::The Crying Earth::

5.1.1 Toxicology

Toxicology (from the Greek words toxicos and logos) is the study of the adverse effects of chemicals on living organisms. It is the study of symptoms, mechanisms, treatments and detection of poisoning, especially the poisoning of people.

Many substances regarded as poisons are toxic only indirectly. An example is "wood alcohol," or methanol, which is chemically converted to formaldehyde and formic acid in the liver. It is the formaldehyde and formic acid that cause the toxic effects of methanol exposure. As for drugs, many small molecules are made toxic in the liver, a good example being acetaminophen (paracetamol), especially in the presence of chronic alcohol use. The genetic variability of certain liver enzymes makes the toxicity of many compounds differ between one individual and the next. Because demands placed on one liver enzyme can induce activity in another, many molecules become toxic only in combination with others. A family of activities that engages many toxicologists includes identifying which liver enzymes convert a molecule into a poison, what are the toxic products of the conversion and under what conditions and in which individuals this conversion takes place.

Toxic Chemicals:

•Hazardous: dangerous
- flammables, explosives, irritants, sensitizers, acids, and caustics

•Toxins: poisonous
- react with specific cellular components to kill cells
- Allergens and antigens: activate immune response
- Immune depressants, unclear how these act on bodily function
- Neurotoxins, fast acting
- Mutagens, alter DNA
- Teratogens: embryo disruptions, thalidomide, alcohol
- Carcinogens: mortality decreasing over last 30 years