Associations of ambient PM_2.5 and O₃ with human mortality: A time-series study in a city of central China

Background Exposure to air pollutants O₃ and PM_2.5 is closely related to population mortality. Most of the domestic research findings are for residents in coastal areas, and less for those in the central and western regions.

Objective To investigate the acute effects of O₃ and PM_2.5 on the mortality of residents in a city of central China.

Methods Data were collected on atmospheric pollutants, meteorological data, and population mortality in a city of central China from January 1, 2015 to June 30, 2021. Meteorological data included daily average temperature, air pressure, and relative humidity. Atmospheric pollution data included daily mean concentrations of PM_2.5, PM₁₀, SO₂, NO₂, and CO and maximum 8 h O₃. Generalized additive model with Poisson distribution was used for estimating the relationships between air pollutants (O₃ and PM_2.5) and population mortality, and further stratified by age, gender, and education.

Results The daily maximum 8 h average concentration of O₃ in the city during the study period was 94.38 μɡ·m⁻³ and the daily average concentration of PM_2.5 was 55.56 μɡ·m⁻³. In the single-pollutant model, the correlations between O₃ concentration and total deaths as well as deaths due to respiratory, circulatory, hypertension, coronary heart disease, and stroke were strongest at lag02, lag2, lag02, lag0, lag02, and lag0, and for every 10 μɡ·m⁻³ increase in concentration of O₃, the associated ER (95%CI) values of daily mortality were increased by 0.09% (−0.08%–0.25%), 0.35% (0–0.71%), 0.43% (0.18%–0.68%), 0.45% (0.02%–0.91%), 0.59% (0.16%–1.02%), and 0.33% (0.01%–0.65%), respectively. The effect of O₃ on total mortality was not statistically significant (P>0.05). The correlations between PM_2.5 concentration and total deaths, as well as deaths due to respiratory, circulatory, hypertension, coronary heart disease, and stroke were strongest at lag1, lag5, lag01, lag05, lag04, and lag01, and for every 10 μɡ·m⁻³ increase in concentration of PM_2.5, the associated ER (95%CI) values of daily mortality increased by 0.02% (−0.09–0.13%), 0.25% (0.01%–0.50%), 0.35% (0.16%–0.54%), 1.18% (0.59%–1.77%), 0.17% (−0.13%–0.40%), and 0.65% (0.38%–0.92%), respectively, with no statistically significant effects of PM_2.5 on total mortality and mortality due to coronary heart disease (P>0.05). During warm season (from May to October), the ER (95%CI) values of total deaths per 10 μɡ·m⁻³ increase in O₃ in male, people aged 6~65 years, people aged >65 years, and people below high school education were 0.46% (0.16%–0.75%), 0.38% (0.08%–0.68%), 0.41% (0.14%–0.66%), and 0.38% (0.14%–0.61%), respectively, while the O₃ effect was not statistically significant (P>0.05) during cool season (from November to April).

Conclusions Atmospheric pollutants (O₃ and PM_2.5) have acute effects on mortality in the city, with the elderly, people with less than a high school education, and those with circulatory disease being more sensitive to O₃ and PM_2.5 exposures.