Chapter 27 - Risk assessment for metal exposures

Abstract

Risk assessment for metallic substances often follows the generally accepted framework format for risk assessment for all toxic substances, which, after problem formulation, involves (1) exposure assessment, (2) hazard identification, (3) hazard characterization/dose-response relationships, and (4) risk characterization. Risk management and risk communication are also addressed. All these steps are of high relevance for metals and metalloids because all living organisms are exposed to these elements. Lead, cadmium, mercury, and the metalloid arsenic have been responsible for many human poisonings and even deaths. It is, hence, imperative that readers of this Handbook have a firm perspective on the exposure levels to metallic substances that produce adverse health effects and the various risk assessment approaches that have been used to protect the health and well-being of living organisms. Because of the increasing use of nanomaterials, a recent concern is the dose metric for inhaled metallic nanoparticles. Regardless of the exposure route, the following risk assessment considerations are important: biomonitoring approaches, identification of the mode of action for toxicity of metallic species for hazard identification, determining dose-effect and dose-response curves, and the development of benchmark doses for various metallic species. All of these considerations are discussed in relationship to protecting sensitive subpopulations because not all individuals within a general population are at equal risk for toxicity. Risk characterization using molecular biomarkers that are capable of detecting early cellular effects to low-dose exposures to metallic substances will play an increasingly important role in assessing risk from exposure to this class of toxic substances on an individual or mixture basis. The issue of metal-/metalloid-induced carcinogenesis is of ever increasing importance because many of the elements associated with these cellular outcomes produce a number of early cellular effects, including the formation of reactive oxygen species, modification of apoptosis, and epigenetic changes. Finally, the issue of risk communication/risk management is of great importance because these issues are critical in addressing the health concerns of exposed populations and the practical, ethical, and economic issues related to reducing hazardous exposures to metallic substances. Newly identified risks must be taken into consideration and risk management measures be efficiently implemented in all countries. Such action is an important component to reach the sustainability goals in Agenda 2030.