Toxicity of pesticides in wastewater: a comparative assessment of rapid bioassays

Acute toxicity of pesticides in water was assessed singly and in mixtures using various responses of the luminescent bacterium Vibrio fischeri, the aquatic invertebrate Daphnia magna, and the MitoScan(TM) assay. The latter utilized fragmented mitochondria to enzymatically convert oxidized beta-nicotinamide adenine dinucleotide (NAD+) to its reduced form, NADH. The rate of the conversion being sensitive to the type and concentration of toxicants. The pesticides tested were carbofuran, cyromazine, fenamiphos, formetanate, and propamocarb. The aqueous solubility of all compounds exceeded 320 mg l-1. All the toxicity bioassays were characterized in terms of relative sensitivity and complementarity. Synergistic and antagonistic toxicity effects were observed with pesticide cocktails relative to pure compound toxicities. The D. magna assay was the most sensitive and best able to detect toxic interactions of mixtures. Cyromazine was the least toxic of the pesticides tested.