Exposure-response relation for occupational exposure to respirable quartz and lung cancer risk: Performance of a quantitative vs a semiquantitative job-exposure matrix

Objectives In order to estimate the exposure-response relation of respirable quartz and lung cancer risk, we developed a quantitative time/job/region specific job-exposure matrix (JEM) based on statistical modelling of historical exposure data. We compared the performance of this quantitative JEM (SYN-JEM) with an already available semi-quantitative general population JEM (DOM-JEM) within a study of pooled community- based lung cancer case-control studies (SYNERGY). Methods Detailed lifetime occupational and smoking history was available for 13 259 cases and 16 232 controls from 11 case-control studies from 12 European countries and Canada. Occupational histories were linked with SYN-JEM and DOMJEM to derive estimates of cumulative exposure. ORs for lung cancer were estimated using unconditional logistic regression adjusted for age, gender, study, cigarette pack-years, timesince- quitting smoking, and ever occupational exposure to five other known lung carcinogens. Results Exposure to respirable quartz was associated with a monotonic increase in risk of lung cancer. Cumulative exposure estimates based on the quantitative SYN-JEM ranged from 0.005 to 104 mg/m3-years. Quartiles of cumulative exposure (categorised using the exposure distribution among exposed controls) showed significant elevated risks ranging from 1.16 to 1.40. SYN-JEM did not perform better than the ordinal DOM-JEM which provided similar ORs. Conclusions We found a positive exposure-response association between occupational exposure to respirable quartz and lung cancer in a large pooled community-based casecontrol study. A semi-quantitative approach showed similar results as the quantitative exposure assessment approach except that with the latter risk can be expressed in terms of mg/m3 quartz years, which would facilitate quantitative risk-assessment.