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Background: Particulate air pollution has been associated with increased cardiovascular deaths and hospital admissions. To help understand the mechanisms, the types of particles most involved, and the types of persons most susceptible, the association between exposure to summertime air pollution and heart rate variability (HRV) was examined in a panel study of 28 elderly subjects.Methods: Subjects were seen once a week for up to 12 weeks and HRV (SDNN, r-MSSD, PNN50, low frequency/high frequency ratio (LFHFR)) was measured for approximately 30 minutes at each session using a defined protocol. Temperature, day of the week, and hour of the day were controlled, and dummy variables for each subject were controlled for subject specific risk factors.Results: PM2.5 was associated with r-MSSD (-10.1% change for an interquartile range (IQR) increase in exposure (95% CI -2.8 to -16.9)) and PNN50, but stronger associations were seen with black carbon, an indicator of traffic particles, which was also associated with SDNN (-4.6% per IQR (95% CI -2.0 to -7.2)) and LFHFR. Secondary particles were more weakly associated with r-MSSD, as was ozone. No associations were seen with SO2 or NO2. CO had similar patterns of association to black carbon, which disappeared after controlling for black carbon. Black carbon had a substantially higher effect on SDNN in subjects who had had a previous myocardial infarction (-12.7%, 95% CI -5.7 to -19.25).Conclusions: Particles, especially from traffic, are associated with disturbances of autonomic control of the heart. [ABSTRACT FROM AUTHOR]

We investigated associations between ambient pollution levels and between-session ST-segment depression in a repeated measures study on 22 older Boston residents observed up to 12 times in the summer of 1999. The protocol involved 25 minutes of continuous Holter monitoring including 5 minutes of rest, 5 minutes of standing, 5 minutes of exercise outdoors, 5 minutes of recovery and 20 cycles of slow, paced breathing. ST-segment level was averaged for each portion of the protocol. Black carbon levels ranged from 0.23 mg/m3 to 4.34, with a mean of 1.39 mg/m3. Black carbon in the 3rd to 8th hour prior to testing was associated with ST-segment depression. Mixed effects and logistic models were adjusted for the individual, time trend, and temperature. In continuous models all participants who had at least 2 observations where ST mean level was below 0 were included. Depending on the model variable numbers of participants could be included. During the recovery period after exercise, 1 mg/m3 of black carbon in the 5th hour prior to testing predicted a 0.07 mm decrement in ST-segment level. During this period, 1 mg/m3 of black carbon predicted an increased risk (OR: 5.8, 95% C.I.: 1.8-18.3) of having an absolute ST-segment level in the lowest 25th percentile of ST segment levels and an increase risk of having an absolute ST-segment level lower than-0.5 mm (OR: 4.4, 95% C.I.: 1.47-12.9). Black carbon, representing predominantly local traffic in Boston, may lead to ST-segment changes and possible ischemia. This study was funded by Program Project grant # 1P01ES09825-01 Star grant number (EPA Cooperative Agreement CR81762; NIEHS Center Grant ES0639 and ES 0002) [ABSTRACT FROM AUTHOR]