Aerosol samples were collected using a high volume air sampler (HV-1000F, Sibata Scientific Technology Ltd., Japan, run at ca. 700 L/min) using quartz filters (QR-100, Advantec, Japan) from 25th July 2001 to 10th September 2002.The air was introduced to the sampler using a metal duct (3 m) with the diameter of 50 cm approx.From 25th July 2001 to 11th March 2002, the sample filters were exchanged every week; from the middle of March 2002 they were exchanged every day.Plastic disposable gloves and a pair of tweezers were used to change the filters.The tweezers were cleaned with ethanol every time before the use. Each of the filters was folded into half with the collecting surface inside, dried in a desiccator and then enclosed in a zippered plastic bag.