Carcinogenic Polynuclear Aromatic Hydrocarbons in the Atmosphere in Chiang Mai, Thailand.

Abstract

Ambient concentrations of 7 mutagenic and/or carcinogenic polycyclic aromatic hydrocarbons (PAHs) were measured in Chiang Mai, Thailand, and compared to those in Tokyo. In Chiang Mai, airborne particulate samples were collected at two sites, i.e., commercial and residential sites (two stations in each site) from July through December in 1989. In Tokyo, sampling was carried out at a commercial/residential site in November 1989. PAHs were extracted by sonication, and analyzed by a multicolumn HPLC/computerized fluorometric detection system. Major observations are as follows ; 1) In both cities, ambient concentrations of PAHs and airborne particulates showed log normal distribution. Geometric mean/standard deviation is appropriate to express the situation of pollution. 2) In Chiang Mai, there was not a large difference in PAH concentrations between commercial and residential sites. This suggested wide-spreaded pollution over the city. On the other hand, concentrations of airborne particulates showed large differences among the sites. PAH concentrations in 1989 were higher than those in 1986. 3) Ambient concentrations of PAHs and airborne particulates concentrations were both low in the rainy season and high in the dry season in Chiang Mai. 4) Ambient concentrations of PAHs (except for rather volatile 4 ring PAHs) and airborne particulates in Chiang Mai were suggested to be higher than those in Tokyo. 5) In Tokyo, a fairly good correlation among concentrations of 7 PAHs and airborne particulates has been observed. In Chiang Mai, there has been good correlation among PAHs concentrations, but a poor correlation between PAHs and airborne particulate concentrations. This suggested that large content of rough particulates in Chiang Mai air may be higher than that in Tokyo. These results suggest that air pollution by PAHs and airborne particulates may be more serious in Chiang Mai than in Tokyo. Size distribution of airborne particulates seems to be different between these two cities.