1. ^aEnvironmental and Occupational Health Sciences Institute, Piscataway, New Jersey, USA
2. ^bRobert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey, USA
3. ^cResearch Fellow at National Center for Environmental Assessment, US EPA, Research Triangle Park, North Carolina, USA
4. ^dSchool of Public Health, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey, USA

Correspondence: Dr. Zhihua (Tina) Fan, Environmental and Occupational Health Sciences Institute, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Rutgers University, 170 Frelinghuysen Road, Piscataway, NJ 08854, USA. Tel.: +1 732 445 3194; Fax: +1 732 445 0116; E-mail: zfan@eohsi.rutgers.edu

Received 15 February 2008; Accepted 6 July 2008; Published online 8 October 2008.

Abstract

There are evidences for exposure to vehicular emissions and adverse cardiopulmonary health effects. This study attempted to further explore these effects on elderly. This study monitored personal PM_2.5 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. The traffic at each work location was video recorded during one of the three morning shifts. The increases in the average personal PM_2.5 concentrations (baseline PM_2.5 was subtracted) of 1.2–87 and 1.1–98 g/m³ were observed during the 1-h morning (PM_2.5-ave-m) and afternoon shift (PM_2.5-ave-a), respectively. Traffic count was not a significant predictor of the PM_2.5-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 (SDNN) were insignificant post-afternoon exposure (-0.3 to -7% with P>0.53). SDNN were negatively associated with PM_2.5-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 PM_2.5 concentration (PM_2.5-peak, baseline PM_2.5 was subtracted) was not a significant predictor for SDNN, and no clear effect of PM_2.5 exposure on heart rate was observed. There was no effect of PM exposure on lung function (P>0.16), either. In conclusion, acute exposure to the PM_2.5 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.