Substantial health benefits of strengthening guidelines on indoor fine particulate matter in China

In 2020, China for the first time developed guidelines for indoor fine particulate matter (PM2.5) in the draft document of indoor air standards, while the associated health implication remains unclear. Here, we first estimated the PM2.5 associated premature deaths was 965 thousand in 2019, with the indoor PM2.5 of outdoor origin accounting for 72.9%. Then, we examined the dynamic mortalities under a scenario matrix of 36 conditions, by incorporating various shared socioeconomic pathways in 2035, the draft guidelines and the contributions of ambient PM2.5 to indoor exposure. Although it may be improbable, the averages of premature deaths associated with ambient PM2.5 will be 1018-1361 thousand in 2035 when the worst-case scenario of guidelines mandating a yearly (rather than daily) indoor PM2.5 concentration of 75 mu g/m(3), compared to the averages of estimation were 816-1304 thousand for better-case scenario of 35 mu g/m(3). Under these scenarios, the increase in the number of premature deaths was mainly driven by population aging. In 2035, an ambitious target of yearly indoor PM2.5 concentrations of 15 mu g/m(3) is anticipated to reduce the number of deaths associated with ambient PM2.5 by approximately 25% of the 2019 baseline. Stricter guidelines to restrict the indoor PM2.5 concentrations are recommended to mitigate the mortality risk in the future.

Automated summary

In 2020, China developed guidelines for indoor PM2.5 for the first time, but the health implications are still unclear. A study estimated that there were 965 thousand premature deaths associated with PM2.5 in 2019, with 72.9% originating from outdoor sources. Using a scenario matrix, the study found that in 2035, if the guidelines mandate a yearly indoor PM2.5 concentration of 75 μg/m³ (instead of daily), the average premature deaths associated with ambient PM2.5 will be 1018-1361 thousand, compared to 816-1304 thousand for a better-case scenario of 35 μg/m³. Stricter guidelines are recommended to mitigate the mortality risk in the future.