Mortality in a cohort of Staffordshire pottery workers: follow-up to December 2008

OBJECTIVES: To examine mortality from lung cancer, chronic obstructive pulmonary disease (COPD) and chronic non-malignant renal disease (cNMRD) in pottery workers exposed to silica.

METHODS: A cohort of Stoke-on-Trent pottery workers (N=5115), previously followed to 1992, was traced for vital status and cause of death to December 2008. Standardised mortality ratio (SMR) analyses, comparing deaths to England and Wales and Stoke-on-Trent, examined underlying cause in 1985-1992 and 1993-2008 and mentioned cause for 1993-2008. Survival analysis considered exposure duration and concentration of respirable silica for lung cancer, COPD and cNMRD, using Cox regression.

RESULTS: Excess risks of lung cancer, COPD and cNMRD were seen against both England and Wales and Stoke-on-Trent for 1985-2008. SMRs for lung cancer and COPD were lower in 1993-2008 and non-significant for lung cancer against Stoke-on-Trent in that period (SMR 1.07 95% CI 0.92 to 1.25). Exposure concentration, estimated for 1943 subjects, was related to lung cancer in smokers for early but not later deaths with mean silica concentration >200 µg/m(3) among deaths to June 1992 (HR 2.80 95% CI 1.21 to 6.50). For COPD an increasing trend with duration and (non-significantly) with mean concentration was seen for early but not later deaths in smokers. No relation was observed between estimated exposures and cNMRD.

CONCLUSIONS: Excess rates of death from COPD and lung cancer were more marked in the period of the first follow-up (1985-1992) than in the second, with any relation to estimated exposure being limited to the earlier period. Conclusions about COPD and exposure were limited by an early selective destruction of files.