ABSTRACT
Airborne fine particles of PM2.5-10 and PM2.5 in Bangkok, Nonthaburi, and Ayutthaya were measured from December
22, 1998, to March 26, 1999, and from November 30,1999, to December 2, 1999. Almost all the PM10 values in
the high-polluted (H) area exceeded the Thailand National Ambient Air Quality Standards (NAAQS) of 120 µg/m3.
The low-polluted (L) area showed low PM10 (34–74 µg/m3 in the daytime and 54–89 µg/m3 at night). PM2.5 in the H area varied between 82 and 143 µg/m3 in the daytime and between 45 and 146 µg/m3 at night. In the L area, PM2.5 was quite low both day and night and varied between 24 and 54 µg/m3, lower than the U.S. Environmental Protection Agency (EPA) standard (65 µg/m3). The personal exposure results showed a significantly higher proportion of PM2.5 to PM10 in the H area than in the L area (H = 0.80 ± 0.08 and L = 0.65 ± 0.04).