Exposure to Traffic Related Air Pollution, Physical Activity and Blood Pressure: A Crossover Study Performed in Real-World Conditions

Abstract

Background Short term exposure to traffic related air pollution (TRAP) is associated with cardiovascular disease, including myocardial infarction, arrhythmia and heart failure, increased morbidity and mortality. However, physical activity is well known for reducing the risk of many adverse health outcomes. The aim of this study was to determine the short-term effects of TRAP on arterial blood pressure in healthy participants and any possible modifying effects of intermittent physical activity. Methods The study took place in the city of Barcelona, Spain, between November 2013 and February 2014; it followed a well controlled crossover study design with repeated measures, involving 30 healthy, non-smoking adults in the age range of 18-60. Study subjects were exposed from 8am to 10am (morning rush hour) to either heavily polluted air on a bridge 5m above Ronda Litoral, the city’s ring road – high TRAP site -, or to low air pollution in a pedestrian square in Parc de la Barceloneta -low TRAP site-. Each of the 30 volunteers underwent all four conditions in random order: exposure to either low or high TRAP, with or without physical activity. During the two hours of exposure, three of them performed moderate-intensity physical activity, riding an ergometer (intermittently cycling for 15 minutes and resting for 15 minutes, to make a total of 1 hour of physical activity) while the other three participants remained seated alongside. Blood pressure (BP) measurements comparing before, during and after exposure to different levels of pollutants during exposure time were taken. Each participant served as his/her own control. Results Our sample included 50% of males and females, with a mean age of 36 (min 19, max 57) and mean body mass index of 24.2 (min 18.1, max 38.6) kg/m 2 . Mean levels of air pollution in the High and Low TRAP site were, respectively: 23.5 (SD 5.4) and 6.5 (SD 4.9) µg/m 3 for Black Carbon, 245131 (SD 76576) and 45991 (SD 21593) particles/cm3 for ultrafine particles, 81.8 (SD 16.7) and 39.6 (SD 14.4) µg/m3 for PM 2.5 , 122.7 (SD 39.6) and 64.7 (SD 44.2) µg/m3 for PM 10 , 40.9 (SD 24.5) and 25.4 (SD 30.7) µg/m3for PM Coarse . The performance of physical activity reduced the systolic blood pressure immediately after exposure to high TRAP (-5.83, p-value=0.006) and low TRAP (-5.59, p-value=0.009). We did not find significant results for diastolic blood pressure. Conclusions In healthy subjects, the performance of physical activity reduces systolic blood pressure even in high TRAP sites.