Long-term effects of coarse particulate matter and modifications by temperature and relative humidity on all-cause mortality in a MDR-TB cohort

<bold>Background:</bold> The association between ambient coarse particulate matter (PM2.5-10) and mortality in MDR-TB patients has not yet been studied. The modifying effects of temperature and humidity on this association are completely unknown. This study aims to evaluate the effects of long-term PM2.5-10 exposures, and their modifications by temperature and humidity on mortality among MDR-TB patients. <bold>Methods:</bold> A Chinese cohort of 3,469 MDR-TB patients was followed up from diagnosis until death, loss to follow-up, or the study’s end, averaging 2,567 days per patient. PM2.5-10 concentrations were derived from the difference between PM10 and PM2.5. Cox proportional hazard models estimated hazard ratios (HRs) per 3.74 μg/m3 (IQR) exposure to PM2.5-10 and mortality for the full cohort and individuals at distinct long-term and short-term temperature and humidity levels, adjusting for other air pollutants and potential covariates. Exposure-response relationships were quantified using smoothed splines. <bold>Results:</bold> Hazard ratios of 1.733 (95% CI, 1.407, 2.135) and 1.427 (1.114, 1.827) were observed for mortality in association with PM2.5-10 exposures for the full cohort under long-term and short-term exposures to temperature and humidity. Modifying effects by temperature and humidity were heterogenous across sexes, age, treatment history, and environment. Nonlinear exposure-response curves suggested a cumulative risk of PM2.5-10-related mortality starting from a low exposure concentration around 15 μg/m3. <bold>Conclusion:</bold> Immediate surveillance of PM2.5-10 is crucial to mitigate the progression of MDR-TB severity due to co-exposures.