Employers must assess the 8-hour TWA exposure for each employee who is or may reasonably be expected to be exposed to silica at or above the action level of 25 micrograms per cubic meter of air (25 μg/m3) using an 8-hour TWA.
The purposes of assessing employee exposures include:
- Identifying where exposures are occurring,
- Helping the employer select control methods and make sure those methods are effective,
- Preventing employees from being exposed above the PEL,
- Providing employees with information about their exposure levels, and
- Allowing the employer to give the physician performing medical examinations information about employee exposures.
Employers can choose between two options for assessing exposures:
- The performance option, or
- The scheduled monitoring option.
