750 Introduction to Industrial Hygiene

Effects

A toxic substance may cause local effects, systemic effects, or both. The effects may also depend on the worker's sensitivity to the substance.

Local Effects: When a toxic substance causes damage at the point where it first contacts the body, that damage is called a local effect. The most common points at which substances first contact the body are the skin, eyes, nose, throat and lungs.

• Example: If ammonia gas is inhaled, it quickly irritates the lining of the respiratory tract (nose, throat and lungs). Almost no ammonia passes from the lungs into the blood. Since damage is caused only at the point of initial contact, ammonia is said to exert a local effect.

Systemic Effects: Toxic substances can also enter the body and travel in the bloodstream to internal organs. Effects that are produced this way are called systemic. The internal organs most commonly affected are the liver, kidneys, heart, nervous system (including the brain) and reproductive system.

• Example: Phenols cause local effects and may then warn that the chemical may be entering the body and producing systemic effects. Other chemicals do not provide any warning at all. For example, glycol ethers (Cellosolve solvents) can pass through the skin and cause serious internal damage without producing any observable effect on the skin.

Both local and systemic effects: Both local and systemic effects can happen with some chemicals.

• Example: An epoxy resin is an example of a substance with local effects on the skin. On the other hand, if liquid phenol contacts the skin, it irritates the skin at the point of contact (a local effect) and can also be absorbed through the skin, and may damage the liver and kidneys (systemic effects).

Sensitivity: Sensitivity means that some people are more affected by a chemical than others. This can depend on a person's age, sex, health, diet, or whether they take medicine, drugs, or alcohol. Some people may feel the harmful effects of a chemical at a lower dose than others. For example, a person with asthma might have a strong reaction to a cleaning product with strong fumes, while someone without asthma may not feel any effect at all.

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