Environmental Toxicology

Author: Sean Doel - Director, WSP Environment & Energy SA

( Article Type: Explanation )

Environmental toxicology is a specialised branch of toxicology that deals with the harmful effects of chemicals, and biological and physical agents, on living organisms including fish, plants, animals and humans. It is a relatively new field of research that has developed rapidly since the publication in 1962 of the book Silent Spring by Rachel Carson that investigated the effects of uncontrolled pesticide use.

Environmental toxicologists draw on a wide variety of scientific disciplines including chemistry, biochemistry, biology and physiology in their efforts to understand the severity and frequency of adverse health effects that exposure to different toxicants in the environment can cause.
This knowledge provides the basis upon which the risks associated with toxicants in the environment can be assessed and public health protected. Environmental toxicological studies and research is housed in a number of international, peer-reviewed databases that provide information on the specific health effects, metabolism and excretion, safe levels of exposure, and numerous other aspects that need to be understood when assessing the risk of exposure to a particular environmental toxicant. Aside from use in the preparation of material safety guides for all substances and products in use globally, toxicological information is also routinely used when human health and environmental risk studies are required to define the potential health risks to a given individual, community or population from either inhalation of an air pollutant, drinking contaminated groundwater or river water, or contact with a hazard material or waste.
The assessment of risk follows a standard four stage process starting with hazard identification, toxicological review, exposure assessment and finally risk characterisation. Acceptable risk levels for public exposure to environmental toxicants are defined on the basis of safe or tolerable daily intakes, for systemic or non-carcinogenic toxicants, and an acceptable cancer incidence level for toxicants that are known to be carcinogenic. Internationally, acceptable cancer incidence levels for public exposure range from one in ten thousand to one in a million. In South Africa, all of our key environmental standards, including air quality, effluent, drinking water, soil contamination, and waste, have been developed on a risk-based approach.