Deposition of sidestream cigarette smoke in the human respiratory tract.

The intake of sidestream cigarette smoke can be calculated if ventilation and smoke concentration are known. However, respiratory tract dose of smoke particulates cannot be determined unless the deposition fraction of inhaled smoke is known. The deposition fraction of mainstream smoke is 70-90%, far higher than expected for most particles in the size range, 0.2-0.5 micron, which is also the range for cigarette smoke. The deposition fraction of sidestream smoke was measured in five normal male subjects. The deposition, the dose of smoke particulates to the respiratory tract can be estimated. The deposition fraction of sidestream smoke is much lower than for mainstream smoke.