Comparison of Particulate Dose from Exposure to Environmental Tobacco Smoke (ETS) and Mainstream Cigarette Smoke Using Radiotracers

Abstract

There has been considerable debate in recent years regarding the health risks resulting from exposure to environmental tobacco smoke (ETS). To date, there has been no direct method of measuring the amount and distribution of tar particulate from ETS deposited in the respiratory tract, or for estimating subsequent clearance. Indeed only one study by Hiller et al. (1982) has reported an ETS deposition fraction of 11 ± 4% in a group of five volunteers. It remains difficult to find representative chemical markers of the ETS particulate aerosol in environmental situations, as many have a significant vapour component on ageing and dilution of the smoke. A I-l-iodohexadecane radiolabel for mainstream smoke (Pritchard et al., 1988; McAughey et al., 1996) was unsuitable for sidestream tobacco smoke as 70% of the label (and particulate mass) evaporated on ageing and dilution (Pritchard et al., 1988b). As an alternative, it is known that the radioactive decay products of the naturally occurring gases Rn (radon) and 220 Rn (thoron) when first formed have a high mobility and easily become attached to particles such as ETS suspended in the atmosphere. The 220 Rn (thoron) series decays via Po to Pb, with a radioactive half-life of 10.6 h (240 keV y-ray emission) which would allow monitoring over an appropriate period.