How Pesticides Work:

Pesticides work by changing the speed of different body functions, increasing them (eg increasing the heart rate or sweating) or decreasing them (sometimes to the point of stopping them entirely, like breathing).

For instance, people poisoned by malathion, an insecticide, may experience increased sweating. This results in a series of event in the body as a response to the chemical. First is the biochemical inactivation of an enzyme. This (1) biochemical change leads to a (2) cellular change (in this case an increase in nerve activity). The cellular change is then responsible for (3) physiological changes, which are the symptoms of poisoning seen or felt in particular organ systems (in this case the sweat glands). The basic progression of effects from biochemical to cellular to physiological assures in most cases of poisoning.

Depending on the specific biochemical mechanism of action, a poison may have very widespread effects throughout the body, or may cause a very limited change in physiological functioning in a particular region or organ. Malathion causes a very simple inactivation of an enzyme that is involved in communication between nerves. The enzyme which parathion, another type of pesticide, inactivates is, however, widespread in the body and thus a variety of effects on many body systems are seen besides sweating.

Toxicity

Toxicity is a general term used to indicate adverse effects produced by pesticides. These adverse effects cam range from slight symptoms such as headache and nausea to severe ones such as coma, convulsions and even death.

Toxicity is normally divided into two types, based on the amount of exposure to a pesticide and the time it takes for toxic symptoms to develop. They are: acute toxicity and chronic toxicity. The former is due to short-term exposure and happens within a relatively short period of times whereas the latter is due to long-term exposure and happens over a longer period.

Most toxic effects are reversible and do not cause permanent damage but complete recovery may take a long time. However, some pesticides may cause irreversible or permanent damage.

Pesticides can effects just one particular organ system or they may produce generalized toxicity by effecting a number of systems. Usually, the type of toxicity is subdivided into categories based on the major organ systems affected.

Because the body only has a certain number of responses to chemical and biological stressors, it is a complicated process sorting out the signs and symptoms and determining the actual cause of human disease or illness. In many cases, it is impossible to determine whether an illness was caused by chemical exposure or by a biological agent (e.g. a flu virus).

A history of exposure to a chemical is one important clue in helping to establish the cause of illness. However, such history does not constitute conclusive evidence that the chemical was the cause. To establish this cause/effect relationship, it is important that the chemical be detected in the body (such as in the blood stream) at level known to cause illness. If the chemical produces a specific and easily detected biochemical effect (like the inhibition of the enzyme acetyl-cholinesterase), the resulting biochemical change in the body may be used as conclusive evidence. People handling chemicals frequently in the course of their jobs who become ill and need medical attention should tell their physician about their previous exposure to chemicals.

Continue to Harmful Effects Of Pesticides