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The Diesel Exhaust in Miners study: a nested case-control study of lung cancer and diesel exhaust.

Silverman DT, Samanic CM, Lubin JH, Blair AE, Stewart PA, Vermeulen R, Coble JB, Rothman N, Schleiff PL, Travis WD, Ziegler RG, Wacholder S, Attfield MD - J. Natl. Cancer Inst. (2012)

Bottom Line: We conducted both categorical and continuous regression analyses adjusted for cigarette smoking and other potential confounding variables (eg, history of employment in high-risk occupations for lung cancer and a history of respiratory disease) to estimate odds ratios (ORs) and 95% confidence intervals (CIs).We observed statistically significant increasing trends in lung cancer risk with increasing cumulative REC and average REC intensity.Among never smokers, odd ratios were 1.0, 1.47 (95% CI = 0.29 to 7.50), and 7.30 (95% CI = 1.46 to 36.57) for workers with 15-year lagged cumulative REC tertiles of less than 8, 8 to less than 304, and 304 μg/m(3)-y or more, respectively.

View Article: PubMed Central - PubMed

Affiliation: Occupational and Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD 20816, USA. silvermd@mail.nih.gov

ABSTRACT

Background: Most studies of the association between diesel exhaust exposure and lung cancer suggest a modest, but consistent, increased risk. However, to our knowledge, no study to date has had quantitative data on historical diesel exposure coupled with adequate sample size to evaluate the exposure-response relationship between diesel exhaust and lung cancer. Our purpose was to evaluate the relationship between quantitative estimates of exposure to diesel exhaust and lung cancer mortality after adjustment for smoking and other potential confounders.

Methods: We conducted a nested case-control study in a cohort of 12 315 workers in eight non-metal mining facilities, which included 198 lung cancer deaths and 562 incidence density-sampled control subjects. For each case subject, we selected up to four control subjects, individually matched on mining facility, sex, race/ethnicity, and birth year (within 5 years), from all workers who were alive before the day the case subject died. We estimated diesel exhaust exposure, represented by respirable elemental carbon (REC), by job and year, for each subject, based on an extensive retrospective exposure assessment at each mining facility. We conducted both categorical and continuous regression analyses adjusted for cigarette smoking and other potential confounding variables (eg, history of employment in high-risk occupations for lung cancer and a history of respiratory disease) to estimate odds ratios (ORs) and 95% confidence intervals (CIs). Analyses were both unlagged and lagged to exclude recent exposure such as that occurring in the 15 years directly before the date of death (case subjects)/reference date (control subjects). All statistical tests were two-sided.

Results: We observed statistically significant increasing trends in lung cancer risk with increasing cumulative REC and average REC intensity. Cumulative REC, lagged 15 years, yielded a statistically significant positive gradient in lung cancer risk overall (P (trend) = .001); among heavily exposed workers (ie, above the median of the top quartile [REC ≥ 1005 μg/m(3)-y]), risk was approximately three times greater (OR = 3.20, 95% CI = 1.33 to 7.69) than that among workers in the lowest quartile of exposure. Among never smokers, odd ratios were 1.0, 1.47 (95% CI = 0.29 to 7.50), and 7.30 (95% CI = 1.46 to 36.57) for workers with 15-year lagged cumulative REC tertiles of less than 8, 8 to less than 304, and 304 μg/m(3)-y or more, respectively. We also observed an interaction between smoking and 15-year lagged cumulative REC (P (interaction) = .086) such that the effect of each of these exposures was attenuated in the presence of high levels of the other.

Conclusion: Our findings provide further evidence that diesel exhaust exposure may cause lung cancer in humans and may represent a potential public health burden.

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Related in: MedlinePlus

Odds ratios (ORs) (solid squares) for lung cancer by expanded categoriesof average respirable elemental carbon (REC) intensity and cumulative REC (Supplementary Table 2, available online). A) Average RECintensity, full range; B) Average REC intensity, less than 128μg/m3; C) Cumulative REC exposure, full range;D) Cumulative REC exposure, less than 1280 μg/m3-y. ORslocated at the mean exposure within category. Models for OR by continuous exposure(d) include a power model, OR(d) =dβ (solid line); a linear model, OR(d)= 1 + β d (dashed line for the full rangeand dashed-dotted line for the restricted range); and a linear-exponentialmodel, OR(d) = 1 + β d exp(γd) (dotted line). Exposure variables were based on a15-year lag. Confidence intervals were omitted for clarity. The log-linear model wasexcluded because it did not fit the data well.
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fig1: Odds ratios (ORs) (solid squares) for lung cancer by expanded categoriesof average respirable elemental carbon (REC) intensity and cumulative REC (Supplementary Table 2, available online). A) Average RECintensity, full range; B) Average REC intensity, less than 128μg/m3; C) Cumulative REC exposure, full range;D) Cumulative REC exposure, less than 1280 μg/m3-y. ORslocated at the mean exposure within category. Models for OR by continuous exposure(d) include a power model, OR(d) =dβ (solid line); a linear model, OR(d)= 1 + β d (dashed line for the full rangeand dashed-dotted line for the restricted range); and a linear-exponentialmodel, OR(d) = 1 + β d exp(γd) (dotted line). Exposure variables were based on a15-year lag. Confidence intervals were omitted for clarity. The log-linear model wasexcluded because it did not fit the data well.

