticide concentrations were lower in a catchment favoring commercial and industrial activities compared with a catchment receiving largely residential inputs. Aerial drift from agricultural applications may play a role in storm-water concentrations.