How NIOSH Conducts Risk Assessments

NIOSH prioritizes chemicals for risk assessment by evaluating the needs of key stakeholders and partners such as the Occupational Safety and Health Administration (OSHA), the Mine Safety and Health Administration (MSHA), organized labor, industry, and National Occupational Research Agenda (NORA) sector councils. NIOSH also considers factors such as how much of the chemical is used in the workplace, how much potential there is for worker exposure, and the severity of the health effects. This includes an evaluation of the available scientific information on the hazard and its associated injury or disease.

NIOSH has a four-step process for conducting occupational risk assessments: identifying the hazard, assessing workplace exposure, assessing the exposure-response relationship, and characterizing the workplace risk.

Four chevrons facing right, each pointing into the next. Each chevron has the text identifying a step. 1 - Identify Hazard, 2 - Assess exposure, 3 - assess exposure response, 4 - Characterize risk

Identifying the hazard +

NIOSH identifies the type and nature of health effects caused by chemicals by studying the scientific literature and assessing field and laboratory data collected by NIOSH. Hazard identification is the first stage of the risk assessment. In the hazard identification stage, the data on health effects are gathered and analyzed to improve understanding of what health effects are or could be caused by the chemical and which health effects should be evaluated in the assessment of the exposure-response relationship.

Assessing workplace exposure +

After identifying a hazard, NIOSH assesses the nature of the workplace exposure and the affected worker population. The amount and degree of occupational exposure is assessed in this step, sometimes through NIOSH Health Hazard Evaluations or epidemiological investigations. The most common routes of chemical exposure in the workplace are inhalation and skin contact.

Assessing the exposure-response relationship +

NIOSH explores the relationship between current or past exposure levels of the hazardous material to assess the opportunity for, and seriousness of, health effects from that exposure. The exposure-response relationship between a hazardous substance and adverse health effects is typically described using statistical models. These models account for factors that may affect the accuracy of exposure-response estimates, such as data quality or the presence of other risk factors.

Characterizing workplace risk +

Information gathered from the three previous steps is distilled to form a clear picture of the nature and magnitude of the work-related risks. This risk characterization is used to inform risk management decisions. Quantitative risk assessments provide the scientific basis for NIOSH recommended exposure limits (RELs) and risk management limits for carcinogens (RML-CAs).

Frequently Asked Questions

What is a recommended exposure limit (REL)? +

NIOSH recommended exposure limits (RELs) are limits for workers exposed to an 8-hour time-weighted average airborne concentration of a chemical during a 40-hour work week over a 45-year working lifetime. RELs are usually based on a quantitative risk assessment, when available, but may also depend on the limit of quantification of the analytical exposure measurement method. RELs are published in NIOSH Criteria Documents and Current Intelligence Bulletins and are compiled in the NIOSH Pocket Guide to Chemical Hazards.

What is a risk management limit for carcinogens (RML-CA)? +

Because there is no known safe level of exposure to carcinogens, NIOSH recommends reduction of exposure to occupational carcinogens as much as possible through elimination, substitution, or engineering controls, before the use of personal protective equipment. When exposures to carcinogens cannot be eliminated, NIOSH: 1) estimates risk for a range of potential exposures, and 2) sets a risk management limit. The risk management limit for carcinogens (RML-CA) provides a starting place for controlling exposures. For more information see the NIOSH Chemical Carcinogen Policy.    

What happens after a risk assessment is completed? +

Risk managers and stakeholders use risk assessment information to develop strategies for minimizing occupational risks. Risk assessments can be used by researchers and occupational safety and health professionals to increase awareness about hazards, to take steps to protect workers, and to prompt them to conduct further research. Government agencies like OSHA and MSHA can use or cite NIOSH risk assessments in making their regulations.

Page last reviewed: February 9, 2017