Crowd-sourced air quality studies: A review of the literature & portable sensors

• Many independent projects to ‘crowd-sense’ environmental data have been attempted.
• Current technology for inexpensive sensors is not sensitive or specific enough to meet demands.
• Advances in analytical chemistry are required for ‘crowd-sensing’ to be an effective tool.
• Collaboration between multiple disciplines is required for success.
• An organized approach to data handling and reporting is required for success.

Development of low-cost, portable, and low-power devices for monitoring airborne pollutants is a crucial step towards developing improved air quality models and better quantitating the health effects of human and animal exposure. This review article summarizes recent developments in the field within the context of the establishment/expansion of high spatial and temporal resolution air quality monitoring networks. Current ‘crowd-sourced’ monitoring efforts are summarized, and recent advances in chemical sensors required for these networks are described. No ‘perfect’ sensing platform, that meets the requirements of low-cost, portability, selectivity, and sensitivity has yet been achieved. This highlights the need for investment in the fundamental analytical chemistry of the sensing platforms required to achieve such ‘smart-cities.’ Such investment should include the development of new sensor technologies, and provide for calibration and performance validation for systems enacted. In addition to summarizing the current state-of-the-art, reflections on future needs are also offered.