Exposure to traffic-related air pollution during physical activity and acute changes in blood pressure, autonomic and micro-vascular function in women: a cross-over study.

Mark S Goldberg,Scott Weichenthal,Marianne Hatzopoulou

doi:10.1186/s12989-014-0070-4

Abstract

BackgroundTraffic-related air pollution may contribute to cardiovascular morbidity. In urban areas, exposures during physical activity are of interest owing to increased breathing rates and close proximity to vehicle emissions.MethodsWe conducted a cross-over study among 53 healthy non-smoking women in Montreal, Canada during the summer of 2013. Women were exposed to traffic pollutants for 2-hours on three separate occasions during cycling on high and low-traffic routes as well as indoors. Personal air pollution exposures (PM2.5, ultrafine particles (UFP), black carbon, NO2, and O3) were evaluated along each route and linear mixed-effects models with random subject intercepts were used to estimate the impact of air pollutants on acute changes in blood pressure, heart rate variability, and micro-vascular function in the hours immediately following exposure. Single and multi-pollutant models were examined and potential effect modification by mean regional air pollution concentrations (PM2.5, NO2, and O3) was explored for the 24-hour and 5-day periods preceding exposure.ResultsIn total, 143 exposure routes were completed. Each interquartile increase (10,850/cm3) in UFP exposure was associated with a 4.91% (95% CI: -9.31, -0.512) decrease in reactive hyperemia index (a measure of micro-vascular function) and each 24 ppb increase in O3 exposure corresponded to a 2.49% (95% CI: 0.141, 4.84) increase in systolic blood pressure and a 3.26% (95% CI: 0.0117, 6.51) increase in diastolic blood pressure 3-hours after exposure. Personal exposure to PM2.5 was associated with decreases in HRV measures reflecting parasympathetic modulation of the heart and regional PM2.5 concentrations modified these relationships (p < 0.05). In particular, stronger inverse associations were observed when regional PM2.5 was higher on the days prior to the study period. Regional PM2.5 also modified the impact of personal O3 on the standard deviation of normal to normal intervals (SDNN) (p < 0.05): a significant inverse relationship was observed when regional PM2.5 was low prior to study periods and a significant positive relationship was observed when regional PM2.5 was high.ConclusionExposure to traffic pollution may contribute to acute changes in blood pressure, autonomic and micro-vascular function in women. Regional air pollution concentrations may modify the impact of these exposures on autonomic function.Electronic supplementary materialThe online version of this article (doi:10.1186/s12989-014-0070-4) contains supplementary material, which is available to authorized users.

Highlights

Traffic-related air pollution may contribute to cardiovascular morbidity
The 2 reactive hyperemia index (RHI) values were each collected from different participants whereas the Heart rate variability (HRV) values reflected 5 separate subjects with 4 of the 11 points coming from a single subject who experienced large changes in the ratio of Low-frequency power (LF) to High-frequency power (HF) on a single study day
PM2.5 is primarily a regional air pollutant and in order to be strongly correlated with pollutants from local sources (e.g. Ultrafine particles (UFP) and black carbon) high personal exposure routes would need to coincide with days with high regional PM2.5

Summary

Introduction

Traffic-related air pollution may contribute to cardiovascular morbidity. Exposures during physical activity are of interest owing to increased breathing rates and close proximity to vehicle emissions. Traffic-related air pollution is known to contribute to cardiovascular morbidity including both acute and chronic health effects [1,2,3,4,5]. While the precise biological mechanisms underlying these associations have yet to be fully elucidated, existing evidence suggests a range of biological pathways including increases in plasma viscosity, altered autonomic function, arrhythmia, impaired vasomotor function, and the promotion of atherosclerosis [4,5,6]. As municipalities move towards the promotion of active transportation in urban environments, it is increasingly important to understand the potential health impacts of physical activity in close proximity to traffic emissions. A review of the long-term health effects of air pollution did not observe strong evidence for gender differences in air pollution health effects [3]

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