Rationale: Short-term exposure to air pollution has been associated with asthma exacerbation and increased healthcare use caused by asthma, but its effect on asthma mortality remains largely unknown. Objectives: To quantitatively assess the association between short-term exposure to air pollution and asthma mortality. Methods: We investigated 4,454 individuals who lived in Hubei province, China, and died from asthma between 2013 and 2018. A case-crossover design and conditional logistic regression models were applied for data analyses. Exposures to particulate matter ≤2.5 μm in aerodynamic diameter (PM2.5), particulate matter ≤10 μm in aerodynamic diameter (PM10), sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), and ozone (O3) were estimated by inverse distance weighted averages of all monitoring stations within 50 km from each case’s home address. Measurements and Main Results: Each interquartile range (IQR) increase of PM2.5 (lag 3; IQR, 47.1 μg/m3), NO2 (lag 03; IQR, 26.3 μg/m3), and O3 (lag 3; IQR, 52.9 μg/m3) were positively associated with asthma mortality, with odds ratios of 1.07 (95% confidence interval, 1.01–1.12), 1.11 (95% confidence interval, 1.01–1.22), and 1.09 (95% confidence interval, 1.01–1.18), respectively. There was no evidence of departure from linearity for these associations. Further adjustment for other pollutants did not change the associations materially. We did not observe significant associations between PM10, SO2, and CO exposures and asthma mortality. Overall, the estimates remained consistent in various sensitivity analyses. Conclusions: Our results provide new evidence that short-term exposures to PM2.5, NO2, and O3 may increase asthma mortality risk. Further studies are needed to confirm our findings in other populations.

BACKGROUND: Extreme temperature events (ETEs), including heat wave and cold spell, have been linked to myocardial infarction (MI) morbidity; however, their effects on MI mortality are less clear. Although ambient fine particulate matter (PM _2.5 ) is suggested to act synergistically with extreme temperatures on cardiovascular mortality, it remains unknown if and how ETEs and PM _2.5 interact to trigger MI deaths. METHODS: A time-stratified case-crossover study of 202 678 MI deaths in Jiangsu province, China, from 2015 to 2020, was conducted to investigate the association of exposure to ETEs and PM _2.5 with MI mortality and evaluate their interactive effects. On the basis of ambient apparent temperature, multiple temperature thresholds and durations were used to build 12 ETE definitions. Daily ETEs and PM _2.5 exposures were assessed by extracting values from validated grid datasets at each subject’s geocoded residential address. Conditional logistic regression models were applied to perform exposure-response analyses and estimate relative excess odds due to interaction, proportion attributable to interaction, and synergy index. RESULTS: Under different ETE definitions, the odds ratio of MI mortality associated with heat wave and cold spell ranged from 1.18 (95% CI, 1.14–1.21) to 1.74 (1.66–1.83), and 1.04 (1.02–1.06) to 1.12 (1.07–1.18), respectively. Lag 01-day exposure to PM _2.5 was significantly associated with an increased odds of MI mortality, which attenuated at higher exposures. We observed a significant synergistic interaction of heat wave and PM _2.5 on MI mortality (relative excess odds due to interaction >0, proportion attributable to interaction >0, and synergy index >1), which was higher, in general, for heat wave with greater intensities and longer durations. We estimated that up to 2.8% of the MI deaths were attributable to exposure to ETEs and PM _2.5 at levels exceeding the interim target 3 value (37.5 μg/m ³ ) of World Health Organization air quality guidelines. Women and older adults were more vulnerable to ETEs and PM _2.5 . The interactive effects of ETEs or PM _2.5 on MI mortality did not vary across sex, age, or socioeconomic status. CONCLUSIONS: This study provides consistent evidence that exposure to both ETEs and PM _2.5 is significantly associated with an increased odds of MI mortality, especially for women and older adults, and that heat wave interacts synergistically with PM _2.5 to trigger MI deaths but cold spell does not. Our findings suggest that mitigating both ETE and PM _2.5 exposures may bring health cobenefits in preventing premature deaths from MI.

Semen quality is a vital determinant for male fertility. The process of spermatogenesis is highly sensitive to fluctuations in temperature. However, the impact of ambient temperature on semen quality remains unclear. We aimed to quantitatively assess the association between ambient temperature and semen quality. Using data from Hubei provincial human sperm bank in Wuhan, China, we conducted a longitudinal study including 10 802 volunteers who lived in Wuhan and passed the initial physical examination for sperm donation between Mar 27, 2013 and April 9, 2018. Semen quality parameters including sperm concentration, total sperm number, total motility, progressive motility, total motile sperm count and progressively motile sperm count were determined in the sperm bank. We used linear mixed models to identify estimate changes of outcomes in relation to ambient temperature (i.e., air temperature and apparent temperature) exposure measured as the mean daily temperature during the 0-90 days before semen collection. Among 10 802 subjects who underwent 41 689 semen examinations, we observed inverted U-shaped exposure-response associations between air temperature exposure and all semen quality parameters, with an identical threshold exposure of 13 °C. For air temperature exposure <13 °C, each 5 °C lower temperature was significantly associated with 1.94 × 106/ml, 7.12 × 106, 0.77%, 0.81%, 6.48 × 106, and 5.87 × 106 decrease in sperm concentration, total sperm count, total motility, progressive motility, total motile sperm count and progressively motile sperm count, respectively. When air temperature exposure was ≥13 °C, each 5 °C higher temperature was significantly associated with 0.70 × 106/ml, 4.09 × 106, 1.01%, 1.06%, 4.31 × 106, and 4.20 × 106 decrease in sperm concentration, total sperm count, total motility, progressive motility, total motile sperm count and progressively motile sperm count, respectively. Age, BMI and smoking did not significantly modify these associations. Similar results were observed for apparent temperature. This study provides a comprehensive picture of nonlinear association between ambient temperature and semen quality, as well as an optimal temperature for the benefit of semen quality. Both lower and higher ambient temperature exposures compared with the optimal temperature were significantly associated with decreased semen quality. The findings highlight the needs and importance to reduce extreme ambient temperature exposures in maintaining optimal semen quality for men. Further investigation is warranted to determine the causality of the association and the underlying mechanisms.