The Role of Medium-sized Cities for Global Tropospheric Ozone Levels

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Brazilian medium-sized cities are those showing highest growing rates in the last decades, above 3% annually. To call attention to the consequences of such strong urban growth on air quality, measurements of ozone concentrations were comparatively performed in Londrina (a growing medium-sized city), Curitiba (a big city) and São Paulo (a megacity). Particularly to the cities of Londrina and São Paulo, both are located at similar latitude (–23.5). Surprisingly, the findings of this study indicated that, there are periods of the year in which the average ozone concentration measured in Londrina can be even higher than those found in large urban areas like São Paulo. The average ozone concentrations at three medium cities are close to those found in São Paulo. It is suggested that the local meteorological conditions (temperature, cloud cover, relative humidity and wind speed), as well as the local chemical regime, could explain the differences in the observed ozone concentrations. As the number of medium-sized urban areas is increasing around the world, especially in South America, special attention should be given by policy makers when defining new air quality monitoring networks and the regulation of new areas planned for the purpose of industrial development.