Where Do You Set the Standard?

Employers need to rely on more than regulated exposure limits to ensure that their workers are safe from hazardous substances.

Is there an instance when following an OSHA standard can be hazardous to workers' health? Experts say that may be the case when it comes to occupational exposure limits (OELs).

For more than three decades, employers with exposure hazards have been required to follow what OSHA calls permissible exposure limits (PELs) for about 500 substances. The problem is that PELs, which are regulatory limits on the amount or concentration of a substance in the air that most workers may be repeatedly exposed to without developing adverse health effects, are based on research conducted primarily in the 1950s and early 1960s.

Since then, new scientific information has become available to indicate that, in most cases, PELs are outdated and do not adequately protect workers. Furthermore, any OSHA review of existing PELs or plans to expand the list could take years.

An American Industrial Hygiene Association (AIHA) white paper on PELs states that "it is a disservice to worker health that the majority of OSHA PELs are based on recommendations that were made [more than] 30 years ago." Consultant John F. Rekus, MS, CIH, CSP, goes a step further and contends that any safety and health manager who relies solely on PELs is guilty of professional negligence.

The concern does not stop there. Thousands of substances have no regulated exposure limits, leaving companies to figure out what chemicals in their workplaces should have an OEL and what that limit should be to protect workers' health.

To fill this void, many employers determine internal limits for specific chemicals with no OEL or a limit that is dated.

Starting from scratch, though, is not always necessary when establishing an internal limit. Industrial hygienists, toxicologists and others who devise limits or monitor concentrations have access to lists of voluntary exposure limits that are more up to date than PELs.

Perhaps the most-used list is the American Conference of Governmental Industrial Hygienists' (ACGIH) annually updated Threshold Limit Values (TLVs). ACGIH has developed hundreds of exposure limits that are more protective than PELs, which are based on TLVs from 1968. AIHA has its Workplace Environmental Exposure Levels, or WEELs, and the National Institute for Occupational Safety and Health has identified Recommended Exposure Limits, or RELs, for more than 650 hazardous substances.

Even with updated guidelines such as TLVs, exposure limits are available for only about 700 of the 70,000 chemicals used in industry. That is why it is essential for companies to assess their workers' health risks and adequately control worker exposures to hazardous substances for which there are no limits, said Keith Tait, CIH, CSP, past chair of AIHA's Exposure Assessment Strategies Committee.

For Tait, assistant director of corporate health and safety for Pfizer, setting internal exposure limits is vital to worker safety. The pharmaceutical company works with more than 1 million substances, the vast majority of which are experimental compounds not on any regulatory or voluntary exposure list.

Companies often treat nonregulated exposure limits, whether internal or from outside groups, more like requirements. Such is the case at E.I. DuPont de Nemours' Sabine River Works plant in Orange, Texas. "We recognize that these limits are recommendations, but for engineering control and administrative control purposes, we treat them as true limits of exposure," said John E. Adkins Jr., Ph.D., CIH, the site's occupational health coordinator. At Sabine River Works, there is the potential for exposure to highly toxic and corrosive chemicals and to some carcinogens. The site manufactures, among other things, ethylene, hydrogen cyanide and nitric acid.

Because a plant may have hundreds or thousands of hazardous chemicals on site, the task of setting exposure limits can be daunting. The challenge motivates Adkins.

"It's actually exciting to be on the cutting edge of technology with respect to keeping up with the changes in exposure limits, learning new effects of chemicals on the human body and working with new monitoring instruments," said Adkins, who has a doctorate in analytical chemistry. "I believe our work really makes a difference when it comes to protecting our people from exposure to hazardous chemicals and sharing our knowledge about the properties and safe use of the chemicals we use and produce here."

Exposure Assessment Strategy

Fatality statistics further point to a need for companies to implement a comprehensive exposure assessment strategy. As many as 10 percent of worker deaths each year in the United States are due to exposure to hazardous chemicals and other substances.

Most employers follow a comprehensive exposure assessment strategy similar to one outlined by John R. Mulhausen, Ph.D., CIH, and Joseph Damiano, MS, CIH, CSP, authors of A Strategy for Assessing and Managing Occupational Exposures (AIHA Press, 1998). The strategy outlined by 3M's Mulhausen and Alcoa's Damiano includes seven steps:

1. Start. Establish the exposure assessment plan, including the role of the industrial hygienist, exposure assessment goals and a written exposure assessment program.

2. Basic characterization. Gather information to characterize the workplace, work force and environmental agents. Use health effects information collected at this stage to establish an OEL.

3. Exposure assessment. In view of the information available from the basic characterization, use exposure profiles and ratings, training and experience, exposure modeling tools, and monitoring data to determine an outcome that includes:

  • Groupings of workers having similar exposures,
  • A definition of an exposure profile for each group of similarly exposed workers, and
  • Judgments about the acceptability of each exposure profile.

