Persistent Organic Pollutants
Toxic substances can act as a poison, producing either immediate (acute) illness following short-term
exposure to high concentrations or delayed (chronic) effects after long term exposure at lower levels. Many of these
materials cause birth defects, gene mutation and/or cancer. Two classes are typically recognized: toxic metals and
persistent organic pollutants. The word persistent, which could well be applied to both classes of toxic substances,
is important because it means that the chemical hangs around long enough to enter the food chain and cause harmful effects.