Background The correlation of unintentional injury mortality to rising temperatures found in several studies could result from changes in behavior that increases exposure to hazards or risk when exposed. An increase of .82 degrees (C) daily maximum temperature in Jiangsu Province, China from 2015 through 2017 provides the opportunity to study further this phenomenon including a potential effect of air pollution. Air pollutants may cause symptoms and distractions that increase risk and avoidance behavior that reduces risk. This study examines data that allows estimates of the potential effects of temperature, precipitation and five air pollutants on injury mortality risk, each corrected statistically for the potential effects of the others.
Methods Daily data on unintentional injury deaths and exposures to temperature, precipitation and pollutants from 9 cities in Jiangsu Province, China during 2015-2017 were analyzed using logistic regression. Application of the regression equations to 2016 and 2017 data substituting 2015 values for each of the predictor variables respectively was used to estimate year-to-year changes in deaths related to changes in the risk factors.
Results Unintentional injury death risk was unrelated to temperature when temperatures were below 25 degrees (C) but increased substantially in relation to higher temperatures. The correlations mainly occurred for non-transport injuries. Fatal injury risk was higher in relation to higher concentrations of PM10, NO2 , and SO2 in certain temperature ranges but lower in relation to higher concentrations of CO in the lowest and highest temperature ranges. Lower risk was associated with O3 at low temperatures but higher risk at high temperatures. Risk was lower on weekends but higher on holidays when temperatures were moderate.
Conclusions The increase in fatal unintentional injuries from 2015 through 2017 was substantially related to the rise in average maximum daily temperature. Negative associations of certain pollutants, particularly O3, with injury risk suggests the possibility that changes in behavior to avoid those pollutants also results in lower injury risk. Most pollutants, however, are related to increased risk.