When earthworms are maintained in soil containing [14C]cypermethrin they accumulate radioactive residues. These residues are not eliminated when the worms are transferred to untreated soil. The accumulated radioactive residue is a complex mixture of conjugates of two metabolites of cypermethrin (3‐phenoxybenzoic acid and (1RS)‐cis, trans‐3‐(2,2‐dichlorovinyl)‐2,2‐dimethylcyclopropanecarboxylic acid). One major constituent of this mixture of conjugates has been identified as N1, N12‐di‐(3‐phenoxybenzoyl)spermine. Feeding studies with quail and rats have established that the residues accumulated by the earthworms are not further bioaccumulated by earthworm predators.
The degradation of pirimiphos‐methyl on grains stored at moisture contents of ≈ 13 and ≈20% has been investigated. Wheat and rice grains were sprayed with [14C]‐ pirimiphos‐methyl and stored at 20°C under controlled humidity conditions for periods of 12 and 24 weeks. At a moisture content of 13%, degradation was slow, so that at least 70% of the radioactive residue was unchanged pirimiphos‐methyl after 24 weeks. Faster degradation occurred at 20% moisture content, but the major component of the radioactive residue (at least 52%) was still unchanged pirimiphos‐methyl after 24 weeks. Two major degradation products were formed on the grains; one (18–23.4% of the residue) was characterised as 2‐diethylamino‐6‐methyl‐pyrimidin‐4‐ol, and the other (1.0–9.7% of the residue) was converted to the first by acid hydrolysis. In addition, trace amounts of O‐2‐ethylamino‐6‐methyl‐pyrimidin‐4‐yl OO‐dimethyl phosphorothioate, 2‐ethylamino‐6‐methyl‐pyrimidin‐4‐ol, 2‐ amino‐6‐methyl‐pyrimidin‐4‐ol and an unidentified compound were also detected.
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