Health equity and burden of childhood asthma - related to air pollution in Barcelona

Background: Air pollution is one of the major health risk factors in urban populations. Air pollution has been associated with asthma in children. Air pollution has also been suggested to be distributed unequally within the cities, something that can lead to urban health inequalities. Aim: We aimed to estimate the number of childhood asthma cases attributable to three main air pollutants; Nitrogen dioxide (NO2), Particulate Matter (PM 2.5), and Black Carbon (BC) in the city of Barcelona, Spain. We also aimed to describe the distribution of those impacts depending on the social deprivation index in Barcelona. Methods: We estimated the number of childhood asthma cases in Barcelona by applying a quantitative Health Impact Assessment (HIA) approach. Air pollution (NO2, PM2.5, and BC) exposure assessment was estimated using a land-use regression model. Two scenarios were assessed and compared the current levels of air pollution with 1) achieving the World Health Organization (WHO) guideline on exposure levels for NO2 and PM2.5 (scenario 1); and 2) achieving the minimum reported levels in a previously published meta-analysis (scenario 2), from where we also obtained the exposure-response functions. The relative risk and population attributable fraction (PAF) for each scenario and pollutant were estimated. Using the asthma incidence rate in Spain the expected number of asthma cases in Barcelona attributable to NO2, PM2.5, and BC for each scenario was estimated. Results: The annual average levels of NO2, PM2.5, and BC at census levels were 56 mu g/m(3), 17.11 mu g/m(3), and 2.88 mu g/m(3), respectively. The number of asthma cases attributable to NO2 and PM2.5 (percentage of total cases) estimated in scenario 1 was 454 (18%) and 478 (19%) respectively. For scenario 2, the estimated number of cases attributable to NO2, PM2.5, and BC were 1230 (48%), 992 (39%) and 789 (31%) respectively. Although NO2 and BC showed differences between asthma cases and areas with different deprivation index, only BC differences were statistically significant between less and more deprived areas. Conclusions: This study estimated that up to 1230 (48%) of asthma cases in Barcelona could be attributable to air pollution each year. This study also found that in Barcelona, less socially deprived groups could be more affected by asthma-related to air pollution than those more socially deprived.