The validity of using the Air Pollution Index (API) to assess health impacts of air pollution and potential
modification by individual characteristics on air pollution effects remain uncertain. We applied
distributed lag non-linear models (DLNMs) to assess associations of daily API, specific pollution indices
for PM10, SO2, NO2 and the weighted combined API (APIw) with mortality during 2003e2011 in
Guangzhou, China. An increase of 10 in API was associated with a 0.88% (95% confidence interval (CI):
0.50, 1.27%) increase of non-accidental mortality at lag 0e2 days. Harvesting effects appeared after 2
days’ exposure. The effect estimate of API over lag 0e15 days was statistically significant and similar with
those of pollutant-specific indices and APIw. Stronger associations between API and mortality were
observed in the elderly, females and residents with low educational attainment. In conclusion, the API
can be used to communicate health risks of air pollution.