## Materials and Methods
### Study Area  
Although health data is complete for time and geographical frames, the air pollution data showed some liabilities. Besides the missing information regarding some air pollutants, there were too few air pollution measuring stations to be able to study the totality of Lisbon Metropolitan Area (LMA) territory with the same grade of certainty, as several municipalities had not a single measuring station within their borders, or in others the air pollution measures could only explain part of the territory (and its reality) as the bulk of population resided outside the territory of influence of the referred stations. This forced us to contain the study to three case studies, which in fact were the most urban municipalities of LMA. Also, due to the lack of data on air pollutants across all territories, we opted to maintain such a scale and develop a statistical analysis, instead of going to a parish/neighborhood scale and working on a spatial analysis base, as the main purpose was to access the municipal scale in LMA. Figure 1: Data, methods, and modeling strategy. So, the study area includes the municipalities of Amadora, Odivelas, and Lisbon in the Lisbon Metropolitan Area. LMA is a territorial unit with a strong urban component, being one of the two existing metropolitan areas in Portugal. It is simultaneously a NUTS II and NUTS III (Nomenclature of Territorial Units for Statistical Purposes) and occupies an area of 3002 km\({}^{2}\), encompassing 18 municipalities. The three studied municipalities are located on the north flank of the Tagus river (Figure 2), being among the municipalities with the highest population density in the whole country [98]. The LMA constitutes the most problematic region in Portugal regarding the emission of pollutants, as it comprises municipalities with significant levels of air pollution and population (which in turn has more pollution inherent to daily life traffic and living, while putting a greater number of individuals at risk) [99]. Furthermore, studies related to this area show frequent exceedances of EU directive targets for air quality [100]. All this with a small territory and share of the economy adjudicated to industry--in fact, in the municipalities of Amadora, Odivelas, and Lisbon only an average of 3.5% of the workforce is employed in the more pollutant industries (like paper, food, chemicals, etc.) [101]. In the studied territories--and across all North LMA and almost the complete LMA--the major contributor to air pollution is traffic (over 60%), being followed at great distance by industry, energy production, and finally households' combustion [102]. However, LMA is not all the same; in fact, it is a heterogeneous region whose municipalities possess very distinct characteristics. The case studies are a good example of this trait. Lisbon municipality is the economic soul of LMA, with a thriving service economy complemented with the tourism sector, comprising the bulk of jobs in the region. Thus, it is the region's driver for growth and development. The cases of Amadora and Odivelas municipalities are much different, as these have activities related  
Figure 2: Spatial distribution of monitoring stations and Location of three municipalities: Amadora, Lisbon, and Odivelas. to logistics and, mainly, residential typology. These municipalities (among others in LMA) feed the workforce needs of Lisbon's dynamic economy [103]. But the differences are not only blurred in the economic part; the demographic and social questions are also dissimilar, as Table 2 shows with its demographic and socioeconomic indicators (important aspects in terms of population vulnerability). Lisbon has a larger concentration of senior population, as is expressed by the ageing index (representing the relation between the senior and young populations) and the elderly dependency index (representing the relation between the senior and active age--adult--populations), making it an older municipality and, thus, with higher vulnerability levels.