ENVIRONMENTAL POISONING - PRESENTATION AND MANAGEMENT

Environmental poisoning is most commonly associated with chronic longt erm exposure to toxins rather than to acute exposure. Such repeated ex posure to sublethal doses of compounds and elements presents problems in risk assessment. This is primarily because the data are unavailable to describe relationships between dose and effect at lower levels of exposure to toxins. Bioavailability of toxins also presents a problem because the data on bioavailability are sparse and seldom as high as t he default of 100% bioavailability commonly used in risk assessment. E xamples are presented of two toxins: arsenic as an elemental anthropog enic and geologic poison and ciguatoxin, a polyether ladder compound, as a toxin produced naturally by dinoflagellates. Bioavailability driv es the toxicity of arsenic from contaminated sites, whereas tissue acc umulation drives the toxicity of ciguatoxin. Considerable benefit is d erived from the harmonization of regulatory processes where there is l inkage of health and environmental factors in the derivation of credib le risk assessment.