Concrete Production Respirable Silica Concerns

December 18, 2017

For the ready mix industry, there is an out to the regulation. Section 5204 does not apply “where the employer has objective data demonstrating that employee exposure to respirable crystalline silica will remain below 25 micrograms per cubic meter of air (25 μg/m3) as an 8-hour time-weighted average (TWA) under any foreseeable conditions.”.

Objective Data Definition: “Objective Data means information, such as air monitoring data from industry-wide surveys or calculations based on the composition of a substance, demonstrating employee exposure to respirable crystalline silica associated with a particular product or material or a specific process, task, or activity. The data must reflect workplace conditions closely resembling or with a higher exposure potential than the processes, types of material, control methods, work practices, and environmental conditions in the employer's current operations.”

A batch plant manager should know the work activities or work areas that will allow the highest exposures to respirable silica. If they have the objective data to prove that those activities will remain below the action level of 25 micrograms per cubic meter of air (25 μg/m3), then there are no concerns. If they do not have this data, it would seem that they are responsible for monitoring employees’ exposure to respirable silica, and taking the correct measures based on the results of the monitoring data. A (very brief) summary of the regulation is below.  

Concrete Production Respirable Silica Concerns

Respirable Silica refers to silica particles that are about 100 times smaller than beach sand.

Prolonged exposure to Respirable Silica can cause silicosis, lung cancer, COPD, and kidney disease.

Respirable silica is most commonly created during crushing, sawing, or grinding activities of any concrete products.

Industrial sand is also a source of respirable silica

OSHA protects workers from unsafe working conditions including those related to respirable silica. (

Permissible Exposure Limit (PEL) is 50 Micrograms per Cubic Meter. This is the maximum allowable limit as an average over 8 hours

Action level is 25 Micrograms per Cubic Meter. This is the average exposure over an 8-hour period at or above which employers must look into mitigation.

Batch Plant Regulatory Requirements - (5204) (

  • Employers must assess exposure to all employees who are reasonably at risk for respirable silica by one of two methods
    • Performance data: Asses using air monitoring data or objective data that accurately characterizes employee’s exposure
    • Scheduled Monitoring: Employer shall perform initial monitoring of potentially exposed employees in their respective “personal breathing zones” for each shift and each job
      • If below action level, employer may discontinue monitoring for that employee
      • If at or above action level, but at or below PEL, employer must repeat monitoring within 6 months
      • If above PEL, employer must repeat monitoring within 3 months
  • Samples must be evaluated by a laboratory with procedures found in Appendix A of the section
  • Employer shall reassess any time a change in production process may bring the levels above action level, or any time there is reason to expect that the levels have risen above the action level
  • Employees must be notified within 15 days of the results
    • Any employee who was exposed to above PEL must receive in writing the corrective actions being taken to reduce exposure
  • Methods of compliance
    • Engineering and work practice controls where feasible
    • Written exposure control plan

The regulation goes into much more detail about the compliance methods and mitigation of exposure. The first step would be to monitor or make sure there is objective data in case the need arises.