Cohort Mortality Study of Roofing Granule Mine and Mill Workers. Part II. Epidemiologic Analysis, 1945–2004

Abstract

The mortality of 2650 employees (93.4% males) in the mine and mill production of roofing granules at four plants was examined between 1945 and 2004. Hypotheses focused on diseases associated with exposure to silica: nonmalignant respiratory disease, lung cancer, and nonmalignant renal disease. Study eligibility required ≥ 1 year of employment by 2000. Work history and vital status were followed through 2004 with < 1% lost to follow-up. Industrial hygiene sampling data (1871 sampling measurements over a 32-year period) and professional judgment were used to construct 15 respirable crystalline silica exposure categories. A category was assigned to all plant-, department-, and time-dependent standard job titles. Cumulative respirable crystalline silica exposure (mg/m(3)-years) was calculated as the sum of the product of time spent and the average exposure for each plant-, department-, job-, and calendar-year combination. The cohort geometric mean was 0.17 mg/m(3)-years (geometric standard deviation 4.01) and differed by plant. Expected deaths were calculated using U.S. (entire cohort) and regional (each plant) mortality rates. Poisson regression was used for internal comparisons. For the entire cohort, 772 deaths (97.4% males) were identified (standardized mortality ratio 0.95, 95% CI 0.88-1.02). There were 50 deaths from nonmalignant respiratory diseases (1.14, 95% CI 0.85-1.51). Lagging exposure 15 years among the male cohort, the relative risks for nonmalignant respiratory disease were 1.00 (reference), 0.80, 1.94, and 2.03 (p value trend = 0.03) when cumulative exposure was categorized < 0.1, 0.1- < 0.5, 0.5- < 1.0, and ≥ 1.0 mg/m(3)-years, respectively. There was a total of 77 lung cancer deaths (1.11, 95% CI 0.88-1.39). Lagging exposure 15 years, the relative risks for males were 1.00 (reference), 1.83, 1.83, and 1.05 (p value trend = 0.9). There were 16 deaths from nonmalignant renal disease (1.76, 95% CI 1.01-2.86). This exposure-response trend was suggestive but imprecise. The study results are consistent with other cohorts with similar levels of exposure to respirable crystalline silica.

Silicosis and urinary analysis

“…MacDonald et al [7] conducted a mortality study and showed that quartz exposure in North American industrial sandblasting workers increased mortality due to lung cancer, but not due to chronic renal disorders or renal cancer. Olsen et al [8] also researched the mortality of silica-exposed workers at 4 plants and demonstrated that 16 workers (2%) had died as a result of nonmalignant renal disease among 772 total deaths. In the same study, 50 deaths (6%) were attributed to nonmalignant respiratory system disease, and a total of 77 (1%) lung cancer deaths.…”

Cohort Mortality Study of Roofing Granule Mine and Mill Workers. Part I: Estimation of Historical Crystalline Silica Exposures

“…These estimates were then used in an exposure-response analysis comparing the cumulative exposures with the probability of developing occupational disease, such as silicosis and exposure-related lung cancer. (7) The process of developing a JEM included the following steps: A team of investigators was assembled to locate, acquire, review, and summarize the available exposure data for the four plants. The team consisted of the lead investigators, consultants, and industrial hygienists with plant experience.…”

“…Using the JEM, cumulative RCS exposures were calculated for each of 2650 workers who met the eligibility criteria. (7) The earliest RCS measurements were collected in 1972, yet estimates of plant and job specific mean exposures were required for those workers with job histories extending back to 1961, 1948, 1947, and 1945 for the Belle Mead, Corona, Little Rock, and Wausau cohorts, respectively. After reviewing the mine and mill histories, the study team determined that the mine and mill operations were relatively stable until the 1970s.…”

“…These estimates were used in an exposure-response analysis evaluating the probability of developing occupational diseases (e.g., silicosis) and exposure-related lung cancer. (7) A database of historical exposures was assembled and given a preliminary analysis. While the exposure database was large compared with many occupational studies, data gaps existed.…”

Effects of silica exposure on the cardiac and renal inflammatory and fibrotic response and the antagonistic role of interleukin-1 beta in C57BL/6 mice

“…Several studies have also found that cardiovascular disease is the leading cause of death in silicosis patients of coal mines (Landen et al 2011;Morozova 2012). The positive relationship between occupational silica exposure and chronic kidney disease [standard mortality ratio (SMR) = 1.76, 95 % confidence interval (CI) 1.01-2.86] was observed by Olsen et al (2012) in an epidemiological study of 2,650 participants. Vupputuri et al (2012) demonstrated that silica exposure was associated with a 40 % increased risk of chronic kidney disease compared with non-exposed controls after adjusting for potential confounders.…”