Active travel (e.g., walking and cycling) has recently been promoted as a solution to reaching carbon neutrality in China. However, the potential negative health burden of active travel due to air pollution exposure is neglected. Consequently, this study proposes a low-exposure route-planning method based on pollutant concentration, trip purpose, and travelers’ demographic characteristics. Taxi-based mobile pollutant monitoring data in Cangzhou city, China, were applied to provide a high-resolution concentration map. We found that exposure varied throughout the day and seasons due to traffic, coal usage, and meteorology. Results show that exercising travelers may avoid 16.8% of exposure experienced by commuting travelers when choosing a route with low exposure but long detours. Because of the lower travel speed, even when taking a low-exposure route, middle-aged and elderly may suffer 22.9% and 10.7% higher exposure, respectively, than younger travelers. These might lead to health inequity related to transportation investment or policies.