Higher Ambient Nitrogen Dioxide Is Associated With An Elevated Risk Of Hospital-Acquired Acute Kidney Injury

Background Previous studies have suggested that long-term exposure to air pollution increased the risk of chronic kidney disease and its progression. However, the effect of air pollution on the risk of acute kidney injury (AKI) has not been studied. We aim to evaluate the transient effect of air pollution on the risk of hospital-acquired AKI (HA-AKI). Methods We selected from the Epidemiology of AKI in Chinese Hospitalized patients (EACH2 study) AKI cases of which the onset date could be unambiguously determined. We obtained city-specific daily averages of the ambient level of particulate matter (PM2.5 and PM10), carbon monoxide (CO), nitrogen dioxide (NO2), sulfur dioxide (SO2) and ozone (O3), from the Ministry of Environmental Protection of China. We used the time-stratified case crossover approach to examine the association between the ambient level of air pollutants and the risk of HA-AKI in the selected cases. Results A total of 11,293 AKI cases that met the inclusion and exclusion criteria were selected. In univariable analysis, the ambient levels of NO2 and SO2, were significantly associated with the risk of HA-AKI. In the multivariable analysis that incorporated all six pollutants in the same model, NO2 was the sole pollutant whose level remained to be associated with the risk of AKI (p < 0.001). The relationship between level of NO2 and the risk of HA-AKI appeared to be linear, with an estimated odds ratio of 1.063 (95% CI: 1.026, 1.101) for each increment of one median absolute deviance in the exposure. The association was consistent across the subgroups stratified by age, gender, baseline estimated glomerular filtration rate, AKI severity, need for intensive care, and season. Conclusions Higher ambient level of NO2 was associated with an increased risk of HA-AKI in hospitalized adults in China.

A Systematic Review and Meta-Analysis of Short-Term Ambient Ozone Exposure and COPD Hospitalizations

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death globally and ozone exposure is a main cause of its disease burden. However, studies on COPD hospitalizations from short-term ambient level ozone exposure have not generated consensus results. To address the knowledge gap, comprehensive and systematic searches in several databases were conducted using specific keywords for publications up to February 14, 2020. Random-effect models were used to derive overall excess risk estimates between short-term ambient-level ozone exposure and COPD hospitalizations. The influence analyses were used to test the robustness of the results. Both meta-regression and subgroup analyses were used to explore the sources of heterogeneity and potential modifying factors. Based on the results from 26 eligible studies, the random-effect model analyses show that a 10 µg/m3 increase in maximum 8-h ozone concentration was associated with 0.84% (95% CI: 0.09%, 1.59%) higher COPD hospitalizations. The estimates were higher for warm season and multiple-day lag but lower for old populations. Results from subgroup analyses also indicate a multiple-day lag trend and bigger significant health effects during longer day intervals. Although characteristics of individual studies added modest heterogeneity to the overall estimates, the results remained robust during further analyses and exhibited no evidence of publication bias. Our systematic review and meta-analysis indicate that short-term ambient level ozone exposure was associated with increased risk of COPD hospitalizations. The significant association with multiple-day lag trend indicates that a multiple-day exposure metric should be considered for establishing ambient ozone quality and exposure standards for improvement of population health. Future investigations and meta-analysis studies should include clinical studies as well as more careful lag selection protocol.