Since the major accidents that occurred in the 1960s, air pollution has commonly been considered as a respiratory risk factor whose effects are most often studied in industrialised countries. Our aim is to show that it is now the turn of low- and middle-income countries to take this risk factor into account. After a discussion of the characteristics of air pollution, how it is diffused and the main known health effects (short- and long-term effects), we describe the specific differences between the cities in the North and the South. As a result of late industrialisation, cities in the South are now faced with pollution from industrial sources and urban traffic with polluting vehicles. The case of Algeria and Morocco illustrates this situation and its potential health risks. In order to prevent the health risks of air pollution in the cities of the South, systems for measuring pollution levels and epidemiological surveillance need to be put in place rapidly. This strategy can only work if it is supported by a strong partnership from industrialised countries.