INTRODUCTION
Bangkok is a metropolitan area with a population greater
than 6 million. It has a tropical climate, with warm to
hot temperatures and humid conditions year-round. The
Thai government has been operating a monitoring system
for PM10 (particulate matter less than 10 m in diameter)
for several years, and the data show frequent daily
averages above 150 mg/m3 and annual average concentrations
twice as high as those in most North American