The purpose of this paper is to quantitatively determine the rate of intrusion of cedar pollen to indoor environment, to estimate the exposure dose and to provide the control measures. Cedar pollens were determined microscopically on settle plates covered with adhesive material in wooden dwellings, flats, and several buildings. The settlements were variable according to the height and position of the rooms. The settlements on the floor were 1.5 to 2 times higher than at the breathing zone and those at just the inside of the windows were 5 to 6 times as much as at the center of the rooms. The rates of settlement were 0.4 to 0.8 p/cm2/day at the center of house and 1.9 to 2.8 at inside of windows. The intrusion rates were about 1.6% at the center of the house, 3.1% at the window and 26% at the places with opened windows. Throughout all the measurements, inside/ outside ratio, which is the simple ratio of settled pollen inside to those outside, was 1 to 2%. The calculated doses inside the room were 1 to 2% of outside. The doses become about twice at the windows and 10 to 20 times at places with opened windows of values at the center of house.
