Suppose there are three chemicals under consideration. You look at the Material Safety Data Sheet (MSDS) and find worker inhalation levels of 100, 10, and “NE” (for not estimated). Which should you choose? Some groups might unwisely select the one labeled “NE,” perhaps on the grounds that an unestablished hazard is less of a liability; or they make the erroneous assumption that “if it is not safe, surely there would be a recommended limit.” In selecting potential cleaning agents and other process chemicals, all other things being equal, the tendency is to choose the substance or product with the higher worker Occupational Exposure level (OEL) or Permissible Exposure Level (PEL). What may not be obvious is that the development of worker exposure levels is subject to far more variability than, for example, a non-volatile residue determination. Recent developments in California may make it even more important to understandthe basis for the inhalation numbers.
OSHA develops national, legally enforceable PELs. PEL development by OSHA has been relatively limited, so it is fortunate that other sources for the recommended inhalation level, often referred to as OELs, are also available. Examples of other sources are government agencies, such as the EPA, professional industrial hygiene organizations like the AIHA, and ACGIH, and even private chemical manufacturers. The transparency of the process, the quantity and quality of the supporting data, and the rationale used to evaluate the data and associated risks can be quite variable among organizations and even for different chemicals evaluated by a given organization.
The California Division of Occupational Safety and Health (DOSH), usually referred to as Cal/OSHA, a state agency chartered to protect workers, develops PELs that are legally enforceable in California. Cal/OSHA is fine-tuning a process to develop proposals for new or revised PELs for airborne contaminants. As of this writing, it was anticipated that between 12 and 20 substances would go through this process every year. One of the parameters for considering substances and for developing the PELs, in this proposed process, are reference exposure levels from the Office of Environmental Health Hazard Assessment (OEHHA, a California agency), and exposure levels from the U.S. EPA. Both the EPA and notably OEHHA have community protection charters. You may be familiar with the extensive Proposition 65 list of chemicals derived from OEHHA risk analysis and with the associated warning signs that proliferate in factories, retail establishments, and even apartment houses in California.
Community exposure limits tend to be lower than worker exposure limits for a number of reasons. For example, the worker population does not include the more sensitive populations of the very young and the very old. Workers are exposed to substances voluntarily for 8 hours per day, 5 days per week, so they have a recovery period. Workers, additionally, have access to education about the chemicals they work with and to protective equipment. In contrast, those in nearby communities may have continuous, involuntary, uninformed exposure to a chemical for 24/7 for a lifetime.
Based on risk factors determined by OEHHA, some analyses indicate a potential for much lower PELs than are those set by other agencies and professional organizations, in many cases by orders of magnitude.1
Given the differences in the approach to inhalation levels for workers and for community members, it seems to me that it would be far preferable for Cal/OSHA to have separate, dedicated staff to develop risk factors specifically geared to worker exposure rather than to extrapolate or adapt factors from studies related to community exposure. Because workers and industry look for quantitative numbers related to worker exposure, the PEL numbers generated by Cal/OSHA may be utilized throughout the U.S. However, it would seem unwise to select a chemical with a totally uncharacterized toxicity profile over one with a relatively low Cal/OSHA PEL number.
There are very positive aspects to the Cal/OSHA plans, particularly the goal of a transparent process with as standardized an approach as feasible an approach to data evaluation. Such transparency will be invaluable to manufacturers, managers, and industrial hygienists. The goal of 12 to 20 substances per year is also laudable. It is, however, important to understand the rationale behind the Cal/OSHA numbers. In fact, understanding the source and rationale of any PEL or OEL is critical to optimizing the worker safety profile.
1. B. Kanegsberg, “Cal/OSHA PEL’s: Community Standards for Worker Exposure Limits?”, Green Files, an SQRC Newsletter, Vol. 2, Issue 1,Jan. 2007, found at http://www.sqrc.org/Newsletter%201/CommStandPEL.pdf.
Barbara Kanegsberg is President of Surface Quality Resource Cen-ter,a non-profit organization with the goal of achieving effective,en-vironmentally-preferred options for surface preparation and manufacturing (www.sqrc.org,email@example.com).
NOTE: A bill (AB 515) to mandate adoption of PELs based on OEHHA risk factors was introduced to the California Assembly on Feb. 20, 2007 by Assemblywoman Sally Lieber. This would likely result in PELs orders of magnitude lower than those currently in place.