Excess deaths associated with long-term exposure to ambient NO2 in China

World Health Organization updated the target of annual mean NO2 from 40 mu g m(-3) to 10 mu g m(-3) in 2021 based on new evidences that showed statistically independent effects of long-term exposure to ambient NO2 and mortality. We estimate the excess deaths associated with long-term exposure to ambient NO2 (DAAN) from non-accidental disease (NAD), cardiovascular disease (CVD) and respiratory disease (RD) in China in 2013-2020 using a counterfactual analytic framework adopted by Global Burden Disease. We use relative risk (RR) values based on a meta-analysis, and assume a linear concentration-response (C-R) function and a threshold value of 10 mu g m(-3). DAAN from NAD vary in 279 (95% Cl: 189-366) to 339 (95% Cl: 231-442) thousand in 2013-2020, comparable to excess deaths attributed to long-term exposure to ambient O-3 in China. DAAN from NAD changes by -43%-+220% using different RR values, C-R function shapes, and threshold values. DAAN from RD reduces while those from CVD increases significantly in 2013-2020. DAAN from RD account for similar to 10% of total DAAN. We found that the reduction of NO2 concentration and baseline mortality of NAD offsets the adverse effects of population growth and aging in 2013-2017. In 2017-2020, the contribution from air pollution reduction surpasses the adverse effects of population growth and aging in most regions. We suggest that continuing the reduction rate of NO2 emissions in 2013-2020 would offset the effects of population growth and aging in 2020-2030. Faster reduction of NO2 sources is required to reduce DAAN in Liaoning, Shanxi, Shanghai, and Anhui, where DAAN from NAD, CVD and RD increased in 2013-2020. Our results should be interpreted with caution because the causality support of long-term exposure to ambient NO2 on mortality from toxicological studies is not firm yet, and NO2 is possibly just a marker of traffic-related pollutants.