Global cost of air pollution $2.9 trillion a year: NGO report
According to the tracker, Shanghai saw an estimated 27 000 deaths from 1 January, more than the 22 000 in Beijing, partly a reflection of the city's higher population.
"This also highlights the fact that Shanghai's pollution is now almost as bad as Beijing's, as Beijing has improved a lot faster," said Lauri Myllyvirta, CREA's lead analyst.
According to official Chinese data, concentrations of small, hazardous airborne particles known as PM2.5 were higher in Shanghai in the first half of the year than in Beijing.
However, Shanghai registered higher rates of sulphur dioxide and nitrogen dioxide, two other major components of smog.
Overall, smog in China in 2020 has declined compared to last year, with Covid-19 lockdowns cutting traffic and industrial activity, but experts warn that efforts to rejuvenate the economy could cause a rebound in the second half of the year.