Sources of Toxic Compounds

Given the enormous number of toxicants, it is difficult to classify them chemically, either by function or by mode of action, since many of them would fall into several classes. Some are natural products, many are synthetic organic chemicals of use to society, while others are by-products of industrial processes and waste disposal. It is useful, however, to categorize them according to the expected routes of exposure or according to their uses. 

Exposure classes include toxicants in food, air, water, and soil as well as toxicants characteristic of domestic and occupational Settings. Toxicant exposure classes are described in detail in Chapter 4. 

Use classes include drugs of abuse, therapeutic drugs, agricultural chemicals, food additives and contaminants, metals, solvents, combustion products, cosmetics, and toxins. Some of these, such as combustion products, are the products of use processes rather than being use classes. All of these groups of chemicals are discussed in detail in Chapter 5. 

Soil invertebrates — predatory invertebrates — terrestrial vertebrates —predatory birds or mammals 

Terrestrial plants — herbivorous animals predatory birds or mammals 

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A series of eight experiments were performed that established the source of toxic compounds in the dominant plant (bracken) differential susceptibility of associated species to toxic effects the probable route of the toxins into the soil toxicity in the natural and toxin-modified soils and reversal of the phenomenon by removal of the toxic source. A brief summary follows. 

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