environmental toxicology

environmental toxicology Environmental toxicology is the qualitative and quantitative study of the adverse or toxic effects of contaminants and other anthropogenic materials on living organisms. Toxic effects may be either lethal, causing death, or sublethal. Sublethal effects include changes in the reproduction, development, growth, pathology, physiology, and behaviour of organisms. The toxicity of a contaminant depends on the physical and chemical properties of the contaminant, the physical, chemical, and biological properties of the ecosystem studied, and the sources and rate of input of the contaminant into the ecosystem.

Environmental toxicologists study the potential of a contaminant to have harmful effects on living organisms. For any particular contaminant, this potential depends on its concentration and the duration of exposure. Toxicity tests are used to evaluate the adverse effects of contaminants on living organisms using standardized, reproducible conditions that enable comparison to be made with other contaminants that have been tested. After any chemical spill, bioassays are performed using the chemical in questions and various species of animals to assess the effects of the spilled material on the organisms. Toxicity depends on both abiotic factors such as pH, temperature, and organic matter, and biotic factors such as the species, life stage, size, and health of the organism. Chemical mixtures may demonstrate a toxicity greater than expected (synergistic) or less than expected (antagonistic) according to the effects of exposure on each individual contaminant in the mixture.

Many toxicological studies were performed after the Exxon Valdez oil spill in 1989 to evaluate the effects of crude oil on the organisms living in Prince William Sound (Alaska). As in other environments, the interaction of chemical, physical, and biological components had to be considered there. Polluted environments may be aquatic (freshwater, estuarine, or marine) or terrestrial, and each environment has its own mechanisms for responding to pollution.

Toxicology also entails the study of the distribution, transformation, transport, and fate of contaminants in plants and animals. Studies conducted after spills determine the horizontal and vertical extent of the contaminant and whether the original material has been transformed into other chemicals (metabolites) that might be more lethal. Environmental toxicologists also study the transport of contaminants through water currents, air currents, movement through porous sediments into groundwater, and volatilization. Toxicologists determine the fate of these chemicals, which can include ingestion by animals and eventual movement up the food chain, chemical uptake through the roots of plants that are then eaten by various animals and man, or absorption or adsorption by sediments ingested by bottom-feeding animals.

J. H. Baker