The Diesel Exhaust in Miners Study: IV. Estimating Historical Exposures to Diesel Exhaust in Underground Non-metal Mining Facilities

Abstract

We developed quantitative estimates of historical exposures to respirable elemental carbon (REC) for an epidemiologic study of mortality, including lung cancer, among diesel-exposed miners at eight non-metal mining facilities [the Diesel Exhaust in Miners Study (DEMS)]. Because there were no historical measurements of diesel exhaust (DE), historical REC (a component of DE) levels were estimated based on REC data from monitoring surveys conducted in 1998–2001 as part of the DEMS investigation. These values were adjusted for underground workers by carbon monoxide (CO) concentration trends in the mines derived from models of historical CO (another DE component) measurements and DE determinants such as engine horsepower (HP; 1 HP = 0.746 kW) and mine ventilation. CO was chosen to estimate historical changes because it was the most frequently measured DE component in our study facilities and it was found to correlate with REC exposure. Databases were constructed by facility and year with air sampling data and with information on the total rate of airflow exhausted from the underground operations in cubic feet per minute (CFM) (1 CFM = 0.0283 m3 min−1), HP of the diesel equipment in use (ADJ HP), and other possible determinants. The ADJ HP purchased after 1990 (ADJ HP1990+) was also included to account for lower emissions from newer, cleaner engines. Facility-specific CO levels, relative to those in the DEMS survey year for each year back to the start of dieselization (1947–1967 depending on facility), were predicted based on models of observed CO concentrations and log-transformed (Ln) ADJ HP/CFM and Ln(ADJ HP1990+). The resulting temporal trends in relative CO levels were then multiplied by facility/department/job-specific REC estimates derived from the DEMS surveys personal measurements to obtain historical facility/department/job/year-specific REC exposure estimates. The facility-specific temporal trends of CO levels (and thus the REC estimates) generated from these models indicated that CO concentrations had been generally greater in the past than during the 1998–2001 DEMS surveys, with the highest levels ranging from 100 to 685% greater (median: 300%). These levels generally occurred between 1970 and the early 1980s. A comparison of the CO facility-specific model predictions with CO air concentration measurements from a 1976–1977 survey external to the modeling showed that our model predictions were slightly lower than those observed (median relative difference of 29%; range across facilities: 49 to –25%). In summary, we successfully modeled past CO concentration levels using selected determinants of DE exposure to derive retrospective estimates of REC exposure. The results suggested large variations in REC exposure levels both between and within the underground operations of the facilities and over time. These REC exposure estimates were in a plausible range and were used in the investigation of exposure–response relationships in epidemiologic analyses.

Particulate matter characteristics, dynamics, and sources in an underground mine

“…The effects of diesel engine emissions on the mine air quality, fine particle concentrations, and occupational exposures have also been widely investigated (Scheepers et al 2003;Noll et al 2007;Vermeulen et al 2010). In a previous study conducted in an underground gold mine, it was shown that diesel exhaust can contribute by a fraction of 78%-98% to the PM 2.5 mass and by >90% to the PM 2.5 carbon concentration (McDonald et al 2003).…”

Association of Chromosome Translocation Rate with Low Dose Occupational Radiation Exposures in U.S. Radiologic Technologists

“…An additional complication is the uncertainty in measurement of dose. A crucial component of the exposure assessment is the comparison with a gold standard or other independent type of corroboration (1, 2). Corroborating measurements of exposure that include biological measurements are particularly valuable if repeated over time (3) and if the measurements are biologically meaningful (4).…”

Evaluation of an exposure assessment used in epidemiological studies of diesel exhaust and lung cancer in underground mines

“…For example we were able to reproduce reasonably well results contained in Figure 1 of Stewart et al (2010), Tables 1, 4 and the table in the Appendix of Coble et al (2010), Table 1 and Figure 2 of Vermeulen et al (2010a), and Tables 1 and 2 and Figure 2 from Vermeulen et al (2010b). We would not expect to get exact matches in many cases due to differences in imputed data.…”

“…DPM, diesel particulate matter; RD, respirable dust; ROC, rcspirable organic carbon; SCD, submicron combustible dust; SD, submicron dust; SEC, Submicron elemental carbon; SOC, submicron organic carbon; TD, total dust, TEC, total elemental carbon; TOC, total organic carbon. a Surveys: the MSHA MIDAS (1976–2001); the DEMS (1998–2001) (Coble et al, 2010; Vermeulen et al, 2010b); the MESA/BoM (1976–1977) (Sutton et al, 1979); the feasibility study for the DEMS in Facility B (1994) (Stanevich et al, 1997): compliance visits by the State of New Mexico, MSHA hard copy reports, and the mining facilities (1954–1996). b Area measurements: personal measurements. The number includes both full-shift and short-term measurements.…”

“…Historical estimates of DE exposures of these workers were obtained from an assessment of DE exposures conducted in the eight mines (Stewart et al, 2010; Coble et al, 2010; Vermeulen et al, 2010a, 2010b). This assessment provided job-specific yearly historical estimates of respirable elemental carbon (REC), selected as a surrogate for DE, beginning with the year in which diesel equipment was first introduced into a mine (1947–1967), through 1998–2001.…”