Routes of Entry
Local vs Systemic
Local vs Systemic Health Effects
A Local effect refers to an adverse health effect that takes place at the point or area of contact. The site may be skin, mucous membranes, the respiratory tract, gastrointestinal system, eyes, etc. Absorption does not necessarily occur. Examples: strong acids or alkalis.
Systemic effect refers to an adverse health effect that takes place at a location distant from the body's initial point of contact and presupposes absorption has taken place. Examples: arsenic effects to the blood, nervous system, liver, kidneys and skin; benzene effects to the bone marrow.
Substances with systemic effects often have "target organs" in which they accumulate and exert their toxic effect.
Some substances that cause systemic effects are cumulative poisons. These substances tend to build up in the body as a result of numerous chronic exposures. The effects are not seen until a critical body burden is reached. Example: heavy metals such as lead.
When exposure occurs to several substances simultaneously the resultant systemic toxic effect may be significantly greater in combination than the additive toxic effect of each substance alone. This is called a synergistic or potentiating effect. Example: exposure to alcohol and chlorinated solvents; or smoking and asbestos.