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Introduction to environmental toxicology

Toxicological tests contribute to chemicals risk assessment, which is the quantitative estimate of the potential effects of various types of chemical exposures (e.g. pesticide residues in food, contaminants in water) on human health and environmental significance. Therefore, considering our society's dependence on chemicals as well as the diversity of chemicals present in the environment, it is essential to assess the potential hazardous effects, emphasizing toxicology as an increasingly important part of the decision-making processes.

Environmental toxicology is a sub-discipline that is continually growing in relevance due to the human and environmental impact of globalisation and industrialisation. It is defined as the study of the fate and effects of chemicals in the environment. Though this definition encompasses toxic chemicals naturally found in the environment (i.e., microbial and plant toxins and animal venom), environmental toxicology is typically associated with the study of environmental chemicals of anthropogenic origin.

Once in the environment, chemicals will pass through different abiotic and biotic degradative processes that compromise their structural integrity and contribute to minimize their potential effects. Thus, this complex field (environmental toxicology) requires attention with regard to the stability of pollutants within soil and water as well as the ability of chemicals to accumulate within the food chain. The 1962 book by Rachel Carson's "Silent Spring" revolutionized how people understand their relationship with the natural environment and fostered the development of Environmental Toxicology - from classical toxicology.

For more information on abiotic and biotic degradation see unit 5.

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Source: http://etox.ucr.edu/gradstudents/currentstudentresources.html

ENVIRONMENTAL TOXICOLOGY can be divided into two main subfields:

  • Environmental health toxicology - is the study of the adverse effects of environmental chemicals on human health. Assessing the toxic effects of chemicals on humans involves the use of standard animal models (e.g. mouse) as well as epidemiological evaluations of exposed human populations (e.g. farmers and factory workers).

mercury-caution_ehp-118-a198-g001_438x0_scale0508pesticide

                                                              Emily Monosson, 2013; http://www.eoearth.org/view/article/152586/ (Left figure)
                                                                KIMO, 2013; http://www.kimointernational.org/HazardousSubstances.aspx (Right figure)

  • Ecotoxicology - The term ecotoxicology was coined by René Truhaut in 1969 who defined it as "the branch of toxicology concerned with the study of toxic effects, caused by natural or synthetic pollutants, to the constituents of ecosystems, animal (including human), vegetable and microbial, in an integral context" (Truhaut, 1977). More recently, Forbes & Forbes (1994) defined ecotoxicology as "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". Hence, ecotoxicology involves the study of the adverse effects of toxicants on a myriad of organisms that make up ecosystems ranging from microorganisms to top predators.

The transport, fate, and interactions of chemicals in the environment constitute a critical component of both environmental toxicology and ecotoxicology.

Individual - is the basic level of ecological organization (e.g. single bird, plant, fish, human).

Population - comprises groups of individuals of the same species existing within a defined geographical location (e.g. populations of humans).

Community - is essential groups of different populations that coexist, again within some defined geographical location, and which interact with each other.

Ecosystem - comprises different communities along with the physical/chemical environment (e.g. aquatic ecosystems such as lakes).

REFERENCES

Burcham PC. (2014). An introduction to toxicology. Springer, London. 327p.

Duffus JH, Nordberg M, Templeton DM. (2007). IUPAC Glossary of Terms Used in Toxicology, 2ndEdition - IUPAC recommendations 2007. Pure Appl. Chem. 79: 1153-1344. Available at: http://sis.nlm.nih.gov/enviro/iupacglossary/frontmatter.html

Forbes VE, Forbes TL. (1994). Ecotoxicology in Theory and Practice. Chapman and Hall, London. 247p.

Hodgson E. (2010). A textbook of modern toxicology. 4th edition. John Wiley & Sons, Inc., Hoboken, New Jersey. 648p.

Klaassen CD. (2008). Casarett and Doull's Toxicology. The Basic Science of Poisons. 8th edition. McGraw-Hill Education, LLC, New York, USA. 1454p.

Robinson L, Thorn I. (2005). Toxicology and ecotoxicology in chemical safety assessment. Blackwell Publishing Ltd., Oxford, UK. 157p.

Truhaut R. (1977). Eco-Toxicology: Objectives, Principles and Perspectives. Ecotoxicology and Environmental Safety 1 (2): 151-173.