Ecotoxicology

Ecotoxicology is concerned with the harmful effects of chemicals. The questions of what constitutes harm and how toxicity is measured need to be addressed.

Ecotoxicology is the branch of toxicology concerned with the study of toxic effects, caused by natural or synthetic pollutants, to the constituents of ecosystems, animal, vegetable or microbial in an integral context.

Moriarty has clarified this definition by stating that ‘toxicology is concerned with effects on single organisms; ecotoxicology is concerned with effects on ecosystems.

Ecotoxicology as a subject area came to prominence in the 1950s and 60s after the publishing of Rachel Carson’s book (REF) on the impact of pesticides such as DDT. Further impetus was provided by problems arising from spills of chemicals and oil. This generated the need for the ‘competent authorities’ ie. Government in all its forms to predict and evaluate the nature and significance of ecological effects resulting from the deliberate or accidental introduction of toxic substances to the environment.

As a result of decades of work, there are now established procedures for establishing the fate and effects of substances introduced into the environment and in many components of ecosystems. However, since many aspects of this are difficult and complex, there is much ongoing research into areas such as sediments and the toxicity of complex mixtures.

Of central importance in both toxicology and ecotoxicology is the relationship between the quantity of chemical to which an organism is exposed and the nature and degree of consequent harmful (toxic) effects. Dose-response relationships provide the basis for assessment of hazards and risks presented by environmental chemicals. This simple basic concept immediately raises questions about the definition of poisons because everything depends on dose. Essentially, no chemical is poisonous if the dose is low enough, whereas all chemicals are poisonous if the dose is high enough (even apparently harmless substances such as sugar and salt can be toxic to animals at high doses).