Responses of healthy young males to fine-particle exposure are modified by exercise habits: a panel study.

BACKGROUND: Aerobic exercise benefits health but increases inhalation of fine particles (PM2.5 ) in ambient air. Acute cardiopulmonary responses to PM2.5 exposure in individuals with different exercise habits, especially in areas with severe air pollution, are not well understood.

METHODS: To examine acute cardiopulmonary responses to PM2.5 exposure modified by exercise habits, a panel of 20 healthy non-smoking male subjects, recruited in Beijing, China, completed seven visits. The exercise frequency per week and preferred exercise place were recorded using a baseline questionnaire to describe exercise habits. Fractional exhaled nitric oxide (FeNO), cytokines in exhaled breath condensate, blood pressure, and pulse-wave analysis (PWA) indices were measured during each visit as biomarkers of acute cardiopulmonary responses. The hourly average mass concentration of PM2.5 and black carbon (BC), and the number concentrations of ultrafine particles (UFP) and accumulation mode particles (AMP) were monitored throughout the follow-up period at an outdoor fixed monitoring station beginning 14 days prior to each visit. Linear mixed-effects models were used to evaluate the associations between acute changes in biomarker levels and exposure to PM2.5 and its constituents. The primary aim was to assess the modification of long-term exercise habits on these associations.

RESULTS: FeNO concentration, systolic blood pressure, ejection duration, aortic augmentation pressure, and aortic pressure index were positively associated with exposure to PM2.5 and its constituents. However, no associations with cytokine levels or diastolic blood pressure were observed. In a stratified analysis, we found that acute cardiopulmonary responses were modified by exercise habit. Specifically, the interquartile ranges (IQR) of increases in the 6-12-h moving average (MA) PM2.5 and AMP exposure were associated with 19-21% and 24-26% increases in FeNO, respectively, in subjects with high exercise frequency; these associations were significantly stronger than those in subjects with low exercise frequency. An IQR increase in 3-11-d MA AMP exposure was associated with a 10-26% increase in aortic augmentation pressure in subjects with low exercise frequency; this association was significantly stronger than that in subjects with high exercise frequency. An IQR increase in 9-13-d MA UFP exposure was associated with a 13-17% increase in aortic augmentation pressure in subjects who preferred outdoor exercise; this association was stronger than that in subjects who preferred indoor exercise.

CONCLUSIONS: In highly polluted areas, frequent exercise might protect against PM2.5 -associated arterial stiffness but exacerbate airway inflammation.