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:

  • What type of health problems may be caused by the exposure and what is the chance of people experiencing these health problems when exposed to different levels?
  • Are there any exposure levels that do not pose a health risk?
  • Are some people more susceptible to the exposure due to factors such as age, gender, genetics, pre-existing health conditions or other factors?
  • Are some people more likely to be exposed to certain chemicals or other substances due to the nature of their work, the food they consume or other reasons?


A classic human health risk assessment is based on four stages:

  1. Issue identification
    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.
  2. Hazard identification and dose-response assessment
    1. Hazard identification
      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.
    2. Dose – response assessment
      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.
  3. Exposure assessment
    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.
  4. Risk characterisation
    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.

Useful resources

Current as at: Tuesday 4 April 2023