Toxicokinetics and safety factors in risk assessment.

For risk assessment of anticholinesterase pesticides, acetylcholinesterase inhibition is a sensitive, reversible indicator of exposure. However, use of smaller factors when data are available in human may not be justified in some specific cases. Direct action of anticholinesterase on receptor sites at various cell types in different target organs may yield to the more severe nature of toxicity. At the present time, uncertainties exist due to our limited capability to clarify many human diseases with complex etiology. The toxicokinetic models available may not accommodate some type of toxicants which their mode of action involve haemodynamic change or vascular cell injury. Anticholinesterase pesticides are still widely used in many asian countries to control a variety of pest species in agricultural practices. The physiology of the effects of these agents are complex and appropriate uncertainty or "safety factors" are needed to be acknowledged and taken into account from total exposure. Risk assessment of anticholinesterase agents is related to complex biological system and we will probably, never, at least in our lifetimes, know everything we would like to know to assess risk. We can only do our best with current information available. However, one should be extremely careful and holistic when applying these uncertainties in risk assessment of anticholine-esterase pesticides.