BACKGROUND: Physical activity (PA) has beneficial, whereas exposure to traffic related air pollution (TRAP) has adverse, respiratory effects. Few studies, however, have examined if the acute effects of TRAP upon respiratory outcomes are modified depending on the level of PA.
OBJECTIVES: The aim of our study was to disentangle acute effects of TRAP and PA upon respiratory outcomes and assess the impact of participants TRAP pre-exposure.
METHODS: We conducted a real-world crossover study with repeated measures of 30 healthy adults. Participants completed four 2-h exposure scenarios that included either rest or intermittent exercise in high- and low-traffic environments. Measures of respiratory function were collected at three time points. Pre-exposure to TRAP was ascertained from land-use-modeled address-attributed values. Mixed-effects models were used to estimate the impact of TRAP and PA on respiratory measures as well as potential effect modifications.
RESULTS: We found that PA was associated with a statistically significant increases of FEV1 (48.5mL, p=0.02), FEV1/FVC (0.64%, p=0.005) and FEF25-75% (97.8mL, p=0.02). An increase in exposure to one unit (1μg/m3) of PMcoarse was associated with a decrease in FEV1 (-1.31mL, p=0.02) and FVC (-1.71mL, p=0.01), respectively. On the other hand, for an otherwise equivalent exposure an increase of PA by one unit (1%Heart rate max) was found to reduce the immediate negative effects of particulate matter (PM) upon PEF (PM2.5, 0.02L/min, p=0.047; PM10, 0.02L/min p=0.02; PMcoarse, 0.03L/min, p=0.02) and the several hours delayed negative effects of PM upon FVC (PMcoarse, 0.11mL, p=0.02). The negative impact of exposure to TRAP constituents on FEV1/FVC and PEF was attenuated in those participants with higher TRAP pre-exposure levels.
CONCLUSIONS: Our results suggest that associations between various pollutant exposures and respiratory measures are modified by the level of PA during exposure and TRAP pre-exposure of participants.
