Science: A nationwide competition to develop the best personal pollution sensor was announced yesterday. The My Air, My Health challenge is being sponsored by three US government agencies: the Environmental Protection Agency and the Department of Health and Human Services and its National Institute of Environmental Health Sciences, writes Meghna Sachdev for Science. The ideal sensor will be highly portable and should both measure air quality and monitor the user’s physiological response to air pollution. Four finalists will each receive $15 000 and the opportunity to present a working prototype to judges, with $100 000 going to the winner. Written proposals are due by 5 October.