THERE was a slight improvement in Hong Kong air quality last month - due to favourable winds rather than a drop in pollution levels, latest figures reveal. Seasonal variations in weather patterns were reflected in the pollution levels throughout the territory. In general, the winds blew most of Hong Kong's dirty air out to sea, according to the Environmental Protection Department's air quality report for September. But low wind speeds trapped the local pollution on September 17, and heavy pollution counts on September 1 and 2 were blamed on a cyclone which kept the 'lid' on Hong Kong. Principal environmental protection officer for air, Raymond Leung Pak-min, said: 'Climate and weather always effect our ratings, but the only way to improve air quality is to reduce the concentrations of man-made pollutants in the air.' Last month there was a drop in the level of sulphur dioxide at all sites. Mongkok topped the filthy air test for the 37th month in a row because the station at Mongkok is located at street level. The other stations are located on rooftops to rate the air breathed at higher levels.