Fairbrother, A., and B. Hope. 2005. Terrestrial Ecotoxicology. Pages 138-142 in P. Wexler, editor. Encyclopedia of Toxicology (2nd edition). Elsevier: Oxford. WED-03-172
Terrestrial ecotoxicology is the study of how environmental pollutants affect land-dependent organisms and their environment. It requires three elements: (1) a source, (2) a receptor, and (3) an exposure pathway. This article reviews the basic principles of each of each element as they occur in terrestrial systems. Pollutants enter the terrestrial environment through direct application, from diffuse sources, or by long-range transport. Terrestrial receptors include soil microbes, invertebrates, plants, amphibians, reptiles, birds, and mammals. Terrestrial organisms can be exposed to pollutants through dermal, oral, inhalation, and food-chain exposures. Two important processes govern the movement of a pollutant into and through a terrestrial food web: bioaccumulation and biomagnification. Understanding the relative importance of these processes, as well as the various exposure pathways, is for an understanding of potential toxic effects. Toxic responses of terrestrial organisms can be assessed following standard laboratory toxicity test protocols; there are no standard methods available for toxicity tests with reptiles. However, most species are not tested directly, but rather a standard set of test organisms is used from which extrapolations are made to other species. For some chemicals, the amount of pollutant present in plant or animal tissues can be used to predict whether or not they will be affected. Bioassays may be conducted in the field to look at potential effects under natural conditions. Population models can be used to determine if toxic effects resulting from exposure to environmental pollutants will significantly alter the ability of a population to sustain itself over time. Pollutants also may result in a change in the community composition of plant or animal species. However, plants and animals can develop tolerance over time and adapt to some environmental pollutants. The ecotoxicological information discussed here can be assembled into a risk assessment by combining exposure and effects data to estimate the likelihood of adverse effects to individual organisms, populations, or communities.