Faculty of Graduate Studies celebrates 50 years

Health researcher digs the dirt on wood dust

by Hilary Thomson
Staff writer

Sucking in the pungent scent of sawdust on a trip to the lumberyard is aromatherapy for some people, but for Paul Demers wood dust and the respiratory system just don't mix.

An epidemiologist who specializes in occupational respiratory disease, Demers investigates the connections between wood dust and cancer.

An assistant professor in the Faculty of Graduate Studies' Occupational Hygiene Program since 1994, Demers is a principal investigator in a four-year study of 26,000 B.C. millworkers at 14 sawmills who have been exposed to wood dust from 1950-85.

"An agency of the World Health Organization classified wood dust as a carcinogen in 1995," says Demers, whose research earned him the designation Medical Research Council of Canada (MRC) /British Columbia Lung Association Scientist this year. "Now we're trying to determine which woods are the culprits and at what exposure level."

The 1995 classification focused on the dust of hardwoods such as oak and mahogany as a cause of sino-nasal cancer. There is one case of sino-nasal cancer for every 100 cases of lung cancer in North America, says Demers, although in Europe the incidence is higher in part due to wood dust exposure.

Airborne dust from softwoods such as hemlock and fir and mixed woods are also being investigated as a cause of cancer as well as asthma and chronic obstructive lung disease.

"Our aim is prevention," says Demers. "We want to determine risk factors and work practices that cause the problem."

Working with woodworkers' unions and mill management, the researchers examine data from employment records and match the information to Statistics Canada data on cancer and deaths due to respiratory illnesses.

Sawmill jobs include dumping and sorting logs and lumber in the yard as well as sawing, moving and inspecting lumber inside the mill and clean up of the work area.

Clean-up procedures that involve vacuuming or sweeping dampened dust are preferable to blowing dust out of the work area using compressed air, says Demers.

He and the research team that includes Occupational Hygiene Program director Kay Teschke, professor of Health Care and Epidemiology Clyde Hertzman and up to six master's and PhD students and data analysts, study procedures at mills from New Westminster to Mackenzie.

"There have been very significant changes in practices over the time period of the study," says Demers. "Although some mills still have 100-year-old equipment, there's a lot less manual labour and more work is done from a sealed-off computer booth."

Recommendations made in 1997 by Demers, Teschke and Assoc. Prof. Susan Kennedy contributed to a Workers' Compensation Board (WCB) decision to cut acceptable levels of wood dust exposure in half to the current level of 2.5 milligrams per cubic metre of air. At this level dust particles are visible hanging in the air.

The abundance of data gathered for the current study is also being used in other research projects in the department.

PhD student Hugh Davies, who holds an MRC studentship award, is looking at the connection between industrial noise and heart disease and master's degree student Lisa Ronald is studying airborne mold levels related to respiratory disease.

Results from the study, due to be completed in 2000, may have implications for other industries such as the manufacture of pulp and paper, doors or furniture.

The Occupational Hygiene Program is an interdisciplinary graduate program and the only graduate-level program west of Toronto in Canada. The first class entered the program in 1992. It was established with an endowment from the WCB that was matched by provincial government funds.

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