Workplace exposure limits are one of the industrial hygienist's most basic tools, but an increasing number of practitioners are concerned that the tool has now become a crutch.
When asked what they do for a living, industrial hygienists sometimes launch into a comprehensive explanation about how they manage worker health issues ranging from toxic chemical use and radiation to ergonomics and indoor air quality. When they want to keep the explanation simple, they say, "I do air monitoring" -- one of the most obvious, traditional functions of industrial hygiene.
"The idea of air monitoring and comparing the results to preset exposure limits is pretty easy for people to understand," said Ken Kushner, CIH, CSP, senior industrial hygienist at Timken Co., Canton, Ohio. "It's what has defined the profession for a long time."
In recent years, however, this foundation of industrial hygiene has come under unprecedented scrutiny, even attack. Critics note that exposure limits have uneven scientific underpinnings and are difficult to keep up-to-date. All too often, they charge, air monitoring is relied upon almost exclusively in deciding if working conditions are healthy or not, even though that goes beyond the intent of exposure limits.
To properly address occupational health, many experts stress, the use of exposure limits needs to be integrated with other important tools of the trade -- careful interpretation of monitoring results, overall workplace evaluation, engineering controls, and professional judgment.
"Exposure limits are attractive to hygienists because, as scientists, we like numbers," said Martha Waters, Ph.D., CIH, MPH, who directs NIOSH's exposure assessment methods group. "The danger lies in attributing too much power to these numbers. They are one tool in the industrial hygiene toolbox, but, without the other components, they really aren't that useful."
Discontent about the widespread use and misuse of PELs, RELs, TLVs, and WEELs is so high in some circles that a handful of people are pushing for radical change -- the abandonment of exposure limits altogether.
Eileen Senn, a CIH with a state health department, has been relentless in her attack on exposure limits, which she mocks as "industrial hygiene's sacred cow."
"We would be better off without the numbers because, nine times out of 10, they are misused to give some place a clean bill of health," charges Senn, whose views on "industrial hygiene with no limits" have made her something of a pariah in her own field and prevent her from naming the eastern state for which she works.
"Exposure limits justify exposures," Senn argues, "but the highest calling of industrial hygiene should be to reduce or eliminate exposures. Most IHs never get to reduce exposures by implementing controls because air monitoring almost never indicates an overexposure. Industrial hygienists are too dependent on exposure limits."
While Senn's overall views are shared by only a few people, many other professionals publicly and privately acknowledge that there are problems with the way exposure limits are developed and used. These people advocate the continued use of exposure limits combined with greater understanding of their basis and application of other tools.
"Exposure limits are one of our most significant contributions as a profession because there is no risk-free environment," says Morton Corn, Ph.D., professor and director of Johns Hopkins University's Div. of Environmental Health Engineering. "Despite all the work it's done, the profession hasn't done enough to explain what the numbers mean and how to use them. We're falling short in implementing an important concept."
The debate about the usefulness of exposure limits is so fundamental that some experts say the very identity of the industrial hygiene profession is at issue.
Playing the Numbers Game
OSHA, NIOSH, and two private organizations -- American Conference of Governmental Industrial Hygienists (ACGIH) and American Industrial Hygiene Assn. …