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INTRODUCTION

KEY POINTS

  • Ecotoxicology is the study of the fate and effects of toxic substances on an ecosystem.

  • Chemodynamics is the study of chemical release, distribution, degradation, and fate in the environment.

  • A chemical can enter any of the four matrices: the atmosphere by evaporation, the lithosphere by adsorption, the hydrosphere by dissolution, or the biosphere by absorption, inhalation, or ingestion (depending on the species). Once in a matrix, the toxicant can enter another matrix by these methods.

  • The biological availability (or bioavailability) of a chemical is the portion of the total quantity of chemical present that is potentially available for uptake by organisms.

  • Pollution may result in a cascade of events, beginning with effects on homeostasis in individuals and extending through populations, communities, ecosystems, and landscapes.

  • Terrestrial toxicology is the science of the exposure to and effects of toxic compounds in terrestrial ecosystems.

  • Aquatic toxicology is the study of effects of anthropogenic chemicals on organisms in the aquatic environment.

Ecotoxicology is the science of contaminants in the biosphere and their effects on constituents of the biosphere. It has an overarching goal of explaining and predicting effect or exposure phenomena at several levels of biological organization (Fig. 30–1).

FIGURE 30–1

Ecological scales relevant to ecotoxicology. Solely biological scales relevant to ecotoxicology range from the molecular to the community levels: solely abiotic scales range from the chemical to the entire habitat. Biotic and abiotic components are usually combined at levels above the ecological community and habitat. The ecological community and physicochemical habitat combined to form the ecosystem. Ecological systems can be considered at the landscape scale, such as the combination of marine, freshwater, and terrestrial systems at a river’s mouth. Recently, the continental and biospheric scales have become relevant as in the cases of ozone depletion, acid precipitation, and global warming.

Relevant effects to nonhuman targets range from biomolecular to global. As the need to predict major effects to populations, communities, ecosystems, and other higher-level entities has become increasingly apparent, more cause-effect models relevant to these higher levels of biological organization are added to the conventional set of toxicology models. Contaminant chemical form, phase association, and movement among components of the biosphere are central issues in ecotoxicology because they determine exposure, bioavailability, and realized dose. Risk to ecological entities is estimated or predicted by combining exposure and effect information. Risk might involve diminished fitness of individuals, increased risk of local population extinction, a drop in species diversity, or reduced nutrient cycling or primary productivity. Because potential ecological endpoints are so diverse, the ecological risk framework tends to be quite flexible (Fig. 30–2).

FIGURE 30–2

The general form of an ecological risk assessment including problem formulation, analysis, and risk characterization stages. Problem formulation is done in dialog with risk managers and stakeholders and involves a clear statement of ...

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