Toxicology is one of the scientific fields that studies the adverse impacts of pollution in environments. Toxicology draws attention to “environmental toxins,” or any substance or chemical found in the environment that has toxic effects on organisms. For toxicologists, the term “environmental” is broadly defined as any type of environment with which living things have contact. A “toxin” is any substance considered to be poisonous because it produces adverse for living organisms down to the cellular level. In some scientific views, toxins are differentiated, and it is common to refer to biological toxins or toxins produced within an organism, and chemical toxins (chemical agents) or toxins introduced into a biological organism externally.
In the toxicological view, not all chemicals added to the environment are toxic pollutants with respect to any given species of organism until they cross a toxicological threshold when adverse impacts on a species can be identified. For example, some chemicals emitted into environments may be processes by an organism normally until the level of exposure exceeds a toxic dose, at which point the pollutant becomes a toxic pollutant. In toxicology, therefore, it is not the mere presence of a pollutant in an environment that is a concern. Concern is raised when the concentration of a pollutant in the environment is large enough to cause toxic effect.
Toxicological research on environmental pollutants can be divided into two broad types: those relevant to ecotoxicology and those studies within environmental toxicology. Ecotoxicology is concerned with examining the toxic effects associated with both natural and synthetic pollutants on organisms in general. In contrast, environmental toxicology is specifically concerned with the effects of environmental toxins on humans.
Walker et al. (2006: i) define pollutants and chemical contaminants as “chemicals that exist at levels judged to be above those that would normally occur in any particular component of the environment.” That is to say, a chemical becomes a pollutant or chemical contaminant when its level in the environment exceeds its normal background level. In this view, the emission of a chemical into the environment is insufficient to classify it as a pollutant. A chemical emission only becomes a pollutant when the emitted chemical exceeds its naturally occurring background level. In this view, pollutants can be distinguished from chemical contaminants due to their effect on organisms. The difference between a chemical contaminant and pollution is that pollution causes an environmental harm, either to the functions of ecosystems or to the species found in ecosystems. In his view a chemical contaminant becomes a pollutant when the chemical produces adverse effects on ecosystems or organisms. (For more extended discussions relevant to the above see, Bazerman and De los Santos, 2005; Forbes and Forbes, 1994; Walker et al., 2006; Zakrzewski, 2002).
Legally, pollution is defined by emission standards. Those standards attempt to make reference to scientific standards for defining pollution. However, pollution laws often allow pollutants to be emitted into the environment even though those emissions may be in excess of background levels or cause adverse ecological or organism health harms. In the US, for example, corporations may obtain pollution permits which allow them to emit pollutants up to a certain number of pounds. Thus, some pollutants are legally emitted into ecosystems.
Bazerman, C. and R.A. De los Santos. (2005). “Measuring Incommensurability: Are Toxicology and Ecotoxicology Blind to What the Other Sees?” In R.A. Harris (ed.), Rhetoric and Incommensurability. Lafayette, IN: Parlor Press, 424-463.
Forbes, V.E. and T.L. Forbes. (1994). Ecotoxicology in Theory and Practice. New York, NY: Chapman and Hall.
Walker, C.H., S.P. Hopkins, R.M. Sibley, and D.B. Peakall. (2006). Principles of Ecotoxicology. Boca Raton, FL: Taylor & Francis.
Zakrzewski, S.F. (2002). Environmental Toxicology. New York, NY: Oxford University Press.