Urban air pollution: a representative survey of PM(2.5) mass concentrations in six Brazilian cities.

In urban areas of Brazil, vehicle emissions are the principal source of fine particulate matter (PM(2.5)). The World Health Organization air quality guidelines state that the annual mean concentration of PM(2.

Vehicular particulate matter emissions in road tunnels in Sao Paulo, Brazil.

In the metropolitan area of São Paulo, Brazil, ozone and particulate matter (PM) are the air pollutants that pose the greatest threat to air quality, since the PM and the ozone precursors (nitrogen oxides and volatile organic compounds) are the main source of air pollution from vehicular emissions. Vehicular emissions can be measured inside road tunnels, and those measurements can provide information about emission factors of in-use vehicles. Emission factors are used to estimate vehicular emissions and are described as the amount of species emitted per vehicle distance driven or per volume of fuel consumed.