ABSTRACT
OBJECTIVE: To study the relationship between light absorption measurements of PM2.5 at various distances from heavy traffic roads and diesel vehicle counts in Mexico City. MATERIALS AND METHODS: PM2.5 samples were obtained from June 2003-June 2005 in three MCMA regions. Light absorption (b abs) in a subset of PM2.5 samples was determined. We evaluated the effect of distance and diesel vehicle counts to heavy traffic roads on PM2.5 b abs using generalized estimating equation models. RESULTS: Median PM2.5 b abs measurements significantly decrease as distance from heavy traffic roads increases (p<0.002); levels decreased by 7% (CI95% 0.9-14) for each 100 additional meters from heavy traffic roads. Our model predicts that PM2.5 b abs measurements would increase by 20% (CI95% 3-38) as the hourly heavy diesel vehicle count increases by 150 per hour. CONCLUSION: PM2.5 b abs measurements are significantly associated with distance from motorways and traffic density and therefore can be used to assess human exposure to traffic-related emissions.
OBJETIVO: Evaluar la relación entre las mediciones de absorción de luz de las PM2.5 a diferentes distancias de vías de tráfico y el aforo vehicular de diesel en la Ciudad de México. MATERIAL Y MÉTODOS: Se realizaron mediciones de PM2.5 y su análisis de b abs en tres zonas de la Ciudad de México. Se usaron modelos GEE para evaluar el efecto de la distancia y el aforo vehicular de tráfico pesado sobre PM2.5 b abs. RESULTADOS: Se observó una tendencia decreciente en la mediana de PM2.5 b abs conforme se incrementó la distancia a las avenidas de alto tráfico (p<0.002); los niveles decrecen en 7% (CI95% 0.9-14) por cada 100 metros de incremento. Las mediciones de PM2.5 b abs se incrementan en 20% (CI95% 3-38) cuando el aforo vehicular a diesel es mayor de 150 en una hora. CONCLUSIONES: Las mediciones de PM2.5 b abs están significativamente asociadas con la distancia de avenidas con alto tránsito vehicular y con vehículos de diesel.