title: 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.
abstract: BACKGROUND
  Traffic-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.
  
  
  METHODS
  We 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 (PM(2.5), 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 (PM(2.5), NO₂, and O₃) was explored for the 24-hour and 5-day periods preceding exposure.
  
  
  RESULTS
  In 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 PM(2.5) was associated with decreases in HRV measures reflecting parasympathetic modulation of the heart and regional PM(2.5) concentrations modified these relationships (p < 0.05). In particular, stronger inverse associations were observed when regional PM(2.5) was higher on the days prior to the study period. Regional PM(2.5) 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 PM(2.5) was low prior to study periods and a significant positive relationship was observed when regional PM(2.5) was high.
  
  
  CONCLUSIONS
  Exposure 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.
authors.affiliation: Air Health Science Division, Health Canada, 269 Laurier Avenue West, K1A 0K9, Ottawa, ON, Canada. scott.weichenthal@hc-sc.gc.ca.
authors.forename: Scott
authors.initials: S
authors.lastname: Weichenthal
authors.affiliation: Department of Civil Engineering, McGill University, Macdonald Engineering Building, 817 Sherbrooke Street West, H3A 0C3, Montreal, Quebec, Canada. marianne.hatzopoulou@mcgill.ca.
authors.forename: Marianne
authors.initials: M
authors.lastname: Hatzopoulou
authors.affiliation: Division of Clinical Epidemiology, McGill University Health Center, 687 Pine Avenue West, H3A 1A1, Montreal, Quebec, Canada. mark.goldberg@mcgill.ca.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Goldberg
mesh_terms: D000293:Adolescent; D000328:Adult; D000393:Air Pollutants / Q000633:toxicity*; D000397:Air Pollution / Q000009:adverse effects*; D001341:Autonomic Nervous System / Q000187:drug effects* / Q000502:physiology; D001642:Bicycling; D001794:Blood Pressure / Q000187:drug effects; D018592:Cross-Over Studies; D005260:Female; D006801:Humans; D019570:Inhalation Exposure / Q000009:adverse effects*; D055806:Microvessels / Q000187:drug effects* / Q000502:physiology; D018986:Motor Vehicles; D009585:Nitrogen Dioxide / Q000008:administration & dosage / Q000633:toxicity; D010126:Ozone / Q000008:administration & dosage / Q000633:toxicity; D052638:Particulate Matter / Q000008:administration & dosage / Q000633:toxicity; D011792:Quebec; D053260:Soot / Q000008:administration & dosage / Q000633:toxicity; D014504:Urban Health; D001335:Vehicle Emissions / Q000633:toxicity*; D055815:Young Adult
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter; D053260:Soot; D001335:Vehicle Emissions; D010126:Ozone; D009585:Nitrogen Dioxide