Considering the large amounts of PAHs emitted into the ambient air in China, it is urgent to take preliminary health risk assessment of citizens through inhalation exposure to PAHs in China. The incremental lifetime cancer risk (ILCR) model was used to get the risk level of Tianjin citizens as an example, and Monte Carlo simulation was adopted to deal with the uncertainty. Exposure analysis found that the average values of B[a]P equivalent (B[a]Peq) daily exposure doses for children in the indoor, traffic and outdoor settings were estimated to be 2,446.8, 478.4, and 321.6 ng day(-1), respectively. And those for adults were 3,344.1, 794.9, and 519.0 ng day(-1), respectively. Much attention must be paid to indoor exposure, as it contributes more than 70% of the B[a]Peq daily exposure dose. ILCR falls within the range of 10(-5)-10(-3), which is higher than the acceptable risk level of 10(-6), and lower than the priority risk level (10(-3)). So this risk should be compared with those of other public health issues in the purpose of risk management. Sensitivity analysis found that the two variables, indoor air PAHs concentration distribution and the cancer slope factor (CSF) of BaP, contribute about 89% of the total risk uncertainty. Thus they are considered as the two main factors influencing the accuracy of the PAHs health risk assessment.