Water. A finite resource, with exponentially increasing demands on it for drinking, for growing food, for sanitation, for manufacturing products. JEM is pleased to present its first self-initiated special issue on one of the biggest environmental challenges that faces our world—water quality and supply.Accessible freshwater supplies are less than 0.01% of the total water on the planet. While water use per capita has decreased in recent years, the global population increases that are expected to reach 9 billion people by the end of this century will put greater stress on this limited resource, and in areas that are already water-poor such as Asia. In the developing world, access to safe drinking water and adequate sanitation is not available to more than 2 billion people. In the developed world, water quality is stressed by nutrient and pesticide leaching from agricultural practices, urban runoff, industrial discharges, air deposition of nitrogen and toxic contaminants, and contaminants of emerging concern such as pharmaceuticals, and endocrine disrupting compounds. Thus our themed issue contains 36 articles covering a wide range of topics, from new contaminants to new technologies for treatment. The articles focus on processes affecting water quality such as factors affecting bacterial contamination in surface waters, to policy issues such as determining standards for nanomaterials in water. Studies cover water issues from China to Portugal to North America. We are especially pleased to have several important critical reviews with nuclear desalination, estrogens in municipal wastewater, long term monitoring of river water nitrate, and bismuth concentrations in surface waters, amongst other topics being reviewed in this issue.We hope you will enjoy this issue as much as we enjoyed commissioning articles and putting it together. We plan on more JEM-initiated special issues on other critical environmental challenges in the coming year. Our last issue focused on “Urban Canyons”, and a special “Emerging investigators issue” featuring the top new research talent in the environmental chemical sciences will feature in 2010.JEM is on a continued trajectory upwards in terms of its impact factor, articles submitted, and articles published. We just passed a special milestone—our 100th issue—and with it, we declared our commitment to publishing research on understanding environmental processes and the implications of emerging technologies, climate change, sustainability, land use practices, industrial development and economics. We also continue to support our traditional emphasis on new analytical techniques that help us understand these complex environmental processes. Most of all, we publish environmental science and chemistry that demonstrates environment impact.With the beginning of the new year and new decade, we look forward to another excellent year at JEM. We thank our many excellent reviewers and thank them for their timeliness—our very short times to publication are in large part to their responsiveness. We thank our authors for their high quality submissions and attentiveness to reviewers comments. Finally, we thank you, the readership, for your continued support of JEM.Professor Deborah SwackhamerChair, JEM Editorial Board