Microbial degradation agricultural chemicals

Synthetic pyrethroids now account for at least 30% of the world insecticide market and are rapidly replacing other agricultural chemicals for control of insect pests. Fenvalerate is one of the more widely used synthetic pyrethroid insecticides. It is derived from a combination of a-cyano-3-phenoxybenzyl alcohol and a-isopropyl phenylacetate ester. Technical fenvalerate is a mixture of four optical isomers, each occurring in equal amounts but with different efficacies against insect pests. Fenvalerate does not usually persist in the environment for >10 weeks, and it does not accumulate readily in the biosphere. Time for 50% loss (Tb 1/2) in fenvalerate-exposed amphibians, birds, and mammals was 6 to 14 h for reptiles, terrestrial insects, aquatic snails, and fish it was >14 h to <2 days and for various species of crop plants, it was 2 to 28 days. Fenvalerate degradation in water is due primarily to photoactivity, and in soils to microbial activity. Half-time persistence in nonbiological materials is variable, but may range up to 6 days in freshwater, 34 days in seawater, 6 weeks in estuarine sediments, and 9 weeks in soils. 

Symmetrical triazines, like other anthropogenic or natural organic chemicals introduced into the environment, are subjected to microbial transformation processes. Environmental sites of most interest are agricultural fields, lakes, rivers, sediments, potable water, and groundwater. These sites also play a key role in the degradation of s-triazines and the eventual complete mineralization (e.g., C02 and NH3) of these compounds. 

As noted, TSCA coverage extends to chemical substances and mixtures used in a broad range of industrial, commercial and consumer applications. Some examples of the types of microbial products that would be subject to TSCA are microorganisms used to produce pesticides and other commercial chemicals, to convert biomass to energy, for pollutant degradation and enhanced oil recovery, in metal extraction and concentration, and in certain non-food agriculture applications, such as nitrogen fixation. 

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