To achieve reasonable surface quality in critical cleaning applications, manufacturers need effective cleaning options, including aggressive solvents. One “sharp scalpel,” n-propyl bromide (nPB), may be more challenging for industry to use, at least in California if not throughout the nation. The reason: on December 17, 2009, the Cal/OSHA Standards Board set a Permissible Exposure Limit (PEL) of 5 ppm for nPB, with a skin notation.

The inhalation limit, expected to take effect in the first quarter of 2010, is legally-enforceable in California. While the recommended level set by ACGIH is 10 and by the EPA is 25 ppm, one can reasonably expect that groups throughout the United States will consider the Cal/OSHA level.

Richard Morford, CEO of Enviro Tech International Inc. of Melrose Park, IL, a supplier of n-propyl bromide-based solvents, commented that “we all agree on the toxicity data, but we did not agree on the uncertainty factors.” Uncertainty factors are used to extrapolate from animal studies to anticipated effects on humans. Morford explains that Cal/OSHA staff “appears to have used default uncertainty factors rather than developing factors appropriate to the data,” adding that “Cal/OSHA gave very short shrift to our feasibility comments.”

I agree. I attended Cal/OSHA Standards Board meetings; and I have regularly attended Cal/OSHA advisory meetings. For many chemicals, California takes a PEL setting approach that lacks perspective. Studies are evaluated to determine any lowest observed effect. PELs are then extrapolated, often from default risk factors, even when available data would allow for a more scientifically defensible approach. Default control numbers are problematic for industrial processes. Toxicology is more complex and chemical-specific; default “safety factors” are even less appropriate.

The Cal/OSHA approach appears to be, the lower the better, if that number can “feasibly” be achieved. Cal/OSHA contends that 5 ppm is feasible in vapor degreasing through ventilation or with respirators. Directed ventilation is counter-indicated with vapor degreasers and conflicts with other Federal and California regulations. The actual target number would be 2.5 ppm, because most safety professionals aim at half the PEL. Cal/OSHA staff also contended that respirators are regularly used. Because of the needs for complex training, the potential for misuse, and since respirators can pose their own dangers to employees, most industrial hygienists consider respirators as a last choice.

Potential negative impacts of the ruling on worker safety:

• Switch to solvents, like chlorinated solvents, where other agencies have provided higher inhalation limits. These chemicals may not be as safe for workers.
• A move to less well-characterized chemicals. “Unknown” does not mean safe.
• Increased use of blends with undisclosed complex mixtures that may have adverse synergistic effects.
• Move to more aggressive processes that pose additional hazards, including high temperature, strong force, and longer process times.

Should we have a stronger Federal OSHA? Of course. Workers throughout the U.S., and throughout the world, deserve perspective and clarity regarding hazards associated with the chemicals they use. More important, they deserve to understand the hazards associated with the processes. Perhaps a mutual education of agencies and of manufacturers is in order.