Acute Short-Term Exposures to PM2.5 Generated by Vehicular Emissions and Cardiopulmonary Effects in Older Adults

Abstract

TM6-O-06 A pilot study was conducted to examine the impact of acute exposure to PM2.5 generated by vehicular emissions on changes in heart rate variability (HRV) and lung function in healthy older adults (mean age, 62 years), school crossing guards in Paterson, NJ. Each subject wore a real-time PM2.5 monitor and a cardiac Holter monitor for 24 hours on 1 working day in 3 separate weeks. Spirometry was performed prior to and after the morning shift, and at the end of monitoring session (24 hours). Traffic information for each working location was video recorded during the morning shift. Exposure to elevated PM2.5 was observed for school crossing guards during their morning shift, with the 1-hour average PM2.5 levels of 12 to 80 μg/m3 and the 1-minute peak PM2.5 concentrations of several hundred μg/m3. The 1-hour average morning PM2.5 was much higher (1–19 times) than that in the afternoon shift due to higher motor vehicle emissions from the morning rush-hour traffic. In addition, the pilot study suggested that the use of traffic count may underestimate the exposure to air pollutants generated by motor vehicle emissions in areas where the average speed is very low and the vehicles are often stopped. This is because vehicles idled while stopped, but they continued emitting air pollutants but did not increase the traffic count. The association between change in lung function and increased PM was explored by a mixed-effect model with controlled for gender, age, and smoking status. A subtle decrease in FEV1 (decrease in 0.019 L per increase of 10 μg/m3 PM2.5) was observed right after the morning shift with increased PM2.5 levels (P = 0.07). The changes in HRV right after exposure, 2 and 4 hours after exposure, were calculated and compared with the increased PM during the morning shift. No significant association was found between elevated PM2.5 levels and the change of HRV measured right after and 4 hours after the morning shift. However, the change in HRV obtained at 2 hours after exposure was negatively associated with elevated PM2.5 levels (slope = −0.22, P = 0.019). The preliminary data obtained from our pilot study provide evidence that short-term acute exposure to vehicular emissions resulted in changes in HRV and lung function. Moreover, the pilot study demonstrated that it is feasible to study cardiovascular and pulmonary effect on active and healthy older adults in a real world situation.