Table 3 shows the comparison of PNC values obtained herein
with those observed in other parts of the world. However, this
comparison should be made with caution; characteristics of the
different sites evaluated, factors such as size range of particles
considered in each study, distance of the measurement location
away from the road, topographic settings, and seasonal influences
should be considered (Kumar et al., 2014). PNCs in this study
(between 4.85×104 cm–3 and 1.50×105 cm–3 for sites affected by
vehicular traffic) exhibited concentration levels similar to those in
developing countries such as China and Taiwan and in some cities
in the United States, Barcelona, and London (Table 3). The high
PNCs observed in this study, especially when compared with those
observed in much of Europe, are primarily caused by the high
sulfur content in the Brazilian fuel and by the age of the fleet in
use.