The Intelligent Transportation Systems (ITS) concept has been recently introduced to define modern embedded systems with enhanced digital connectivity, combining people, vehicles and public infrastructure. The smart transducer concept has been also established by the IEEE 1451 Standard to simplify the scalability of networked electronic equipments. Both of them, smart transducers and ITS, have become a reality in the last decade. This study describes the design and implementation of an environmental wireless sensor network that characterises air quality in Asuncion, Paraguay. Mobile sensor devices in public transport vehicles provide an effective mechanism to develop an efficient solution for this characterisation. The development of the sensor network is presented and experimental results obtained for the characterisation of the proposed environmental monitoring system are provided.