PRINCIPLES OF ENVIRONMENTAL TOXICOLOGY AND CONTAMINATION (PART I)

Table of Contents

1. Index
2. UNIT 1 - General principles
   1. Definition of toxicology and toxicity
   2. The terms toxin and toxicant
   3. Introduction to environmental toxicology
3. UNIT 2 - Main sources of environmental contamination
4. UNIT 3 - Air Pollution
5. Unit 4 - Water and soil Pollution
6. Glossary of key terms associated with environmental toxicology

The terms toxin and toxicant

The term toxin generally refers to toxic substances that are produced by biological systems such as plants, animals, fungi, or bacteria (e.g. zeralanone is a toxin produced by a mould). On the other hand, the term toxicant is used when speaking of toxic substances that are produced by or are a by-product of anthropogenic (human-made) activities (e.g. the dioxin TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin)).

Some toxicants can be produced by both natural and anthropogenic activities. As an example, the polyaromatic hydrocarbons are produced by the combustion of organic matter, which may occur through natural processes (e.g. forest fires) and anthropogenic activities (e.g. combustion of coal for energy production; cigarette smoking). Distinguishing a "toxin" from a "toxicant" is not always easy. For example, many pesticides, such as the pyrethroids, are synthetic analogs of natural products. Thus and although technically incorrect, many physicians and others involved in the diagnosis and treatment of poisonings often use the term "toxin" to refer to any toxic substance, regardless of origin.