Fig. 2
Annual average levels of a NOx, b NO2, c SO2, d O3 and e PM10 in ambient air of Malaysia from 2006 to 2015. Note: solid black circles denote individual exposure levels to these pollutants (NOx, NO2, SO2, O3 and PM10) during the survey years while transparent circles denote annual averages of the five pollutants present in the ambient air