Public policies aiming at decreasing air pollutants such as fine particulate matter (PM2.5) are often designed without targeting an explicit health benefit and without carrying out cost-benefit analyses, therefore possibly limiting their adoption. We developed a transdisciplinary backward and forward approach at the conurbation level (Grenoble, France): we first defined health objectives, identified which PM2.5 reductions and urban policies allowed to meet the health targets (backward approach), and finally conducted health impact and cost-benefit analyses of these policies (forward approach). Three health targets were defined, corresponding to decreases by 33%, 50% and 67% in PM2.5-attributable mortality in 2030, compared to 2016. The urban policies were related to the wood heating and transport sectors, the main emitting sectors in the considered area. The forward approach considered the health impact and co-benefits of these policies also related to changes in physical activity and GHG emissions. The most ambitious health target could be achieved in 2030 by replacing all inefficient wood heating equipment by pellet stoves and by reducing by 36% the traffic of private motorized vehicles. Such a reduction requires to increase active modes share (walking, biking…), which would also induce increases in physical activity and additional health benefits beyond the initial target. Wood heating system replacement and strategies maximizing active mobility, which did not require massive investment in public transport, were the most cost-effective policies. For each Euro invested, the total benefit was about 30€ for policies focusing on wood heating, and 1 to 66€ for policies on traffic. Annual net benefits were between €468 and €615 per capita for policies with report on active transportation modes, compared to between €151 and €258 without. Urban policies strongly reducing air pollution-attributable mortality can be identified by backward transdisciplinary approaches, and be cost-efficient.