Abstract We present A-PIE, a hybrid privacy-preserving mechanism for Participatory Sensing Systems that provides a high level of privacy protection as well as a high quality of information while minimizing the energy consumption. A-PIE takes into consideration the variability of the variable of interest to identify clusters, and divides the target area in cells of different sizes. A-PIE applies anonymization or double-encryption to balance privacy protection, quality of information and energy consumption based on the cell’s size. Extensive experimentation, using a real air monitoring system, shows the superior performance of the proposed mechanism when compared with most important privacy-preserving mechanisms.