Preliminary analysis of air quality data from large cities

In the past few years, the more developed countries have made great efforts to improve air quality through the adoption of clean air plans which have included measures such as: stricter emission and air quality regulations, continuous air quality monitoring in urban and industrial centres and the use of cleaner fuels such as natural gas, among others. At the same time, in developing countries, there is a clearly perceivable phenomenon of migration from the countryside to the city, which has brought as a consequence greater emissions into the atmosphere, mainly produced by the increase in the number of vehicles circulating, with the additional difficulty that in these countries the tendency is to have a stock of older, worse maintained vehicles than in developed countries, where the number of vehicles in circulation has likewise increased. These factors have produced far-reaching changes in air quality maps in urban contexts, especially in the 1990s, which is when the majority of clean air plans were tightened up. As the enormous amount of air quality information that is currently available on the Internet. In this study we present a preliminary compilation of air quality information in a form that makes possible an overall evaluation of the tendencies that have emerged in the 1990s in air quality in urban and industrial centres in both developed and developing countries. In the same way the values found will be compared with the maximum concentration levels of atmospheric pollutants recommended by the World Health Organisation (WHO) and the World Bank (WB) with the end of giving an overview of the state of air quality in the me-a-cities of the world.