Inter-relation between environmental monitoring data,human exposure and health effects

To determine whether a population has been affected by a chemical, evidence of exposure must be established. The mere presence of a chemical in the surroundings of a population may not, in all instances, result in actual exposure. Not all such exposures will cause health effects; nor is it always possible to establish that illness has or will result from exposure to chemicals. The inability to establish health effects in humans cannot a priori be translated to mean that a specific chemical is harmless. On the other hand, it must be determined whether health studies would be fruitful. If exposure was so minimal that no health effects are expected, then no health studies should be conducted.