Environmental Contaminants and Toxicology Reader

Table of Contents

Lead Author: Emily Monosson (other articles)
Article Topics: Ecotoxicology, Toxicology, Environmental health, Environmental monitoring, Human health and Risk assessment
This article has been reviewed and approved by the following Topic Editor: Sidney Draggan (other articles)
Last Updated: May 8, 2008

Introduction

Humans have been producing and releasing environmental contaminants ever since the discovery of fire. Contaminants include both naturally occurring chemicals released in unnaturally high concentrations, and chemicals that are novel to natural environments, produced by human activity and released either intentionally or accidentally.

Toxicology is the science devoted to understanding the impact of these chemicals on plant and animal (including human) individuals and populations. Understanding adverse effects of chemical contaminants leads to improved regulation, management and control of potentially toxic chemicals. But, of course, new chemicals are constantly produced, used and released into the environment, requiring continued research and analysis. As the ability to detect lower and lower concentrations of contaminants in the environment continues to increase, toxicologists continue to reveal adverse impacts of smaller and smaller amounts. Significantly, they are acknowledging increasingly the potential for the combined impact of multiple contaminants present in small quantities.

This e-text is designed to introduce the reader to contaminants and toxicology. All content was written by qualified scientists who are experts in their respective topic area. Content is reviewed thoroughly by a topic editor prior to publication.

Authors are welcome to expand and edit the contents list; please contact Emily Monosson with suggestions. If you are interested in writing an article for this collection, please consult the How to Contribute page for more information on getting involved.

Toxicology Basics

Introduction

The following sections will provide basic concepts that will help you ask the right questions about the impacts of contaminants on living systems, beginning with a historical perspective.

Dose makes the poison

One of the basic tenets of toxicology is that "The Dose Makes the Poison." Though the reality is a little more complicated, the point is: One cannot begin to evaluate the impacts of chemical contaminants without considering exposure and dose.

Interaction of contaminants with living systems

Once an organism is exposed to a toxicant, the effect of that substance will depend on what happens to it as it travels through the body. Consideration of absorption, distribution and excretion (ADE) are essential to understanding the potential for a chemical to cause harm.

Impacts on specific systems

Beyond the basics of ADE, a toxicologist considers how chemicals interact at the cellular level. For example, sometimes chemicals are detoxified by enzyme systems within certain cells, and sometimes, they are activated. Sometimes they need no activation, and can bind to receptors meant for other chemicals in the body.

Combined contaminant exposures

Until most recently, most toxicologists studied the impact of single chemicals, an unrealistic scenario in many, particularly environmental cases. The study of chemical mixtures is a growing field of toxicology.

Toxicity Testing and Risk Assessment

When new chemicals are developed, and as various producers, users and regulators try to evaluate their potential impact on both humans and the environment, chemicals are tested, exposures are estimated and potential risk is evaluated.

Government agencies and legislation in the United States

There are a number of Federal agencies charged with protecting humans and the environment from potentially adverse impacts caused by chemical substances through various laws, policies and regulations (this is not a complete list please feel free to add.)

Agencies

Environmental Justice and communities

The realization that many contaminated sites are disproportionately located near communities of color and near low-income communities led to a growing Environmental Justice movement and field of study. Additionally, researchers are beginning to realize that traditional and community knowledge about exposure, contamination, and environmental change provides valuable information to environmental and health assessment.

Reducing contaminant impacts

Reduce

Recycle

Chemical contamination worldwide

(In)famous sites of the twentieth century

Chemicals of note

Chemical contaminants of recent concern

Organochlorines

Air Pollutants

Metals

Miscellaneous

Glossary

Biographies

Citation
Monosson, Emily (Lead Author); Sidney Draggan (Topic Editor). 2008. "Environmental Contaminants and Toxicology Reader." In: Encyclopedia of Earth. Eds. Cutler J. Cleveland (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment). [First published in the Encyclopedia of Earth November 7, 2007; Last revised May 8, 2008; Retrieved November 21, 2009]. <http://www.eoearth.org/article/Environmental_Contaminants_and_Toxicology_Reader>
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