the day, to use a measuring method with a sufficient
time-resolution function. In the meantime, it may be
reasonable to estimate personal exposure level at the
roadside using existing data. As shown in Table 4, PM10
was well correlated with NO2 but not with SO2, suggesting
automobile exhaust as the major source of the airborne
particles. Further analysis to differentiate the
health effects of PM10 from those of NO2
may not be
possible; however, we would like to emphasize the urgent
necessity to monitor health effects of automobile
air pollution on highly exposed groups such as traffic
police. We believe the findings of the present study are
of benefit to improve air pollution control in Thailand,
both in monitoring particle levels and in further research
into the deleterious health effects of PM.