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Interpretation and use of occupational exposure limits for chronic disease agents.
Occup Med: State of the Art Rev 1996 Jul; 11(3):561-590
Occupational exposure limits (OELs) for chronic disease agents were reviewed and discussed, both as a product of occupational exposure risk assessment and as an essential component of occupational exposure risk management. In general, the OEL has at last three components: concentration, averaging time, and target, the last component being in most cases the individual worker. Making a change in any of the three components, necessarily changes the effect on the other two. For chronic disease agents, an OEL is usually based on a long term working lifetime mean exposure which is deemed to be acceptable for a group of workers. However, the OEL is defined as an upper limit for each single shift time weighted average (TWA) exposure as this is the only practical way to ensure that the true long term working lifetime mean exposure is maintained at protective levels. An OEL, once established, is viewed as a quality control issue. Those charged with risk assessment at each company should focus on ensuring that risk to each employee is controlled constantly. Monitoring at regular intervals is essential to this end. When setting OELs, it is important to extrapolate the data from the cohort to the individual worker, to select a level of significant risk, and to control lifetime risk with measurements of single shift exposures. Misinterpretation and misuse of the concept of OELs were considered, including using OELs as fine lines between safe and dangerous, using an 8 hour time weighted average (TWA) OEL to assess short term exposure, using 8 hour TWA OELs to devise community air quality standards, applying 8 hour TWA OELs to novel work schedules, comparing an exposure group's average exposure to a TWA OEL, extending the averaging time from a single shift to multiple shifts, and interpreting the TWA OEL as a long term average.
NIOSH-Author; Risk-analysis; Epidemiology; Standards; Regulations; Exposure-limits; Industrial-hygiene; Long-term-exposure; Time-weighted-average-exposure; Occupational-exposure
Issue of Publication
Occupational Medicine: State of the Art Reviews. Occupational Epidemiology
Page last reviewed: November 20, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division