With OSHA’s recent silica dust rule significantly reducing the permissible exposure limit (PEL) for silica dust, some groups have been working to quantify the levels at which workers are currently exposed. In Washington State, one worker — an abrasive blaster — had their exposure measured at 130 times the PEL!
The results of another recently published study, this time of construction workers in Massachusetts, aren’t quite so drastic, but they still show very high levels of silica exposure are common.
The researchers assessed exposure to respirable crystalline silica and respirable dust during demolition, crushing, and chipping. They took 51 personal breathing zone samples from several types of employees:
- Operating engineers working at demolition and crushing sites
- Laborers performing miscellaneous tasks at demolition sites
- Crushing machine tenders at crushing sites
- Chipping workers at substructure bridge repair sites
They also sampled air at the perimeter of these sites to assess potential bystander workers’ exposures.
Overall, chipping workers had the highest level of exposure, more than 10 times the PEL. They were followed by crushing machine tenders, who were exposed at almost twice the PEL. Laborers and operating engineers both had exposures below the PEL.
Unlike the measurement from the abrasive blaster in the Washington State study, the dangerous exposure levels weren’t isolated measurements — 80% of samples collected on chipping workers and 50% collected on crushing machine tenders were above the PEL. The researchers noted that “the highest concentrations measured would have exceeded the PEL within 15 [minutes of] chipping and within 2 [hours] of crushing with no further exposure.” In addition, area samples indicate that bystander workers at crushing sites could be exposed at high levels.
The researchers also looked at the impact of using dust suppression methods, like respirators and water spraying systems. They found that the effectiveness of these methods varies:
- For chipping workers, using respirators was not sufficient to bring exposure below the PEL.
- For crushing tenders, the use of a water spraying system was able to bring exposure below the PEL.
Overall, the researchers concluded that reducing silica exposures to acceptable levels “remains challenging for chipping workers and crushing machine tenders.”
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