The underappreciated role of transboundary pollution in future air quality and health improvements in China

Studies assessing the achievability of future air quality goals in China have focused on the role of reducing China's domestic emissions, yet the influence of transboundary pollution of foreign origins has been largely underappreciated. Here, we assess the extent to which future changes in foreign transboundary pollution would affect the achievability of air quality goals in 2030 and 2060 for China. We find that in 2030, under the current-policy scenario in China, transboundary contributions to population-weighted PM2.5 in China would be reduced by 29 % (1.2 mu g m-3) as foreign countries transition from the fossil-fuel-intensive to the low-carbon pathway. By 2060, the difference would be increased to 45 % (1.8 mu g m-3). Adopting the low-carbon instead of the fossil-fuel-intensive pathway in foreign countries would prevent 10 million Chinese people from being exposed to PM2.5 concentrations above China's ambient air quality standard (35 mu g m-3) in 2030 and 5 million Chinese people from being exposed to PM2.5 concentrations above the World Health Organization air quality guideline (5 mu g m-3) in 2060. Meanwhile, China adopting the carbon-neutral pathway rather than its current pathway would also be helpful to reduce transboundary PM2.5 produced from the chemical interactions between foreign-transported and locally emitted pollutants. In 2060, adopting a low-carbon pathway in China and foreign countries coincidently would prevent 63 % of transboundary pollution and 386 000 associated premature deaths in China, relative to adopting a fossil-fuel-intensive pathway in both regions. Thus, the influence of transboundary pollution should be carefully considered when making future air quality expectations and pollution mitigation strategies.