Quantifying risk levels due to environmental exposures in a given population presents major methodology difficulties. The core disciplines involved include safety, healthcare and medicine, public health, toxicology, epidemiology, and industrial hygiene. Toxicology is the study of the adverse effects of substances on living organisms, and the assessment of the probability of their occurrence. Of note is the concept of the dose-response relationship. Only the dose differentiates a poison from a remedy.
Epidemiology is the systematic method of identifying hazards and quantifying the magnitude of risk.
It evaluates the patterns of occurrence of a phenomenon across a population such as a disease across the human population. Such studies can be complex and therefore require great care in data collection and interpretation. They depend on quality of the data, reliability of the methodology, and validity of the interpretation. Industrial hygiene is the health profession devoted to the recognition, evaluation, and control of environmental standards. At times several agents contribute in concert to the outcome for the organism, whereas individually they do not result in the effect.