'TLVs and Unusual Conditions' Webinar Highlights

Industrial hygienists should take factors such as concurrent exposures, underlying chronic disease, and unusual work shifts into account when evaluating workers' exposures, these experts advised.

Part 1: TLVs and Adjustments Due to Workplace Conditions

Presented in two parts on Oct. 28, 2008, and Jan .29, 2009, the American Conference of Governmental Industrial Hygienists' "TLVs and Unusual Conditions" webinar offered expert advice on properly using the ACGIH Threshold Limit Values when unusual conditions prevail. The presenters discussed individual factors that can influence workers' exposures, such as work performed at high altitudes, extended shifts that exceed eight hours, and concurrent exposures.

First to present in both parts, which are available on separate CDs here and here from ACGIH, were principals of OHG Consulting Inc. of Winnipeg, Canada. Douglas Wylie, CIH, a director of OHG and former industrial hygienist for the Manitoba Department of Labour's Workplace Safety and Health Division, began Part 1 by describing the assumptions built into the TLVs: an eight-hour work day, five work days per week, etc. If conditions are consistent with the assumptions, hygienists should utilize the TLV as written. But if conditions don't match the assumptions, they should compensate for the differences using readily available information that is consistent with existing IH methods, he explained.

Dean R. Lillquist, Ph.D., CIH, director of OSHA's Salt Lake Technical Center and president of the Foundation for Occupational Health & Safety's board of trustees, followed by discussing how temperature and pressure affect airborne concentrations. He referred listeners to "The effects of temperature and pressure on airborne exposure concentrations when performing compliance evaluations using ACGIH TLVs and OSHA PELs," a paper Lillquist and co-author Dale J. Stephenson published in Applied Occupational and Environmental Hygiene (October 2001, Volume 16, page 941), and explained why a worker breathing normally is exposed to a different amount of carbon disulfide at Salt Lake City's altitude than he or she would be at normal pressure. Lillquist provided equations and explanations for calculating exposures at differing pressures and temperatures.

Wylie completed Part 1 with a discussion of adjustments for unusual hours worked and for multiple exposures. Exposures to multiple substances are relatively common, he said, citing the variety of substances typically found in grain dust. TLVs explain what to consider in many cases, but concurrent exposures to physical and chemical agents, such as vibration and lead, are not as widely considered, he said.

A growing body of evidence indicates concurrent exposure to noise and solvents increases the noise dose, Wylie said, who said extended hours are beginning to be recognized in standards. He recommended making use of a Web-based system offered by Quebec's Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST) for adjusting time-weighted averages to account for unusual work schedules.

Part 2: TLVs and Adjustments Due to Worker Conditions

Wylie's colleague at OHG, John Elias, MPH, CIH, ROH, said at the outset of Part 2 that TLVs are not fine lines between safe and unsafe conditions. Different workers vary considerably in their biological response to a particular exposure level, which "tends to create some problems," he observed.

There may be even greater differences between how "normal" people and sensitized individuals respond, Elias said.

"In my mind, TLVs cannot be used as absolutes," he explained. "TLVs are levels to which all workers may be exposed without adverse effects. . . . Some people think that the job of the industrial hygienist is essentially clerical. [But] much of the information we need to protect workers is confidential medical information."

An individual's metabolism affects toxicity, said Elias. He discussed the additive effects caused by several chemicals and cited the example of cigarettes: Asbestos workers who smoke have up to 90 times the chances of dying of lung cancer as asbestos workers who do not smoke. And a worker who doesn't wash his hands before smoking can inhale dusts, lead, mercury, or formaldehyde on cigarettes as a result, he said.

He suggested consulting two resources for information on such effects: the Navy and Marine Corps Public Health Center and the Minnesota Department of Health's Health Risk Values for chemicals in ambient air.

Dr. Rachel Rubin, MD, MPH, of MacNeal Occupational Health Services and the University of Illinois at Chicago School of Public Health, discussed several "vulnerable" populations of workers and said many workers today do not fit the "average worker" profile for age, weight, and other statistics. Underlying chronic disease is a concern, especially with workers tending to stay in the workforce longer and longer for economic reasons. A working lifetime of toxicant exposure, use of medications, and use of alcohol, drugs, or tobacco are factors industrial hygienists and health professionals must consider, but there are no clear rules for how to do it, she said.

Rubin suggested using training and refresher courses, wellness programs to help workers maintain their health as they age, and outreach to community health providers and to occupational medicine services used by workplaces. She recommended an online article, "Interaction of Chemicals in the Body," that is available here.

Someone attending the webinar asked whether she's concerned that TLVs are based on historical data of workers who do not match today's workforce, she answered, "I think that this is something that should be taken into account. It's hard to say exactly the way things are going to go." Toxicology data historically has been based on fit workers, said Rubin, adding, "We possibly may need to create animal models that are more consistent with the current human form, so to speak."

For more information about these and other ACGIH webinars, contact ACGIH Education Development Manager Tammy Vanderbilt at ACGIH, 1330 Kemper Meadow Drive, Cincinnati, OH 45240, phone 513-742-6177, fax 513-742-3355, e-mail [email protected]

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