Impact of vehicular pollution on carboxyhemoglobin levels and respiratory response in urban cyclists

Abstract

BACKGROUND AND AIM: The present case-crossover study evaluated changes in carboxyhemoglobin (COHb) levels and spirometry values of 37 volunteers caused by vehicular pollution on a bike path parallel to a road with a high vehicular flow in two exposure scenarios (high exposure on weekdays and low exposure on Sundays) in the city of Bogotá, Colombia METHODS: For each scenario, ultrafine particles (UFP), carbon monoxide (CO), nitrogen dioxide (NO2), sulfur dioxide (SO2), and carbon black concentrations were measured, as well as vehicular flow and speed at two points on the road of interest, to explore the possible associations among these variables and exposure to each pollutant. RESULTS:Significant differences were obtained for UFP, CO, NO2, and SO2 concentrations between the high- and low-exposure scenarios, and between the estimated exposure doses (EED) of UFP, CO, and SO2. A strong correlation was found between the EED of CO and the percentage change in COHb before and after each bike ride (r=0.7571). Concerning UFP, a greater weight of background pollution was found in the high exposure scenario, followed by the impact of meteorological variables, and emission sources along the road under study. CONCLUSIONS:To explain the variability of respiratory parameters, the only statistically significant model was obtained for peak expiratory flow (25-75%) of the forced expiratory maneuver (MMEF25-75%), having EED of CO and average UFP size as explanatory variables. Cyclists arrived at the endpoint of the ride with high COHb levels due to exposure to air pollutants along the route they used to arrive at the study site. KEYWORDS: Air pollution, Mixtures, Biomarkers of exposure, Respiratory outcomes, Short-term exposure