MA6 Environmental Chemistry and Toxicology of Chiral Pollutants
202 Oregon Ballroom
8:00 AM - 12:00 PM, Monday
() Enantioselectivity in Aquatic Toxicity and Biodegradation for Current Chiral Insecticides.
Gan, J.1, 1 University of California, Riverside, CA
ABSTRACT- Most studies on pesticide enantioselectivity so far have focused on a few chiral chlorinated insecticides (e.g., 
-HCH and chlordane) and some chiral herbicides or fungicides. There is a general lack of research on the currently used chiral insecticides. All compounds in the synthetic pyrethroid class and many in the organophosphate insecticide class have one or more chiral centers, and these insecticides are commonly of great water quality concern because of their wide-spectrum acute aquatic toxicity. In this study, we isolated individual enantiomers from a number of pyrethroid and organophosphate insecticides by using chiral-selective HPLC and evaluated enantioselectivity in acute toxicity to Ceriodaphnia dubia and Daphnia magna, as well as during biodegradation in the sediment phase. In cis-bifenthrin and cis-permethrin, the (+) enantiomer contributed 94-97% of the observed toxicity in the racemate. In the chiral organophosphate insecticides, the (-) enantiomer contributed 87-94% of the total toxicity in the racemate. Significant enantioselectivity was also found for the synthetic pyrethroids during their degradation in sediment under either field or laboratory conditions. Enantioselectivity in these processes is expected to result in ecotoxicological effects that cannot be predicted from our existing knowledge, and must be considered in future risk assessment and regulatory decisions.
Key words: chiral, enantioselectivity, pesticides, agrochemicals