Pesticide Toxicity to Parasitoids: Exposure, Toxicity and Risk Assessment Methodologies

Abstract

Pesticides enter into aquatic ecosystem by many ways viz., drift, wash off and drain from agro-ecosystem or by deliberate application in the water. Fish live in water and thus continuously get exposed to the contamination by contact, respiration and by contaminated food intake. Acute toxicity assessment of pesticides to fish is mostly carried out through water contamination bioassays as static, static-renewal and flow-through systems apart from injection and through dietary exposures. Literature on the sublethal effects as alteration of behaviour (sensation, locomotion, feeding, learning etc.), physiology (respiration, metabolism, reproduction etc.), biochemistry of enzymes, blood and hormones apart from histopathology, carcinogenicity and mutagenicity were reviewed and compiled. Different methods to assess these sublethal effects along with genotoxicity of pesticides as disrupting in genes, chromosomes, {DNAs} and {RNAs} are given in detail. Pesticide toxicity on endocrine, cardiovascular, nervous, digestive and reproductive systems and their procedures to assess those sublethal toxic effects are explained. Only a few studies on semi-field/mesocosm and field toxicity assessments are available in the literature. Risk assessment of pesticides in aquatic ecosystem by the estimation of acute and chronic toxicity, calculation of risk estimates, multi tier approach of risk assessment, comparison with target and non-target susceptibility are given in detail. Human beings and predators are also at high risk of consumption of pesticide contaminated fish owing to bioaccumulation and biomagnification and thus, assessment of risk in consuming contaminated fish is also included.