Acute exposure to elevated PM2.5 generated by traffic and cardiopulmonary health effects in healthy older adults

There are evidences for exposure to vehicular emissions and adverse cardiopulmonary health effects. T his study attempted to further explore these effects on elderly. T his study monitored personal PM2.5 concentrations and ambulatory electrocardiograms continuously for 24 h on 1 working day in 3 separate weeks for 11 school crossing guards. Spirometry was also performed before and after the morning shift. T he traffic at each work location was video recorded during one of the three morning shifts. T he increases in the average personal PM2.5 concentrations (baseline PM2.5 was subtracted) of 1.2-87 and 1.1-98 mu g/m(3) were observed during the 1-h morning (Delta PM2.5-ave-m) and afternoon shift (Delta PM2.5-ave-a), respectively. Traffic count was not a significant predictor of the Delta PM2.5-ave-m (P = 0.78). Mean heart rate variability (HRV), measured as 5-min standard deviation of normal-to-normal (SDNN) beats during the 10-min rest periods, decreased 18-26% (P < 0.02) 15 min, 2 and 4 h after the morning shift, but changes in SDNN (Delta SDNN) were insignificant post-afternoon exposure (-0.3 to -7% with P > 0.53). Delta SDNN were negatively associated with Delta PM2.5-ave-m, with the strongest association at 2 h after the morning shift (P < 0.01) but insignificant 4 h after the morning exposure. The peak PM2.5 concentration (Delta PM2.5-peak, baseline PM2.5 was subtracted) was not a significant predictor for Delta SDNN, and no clear effect of PM2.5 exposure on heart rate was observed. T here was no effect of PM exposure on lung function (P > 0.16), either. In conclusion, acute exposure to the PM2.5 resulting from mobile sources can cause acute decline in HRV in healthy older adults, suggesting one of the biological mechanisms for the adverse cardiovascular health effects associated with traffic-related air pollution. Traffic count may not be an appropriate surrogate measure of acute personal exposure to vehicular emission in traffic congested areas. Journal of Exposure Science and Environmental Epidemiology (2009) 19, 525-533; doi: 10.1038/jes.2008.46; published online 8 October 2008