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

Abstract

A study was conducted to construct a job exposure matrix for the roofing granule mine and mill workers at four U.S. plants. Each plant mined different minerals and had unique departments and jobs. The goal of the study was to generate accurate estimates of the mean exposure to respirable crystalline silica for each cell of the job exposure matrix, that is, every combination of plant, department, job, and year represented in the job histories of the study participants. The objectives of this study were to locate, identify, and collect information on all exposure measurements ever collected at each plant, statistically analyze the data to identify deficiencies in the database, identify and resolve questionable measurements, identify all important process and control changes for each plant-department-job combination, construct a time line for each plant-department combination indicating periods where the equipment and conditions were unchanged, and finally, construct a job exposure matrix. After evaluation, 1871 respirable crystalline silica measurements and estimates remained. The primary statistic of interest was the mean exposure for each job exposure matrix cell. The average exposure for each of the four plants was 0.042 mg/m(3) (Belle Mead, N.J.), 0.106 mg/m(3) (Corona, Calif.), 0.051 mg/m(3) (Little Rock, Ark.), and 0.152 mg/m(3) (Wausau, Wis.), suggesting that there may be substantial differences in the employee cumulative exposures. Using the database and the available plant information, the study team assigned an exposure category and mean exposure for every plant-department-job and time interval combination. Despite a fairly large database, the mean exposure for > 95% of the job exposure matrix cells, or specific plant-department-job-year combinations, were estimated by analogy to similar jobs in the plant for which sufficient data were available. This approach preserved plant specificity, hopefully improving the usefulness of the job exposure matrix.

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

“…In the companion article, Hewett et al (12) described the construction of the JEM used in the present study as well as its limitations, which included: (1) the reasons why industrial hygiene sampling occur (typically when high exposures are of concern); (2) the number of industrial hygiene measurements made and the changing methods used over time to measure dust and the respirable fraction of silica;…”

“…In the companion article, Hewett et al (12) provide the detailed methods by which RCS exposure was determined across plant-, department-, job-, and time-dependent categories. This effort contributed to the creation of the study's JEM.…”

“…A companion article, Part I in this issue, details the production activities at these plants and the construction of the job exposure matrix (JEM) used in this study. (12) …”

Formative research to reduce mine worker respirable silica dust exposure: a feasibility study to integrate technology into behavioral interventions

“…Because mining is one of the leading industries for occupational exposure to respirable silica dust [26, 28, 35, 58, 63], this occupational health issue is both critical and timely. Mobile mine workers, bagging operators, surface drill operators, and workers for other types of mechanized equipment, including dozers, loaders, and haul trucks have some of the highest exposure rates within the industry [49].…”

Instituting a filtration/pressurization system to reduce dust concentrations in a control room at a mineral processing plant

“…In June 1997, the International Agency for Research on Cancer (1997) found sufficient evidence to declare that inhaled crystalline silica in the form of quartz and cristobalite is carcinogenic. Mining is one of the leading industries for occupational exposure to silica dust (Scarselli et al, 2011; Vacek et al, 2011; Kreiss and Zhen, 1996; Healy et al, 2014; Merget et al, 2001; Hewett et al, 2012). Control rooms located in dusty areas in some mines are of particular concern (Colinet et al, 2010).…”