Introduction As part of a project to investigate the causes of COPD in the UK, we have estimated the current burden of occupational COPD using a JEM and novel age-time window approach to estimate population attributable fractions (PAFs) for disease prevalence.

Methods The method uses age-time windows across the period at which exposure in the workplace could have led to cases of COPD prevalent now. Numbers currently exposed to vapours, gases, dusts and fumes by 4-digit SOC code allocated to high/medium/low exposure levels, adjusted for historically changing employment levels, are estimated in time windows from up to 30 years ago as COPD is rare in younger ages, indicating a lag from initial exposure to disease onset. Workers’ assumed ages in these windows indicate current ages of those at risk from occupational COPD. Age-specific PAFs are estimated and applied to current COPD by age. Overall PAF is the fraction these cases represent of total COPD.

Results We estimate occupational PAF of COPD in the UK is 15.3% for men, 3.2% for women, or annually 18,600 cases in men, 5,300 in women, assuming disease onset up to 30 years after initial exposure and no recovery after exposure ceases. Assuming shorter onset lags has little effect as exposed workers are younger, but introducing recovery lags reduces PAFs.

Conclusions The method allows for lags in disease onset and recovery to be accounted for in estimating occupational PAFs for disease prevalence, and takes account of retired and ex- workers currently at risk of disease.