Ultimate fate and toxicological consequences of insecticide pyriproxyfen and its metabolites in soil ecosystem

Abstract

Insecticide pyriproxyfen (PYR) is very specific to insect pests and possess low mammalian toxicity. Its degradation can result in formation of about 10 metabolites in the environment. Some of the metabolites are reported to be very toxic and mobile in nature. Their potential to cause toxicity through environmental contamination may raise serious concern. Available literature is short of the information on formation of different metabolites in soil, their ultimate fate and toxicological consequences. We studied metabolic pathway of PYR by observing dissipation behavior of different metabolites in soil under sub-tropical agro-climatic conditions of north India. Soil under field conditions was treated with PYR at (T1) 100 and (T2) 200 g a.i./ha. Samples were drawn periodically, processed and analyzed using GC-MS tandem mass spectrometry. Six metabolites namely 4-OH-PYR, POP, POPA, 4-OH-POPA, PYPA and PYPAC were formed during degradation process. Most metabolites appeared very early and attained maximum concentration on day one of PYR application. However, their residues persisted for more than 30 days with variable half-lives ranged from 2.6 to 30 days. The toxicological study revealed that metabolites C, E and F were highly pernicious to soil enzymes sucrase, catalase, urease and dehydrogenase. PYR do not posed any detrimental effects in adult honeybees. Considering the persistence behavior and toxicological consequences of metabolites, further investigations are needed for preventing their harmful effect on non-target organisms and associated environment. Summary: Degradation of pyriproxyfen revealed 6 metabolites most of which persisted for more than 30 days in soil. Metabolites C, E and F caused toxicity to soil enzymes. Parent PYR do not caused any detrimental toxicity effect in adult honeybees.