ST-SEGMENT LEVEL ASSOCIATED WITH BLACK CARBON IN ELDERLY BOSTON RESIDENTS.

Abstract

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)