A human environmental health risk assessment is the process to estimate the nature and probability of adverse health effects in humans who may be exposed to chemicals or other harmful substances in the environment. Risk assessment is intended to provide information to all parties concerned so that the best possible decisions are made.
A human health risk assessment should address questions such as:
A classic human health risk assessment is based on four stages:
This is a process to identify issues for which risk assessment is useful. It establishes a context for the risk assessment. This is done by identifying the concerns that the risk assessment needs to address.
Hazard identification is the process of determining what adverse effects are likely to occur from an exposure to a chemical or other substance and whether any adverse health effects are likely to occur in humans. It examines the available scientific data for a given chemical (or group of chemicals or other substances) and develops a weight of evidence to characterise the link between the negative effects and the chemical/other agent.
A dose-response relationship describes how the likelihood and severity of adverse health effects (the responses) are related to the amount and type of exposure to the substance.
Exposure assessment is the process of measuring or estimating the magnitude, frequency, and duration of exposure to a chemical or other substance in the environment, or estimating future exposures for a chemical that has not yet been released. An exposure assessment includes some discussion of the size, nature, and types of human populations exposed to the substance, as well as discussion of the uncertainties in the above information. Exposures are commonly estimated indirectly through measured concentrations in the environment, models of exposure, and estimates of human intake over time.
A risk characterisation conveys the risk assessor's judgment as to the nature and presence or absence of risks, along with information about how the risks were assessed, where assumptions and uncertainties still exist, and where policy choices will need to be made.