Impact of interventions to prevent asbestos-related respiratory disease in an exposed worker registry using a simplified G-computation

The Ontario Asbestos Workers Registry is a regulatory exposure registry obligating employers to report the number of work hours with asbestos-containing materials for each of their workers. Currently, each worker is notified of the need for a medical examination once they have accrued 2000 reported hours of work with asbestos. We sought to evaluate the impact on disease prevention of alternative policies limiting asbestos work hours among registry participants. A cohort of 26 164 asbestos workers were followed for cancer and nonmalignant disease diagnoses between 1986 and 2019. Analyses of the association between cumulative asbestos work hours and respiratory disease incidence rates showed substantially elevated disease rates well before reaching 2000 asbestos work hours. Using a simplified application of parametric G-computation (G-POSH), limiting cumulative asbestos work hours to 100 h would have prevented 76 asbestosis, 36 pulmonary fibrosis, 27 mesothelioma, and 79 lung cancer cases at the end of follow-up compared to the observed risk in the cohort. Limiting exposure to 2000 asbestos work hours had a smaller but still substantial impact on disease prevention, particularly among workers in the construction industry. Regulatory agencies should intervene sooner to prevent respiratory disease among workers in the registry.