The Cutting Edge – January 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 one of a two-part series on wood dust. Next month's issue will feature an interview with leading wood dust researcher Henry Glindmeyer of Tulane University regarding the six-year study Tulane expects to complete in 2004.

One of the most common byproducts of furniture and cabinet manufacturing is wood dust. For most of the history of the industry, wood dust was treated merely as a nuisance. Some employees experienced nasal congestion or allergic reactions, but as ventilation equipment and work practices improved, discomfort was not widely reported.

The first studies linking wood dust to serious health effects came in the 1960s. English researchers found an unusual concentration of nasal cancers in the High Wycombe area, where that nation’s furniture industry was then centered. The occurrence of a very rare type of nasal tumor was over 500 times more common among longtime woodworkers than in the population as a whole. Subsequent studies in other parts of Europe also revealed a higher incidence of nasal tumors among woodworkers, but the differences were not as dramatic as in England.

When studies were conducted in the United States, however, the pattern disappeared. A 1977 study of North Carolina furniture workers (then numbering 79,000) revealed three nasal cancer deaths during the preceding ten-year period. A nationwide study conducted in 1982 found no excess of nasal cancer among U.S. furniture workers compared to the general population.

A number of theories have emerged to explain the differences in findings between the United States and Europe. There is evidence that the dust levels in European plants were much higher during the years in question. Because the latency period for adenocarcinoma is about 40 years, tumors observed in the early studies reflected pre-World War II exposures. Some researchers theorize that a cancerous ingredient occurs only in certain species, such as yew and teak, which are more widely used in Europe.

OSHA Attempts to Set Exposure Limits
The minimal cancer risk associated with wood dust in this country has so far led to a reasonable regulatory approach. During the 1970s and 1980s, the U.S. Occupational Safety and Health Administration (OSHA) regulated wood dust as a “nuisance dust” with a Permissible Exposure Limit (PEL) of 15 mg/m3. This level was readily met by the industry, which was already beginning to retrofit plants with cyclone systems, baghouses and other dust control equipment.

In fact, when OSHA considered more stringent limits in the late 1980s, AFMA and other wood industry associations sponsored a 45-plant study to determine what levels would be feasible. The results were troubling. The cost of retrofitting plants with state-of-the-art dust collection systems and modifying work practices to achieve a proposed 1mg/m3 standard for hardwood dust was estimated at more than $1 billion annually. Since most plants use both hardwoods and softwoods, operations would necessarily be restricted to the lower limits.

Based on this research, in 1989 the wood industry recommended and OSHA moved to adopt a 5 mg/m3 threshold for both hardwood and softwood dust, with a separate 2.5 mg/m3 limit for the allergenic species Western Red Cedar. Unfortunately, this consensus standard was grouped together by OSHA with several hundred more controversial workplace standards. In response to legal challenge from several industries and unions, an appellate court overturned the entire package of standards, saying OSHA had failed to support the permissible exposure levels for some substances with sound science.

While in theory, the wood dust PEL reverted back to 15 mg/m3, AFMA continued to recommend adherence to the 1989 standard to ensure worker health and comfort. Furthermore, several state occupational agencies – including North Carolina – have used the 1989 standard as the basis for citations.

OTHER STANDARD-SETTING BODIES RAISE CONCERNS
Since OSHA’s last look at the issue, several medical research groups and an organization of workplace safety technicians have issued reports raising additional concerns about wood dust.

In 1994, The International Agency for Research on Cancer (IARC) met in Lyon, France, and voted to classify both hardwood and softwood dusts as nasal carcinogens. Dr. Harris Pastides represented woodworking industries from the United States at the conference, and through his efforts the IARC report acknowledged that the link with nasal cancer was not borne out in modern U.S. facilities.

In 1996, the American Council of Governmental Industrial Hygienists (ACGIH) classified hardwood dust as a human carcinogen. However, after several rounds of testimony from industry experts, ACGIH followed IARC’s lead and noted the dearth of cancer cases in U.S. workplaces. The ACGIH did express concern about non-cancer effects such as declines in lung function. The council argued that wood dust might have to be controlled at the 2 mg/m3 level to guard against such effects. ACGIH is expected to propose a revised recommended exposure level in early 2004.

Researching Non-Cancer Effects

Based on the concerns highlighted by ACGIH, industry groups realized that the next round of standard-setting by OSHA was likely to center on lung function rather than carcinogenicity. We also quickly learned that only a small number of flawed studies had been performed on this topic.

In response, AFMA and almost two dozen other woodworking industry groups launched a $1.9 million, six-year study at Tulane University Medical School evaluating dust exposure levels for more than 1,500 workers in 10 wood products facilities. The respiratory health of these employees will be tracked over time to determine if any adverse effects on lung function occur, and, if so, at what level and length of exposure. The study is designed to separate potential “confounding” factors such as cigarette smoking, obesity and work experience in other industries. The Tulane researchers believe the study, now in its fifth year, will provide regulators with a credible basis for future standard setting.

Next month: A closer look at the Tulane study on pulmonary health.
Contact: Russ Batson batsonr@afma4u.org or Bill Perdue