Toxicology is the study of the adverse effects of chemicals on living organisms. REACH regulation plays a critical role in toxicology as it mandates manufacturers and importers to gather information on the properties and uses of substances they produce or import in quantities above one tonne per year. This data helps in assessing the potential adverse effects of these substances on human health and the environment. By requiring this information, REACH ensures that the risks associated with chemical exposure are identified and managed effectively.