TABLE OF CONTENTS Toxicology is the fundamental science of poisons. A poison is generally considered to be any substance that can cause severe injury or death as a result of a physicochemical interaction with living tissue. However, all substances are potential poisons since all of them can cause injury or death following excessive exposure. On the other hand, all chemicals can be used safely if exposure of people or susceptible organisms to chemicals is kept below defined tolerable limits, i.e. if handled with appropriate precautions. If no tolerable limit can be defined, zero exposure methods must be used.
Exposure is a function of the amount (or concentration) of the chemical involved, and the time and frequency of its interaction with people or other organisms at risk. For very highly toxic substances, the tolerable exposure may be close to zero. In deciding what constitutes a tolerable exposure, it is essential to have data relating exposure to the production of injury or adverse effect. A problem often arises in deciding what constitutes an injury or adverse effect.
An adverse effect is defined as an abnormal, undesirable or harmful change following exposure to the potentially toxic substance. The ultimate adverse effect is death but less severe adverse effects may include altered food consumption, altered body and organ weights, visible pathological changes or simply altered enzyme levels. A statistically significant change from the normal state of the person at risk is not necessarily an adverse effect. The extent of the difference...
