Participatory Sensing (PS) is a new fast-growing sensing approach that involves the participation of mobile phone users, and the corresponding communication infrastructure, to create a large-scale monitoring system.Using PS-based system makes it possible to measure and detect variables and events with an improvement in spatial and time resolution over traditional monitoring system.Pollution-Spots proposes an air pollution monitoring solution by means of using an infrastructure of fixed low-cost sensing devices, and reporting the measurements using a PS approach.The sensing devices acquire the variables and the pedestrian forwards this information, completing the cycle with no extra cost of data transport and/or human resources.However, including humans to the sensing loop, rises new challenges, such as protecting user private data, motivating user's participation, and reducing mobile phone's power consumption, all while maintaining the quality of the collected data.Pollution-Spots proposes a combined algorithm that protects the participant's private information and also implements a gamification technique to encourage the participation without any monetary reward.The proposed system has proven to be energy efficient when compared to similar approaches, with the additional benefit of considering the quality of the collected information, which is normally affected by privacy protection algorithms.