Table of contents  •  Who we are ... people and programs  •  Where we've been ... and where we're going  •  
Facts and figures  •  Acknowledgments


What we do ... and whom we serve  •  Breathing Safely in the Dusty Trades

Sacred objects,
safely returned

Beyond the laboratory walls

Breathing safely in the dusty trades

Particulate air pollution

Probing genetic variations

Silicosis is one of the oldest known occupational diseases, yet in certain occupations and certain parts of the world, silica dust continues to shorten the lives of workers. Several Department of Environmental Health researchers are involved in national and international efforts to better understand and control silica exposure.

	Stone carvers in Thailand work with hand tools

Cancer potential

Fine dusts containing silica from industrial sources such as quarries, ceramics, and construction materials can cause silicosis, a scarring of the lungs. In the past 15 years, several researchers, including the Department's Professor Harvey Checkoway, have become concerned that even low-level silica exposures can cause lung cancer. During the late 1980s and early 1990s, Checkoway directed an epidemiological study of lung cancer and silicosis risks in the diatomaceous earth industry in southern California. Diatomaceous earth is a light, fragile siliceous material used in water and beverage filters.

The study team included DEH co-investigators Nicholas Heyer (now at Battelle), Paul Demers (now at the University of British Columbia), and Associate Professor Noah Seixas. The study found strong dose-response trends for silicosis and for deaths from lung cancer and nonmalignant respiratory diseases. Data from the diatomaceous earth study have since been used by the National Institute for Occupational Safety and Health (NIOSH) to make risk assessments for lung cancer and silicosis, the results of which may eventually be incorporated into the Occupational Safety and Health Administration's (OSHA's) occupational standard setting.

In 1996, the International Agency for Research on Cancer (IARC) invited Checkoway to serve on its working group to review evidence for the cancer-causing potential of silica. He chaired its epidemiology subcommittee. The IARC review concluded that crystalline silica from occupational exposures is carcinogenic to humans. The most convincing evidence was for lung cancer.

Construction safety Silica exposures are greater in construction than in any other American industry. The Department's Mary Ellen Flanagan is part of a nationwide effort to develop a database of silica exposures for workers during specific construction tasks. Rock drilling, sand blasting, concrete cutting, and demolition of concrete and masonry structures generate silica dust.

The database could be used as OSHA develops new construction standards in response to the IARC findings. Researchers generally need a large database of exposure information to get beyond "what's the exposure?" to "what's the solution?" said Flanagan, who did much of the database design for a team from the American Conference of Governmental Industrial Hygienists (ACGIH).

A mason cuts concrete block at a Seattle construction site

Her database, which is now maintained at West Virginia University, includes more than 500 samples, with information on tasks, tools, indoor or outdoor environment, and control measures. By next year it should be available to contri-buting researchers on the World Wide Web.

Flanagan is part of the department's Field Research and Consultation Group, which has worked with labor and management in several construction trades to reduce silica exposure. The group has conducted controlled studies at the International Masonry Institute in Seattle and conducted field studies at job sites.

Masons and bricklayers were happy to participate in the study "because we have been exposed so much," said Mark Maher of the Masonry Institute. "We want to have a healthy, long-term workforce, and we want our workers to enjoy a long retirement." He described the Field Group research as "a real win-win thing" that provides the University a place to do its research, and the masons an opportunity to have their questions answered.

That has happened in several trades in the construction industry, Seixas said. "The industry came to us. They recognized that they had a problem, and it was one the Department could address through training and research."

The industry has a voice in developing the Department's continuing education courses, such as a recent class entitled "Current Issues in Construction Safety," which addressed silica control.

Asian miners & stonecutters

The International Scholars in Occupational and Environmental Health program has brought two researchers from southeast Asia to campus to do silica research, and has trained others in Vietnam and Thailand.

Tanongsak Yingratanasuk (third from left) presents his research to Drew Brodkin, Scott Barnhart, and Noah Seixas of the DEH faculty

Tanongsak Yingratanasuk, director of the Industrial Hygiene program at Burapha University in Thailand, studied in Seattle the past two years, earning his Master of Science degree in Industrial Hygiene and Safety under Seixas' direction. His thesis was an assessment of lung diseases and silica exposure at a stone carving company in Thailand.

Phan Hong Son, of Vietnam's National Institute of Occupational and Environmental Health, is on campus now, studying silicosis incidence in his country using a geographic information system (GIS). He is also working on a chest radiology grant with Associate Professor Scott Barnhart.

Although many Asian countries have adopted occupational health and safety standards, some lack the technology to conduct workplace evaluations, said Associate Professor Matthew Keifer, director of the UW's International Scholars program. "We are giving the countries the information they need to make the workplace safer," he said.

The International Scholars program is funded by NIOSH and by two programs within the National Institutes of Health: the Fogarty International Center and the National Institute of Environmental Health Sciences (NIEHS).

For further reading

Becker P, Flanagan ME, Akladios M. Development of an ACGIH construction industry silica exposure database overview. Applied Occup Environ Hyg. 2001;16(8):781-783.

Checkoway H, Heyer NJ, Demers PA, Breslow NE. Mortality among workers in the diatomaceous earth industry. Brit J Ind Med 1993;50:586-597.

Checkoway H, Heyer NJ, Seixas NS, et al. Dose-response associations of silica with non-malignant respiratory disease and lung cancer mortality in the diatomaceous earth industry. Am J Epidemiol 1997;145:680-688.

Checkoway H, Hughes JM, Weill H, Seixas NS, Demers PA. Crystalline silica exposure, radiological silicosis, and lung cancer mortality in diatomaceous earth industry workers. Thorax 1999;54:56-59.

Continuing Education Web site,
http://depts.washington.edu/ehce

Croteau G. The effect of local exhaust ventilation control on dust exposures during masonry activities. Master's thesis 2000, University of Washington.

International Agency for Research on Cancer (IARC). Evaluation of Carcinogenic Risks to Humans. Silica, some silicates, coal dust, and para-aramid fibrils. Volume 68. Lyon, France: IARC Publications, 1997.

Majar, M. Respirable dust and silica exposure assessment in construction tasks. Master's thesis 2001, University of Washington.
http://depts.washington.edu/ envhlth/news/abstract01/abstracts_majar.html

National Institute for Occupational Safety and Health, 1996. NIOSH Alert: Preventing silicosis and deaths in construction workers. DHHS (NIOSH) Publication No. 96-112.

Rice F, Park R, Stayner L, Smith R, Gilbert S, Checkoway H. Crystalline silica exposure and lung cancer mortality in diatomaceous earth industry workers: a quantitative risk assessment. Occup Environ Med 2000;58:38-45.

Yingratanasuk T. An assessment of lung diseases and silica exposure in a stone carving company in Chonburi Province, Thailand. Master's thesis 2001, University of Washington.
http://depts.washington.edu/ envhlth/news/abstract01/abstracts_yingratanasuk.html