Short-term joint effects of ambient air pollutants on emergency department visits for respiratory and circulatory diseases in Colombia, 2011–2014

Abstract Background We evaluated the short-term effect of mixtures of ambient air pollutants on respiratory and circulatory morbidity in four Colombian cities. Methods Daily Emergency Department (ED) visit records for respiratory and circulatory selected diagnosis and daily concentrations for six criteria air pollutant were obtained in four of the five major cities in Colombia: Bucaramanga, Bogota, Cali, and Medellin during 2011–2014. Using conditional Poisson time series analysis with fixed effects, we assessed the effect of air pollutants on health outcomes using single-pollutant, two-pollutant and specific mixtures-of-pollutant models controlling for meteorology and time trends. The percentages of change in the rate of ED visits and their 95% confidence interval were estimated for the joint effect of pollutants. Results In single-pollutant models increases in gases concentrations were associated with increases in ED visits for respiratory and circulatory diseases. The two-pollutant models for respiratory diseases showed that the effect of NO 2 alone (% change 2.86 95% CI 1.87–3.85) is higher than the joint effect of any of its combinations except for its combination with SO 2 (% change 3.05 95%CI 1.04–5.05). The two-pollutant models for circulatory diseases showed synergistic effects between NO 2 and PM 2.5 (% change 2.13 95%CI 0.001–4.26). Specific mixtures models showed that the mixture of “traffic-related pollutants” has the higher joint effect on circulatory morbidity and respiratory morbidity. Conclusions The results show the dominant effect of NO 2 in air pollution mixtures on respiratory and circulatory morbidity, and the synergistic effect of NO 2 and SO 2 in air pollution mixtures on respiratory morbidity.