Association between Long-Term Exposure to PM_(2.5) Inorganic Chemical Compositions and Cardiopulmonary Mortality: A 22-Year Cohort Study in Northern China

Particulate matter with diameters≤2.5μm(PM_(2.5))has been identified as a significant air pollutant contributing to premature mortality.Nevertheless,the specific compositions within PM_(2.5) that play the most crucial role remain unclear,especially in areas with high pollution concentrations.This study aims to investigate the individual and joint mortality risks associated with PM_(2.5) inorganic chemical compositions and identify primary contributors.In 1998,we conducted a prospective cohort study in four northern Chinese cities(Tianjin,Shenyang,Taiyuan,and Rizhao).Satellite-based machine learning models calculated PM_(2.5) inorganic chemical compositions,including sulfate(SO_(4)^(2–)),nitrate(NO_(3)^(–)),ammonium(NH_(4)^(+)),and chloride(Cl^(-)).A time-varying Cox proportional hazards model was applied to analyze associations between these compositions and cardiorespiratory mortality,encompassing nonaccidental causes,cardiovascular diseases(CVDs),nonmalignant respiratory diseases(RDs),and lung cancer.The quantile-based g-computation model evaluated joint exposure effects and relative contributions of the compositions.Stratified analysis was used to identify vulnerable subpopulations.During 785,807 person-years of follow-up,5812(15.5%)deaths occurred from nonaccidental causes,including 2932(7.8%)from all CVDs,479(1.3%)from nonmalignant RDs,and 552(1.4%)from lung cancer.Every interquartile range(IQR)increase in SO_(4)^(2–)was associated with mortality from nonaccidental causes(hazard ratio:1.860;95%confidence interval:1.809,1.911),CVDs(1.909;1.836,1.985),nonmalignant RDs(2.178;1.975,2.403),and lung cancer(1.773;1.624,1.937).In the joint exposure model,a simultaneous rise of one IQR in all four compositions increased the risk of cardiorespiratory mortality by at least 36.3%,with long-term exposure to SO_(4)^(2–)contributing the most to nonaccidental and cardiopulmonary deaths.Individuals with higher incomes and lower education levels were found to be more vulnerable.Long-term exposure to higher levels of PM_(2.5) inorganic compositions was associated with significantly increased cardiopulmonary mortality,with SO_(4)^(2–)potentially being the primary contributor.These findings offer insights into how PM_(2.5) sources impact health,aiding the development of more effective governance measures.

Psychosocial Stress Modifies the Acute Cardiac Health Effects of Traffic-Related Air Pollution

Previous studies have shown that exposure to black carbon(BC,a tracer of traffic-related air pollution)and psychosocial stress are both associated with adverse cardiac effects,but whether psychosocial stress could modify the cardiac effects of BC is unclear.To investigate the potential modifying effect of psychosocial stress on the associations between acute exposure to BC and typical cardiac health variables,real-time personal 24 h measurements were conducted in a repeated-measure study among adults with elevated blood pressure(high-risk group)and a panel study among normal adults(low-risk group)in China.Measured cardiac health variables included ST-segment depression events,heart rate,and heart rate variability(HRV)variables.Perceived Stress Scale,State Anxiety Inventory and Self-rating Depression Scale were used to assess the recent psychosocial stress status of the participants,and a composite stress index was established based on these scales.Generalized linear mixed-effects model was used to analyze the associations between BC exposure and cardiac health variables and potential effect modification by psychosocial stress.A total of 9724 h measurements among 97 participants in the repeated-measure study and 20224 h measurements among 87 participants in the panel study were included in the final analysis.Acute BC exposure was significantly associated with increased ST-segment depression events and heart rate and decreases in HRV in both studies.The marginal effects of acute BC exposure on most cardiac health variables generally tended to be amplified under higher vs low levels of psychosocial stress in both studies,with the composite stress index apparently modifying the associations of BC exposure with most ST-segment depression events and HRV variables.These findings suggest that psychosocial stress may increase the participants’cardiac susceptibility to BC exposure,which could be helpful for the identification of susceptible individuals in the context of traffic-related air pollution.