downtown area of Bangkok from 1992 to 1995. Daily
average concentrations were calculated at every location
with at least 18 hr of data for each 24-hr period. For the
period under study, January 1992 through November
1995, the daily PM10 concentration data were the most
complete for the monitoring unit at the MOSTE headquarters.
Data for this location were used as the primary
measure of daily PM10 concentrations in Bangkok for this
analysis. However, even at this location, PM10 measurements
were available for only about 40% of the days in
the study period. The correlations among the daily PM10
concentrations at the four monitoring locations were
highest for the two locations for which we have the largest
amount of data; PM10 measurements at MOSTE and a
site at Odean Circle are available on the same days for
268 days and have a correlation coefficient of 0.9. The
high correlation and comparable daily PM10 concentrations
at the two monitoring locations with the most data
available suggest that each is a reasonable indicator of
day-to-day fluctuations in PM10 concentrations in
Bangkok, and that it is acceptable to use one of these
monitoring locations to measure daily PM10 concentrations
in Bangkok for the purposes of this analysis. There
is a seasonal pattern in the PM10 concentrations, with
higher levels in the winter (November–February) and
lower levels in the rainy season (May–October).