This assessment, during which internal limits are selected and defined, will determine whether an exposure is acceptable, uncertain or unacceptable. In the absence of a formal OEL, determine a "working" OEL to rate exposures and differentiate acceptable from unacceptable exposures. If a formal or working OEL is absent, the exposure assessment cannot be completed.

4. Further information gathering. Implement exposure monitoring or the collection of more information on health effects so that uncertain exposure judgments can be resolved with higher confidence.

5. Health hazard control. Implement control strategies for unacceptable exposures. Put these exposures on a prioritized list for control through less toxic chemical substitution, engineering controls, personal protective equipment (PPE), administrative controls and work practice changes.

6. Reassessment. Periodically perform a comprehensive re-evaluation of exposures. Determine whether routine monitoring is required to verify that acceptable exposures remain that way.

7. Communications and documentation. The communication of exposure assessment findings and the maintenance of exposure assessment data are essential features of an effective process.

Mulhausen and Damiano, in their book, state that "a comprehensive approach is the best way for organizations to understand and manage the ever-broadening realm of occupational health-related risks." This approach shifts away from compliance monitoring, which focuses on the maximum-risk employee to determine whether exposures are above or below established limits.

"In a new industrial hygiene program, compliance monitoring is probably where you start," Mulhausen said. "Most programs have moved on to the next step, to focus on understanding exposures in a broader sense and moving beyond the narrow list of OSHA PELs to include other chemicals."

Setting Internal Limits

Industrial hygienists who have taken this next step should seek technical input from colleagues such as toxicologists, occupational medical personnel and epidemiologists. Many companies include these types of professionals on committees that meet to review limits. These committees also decide whether to accept a voluntary guideline or an internal recommendation on a limit, generally measured as parts per million (ppm).

When there is little or no information available on an exposure limit through literature searches or from studies, companies may rely on laboratory or epidemiological data, analogies, extrapolations or judgments. At DuPont, a business unit can fund a lab toxicology assessment for a chemical if there is a need. The company's Haskell Laboratory for Industrial Medicine and Toxicology in Newark, Del., will identify a dose-response relationship and recommend an exposure limit.

Companies may choose to adopt a more conservative limit than required for a PEL or recommended for a voluntary OEL. "Whenever we have an indication that a limit may not be sufficient to protect workers, we will review that limit" with the company's Acceptable Exposure Limit Committee, Adkins said.

Haskell Lab, which has the resources and expertise to move more quickly than OSHA can, has set some internal exposure limits that are lower than a PEL or a TLV, Adkins said. One example of a chemical whose exposure limit has been lowered by ACGIH and by DuPont is acetone. The PEL for acetone is 1,000 ppm. The TLV and DuPont's exposure limit are 500 ppm for an 8-hour, time-weighted average.

"Our current limit was set after OSHA established the PEL for acetone, and our limit was set using studies not available to OSHA when they established their limit," Adkins said.

Using a more conservative exposure limit could entail added costs regarding engineering controls or PPE, which may require convincing management that the extra expense is worthwhile. At DuPont, Adkins said, the company will weigh the benefits against the costs, but usually will go with the lower limit.

During exposure assessment, especially when dealing with a working OEL, an exposure band may be used instead of a limit. Bands are a range of numbers, typically a factor of 10, such as 1 microgram to 10 micrograms per cubic meter. "The reason for the band," Pfizer's Tait said, "is because, in many cases, we know less about that chemical, and there is uncertainty what a limit number should be."

A Broader Viewpoint

While most occupational exposures are in the air, there are other ways that substances can affect the body, including ingestion, skin contact and whole-body radiation. "The prevailing philosophy in the profession has been that if we just control air exposures, everything is going to be fine," Tait said. "That is not a good assumption. That is only applicable for airborne substances. With many solids, contact occurs through the skin by direct handling. We need to think more broadly and include eye, skin and ingestion hazards, such as those which may cause reproductive or allergic sensitization."

An expanded viewpoint of occupational exposure limits may include a worldwide perspective.

Clariant, a specialty chemical company based in Switzerland and operating 130 plants in 90 countries, has global guidelines for health hazards that include internal limits for chemicals. Its Industrial Health Committee members evaluate OELs from many countries and select the limits that they feel are most appropriate for a chemical. A country's stricter legal limit, however, supersedes any internal limit.

Elizabeth Pullen, CIH, Clariant's industrial hygiene manager for U.S. operations, worked for U.S.-based companies for 15 years and assumed that industrial hygienists worldwide approached exposure assessments in a similar way. "I now realize that some of our cultural differences affect the ways we approach these issues," she said. "For example, in Switzerland, they seem to put more focus on the engineering and control of potential exposures. In the U.S., we tend to put more focus on monitoring and characterizing the potential exposures before we attempt to control them."

The key for multinational companies, Pullen said, is to learn to adapt to different cultures.

Multinational and compliance issues aside, industrial hygienists have plenty of factors to consider when it comes to assessing exposures in their workplaces, Tait said. "Determining an appropriate (limit) number will help a company manage risk, ensure that workers are protected and operations are not jeopardized, avoid a lawsuit, and prevent a business interruption."

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