5 measurements reported in the present study. During this study, the exposure levels measured inside the cars in all conditions quickly exceeded background levels, putting occupants at increased health risk in terms of 24-hr and annual exposure. The levels of PM2.5 observed in Condition 1 would be classified as an ��unhealthy�� condition in which all members full article of the population would be at risk of serious health effects, especially those with compromised health. To provide some context to the PM2.5 levels recorded in this study, in a recent report of PM2.5 levels in Irish pubs throughout the world, the average level of PM2.5 in 48 Irish pubs that allowed smoking was 340 ��g/m3 (Connolly et al., 2006). In Condition 1 (motionless car with all windows closed), the average level during cigarette smoking (M=3,850.

9 ��g/m3, range=1,696.8�C7,654.7 ��g/m3) was over 11 times the level in an Irish pub in which smoking was allowed. At the other extreme, in Condition 3 (all windows open all the way while driving), the PM2.5 level was the lowest (M=60.4 ��g/m3, range=15.7�C220.5 ��g/m3). In Condition 2 (all windows closed), the average level (M=2,412.5 ��g/m3, range=760.6�C6,156.6 ��g/m3) was about 7 times higher than in the average Irish pub. In Condition 5 (air conditioning), the average level (M=844.4 ��g/m3, range=202.0�C2,504.5 ��g/m3) was almost 2.5 times higher than in the average Irish pub. In Condition 4 (holding the cigarette outside the half-open driver’s window), the average level (M=222.5 ��g/m3, range=66.7�C960.

0 ��g/m3) was slightly lower than the levels in the average Irish pub in countries where smoking was allowed in bars/pubs. Reports of high levels of PM2.5 exposure in restaurants and bars have been used by legislators to implement smoke-free policies (Hyland et al., 2004; Repace, 2004; Travers et al., 2004, 2007). The present study reports conditions where peak exposure levels met or exceeded those reported in some of the smokiest bars and restaurants prior to the implementation of a smoking ban (Repace, 2004; Travers et al., 2004, 2007). Peak levels in the conditions in which the windows were open did not reach the same levels, probably because open windows increase the number of air exchanges in the small space. However, even with the windows open, exposure was not eliminated completely.

We explicitly tested this in Condition 3, which we created as an extreme (possibly maximal) example of full ventilation and airflow in a car. In Condition 3, all the windows were completely open while driving��a condition that may not be tolerable in practice, especially during winter. Even here, the average exposure level was 60.4 ��g/m3 during the time that the cigarette was smoked, which was four times greater than the average Carfilzomib outdoor values measured at baseline and at a level considered unhealthy to children and other sensitive groups with prolonged exposure (U.S. Office of Air Quality, 1999).