This paper presents some new exergy-based parameters for PEM fuel cells to study how some of their operating aspects and system characteristics affect the environment and sustainability, based on some actual and literature data. The exergetic parameters of a PEM fuel cell developed here, in conjunction with environmental impact and sustainable development, are exergy efficiency, exergetic stability factor, environmental benign index and exergetic sustainability index. Any increase in efficiency improves exergetic sustainability. However, any increase in waste exergy ratio, exergy destruction factor, environmental destruction coefficient and environmental destruction index results in an increasing environmental impact of the PEM fuel cell and hence, a decreasing sustainability. Such parameters are expected to quantify how PEM fuel cells become more environmentally benign and sustainable. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.