Mentions: Table 2 shows the effect of cigarette smokingoverall and cross-classified by location of employment (ie, surface only and everunderground). Overall, for both surface-only and ever underground workers combined, the riskof lung cancer was statistically significantly associated with smoking status (never,former, current smoker) and smoking intensity (former smoker of ≥2 packs per day vs neversmoker: OR = 5.40, 95% CI = 2.23 to 13.06; current smoker of ≥2 packs perday vs never smoker: OR = 12.41, 95% CI = 5.57 to 27.66) (Table 2). We also observed an interaction betweencigarette smoking and location of employment, after adjustment for cumulative REC, lagged 15years (Pinteraction = .082). The lung cancer risks associated with moderate (1 to<2 packs per day) and heavy smoking (≥2 packs per day) were higher among workers whoonly worked at the surface than among those who ever worked underground for both current andformer smokers. For example, the odds ratio for current smokers of one to less than twopacks per day who worked only at the surface was 13.34 (95% CI = 4.50 to 39.53)compared with an OR of 4.51 (95% CI = 1.50 to 13.58) for those who ever workedunderground (Table 2). Because the effect ofsmoking appeared to be diminished among underground workers compared with that among surfaceworkers, we included the cross classification of location of employment, smoking status, andsmoking intensity in all models used to estimate lung cancer risk by diesel exposure (Tables 1, 3,and 7; Figure1), unless noted otherwise. It is also noteworthy that among never smokers,underground and surface-only workers had similar risks after adjustment for 15-year laggedcumulative REC (OR = 0.90; 95% CI = 0.26 to 3.09) (Table 2), suggesting that the risk experienced by surface-only workerswas mainly due to smoking.


The Diesel Exhaust in Miners study: a nested case-control study of lung cancer and diesel exhaust.

Silverman DT, Samanic CM, Lubin JH, Blair AE, Stewart PA, Vermeulen R, Coble JB, Rothman N, Schleiff PL, Travis WD, Ziegler RG, Wacholder S, Attfield MD - J. Natl. Cancer Inst. (2012)

Odds ratios (ORs) (solid squares) for lung cancer by expanded categoriesof average respirable elemental carbon (REC) intensity and cumulative REC (Supplementary Table 2, available online). A) Average RECintensity, full range; B) Average REC intensity, less than 128μg/m3; C) Cumulative REC exposure, full range;D) Cumulative REC exposure, less than 1280 μg/m3-y. ORslocated at the mean exposure within category. Models for OR by continuous exposure(d) include a power model, OR(d) =dβ (solid line); a linear model, OR(d)= 1 + β d (dashed line for the full rangeand dashed-dotted line for the restricted range); and a linear-exponentialmodel, OR(d) = 1 + β d exp(γd) (dotted line). Exposure variables were based on a15-year lag. Confidence intervals were omitted for clarity. The log-linear model wasexcluded because it did not fit the data well.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC3369553&req=5

