An Assessment of the Ecotoxicological Effects of Deltamethrin and Cypermethrin Using the Microbial Assay for Risk Assessment (Mara)

Abstract

Rapid microscale toxicity test makes it possible to screen large numbers of compounds. This test greatly simplifies toxicity identification, evaluation, and other effect directed to chemical analyses of environmental samples. The microbial assay for risk assessment (MARA) is a24 hour multi-species test that seeks to address this problem by using a battery of ten bacteria and yeast. There has been little independent evaluation of this test, and no published information on its sensitivity to pyrethroid insecticides. A series of Microbial assay for risk assessment (MARA) was carried out to assess the effect of deltamethrin and cypermethrin; two synthetic pyrethroid insecticides. Results obtained indicate cypermethrin and deltamethrin were nontoxic to most of the microorganisms at environmentally relevant concentrations. However, two microorganisms were sensitive to the two insecticides indicating application of these insecticides at the recommended concentrations may be modifying the microbial community by inhibiting the growth of sensitive microorganisms, and enhancing that of tolerant ones. Our results also show a similar toxicity pattern from the MARA test for both insecticides. Showing there is a potential for establishing a toxicity fingerprint for pyrethroid insecticides with more research. The results obtained from this research confirm the fact that species sensitivities to pesticides are different; therefore, for a better protection of the aquatic environment and all its resources, information is needed on the sensitivities of a wide range of species at different trophic levels.