To provide more insight into the toxic air pollutant variations in Hong Kong, the results at PolyU station were compared with the data collected at the two EPD air quality monitoring stations in Central/Western and Tsuen Wan. Monthly average concentrations of toxic air pollutants (VOCs, carbonyls and PAHs) collected at the Central/Western and Tsuen Wan stations during April 1999 to April 2000 for VOCs and carbonyls, and April 1999 to February 2000 for PAHs, were used for the comparison.

The Central/Western monitoring station was classified as representing urban residential areas, while the Tsuen Wan monitoring station represented mixed urban residential, commercial and industrial areas. It should be noted that these two monitoring stations are aimed to provide TAP information in ambient air, while the PolyU station was chosen to represent urban roadside areas characterised by heavy traffic emissions. The roadside and ambient data are influenced by different factors and they may not be directly comparable. The comparison of these data made in this report serves to illustrate trends of TAP levels recorded at the three stations using the limited information available.