Long-term exposure to black carbon and mortality: a 28-year follow-up of the GAZEL cohort

Background: The current evidence on health effects of long-term exposure to outdoor airborne black carbon (BC) exposure remains scarce. Objectives: To examine the association between long-term exposure to BC and mortality in a large populationbased French cohort, with 28 years of follow-up. Methods: Data from the GAZEL cohort were collected between 1989 and 2017. Land use regression model with temporal extrapolation wa used to estimate yearly BC and PM2.5 exposure at the residential addresses from 1989 until censoring for 19,906 participants. Time-varying Cox models with attained age as time-scale was used to estimate the associations between BC and all-cause and cardiovascular mortality, after adjusting for individual and area-level covariates. To handle confounding by PM2.5, we used the residual of BC regressed on PM2.5 as an alternate exposure variable. For all-cause mortality, we also examined effect modification by sex, smoking status, BMI and fruit/vegetable intake. Results: The median of 20-year moving average of BC exposure was 2.02 10