Risk Analysis and Four steps to conduct risk analysis used by EPA

While there are many definitions of the word risk, EPA considers risk to be the chance of harmful effects to human health or to ecological systems resulting from exposure to an environmental stressor.

A stressor is any physical, chemical, or biological entity that can induce an adverse response. Stressors may adversely affect specific natural resources or entire ecosystems, including plants and animals, as well as the environment with which they interact.

Purpose of Risk assessment:

The purpose of risk assessment is to evaluate qualitative and quantitative information about hazards. For a given substance or element that can cause harm, a hazard is the source of risk, that is, the combination of the probability and magnitude of an adverse effect.

Generally, risk assessment is conducted through four processes:

1. hazard identification,
2. dose-response assessment,
3. exposure assessment,
4. and risk characterization.

The United States Environmental Protection Agency (US EPA) defines these four steps.

First, hazard identification is the process that examines whether chemicals have harmful effects on humans or ecosystems in certain situations. Key components of hazard identification involve analyzing the mode of action (MOA) and evaluating the weight of evidence (WOE).

Dose-response assessment examines the mathematical relationship between exposure degree and toxic effect. Typically, as the dose increases, so does the measured response. In a non-linear dose–response that has a threshold value for the response, values such as no-observed-adverse-effect level, lowest-observed-adverse-effect level, benchmark dose, and reference dose are mathematically calculated. In a linear dose-response that has no threshold, cancer risk and slope factor are considered.

 Exposure assessment examines the frequency, duration, and levels of exposure to the chemical. Considering the range of exposure, this process quantifies the exposure.

Lastly, risk characterization derives conclusions about the chemical’s risk, by integrating previous processes and provides a basis for policymaking for relevant chemicals. Chemical risk assessment is also based on mathematical and statistical models concerning biochemical and physiological factors, such as physiologically-based toxicokinetic modeling with Absorption, Distribution, Metabolism, and Excretion data generated by in vitro and in vivo experiments and quantitative structure–activity relationship tools