A lecture by Dr Rick Leah
(Long version of Notes prepared by Dr R T Leah, Biological Sciences, University of Liverpool but including material summarized and adapted from various locations on the www*)
The impact of toxic chemicals on wildlife and humans has been of great concern for the last fifty years. Unfortunately this is a very large, complex subject area which can only be covered superficially within the time available. However, this lecture is intended to give an introduction to fundamental aspects of how some pollutants interact with living organisms to cause deleterious effects. The complexity will be explained and simplified where possible. You should understand at least a little about the biology of key organisms and how pollutants cause damage at a physiological level. You should be aware of how pollutants can induce change in organisms which can be used as a ‘biomarker’ of the presence and action of the pollutants (although this will form the subject of a later lecture in this course).
Thus as the main outcome of this lecture you should have an appreciation of the wide range of contemporary issues that are caused by toxic chemicals in the environment and what regulatory authorities are doing to monitor and control them. You should understand the main hazards that toxic chemicals pose and how risk to humans and wildlife is controlled. You should be aware of the main groups of pollutants of contemporary concern.
The material covered will be useful for the consideration of two case studies on the impact of toxic chemicals in the Great Lakes of North America and the Baltic Sea in later lectures.
Environmental Toxicology or Ecotoxicology?
It was after World War II that increasing concern about the impact of toxic chemicals on the environment led Toxicology to expand from the study of toxic impacts of chemicals on man to that of toxic impacts on the environment. This subject became known as Environmental Toxicology.
Ecotoxicology is a relatively new discipline and was first defined by René Truhaut in 1969. It attempts to combine two very different subjects: ecology ("the scientific study of interactions that determine the distribution and abundance of organisms" Krebs 1985) and toxicology ("the study of injurious effects of substances on living organisms", usually man). In toxicology the organisms sets the limit of the investigation whereas Ecotoxicology aspires to assess the impact of chemicals not only on individuals but also on populations and whole ecosystems.
During the early years, the major tools of Environmental Toxicology were: detection of toxic residues in the environment or in individual organisms and testing for the toxicity of chemicals on animals other than man. It was however, a very big jump in understanding from an experimental animal to a complex, multivariate environment and the subject of ECOTOXICOLOGY developed from the need to measure and predict the impact of pollutants on populations, communities and whole ecosystems rather than on individuals. There is an on-going debate as to the exact scope and definition of ecotoxicology.
The simplest definition found to date is that ecotoxicology is "the study of the harmful effects of chemicals upon ecosystems" (Walker et al, 1996).
A more complete definition of Ecotoxicology comes from Forbes & Forbes 1994 “the field of study which integrates the ecological and toxicological effects of chemical pollutants on populations, communities and ecosystems with the fate (Transport, transformation and breakdown) of such pollutants in the environment”.
and several books have been written recently which discuss this in some depth, these include:
Cairns, J Jr & Niederlehner B R (1994) Ecological Toxicity Testing. CRC Press Inc: Boca Raton
Forbes, V E & Forbes T L (1994) Ecotoxicology in Theory and Practice. Chapman & Hall...