Dose-response relationships for silicosis from a case-control study of North Carolina dusty trades workers.
Rice-CH; Harris-RL Jr.; Checkoway-H; Symons-MJ
Silica, silicosis, and cancer: controversy in occupational medicine. Goldsmith DF, Winn DM, Shy CM, eds. New York: Praeger, 1986 Jan; :77-86
Lifetime exposures to quartz (14808607) were estimated and compared to incidence of disease in workers employed in mineral mining, granite quarrying, hard rock mining, and foundries. The study group included 216 male silicotics and 672 healthy workers in the dusty trades. Cases were matched to one to four comparisons by race, year of birth within 5 years, and year of hire within 5 years. There were 115 cases for which no match could be found. These nonmatched cases were older and had been hired earlier, therefore failure to find matched noncases was attributed to the practice of purging files of healthy individuals 5 years after leaving the industry. Results of industry wide environmental dust samplings were used to calculate estimates of silica exposure for all workers based on two different methods for converting particle counts to mass. The occupational work histories obtained during yearly medical screening were available for all workers who developed silicosis. Histories for the control individuals were available for all workers employed since 1974. A statistically significant risk of silicosis was present at an average cumulative exposure of 98 million particle years and was not detected at an average cumulative exposure of 37 particle years. Over an average working lifetime of 40 years, these values may be expressed as average annual exposures of 250 and 100 micrograms per cubic meter, depending on the conversion method applied. The lower value was equivalent to the current OSHA permissible exposure limit (PEL) for dust containing 100 percent quartz.
NIOSH-Grant; Occupational-exposure; Occupational-respiratory-disease; Silica-dusts; Foundry-workers; Mine-workers; Morbidity-rates; Epidemiology
Goldsmith-DF; Winn-DM; Shy-CM
Silica, silicosis, and cancer: controversy in occupational medicine
Environmental Sciences & Engr University of North Carolina Occupational Hlth Studies Grp Chapel Hill, N C 27514