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Articles by D Yereb
Total Records ( 2 ) for D Yereb
  J. B Coble , P. A Stewart , R Vermeulen , D Yereb , R Stanevich , A Blair , D. T Silverman and M. Attfield
 

Air monitoring surveys were conducted between 1998 and 2001 at seven non-metal mining facilities to assess exposure to respirable elemental carbon (REC), a component of diesel exhaust (DE), for an epidemiologic study of miners exposed to DE. Personal exposure measurements were taken on workers in a cross-section of jobs located underground and on the surface. Air samples taken to measure REC were also analyzed for respirable organic carbon (ROC). Concurrent measurements to assess exposure to nitric oxide (NO) and nitrogen dioxide (NO2), two gaseous components of DE, were also taken. The REC measurements were used to develop quantitative estimates of average exposure levels by facility, department, and job title for the epidemiologic analysis. Each underground job was assigned to one of three sets of exposure groups from specific to general: (i) standardized job titles, (ii) groups of standardized job titles combined based on the percentage of time in the major underground areas, and (iii) larger groups based on similar area carbon monoxide (CO) air concentrations. Surface jobs were categorized based on their use of diesel equipment and proximity to DE. A total of 779 full-shift personal measurements were taken underground. The average REC exposure levels for underground jobs with five or more measurements ranged from 31 to 58 µg m–3 at the facility with the lowest average exposure levels and from 313 to 488 µg m–3 at the facility with the highest average exposure levels. The average REC exposure levels for surface workers ranged from 2 to 6 µg m–3 across the seven facilities. There was much less contrast in the ROC compared with REC exposure levels measured between surface and underground workers within each facility, as well as across the facilities. The average ROC levels underground ranged from 64 to 195 µg m–3, while on the surface, the average ROC levels ranged from 38 to 71 µg m–3 by facility, an ~2- to 3-fold difference. The average NO and NO2 levels underground ranged from 0.20 to 1.49 parts per million (ppm) and from 0.10 to 0.60 ppm, respectively, and were ~10 times higher than levels on the surface, which ranged from 0.02 to 0.11 ppm and from 0.01 to 0.06 ppm, respectively. The ROC, NO, and NO2 concentrations underground were correlated with the REC levels (r = 0.62, 0.71, and 0.62, respectively). A total of 80% of the underground jobs were assigned an exposure estimate based on measurements taken for the specific job title or for other jobs with a similar percentage of time spent in the major underground work areas. The average REC exposure levels by facility were from 15 to 64 times higher underground than on the surface. The large contrast in exposure levels measured underground versus on the surface, along with the differences between the mining facilities and between underground jobs within the facilities resulted in a wide distribution in the exposure estimates for evaluation of exposure–response relationships in the epidemiologic analyses.

  R Vermeulen , J. B Coble , D Yereb , J. H Lubin , A Blair , L Portengen , P. A Stewart , M Attfield and D. T. Silverman
 

Diesel exhaust (DE) has been implicated as a potential lung carcinogen. However, the exact components of DE that might be involved have not been clearly identified. In the past, nitrogen oxides (NOx) and carbon oxides (COx) were measured most frequently to estimate DE, but since the 1990s, the most commonly accepted surrogate for DE has been elemental carbon (EC). We developed quantitative estimates of historical exposure levels of respirable elemental carbon (REC) for an epidemiologic study of mortality, particularly lung cancer, among diesel-exposed miners by back-extrapolating 1998–2001 REC exposure levels using historical measurements of carbon monoxide (CO). The choice of CO was based on the availability of historical measurement data. Here, we evaluated the relationship of REC with CO and other current and historical components of DE from side-by-side area measurements taken in underground operations of seven non-metal mining facilities. The Pearson correlation coefficient of the natural log-transformed (Ln)REC measurements with the Ln(CO) measurements was 0.4. The correlation of REC with the other gaseous, organic carbon (OC), and particulate measurements ranged from 0.3 to 0.8. Factor analyses indicated that the gaseous components, including CO, together with REC, loaded most strongly on a presumed ‘Diesel exhaust’ factor, while the OC and particulate agents loaded predominantly on other factors. In addition, the relationship between Ln(REC) and Ln(CO) was approximately linear over a wide range of REC concentrations. The fact that CO correlated with REC, loaded on the same factor, and increased linearly in log–log space supported the use of CO in estimating historical exposure levels to DE.

 
 
 
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