ENVIRONMENTAL TOXICOLOGY AND RISK ASSESSMENT

Abstract

Environmental toxicology and risk assessment have become increasingly important fields of environmental science because of the growing release, persistence, transformation, and biological accumulation of hazardous substances in ecosystems. Rapid industrialization, urbanization, agricultural intensification, mining, transportation, pharmaceutical consumption, plastic production, and inadequate waste management have introduced a wide range of chemical contaminants into air, water, soil, sediments, and biological systems. Conventional pollutants such as heavy metals, pesticides, petroleum hydrocarbons, industrial chemicals, and persistent organic pollutants continue to pose serious ecological and human-health concerns, while emerging contaminants such as pharmaceuticals, personal-care products, endocrine-disrupting chemicals, per- and polyfluoroalkyl substances (PFAS), microplastics, nanoplastics, and transformation products have created additional challenges for environmental risk assessment. Recent research emphasizes that many contaminants cannot be evaluated adequately through traditional single-chemical and single-species approaches because environmental exposure commonly involves mixtures, chronic low-dose exposure, transformation products, bioaccumulation, trophic transfer, and interactions among chemical and biological stressors. (DOI) Environmental toxicology provides the scientific basis for understanding how contaminants interact with organisms at molecular, cellular, physiological, population, community, and ecosystem levels. Toxicological endpoints such as oxidative stress, endocrine disruption, genotoxicity, neurotoxicity, reproductive impairment, immunotoxicity, altered metabolism, behavioral changes, and mortality are increasingly used to characterize environmental hazards. Risk assessment complements toxicological research by evaluating the probability and magnitude of adverse effects under realistic exposure conditions. The process generally involves hazard identification, dose-response assessment, exposure assessment, and risk characterization. However, uncertainty remains a major component of environmental risk assessment because environmental concentrations fluctuate, contaminants undergo transformation, organisms differ in sensitivity, and data are often unavailable for many species and chemical combinations.