fig1: Odds ratios (ORs) (solid squares) for lung cancer by expanded categoriesof average respirable elemental carbon (REC) intensity and cumulative REC (Supplementary Table 2, available online). A) Average RECintensity, full range; B) Average REC intensity, less than 128μg/m3; C) Cumulative REC exposure, full range;D) Cumulative REC exposure, less than 1280 μg/m3-y. ORslocated at the mean exposure within category. Models for OR by continuous exposure(d) include a power model, OR(d) =dβ (solid line); a linear model, OR(d)= 1 + β d (dashed line for the full rangeand dashed-dotted line for the restricted range); and a linear-exponentialmodel, OR(d) = 1 + β d exp(γd) (dotted line). Exposure variables were based on a15-year lag. Confidence intervals were omitted for clarity. The log-linear model wasexcluded because it did not fit the data well.
Mentions: Table 2 shows the effect of cigarette smokingoverall and cross-classified by location of employment (ie, surface only and everunderground). Overall, for both surface-only and ever underground workers combined, the riskof lung cancer was statistically significantly associated with smoking status (never,former, current smoker) and smoking intensity (former smoker of ≥2 packs per day vs neversmoker: OR = 5.40, 95% CI = 2.23 to 13.06; current smoker of ≥2 packs perday vs never smoker: OR = 12.41, 95% CI = 5.57 to 27.66) (Table 2). We also observed an interaction betweencigarette smoking and location of employment, after adjustment for cumulative REC, lagged 15years (Pinteraction = .082). The lung cancer risks associated with moderate (1 to<2 packs per day) and heavy smoking (≥2 packs per day) were higher among workers whoonly worked at the surface than among those who ever worked underground for both current andformer smokers. For example, the odds ratio for current smokers of one to less than twopacks per day who worked only at the surface was 13.34 (95% CI = 4.50 to 39.53)compared with an OR of 4.51 (95% CI = 1.50 to 13.58) for those who ever workedunderground (Table 2). Because the effect ofsmoking appeared to be diminished among underground workers compared with that among surfaceworkers, we included the cross classification of location of employment, smoking status, andsmoking intensity in all models used to estimate lung cancer risk by diesel exposure (Tables 1, 3,and 7; Figure1), unless noted otherwise. It is also noteworthy that among never smokers,underground and surface-only workers had similar risks after adjustment for 15-year laggedcumulative REC (OR = 0.90; 95% CI = 0.26 to 3.09) (Table 2), suggesting that the risk experienced by surface-only workerswas mainly due to smoking.

Bottom Line: We conducted both categorical and continuous regression analyses adjusted for cigarette smoking and other potential confounding variables (eg, history of employment in high-risk occupations for lung cancer and a history of respiratory disease) to estimate odds ratios (ORs) and 95% confidence intervals (CIs).We observed statistically significant increasing trends in lung cancer risk with increasing cumulative REC and average REC intensity.Among never smokers, odd ratios were 1.0, 1.47 (95% CI = 0.29 to 7.50), and 7.30 (95% CI = 1.46 to 36.57) for workers with 15-year lagged cumulative REC tertiles of less than 8, 8 to less than 304, and 304 μg/m(3)-y or more, respectively.

View Article: PubMed Central - PubMed

Affiliation: Occupational and Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD 20816, USA. silvermd@mail.nih.gov

ABSTRACT

Background: Most studies of the association between diesel exhaust exposure and lung cancer suggest a modest, but consistent, increased risk. However, to our knowledge, no study to date has had quantitative data on historical diesel exposure coupled with adequate sample size to evaluate the exposure-response relationship between diesel exhaust and lung cancer. Our purpose was to evaluate the relationship between quantitative estimates of exposure to diesel exhaust and lung cancer mortality after adjustment for smoking and other potential confounders.

Methods: We conducted a nested case-control study in a cohort of 12 315 workers in eight non-metal mining facilities, which included 198 lung cancer deaths and 562 incidence density-sampled control subjects. For each case subject, we selected up to four control subjects, individually matched on mining facility, sex, race/ethnicity, and birth year (within 5 years), from all workers who were alive before the day the case subject died. We estimated diesel exhaust exposure, represented by respirable elemental carbon (REC), by job and year, for each subject, based on an extensive retrospective exposure assessment at each mining facility. We conducted both categorical and continuous regression analyses adjusted for cigarette smoking and other potential confounding variables (eg, history of employment in high-risk occupations for lung cancer and a history of respiratory disease) to estimate odds ratios (ORs) and 95% confidence intervals (CIs). Analyses were both unlagged and lagged to exclude recent exposure such as that occurring in the 15 years directly before the date of death (case subjects)/reference date (control subjects). All statistical tests were two-sided.

Results: We observed statistically significant increasing trends in lung cancer risk with increasing cumulative REC and average REC intensity. Cumulative REC, lagged 15 years, yielded a statistically significant positive gradient in lung cancer risk overall (P (trend) = .001); among heavily exposed workers (ie, above the median of the top quartile [REC ≥ 1005 μg/m(3)-y]), risk was approximately three times greater (OR = 3.20, 95% CI = 1.33 to 7.69) than that among workers in the lowest quartile of exposure. Among never smokers, odd ratios were 1.0, 1.47 (95% CI = 0.29 to 7.50), and 7.30 (95% CI = 1.46 to 36.57) for workers with 15-year lagged cumulative REC tertiles of less than 8, 8 to less than 304, and 304 μg/m(3)-y or more, respectively. We also observed an interaction between smoking and 15-year lagged cumulative REC (P (interaction) = .086) such that the effect of each of these exposures was attenuated in the presence of high levels of the other.

Conclusion: Our findings provide further evidence that diesel exhaust exposure may cause lung cancer in humans and may represent a potential public health burden.

Show MeSH
Related in: MedlinePlus