Toxicologia Ambiental e Analítica

A Critical Appraisal of the Threshold of Toxicity Model for Non- Carcinogens

Abstract

Henk A Tennekes

Most regulatory agencies assume that there is no safe level of exposure to carcinogens but that a threshold, or “safe” exposure level exists for non-carcinogens. However, recent discoveries have cast serious doubt on the validity of this concept. Five examples of non-carcinogens without an apparent threshold (neonicotinoids, dioxin, dieldrin, endocrine disruptors, and sulfhydryl-reactive metals) are presented. It is also clear by now that the threshold model for non-carcinogens may seriously underestimate actual risk. Risk assessments can no longer assume thresholds for non-carcinogens when the shape of the dose-response curve is linear at low concentrations. Risk management of such chemicals should be based on the ALARA principle (“as low as reasonably achievable”).