Relationships between air pollutants and mortality in Portugal – an environmental health assessment

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Introduction: The burden of disease attributable to environmental risks has received worldwide attention, as shown by reports of the increasing number of premature deaths and disability adjusted life years (DALY) linked to ambient air pollution [1,2]. Air pollution is responsible for 6.8% of total DALY and 11.2% of deaths from all causes worldwide, and for 1.9% of total DALY and 3.6% of the deaths from all causes in Portugal [3]. Concerning major causes of death in the country, in 2016 the burden of diseases attributable to air pollution was 8.7% for ischemic heart disease, 6.6% for stroke, 6% for lung cancer and 15.3% of chronic obstructive pulmonary disease. Realizing how much disease and ill health can be prevented by reducing or eliminating environmental risk factors is important, but designing public health policies and interventions at the national and regional level in Portugal requires the knowledge of the specific environment-health interaction concerning air pollution. This work aims at shedding light on that specific interaction in Portugal, in the period 2010 – 2015. Materials and methods: Data for the main causes of death - diseases of the circulatory and digestive system, respiratory tract and malignant tumors - and levels of environmental exposures to main air pollutants - particulate matter (PM10 and PM2.5), ozone (O3), nitrogen dioxide (NO2) and sulphur dioxide (SO2) - collected in 46 municipalities in Portugal in 2010 - 2015, were retrieved from Portuguese databases [4,5]. General linear models (GLM) were used to analyze time variations and differences between regions for the environmental exposures and for mortality rates. Backward regression models (BRM) were used to assess the relationship between levels of air pollution and mortality from main causes. Results: GLM results show a downward tendency for the air concentration of PM10, NO2 and O3, with different patterns in urban, suburban and rural region. Concomitantly, mortality from main causes has remained fairly constant, except for diseases of the respiratory tract, which has increased, and is higher in the rural areas. Additionally, BRM identified significant associations between rates of mortality from diabetes, diseases of the circulatory system and malignant tumors, with PM10 and NO2 air concentrations. The model provides a rough estimate of 15 deaths from main causes that could have been avoided per 10000 inhabitants with a 10µg/m3 reduction of the atmospheric level of PM10 and NO2. Discussion and conclusions: significant relationship between mortality rate by main causes and atmospheric concentrations of relevant pollutants has been suggested, providing an estimate of how many lives could be spared by tangible reduction of pollution level.