Search the LHSFNA website
Published: Winter, 2004; Vol 6, Num 1

 

Studies Assess Respirators and Engineering Controls:

Limiting Silica Dust Exposure

"We've always stressed the importance of respirator use," says LHSFNA Occupational Safety and Health Director Scott Schneider, "and we will continue to do so. Even when they work poorly, they're far better than nothing."

But they do work poorly in many cases - because they are not properly fitted, because they are not worn properly worn, because they are removed at a moment's break and not reapplied right away.

Also, as two new silica studies show, they sometimes do not work because they are not strong enough for the job.

In a study of silica exposures in construction,* researchers found that laborers have a probability of overexposure to silica that is between 64.5 and 100 percent.

Laborers were "routinely exposed to silica in the range of 0.1 - 1.0 mg/m3," that is, "2 - 20 times the OEL" (occupational exposure limit), wrote the researchers. They summarized that "the magnitudes of silica exposure among (laborers) were sufficient to preclude the use of respirators with protection factors <10. Thus, it is unlikely that disposable and half-mask respirators would afford sufficient protection to (laborers) while they are operating mechanized hand tools" (emphasis added).

The study went on to say that the use of wet dust suppression produced a three-fold reduction in silica exposure for laborers.

These results are confirmed by another recent study** of common construction tasks. Researchers concluded, "Protection was inadequate with the use of respiratory protection nearly half the time, and higher levels of respiratory protection involve respirators that are more expensive and require greater maintenance (powered by air-purifying or supplied air), which bolsters the argument for greater use of engineering controls. Another important reason for promoting engineering controls is that respirators do not protect nearby workers."

Schneider notes these finding and concludes, "While we stress the need to wear respirators, we also stress the need to develop engineering controls that will keep silica dust exposures below the OEL. Respirators never will be adequate in all situations, but effective engineering controls could solve the problem. We urge Laborers, local unions and contractors to pay more attention to this developing option" (see also Signatory Contractor Lends Brainpower to NJ Silica Partnership).

*Annotated Occupational Hygiene, Vol 47, No 2, pp 111-122 (2003)
**AIHA Journal, 64:319-328 (2003)

[Steve Clark]