Findings for Silica in Construction

Cal/OSHA has issued a final rule which establishes a new permissible exposure limit of 50 micrograms of respirable crystalline silica per cubic meter of air (50 μg/m3) as an 8-hour time-weighted average (equivalent to 0.05 mg/m3).  The new silica rule also includes other provisions to protect employees, including hazard communication, medical surveillance, methods for controlling exposure, recordkeeping, requirements for exposure assessment, and respiratory protection.

With regards to our clients in the construction industry, particularly drywall contractors, we’ve had some interesting findings that have affected air sample results collected for silica.  For example, in one particular case that had two days of sampling for the same activity (e.g., overhead drilling) there was a significant difference in respirable particulates from the first day of overhead drilling to the second day of overhead drilling.  The vacuum attachment for the power tool was used in both cases, with the exception of tight spaces (i.e. in between two studs).  The differences in concentrations collected from the same breathing zone indicated that handedness (i.e. worker being left-handed or right-handed), position of the drill over the worker, and in worst-case measurements (in which the worker’s tasks have the greatest chance of exposure) where the debris generated from the overhead drilling falls all had impact on the concentration of dust and silica levels to which the worker would be potentially exposed.  These factors are rarely, if ever discussed in the literature.

In cases where the Cal/OSHA PEL for silica was exceeded, we recommend that our clients: 1) increase their use of engineering controls (e.g., local exhaust ventilation or wet-down methods) to further reduce the dust level exposures below the PEL; 2) have workers participate in a respiratory protection program; 3) periodically repeat air monitoring for particulate matter (including silica) to maintain documentation of workplace conditions and whenever a change in operating conditions may result in a significant change in employee exposure levels.  Bottom line is whoever takes measurements for respirable silica needs a thorough understanding of the work tasks before measurements start.

If interested, please reach out to us to conduct air monitoring for silica to ensure you and your company are in compliance with the new silica standard.