What is the threshold limit value time weighted average (TLV-TWA) generally defined as?

The threshold limit value time weighted average (TLV-TWA) is generally designed to indicate the average exposure level to a specific chemical over a normal 8-hour workday and a 40-hour workweek, which is considered safe for nearly all workers. This value is established to ensure that most employees can withstand this level of exposure repeatedly without adverse health effects.

In practice, TLV-TWA reflects the concept that over time, workers may face varying levels of exposure, so the average should not exceed this threshold over the designated period. This helps ensure that, by averaging out peak exposures with lower levels, the overall risk remains within a generally accepted safety margin.

Understanding TLV-TWA is crucial for occupational health and safety professionals as it aids in the evaluation of workplace hazards and the implementation of necessary controls to protect worker health over extended periods.