Less than 2% of municipalities monitor air quality (ISS, 2014). At a national level, average exposure to air pollution from PM2 5 is relatively low in Brazil compared to most OECD countries (Annex l. B), but this average hides wide differences across urban and rural areas. This difference may partly be linked to the distinct smog composition in Brazilian urban areas, which is related to the reliance on ethanol in road transport10 (IEMA, 2014, MCTI, 2010), however, it may also be explained by the fact that fewer data points are available for CO, S02 and N02.