Emissions from maritime shipping between the two world powers affect health in many nations.

Air pollution created by ocean freight shipping between the United States and China causes health problems in multiple countries around the northern Pacific Ocean — not just in the two trade partners.

A team led by Huan Liu and her colleagues at Tsinghua University in Beijing analysed goods shipped by sea between the two countries in 2016, including US soya beans shipped to China and Chinese electronics shipped to the United States. The scientists also counted the number of ship journeys to calculate the amounts of greenhouse gases and air pollution emitted by the transportation of this cargo. Finally, the researchers modelled the path of particulates as they spread from ships through the atmosphere.

The scientists calculated that in 2016, US–China trade accounted for 2.5% of global carbon-dioxide emissions from shipping. Air pollution from the shipping also harmed the health of people in many countries, including Japan, South Korea and Vietnam.

Nations can take these findings into account when deciding how to share responsibility for cutting emissions from shipping, the authors say.