Roadside PM10 was measured simultaneously with the
Thailand Pollution Control Department (PCD) monitoring
station at the same site and at the intersections where
police work. The result from dual simultaneous measurements
of PM10 showed a good correlation (correlation
coefficient: r = 0.93); however, PM levels near the roadside
at the intersections were higher than the concentrations
at the monitoring station. The relationship between
ambient PM level and actual personal exposures was examined.
Correlation coefficients between the general
ambient outdoors and personal exposure levels were 0.92
for both PM2.5 and PM10.
Bangkok air quality data for 1997–2000, including
24-hr average PM10, NO2, SO2, and O3 from eight PCD
monitoring stations, were analyzed and validated. The
annual arithmetic mean PM10 of the PCD data at the
roadside monitoring stations for the last 3 years decreased
from 130 to 73 µg/m3, whereas the corresponding
levels at the general monitoring stations decreased
from 90 to 49 µg/m3. The proportion of days when the
level of the 24-hr average PM10 exceeded the NAAQS
was between 13 and 26% at roadside stations. PCD data
showed PM10 was well correlated with NO2 but not with
SO2, suggesting that automobile exhaust is the main
source of the particulate air pollution. The results obtained
from the simultaneous measurement of PM2.5 and
PM10 indicate the potential environmental health hazard
of fine particles. In conclusion, Bangkok traffic
police were exposed to high levels of automobilederived
particulate air pollution.