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Poisoning (Acute and Chronic).
A chemically induced disturbance in the functions of a biological system or a chemical injury to a body organ may be defined as poisoning. These toxic effects can be caused by exposure to exogenous (environmental) compounds. A compound is normally classed as a poison if it damages an organ with a very small dose. Clinical symptoms after exposure to a poison are normally quite characteristic as the toxic effects of poisons are often specific. Some compounds can cause damage to organs when given in a high dose, hence these can also be considered to act as poisons. The study of these poisons comes under toxicology. The study that deals with problems related to poisonings in humans and their treatment is called Clinical toxicology. Poisoning may be acute or chronic.
In acute poisoning the body is exposed to the toxic substance in a high dose, on one occasion and during a short period of time. The symptoms of acute poisoning develop in close relation to the exposure. Venomous bites or stings, massive drug overdoses, poisonings after mushroom meals and alcohol poisonings are a few examples of acute poisonings.
In chronic poisoning the organism is on the contrary exposed repeatedly to toxic agents during a long period, but every exposure means that just a low dose of the poison is entering the body. Normally no symptoms develop in relation to each exposure, although that may happen (e.g. in chronic exposure to solvents). Instead the person gradually becomes ill after a period of months or may be years. In chronic poisoning the toxic substance may accumulate in body tissues (organs) or cause a small irreversible damage after each exposure. After a long time, enough poison may have been accumulated in the body, or the damage may become significant enough, to cause clinical symptoms. Long-term exposures to heavy metals like lead, mercury or cadmium, inhalation of organic solvents in the occupational context, and exposure to pesticides are examples of chronic poisonings.