This study employs sensitive methods to address the issue of exposure to secondhand smoke among children and women in an understudied developing country setting (Syria). The study combines data collected by the Syrian Center for Tobacco Studies as part of two international studies conducted in 2006: the Secondhand Smoke Exposure among Women and Children study (Johns Hopkins) and the Global Air Monitoring Study (Roswell Park Cancer Institute). We employed objective measures (hair nicotine, and ambient household nicotine assessed by passive monitors) to assess children's and mothers' exposure to secondhand smoke at home, and used the TSI SidePak personal aerosol monitor to sample respirable suspended particles less than 2.5 microm diameter (PM(2.5)) in the air in public places (40 restaurants/cafés in Aleppo). In homes, the mean ambient nicotine level (+/- standard deviation, SD) was 2.24 +/- 2.77 microg/m(3). Mean level of hair nicotine was 11.8 ng/mg among children (n = 54), and was higher if the mother was a smoker (19.4 +/- 23.6 ng/mg) than nonsmoker (5.2 +/- 6.9 ng/mg) (p < .05). Mean hair nicotine among nonsmoking mothers (n = 23) was 1.17 +/- 1.56 ng/mg. Children's hair nicotine level was strongly correlated with ambient household nicotine and number of cigarettes smoked daily in the house (r = .54 and r = .50, respectively, p < .001), and also was related to having a father who smoked in the children's presence. In public places, average PM(2.5) in the monitored 40 hospitality venues was 464 microg/m(3) and correlated with smoker density measured as cigarettes-waterpipes/100 m(3) (r = .31, p = 0.049). Thus, children in Syria are exposed to high levels of secondhand smoke at home, in which mothers' smoking plays a major role. Also, levels of respirable hazardous particles are high in public hospitality venues, putting customers and workers at serious health risks. Efforts to limit exposure of children and women at home and to adopt clean air policies should become a public health priority in Syria and the Arab region.