Effects analysis of time-varying or repeated exposures in aquatic ecological risk assessment of agrochemicals.
Exposure to agrochemicals in the aquatic environment often occurs as time-varying or repeated pulses. Time-varying exposures may occur due to runoff events and spray drift associated with precipitation and application events. Hydrologic dilution, dispersion, and degradation also produce pulsed exposures. Standard laboratory toxicity tests using constant exposure concentrations typically do not investigate the toxicity of time-varying or repeated exposures. Detoxification, elimination, and recovery may occur within organisms or populations during the periods between exposures. The difficulty of estimating effects of realistic time-varying exposures from measurements made under constant exposure conditions is often an important source of uncertainty in ecological risk assessment of pesticides. This article discusses the criteria and tools for deciding whether time-varying exposures are relevant in a particular risk assessment, approaches for laboratory toxicity testing with time-varying exposure, modeling approaches for addressing effects oftime-varying exposure, deterministic and probabilistic ecological risk characterization of time-varyingexposures and toxicity, and uncertainty analysis.
Rohm and Haas Company, Toxicology Department, Spring House, Pennsylvania 19477, USA. kreinert@rohmhaas.com
Kevin H
KH
Reinert
Jeffrey M
JM
Giddings
Laura
L
Judd
D000818:Animals; D017753:Ecosystem; D008962:Models, Theoretical; D010507:Periodicity; D010575:Pesticides / Q000009:adverse effects* / Q000032:analysis; D011891:Rain; D015203:Reproducibility of Results; D018570:Risk Assessment; D018675:Toxicity Tests; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000009:adverse effects* / Q000032:analysis
D010575:Pesticides; D014874:Water Pollutants, Chemical