March 12, 2020

NIOSH Incorporates Written Plans in Risk Assessment Process

A new NIOSH document describes the agency’s process for conducting chemical risk assessments. As explained in “Current Intelligence Bulletin 69: NIOSH Practices in Occupational Risk Assessment” (PDF), the process involves determining the type of hazard associated with a chemical or other agent, collating scientific evidence, evaluating data, determining how much exposure would be harmful to workers, and considering all available evidence when making recommendations regarding risk.

According to the document, the purpose of NIOSH risk assessments is to determine the relationship between an occupational exposure and adverse health effects. The risk assessment is expected to produce either a Recommended Exposure Limit or a Risk Management Level for Carcinogens (RML-CA). The RML-CA, which NIOSH introduced in December 2016 as part of its chemical carcinogen policy (PDF), represents the daily maximum 8-hour time-weighted average concentration of a carcinogen above which workers should not be exposed.

NIOSH risk assessments follow the approach recommended by the National Research Council of the National Academies in its 2009 publication Science and Decisions: Advancing Risk Assessment. This approach involves development of a written risk assessment plan that describes a conceptual model of the hazard, persons at risk, and potential adverse effects; and identifies the risk-related metrics to be used. Previous NIOSH criteria documents and current intelligence bulletins have not included a formal written risk assessment.

One difference between the NIOSH and NRC approaches is that NIOSH does not include an exposure assessment step. NIOSH explains that an exposure assessment typically applies to a specific population of workers and therefore is not necessary for the agency’s risk assessments because the NIOSH mission is to protect all workers.

Other steps in the NIOSH risk assessment process include hazard identification, dose-response assessment, and risk characterization.

The NIOSH document endorses a weight-of-evidence approach when assessing the quality of studies during the hazard identification step. The factors NIOSH will consider in assessing the quality of a study include strength of association, consistency, specificity, plausibility, and coherence, among others.