title: Radiographic evidence of silicosis risk in the diatomaceous earth industry.
abstract: There is limited and conflicting evidence regarding the exposure-response relationship between exposure to crystalline silica and silicosis; the level of risk to current workers remains uncertain. We conducted an epidemiologic investigation of 1,809 workers in the diatomaceous earth industry, where exposures to crystalline silica are primarily to the cristobalite form. On the basis of the median of three independent readings, 81 (4.5%) workers were judged to have opacities on chest radiographs (small opacities, profusion >= 1/0, and/or large opacities). Age-adjusted relative risk of opacities increased significantly with cumulative exposure to crystalline silica. The concentration of respirable crystalline silica to which workers were exposed (highly correlated with period of hire) was an important determinant of risk after accounting for cumulative exposure. For workers with an average exposure to crystalline silica of <= 0.50 mg/m3 (or hired >= 1950), the cumulative risk of opacities for a cumulative exposure to crystalline silica of 2.0 mg/m3-yr was approximately 1.1%; for an average exposure > 0.50 mg/m3 (or hired < 1950), the corresponding cumulative risk was 3.7%. These findings indicate an exposure-response relationship between cumulative exposure to crystalline silica and radiographic opacities; moreover, the relationship was substantially steeper among workers exposed at the highest average concentrations of crystalline silica.
authors.affiliation: Department of Biostatistics and Epidemiology, and Department of Medicine, Tulane University, New Orleans, Louisiana, USA. hughes@mailhost.tcs.tulane.edu
authors.forename: J M
authors.initials: JM
authors.lastname: Hughes
authors.forename: H
authors.initials: H
authors.lastname: Weill
authors.forename: H
authors.initials: H
authors.lastname: Checkoway
authors.forename: R N
authors.initials: RN
authors.lastname: Jones
authors.forename: M M
authors.initials: MM
authors.lastname: Henry
authors.forename: N J
authors.initials: NJ
authors.lastname: Heyer
authors.forename: N S
authors.initials: NS
authors.lastname: Seixas
authors.forename: P A
authors.initials: PA
authors.lastname: Demers
mesh_terms: D000328:Adult; D000367:Age Factors; D001194:Asbestos / Q000009:adverse effects; D001195:Asbestosis / Q000000981:diagnostic imaging / Q000453:epidemiology; D002140:California / Q000453:epidemiology; D002617:Chemical Industry; D015331:Cohort Studies; D003460:Crystallization; D007692:Diatomaceous Earth; D004391:Dust / Q000009:adverse effects; D005500:Follow-Up Studies; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D016273:Occupational Exposure; D016012:Poisson Distribution; D013902:Radiography, Thoracic; D012044:Regression Analysis; D012307:Risk Factors; D012822:Silicon Dioxide / Q000009:adverse effects; D012829:Silicosis / Q000000981:diagnostic imaging* / Q000453:epidemiology; D012907:Smoking / Q000453:epidemiology; D016019:Survival Analysis; D013997:Time Factors
chemical_list: D004391:Dust; D001194:Asbestos; D007692:Diatomaceous Earth; D012822:Silicon Dioxide