The Cutting Edge™ - February 2004

Safety News

WMMA® is one of 18 associations representing all sectors of wood and wood products industries which have funded a six-year health study of wood workers and the effects of wood dust. The purpose of the study is:

• To examine wood dust exposures and respiratory health
• To determine whether an exposure-response relationship exists
• To provide sound, scientific basis for ensuring the continued health and safety of those who work in our industries

This Tulane Wood Dust Study is due to conclude in December 2004. The following article was published by another sponsoring association, AFMA, in a recent member newsletter. This article is part two of a two-part series on wood dust.

Last month, we traced the history of the wood dust issue, and the concerns over nasal cancer that drove regulatory thinking about wood dust for several decades. This month, we examine the current focus on non-cancer health effects, and discuss the pending Tulane University study with lead researcher Dr. Henry Glindmeyer.

The American Conference of Governmental Industrial Hygienists (ACGIH) began reviewing the scientific literature on wood dust in the mid-1990’s, with an eye to updating their recommended exposure limits. The ACGIH levels, called Threshold Limit Values (TLV’s) are advisory, but in practice carry great weight with OSHA and other standard-setting bodies.

In the course of their deliberations, members of the ACGIH panel expressed increased interest in non-cancer effects such as declines in pulmonary (lung) function by workers exposed to wood dust. Unlike the extremely rare nasal tumors that guided previous standard-setting activity, declines in lung capacity over a working lifetime are as pervasive as aging itself. The pace of decline can be accelerated by obesity, cigarette smoking and other health factors. Any credible effort to characterize the effect of wood dust exposure on pulmonary health effects would need to account for such “confounding” factors.

Unfortunately, the existing research studies uncovered by ACGIH were flawed on this and other fronts. Most involved one-time (“cross sectional”) measurements that provided a glimpse of the employee’s respiratory health at that moment, not what it had been in the past. Most studies involved small numbers of workers, and many provided only qualitative estimates of wood dust exposures rather than precise measurements. All of these shortfalls had the potential to overstate the risks of wood dust exposure and lead standard-setting bodies to adopt unnecessarily stringent exposure limits.

Recognizing this, wood industry leaders organized to fund a six-year (“longitudinal”) study of several thousand workers that would provide a reliable basis for standard-setting. Costs were shared by over a dozen associations, including AFMA, the American Forest & Paper Association (AF&PA), the Wood Machinery Manufacturers Association (WMMA®) and the Kitchen Cabinet Manufacturers Association (KCMA). Tulane University Medical School was chosen from among the handful of research bodies that had conducted studies of this scale. Dr. Henry Glindmeyer of Tulane, the lead researcher, had overseen a similar investigation of the respiratory impacts of cotton dust in textile mills.

From the outset of the study in 1999, the Tulane team utilized the newest available technology. Employees at the ten plants, four of which are operated by AFMA companies, are fitted with small dust sampling modules which can be clipped onto their clothing. The same employees are tested for lung capacity at least once a year, using a machine which measures forced expiration of air into a tube. The sampling and breathing devices were designed to prevent false results caused by tampering or misuse. The resulting data is encoded to protect the identity of plants, and transferred electronically to a high-security computer at the medical school. In addition, the dust samples are being analyzed by spectography (exposure to light of various wavelengths) to determine their species of origin.

(In late 2003), staff from AFMA’s Government Affairs and Technical Services offices were briefed on the progress of the study by the Tulane research team. While at the lab, we posed a few questions to Dr. Glindmeyer about the project and its significance for the wood industry. By way of background, Dr. Glindmeyer holds a masters degree in mechanical engineering and a doctorate in biomedical engineering. He teaches at Tulane’s Medical School, Engineering School and School of Environmental Sciences. His 25 years of research on the respiratory health of industrial workers have been relied on by key regulatory bodies to identify appropriate occupational exposure levels.

Hank, what were the deficiencies you found in earlier studies of wood dust & pulmonary health?

Long-term studies on non-cancer respiratory health were lacking. The vast majority of existing studies were cross-sectional, with poor dose-response information. The current study is designed to fill this important data gap.

Can your research isolate the impact of wood dust exposure from other influences that play a role in respiratory health?

The study is designed to account for a variety of influencing factors. These include confounding exposures unrelated to wood processing-- factors such as cigarette smoking, environmental tobacco smoke, age, gender, weight, past infections and the impact of childhood respiratory diseases.

Can you describe the technology being used to collect the data?

The current study uses the latest technology available for both exposure monitoring and health assessment. The exposure monitoring device (the Respicon © particulate sampler manufactured by TSI Inc.) provides precise estimates of individual exposure at various workstations. These are broken down by particle size. New technology developed and validated by Tulane scientists allows us to estimate the proportion of wood dust in these samples, as distinguished from other airborne substances such as diesel particulates.

On the health assessment side, lung function measurements can be incorporated into the employee’s regularly scheduled physical and conducted by the plant nurse. Participants are asked to exhale forcefully into a respirometer, a device that measures the volume and velocity of air generated. We utilize the latest computer networking capabilities to collect and assimilate this data from remote manufacturing facilities (minimizing the presence of outside personnel in the plant).

Is the pending study the type that would provide a sound basis for standard setting?

The current study (involving 1500 workers) is the largest of its kind on wood dust, and will provide data that can better inform decisions on workplace standard-setting.

AFMA will continue to monitor the progress of this project, the data collection for which should be completed by this time next year. On behalf of the entire industry, we express our appreciation to the companies and employees who have participated in this important industry effort.

Contact: Russell Batson (batsonr@afma4u.org) or Bill Perdue (bperdue@afma4u.org).

To read last month’s first report, click here Wood Dust Study Status Report.