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Worldwide epidemiological studies have demonstrated that short-term associations of particulate matter (PM), might be further complicated by ambient temperatures, and increase human mortality. In China, among various PM indices, the health effects of black carbon (BC) are less understood due to the lack of data availability. Additionally, it is unclear how temperature modifies simultaneous and adverse effects of BC, and fine (PM size <2.5 μm; PM 2.5), and coarse particles (PM 2.5-10), on mortality outcomes. We adopted time-series Poisson generalized additive models to investigate temperature modifying effects on the association between three different PMs (BC, PM 2.5 , and PM 2.5-10) and mortality (non-accidental, respiratory and cardiovascular mortality) in Beijing, China, from 2010 to 2016. Average daily BC, PM 2.5 , and PM 2.5-10 concentrations were 4.95, 72.3, and 52.1 μg/m3, respectively, which were all significantly associated with daily mortality. High temperature strongly amplified effects of BC, PM 2.5 , and PM 2.5-10 on human mortality, especially BC effects that were most pronounced at >28 °C. Harmful effects were estimated for increases in non-accidental, respiratory, and cardiovascular mortality per interquartile increments in BC (4.11 μg/m3), PM 2.5 (62.37 μg/m3), and PM 2.5-10 (46.71 μg/m3) concentrations from the moving average of current and previous day (lag01) under high temperature (>28 °C). Mortality increases in non-accidental, respiratory, and cardiovascular categories were 5.12% (95% confidence interval [CI]: 4.79, 5.45), 7.41% (95%CI: 6.42, 8.40), and 6.36% (95%CI: 2.45, 10.3) for BC; 3.85% (95%CI: 3.27, 4.43), 6.64% (95%CI: 5.63, 7.65), and 4.54% (95%CI: 3.31, 5.78) for PM 2.5 ; and 2.56% (95%CI: 1.45, 3.67), 3.41% (95%CI: 1.53, 5.29), and 3.19% (95%CI: 2.44, 3.94), for PM 2.5-10 , respectively. These findings suggest that controlling the emission of ambient particles, especially BC, and improving air quality during summer would substantially benefit population health. Furthermore, BC should be considered as a crucial air quality indicator to reflect PM health risk. Image 1 • To test the synergistic effects of temperature and black carbon (BC) on mortality. • High temperature amplified the harmful effects of BC and PM on mortality. • The modifying effects of temperature on BC were different from that on PMs. [ABSTRACT FROM AUTHOR]

Due to its twofold effects on climate change and air quality, black carbon (BC) is of wide concern in the atmospheric sciences. Considerable uncertainty exists as to the health effects of atmospheric BC for the limited epidemiological and toxicological studies. As combustion-derived BC is one important component of PM 2.5 (particles with aerodynamic diameters less than 2.5 μm), the question remains of whether or not BC may play an important role in PM 2.5 -related health risks. To quantitatively analyze the short-term health effects of BC and PM 2.5 , a confounder-adjusted semi-parametric generalized additive model (GAM) of a time series study was used to calculate the concentration-response relationship between BC and PM 2.5 and daily cardiovascular disease (CVD) mortality from 2006 to 2011 in Beijing. During the study period, the mean daily concentrations of BC and PM 2.5 were 6.8 μg/m3 and 75.9 μg/m3, respectively. The results showed that BC was significantly associated with CVD mortality, and an interquartile range (IQR) increase in BC (5.7 μg/m3) and PM 2.5 (64. 5 μg/m3) were associated with 2.70% (95% CI: 2.20, 3.21) and 4.06% (95% CI: 3.47, 4.65) increase in CVD mortality. The health risk associated with BC may less than that of PM 2.5. When adjusted for nitrogen dioxide (NO 2) and sulfur dioxide (SO 2), the effects of BC remained statistically significant. It showed the relatively difference between BC and PM 2.5 when it comes to the modification effects of age, gender and educational attainment. These findings provide valuable evidence to the rare studies of the concentration-response relationship of BC with human health in developing countries. Image 1 • Few studies in Asian developing countries have examined the health effects of BC. • We observed significant associations of BC and PM 2.5 with daily cardiovascular mortality in Beijing. • The health risk associated with ambient BC may less than that of PM 2.5. [ABSTRACT FROM AUTHOR]

Black carbon (BC) and its mixing state were measured with a ground-based single particle soot photometer in urban Beijing during the extremely polluted winter of 2013. Up to 70 ± 14% of the BC-containing particles were thickly-coated during periods of haze, compared to 37 ± 9% on non-hazy days. The thickly-coated number fraction (NF BC-thick ) increased with increasing BC, reaching a plateau at ∼80–90% when BC concentrations were ≥15 μg m −3 and visibility was ≤2 km. Regional inflows brought more aged, highly thickly-coated BC to Beijing during haze. The absorption coefficient showed a distinct linear correlation with BC concentration; the mass absorption efficiency (MAE) of BC was acquired, with an overall mean of 4.2 ± 0.01 m 2 g −1 at 870 nm. The MAE of BC amplified with increasing ambient relative humidity. This was largely explained by the increase in NF BC-thick , which was likely due to the enhanced production of secondary aerosol under humid conditions. [ABSTRACT FROM AUTHOR]