In looking to reduce the environmental impact of inhalation medicine delivery, one possible route is to develop a pressurises metered dose inhaler (pMDI) system that maintains all of the therapeutic advantages of the pMDI platform but which has a competitive carbon footprint to alternative technologies, particularly dry powder inhalers (DPI). Whilst carbon footprint is clearly important, it should be recognised that it is only one of several factors that contribute to the acceptability and sustainability of a delivery platform. These factors include patient safety in use and satisfactory formulation performance with a range of common actives and excipients across a range of metrics. Life Cycle Analysis (LCA) was used to compare the environmental impacts, particularly the carbon footprint, of a pMDI system using a new candidate propellant (HFA-152a (1,1,-difluoroethane)) with that of the equivalent HFA-134a pMDI and with a representative Diskus™-type dry powder inhaler (DPI)[]. This cradle-to-grave LCA study was conducted according to ISO 14040/14044 methodology and shows that the carbon footprint of an HFA-152a pMDI is reduced by > 90% compared to an equivalent HFA-134a MDI and is essentially equivalent to that of the DPI device. Although the program is still in progress, results to date from an HFA-152a inhalation safety program show great promise with propellant-only clinical trials already planned. In some cases, formulations based on HFA-152a show a number of potentially valuable performance advantages, particularly with respect to improved chemical stability.