Pekkanen et al. (2002) assessed ST segment depression during exercise in 342 tests of 45
subjects with coronary disease in Helsinki during the winters of 1998–1999. Air pollution
was monitored at a central site, and levels of particulate air pollution 2 days before the test
were associated with an increased risk of ST segment depression. The central site recorded
the number of ultrafine particles (10–100 nm), number of particles 100–1000 nm (accumulation
mode), and particle mass asPM2.5. EachPMmeasurewas associated with an increased
risk of ST-segment depression, but the effects of ultrafine PM and PM2.5 were independent,
suggesting separate sources. In a subsequent analysis of the same data, filter absorbance was
assessed as a measure of EC or black carbon (Lanki et al., 2006). Filter samples were also
analyzed for elemental composition using X-ray fluorescence spectrometry and principal
component analysis to apportion PM mass to sources. Traffic- and diesel-related PM as
indicated by the extent of filter absorbance were associated with the greatest risk of ST
depression (Lanki et al., 2006). Gold et al. (2005) studied ST segment changes in 24 active
Boston residents 61–88 years of age, each monitored up to 12 times from June through
September 1999. Black carbon level in the previous 12 h and the level 5 h before testing
predicted ST-segment depression. These results suggest an adverse effect of traffic-related
emissions, including diesel exhaust, on people likely to be at risk for cardiac ischemic events