Cardiorespiratory Effects of Concentrated Ambient PM2.5: A Pilot Study Using Controlled Human Exposures

Abstract

Epidemiological studies suggest that there may be adverse human health effects associated with exposure to ambient fine particles (PM2.5). In a preliminary study, we examined the health effects of PM2.5 concentrated from ambient air (CAP) in downtown Toronto using the Harvard ambient particle concentrator. Four young healthy volunteers were each exposed to filtered air (FA) and low, mid, and high CAP levels ranging from 23 to 124 μg/m³ for 2 h. Response measures included pulmonary function, symptom reports, inflammatory cells, blood coagulation factors, and cardiac effects. Exposures were followed by 30 min of exercise at <1 target heart rate of 130 bpm, during which subjects were evaluated for cardiac response. Review of 12-lead electrocardiograph (ECG) data by a cardiologist revealed no clinically significant cardiac effects during exposure, the following exercise period, or 24 h after exposure. Following the high CAP exposure, plasma fibrinogen measured postexercise showed a trend to increase above the preexposure value (mean increase of 10%) when compared with the FA response (mean increase of 2%). The only statistically significant effect on pulmonary function (p < .01) was a small mean decrease of 6.4% in thoracic gas volume after high CAP exposure compared with a mean increase of 5.6% after FA. This was not accompanied by an increase in respiratory symptoms. There was no respiratory cellular inflammatory response as evaluated by induced sputum; however, there was a trend toward an increase in the percentage of nasal neutrophils after CAP exposures. The results from this pilot study indicate that exposure of young healthy volunteers to these levels of concentrated ambient PM2.5 in Toronto may not cause significant acute health effects. Additional research with more subjects and susceptible individuals will be required to further examine the cardiorespiratory effects of PM2.5.