Environmental chemicals, respiratory hypersensitization and international chemical safety

Allergic hypersensitization to a variety of chemicals, natural and synthetic, is a worldwide health problem. Respiratory tract hypersensitization is responsible for significant morbidity and, in some cases, mortality. An important step in managing and controlling health risks, such as allergic hypersensitization, is to identify the chemical hazard, define dose-effect and dose-response relationships, evaluate exposure, and characterize risk. In practical terms, the risk and safety assessment processes lead to the designation of control limits for exposure to chemicals in air, food, water, and consumer products. The objective of exposure limits is to protect the whole human population, including the most susceptible individuals and 'at risk' groups. The existence of susceptible individuals is a factor that must be taken into account when quantitative chemical risk assessments are being made, and should be covered in the risk characterization. Within a population, individual susceptibility is influenced by genetic and environmental factors and these have regional and national differences. There may be cases where hypersusceptible individuals and groups, such as asthmatic children, are not fully protected by regulatory exposure limits. The International Programme on Chemical Safety, as the global programme on identifying and assessing chemical risks to human health and the environment in order to assist countries in effective management, is striving to elucidate the toxicological basis for chemically-associated disease and advance the basic science and methodology of chemical risk and safety assessment.