Technical report for combined effects of radiation and asbestos in producing pulmonary fibrosis.
Takaro-TK; Griffith-W; Omri-K; Checkoway-H
NIOSH 2004 Jan; 1-29
Workers exposed to asbestos may encounter radiation as radon or from other sources. Both asbestos and radiation are etiologic agents in pulmonary fibrosis. The aim of this study is to determine whether concomitant radiation exposure in asbestos workers increases the incidence of pulmonary fibrosis. 2263 asbestos exposed former nuclear weapons workers from a medical surveillance program form the study cohort. P A chest radiographs and spirometry were performed for screening. Fibrosis was defined by B-read opacity profusion category on chest radiographs ?:. 1/0, or spirometric evidence of restrictive or mixed disease. The cohort is largely male (91.0%) with an average age of 63.3 years. 1157 workers had complete work histories, including external radiation badge doses and laboratory data. The demographic and fibrosis endpoints were similar in the entire cohort vs. the 1157 analyzed. Asbestos exposure based upon years in a potentially exposed job was divided into low " 13 years) and high ( ?:.13 years) dose groups. 31 (5.4%) of the high dose vs.24 (4.1%) of the low dose group had ILO scores ?:. 110 indicating pulmonary fibrosis while 147 (25.7%) of the high dose group verses 121 (20.7% ) of the low dose group have meet the case definition of pulmonary fibrosis (spirometry combined with parenchymal disease) (p < 0.05). In a 2 x 4 table analysis (binary fibrosis x binary asbestos and radiation exposure) 90 (32.3%) in the high asbestos/ high radiation (> 20mSv deep dose) group met the cases definition for fibrosis vs. 81 (19.2%) in the low/low group (p =0.065). A dose response was seen for fibrosis risk with increasing radiation at exposure rates around the occupational standard. Worker protection standards are based upon single exposures not accounting for the constellation of exposures frequently encountered. Deep dose external radiation may add to the fibrotic effect of asbestos in workers exposed to both toxicants.
Radiation-effects; Radiation-exposure; Asbestos-dust; Asbestos-fibers; Pulmonary-system-disorders; Pulmonary-disorders; Fibrosis; Occupational-exposure; Etiology; Spirometry; Nuclear-hazards; Nuclear-wastes; Demographic-characteristics
Tim K. Takaro, MD, MPH, MS., Occupational and Environmental Medicine Program, University of Washington, 4225 Roosevelt Way NE, Suite 100, Seattle, WA 98105
Final Grant Report
National Institute for Occupational Safety and Health
University of Washington, Seattle, Washington