Differentiating the associations of black carbon and fine particle with daily mortality in a Chinese city

There is only limited monitoring data of black carbon for epidemiologic analyses. In the current study, we used the distributed lag models to evaluate the association between mortality outcomes (both total and cause-specific) and exposure to black carbon and fine particle (PM2.5) in Shanghai, China. During our research period, the mean daily concentrations of black carbon and PM2.5 were 3.9 μg/m3 and 53.9 μg/m3, respectively. The regression results showed that black carbon was significantly associated with total and cardiovascular mortality, but not with respiratory mortality. An inter-quartile range increase (2.7 μg/m3) of black carbon corresponded to a 2.3% (95% confidence interval [CI]: 0.6–4.1), 3.2% (95% CI: 0.6–5.7), and 0.6% (95% CI: −4.5 to 5.7) increase in total, cardiovascular and respiratory mortality, respectively. When adjusted for PM2.5, the effects of black carbon increased and remained statistically significant; in contrast, the associations of PM2.5 with daily mortality decreased and became statistically insignificant after adjustment for black carbon. To our knowledge, this is the first study in China, or even in Asian developing countries, to report the acute effect of black carbon and PM2.5 on daily mortality simultaneously. Our findings suggest that black carbon is a valuable additional air quality indicator to evaluate the health risks of ambient particles.

► Black carbon is not only a warming agent but also damaging to health.
► Black carbon was significantly associated with daily mortality when adjusted for fine particle.
► Fine particle was not significantly associated with mortality when adjusted for black carbon.
► Black carbon is a valuable additional particle indicator to evaluate the health risks.