Abstract
Exposure to nitrogen oxides (NOx) emitted by burning fossil fuels has been associated with respiratory diseases. We aimed to estimate the effects of NOx exposure on mortality owing to respiratory diseases in residents of Taubaté, São Paulo, Brazil, of all ages and both sexes. This time-series ecological study from August 1, 2011 to July 31, 2012 used information on deaths caused by respiratory diseases obtained from the Health Department of Taubaté. Estimated daily levels of pollutants (NOx, particulate matter, ozone, carbon monoxide) were obtained from the Centro de Previsão de Tempo e Estudos Climáticos Coupled Aerosol and Tracer Transport model to the Brazilian developments on the Regional Atmospheric Modeling System. These environmental variables were used to adjust the multipollutant model for apparent temperature. To estimate association between hospitalizations owing to asthma and air pollutants, generalized additive Poisson regression models were developed, with lags as much as 5 days. There were 385 deaths with a daily mean (±SD) of 1.05±1.03 (range: 0-5). Exposure to NOx was significantly associated with mortality owing to respiratory diseases: relative risk (RR)=1.035 (95% confidence interval [CI]: 1.008-1.063) for lag 2, RR=1.064 (95%CI: 1.017-1.112) lag 3, RR=1.055 (95%CI: 1.025-1.085) lag 4, and RR=1.042 (95%CI: 1.010-1.076) lag 5. A 3 µg/m3 reduction in NOx concentration resulted in a decrease of 10-18 percentage points in risk of death caused by respiratory diseases. Even at NOx concentrations below the acceptable standard, there is association with deaths caused by respiratory diseases.
Highlights
Nitric oxide (NO), nitrous oxide (N2O) and nitrogen dioxide (NO2) generate nitrogen oxides (NOx), which are considered primary air pollutants, as well as carbon monoxide (CO), polycyclic aromatic hydrocarbons (PAHs) and particulates emitted from identifiable sources
Mean values of pollutants PM2.5, NOx, O3 and CO did not exceed the standard set by Brazil’s State Decree No 59113/2013, based on guidelines established by the World Health Organization (WHO) establishing new air quality standards through a gradual and progressive set of targets, such that air pollution is reduced to acceptable levels over time [22]
An association between exposure to NOx and deaths from respiratory disease was observed in Taubaté, the levels of NOx reported in this study were below those established by Cetesb [22]
Summary
Nitric oxide (NO), nitrous oxide (N2O) and nitrogen dioxide (NO2) generate nitrogen oxides (NOx), which are considered primary air pollutants, as well as carbon monoxide (CO), polycyclic aromatic hydrocarbons (PAHs) and particulates emitted from identifiable sources. These pollutants act as precursors of secondary air pollutants, such as ozone (O3), nitric acid (HNO3) and others [1]. NOx participate in the formation of photochemical smog consisting of products resulting from interaction with organic compounds and, together with sulfur dioxide (SO2), contribute to the formation of acid rain [2]. NO2 is a very toxic gas that can trigger cell damage and inflammatory processes throughout the respiratory system, from the nose to the pulmonary alveoli [1]
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