 Zero Emission Cities Current advances in materials technology, renewable energy systems and building design offers the promise of zero emission cities in the future. By using new high-tech materials and a little town planning, it is hoped that we can build these cities to be clean and green, as well as self-sufficient for food and water. We ask people, what excites you, what frightens you, and how will it change the way you live? These were some of their responses. How much work is being done to look at the unintended consequences of building zero emission cities? The innovation required to implement such change would be enormous to say the least, and changing our thinking on cities would have enormous technological, social, economic and political implications. It sometimes seems that those promoting new technologies have deeper pockets and greater motivations than those making the critical assessments. For instance, the high-tech materials that would be used for the construction of the new buildings, air and water filtration systems, as well as energy capture, would likely be composed of nanomaterials. But who can we trust to make sure as a society we will not experience a health or environmental risk to the exposure of these nanomaterials? Governments, NGOs and researchers are now coming together to look beyond the minimum protections that current regulations require and ensure that we map as many of the potential consequences as possible. For example, there is currently a lot of work being done into mapping the life cycle of a nanoparticle to investigate the potential health and environmental risks. Corporations too must engage with these organisations, meaningfully to determine the level of risk that their products represent, or they may be liable for damages in the future. Does creating these cities remove us further from our connection with the natural environment? Self-sufficient cities will represent a major shift in the way we produce food for urban systems and would likely rely on genetically modified rooftop gardens as the source of supply. Does this represent the removal of a link to traditional agriculture? And does it really make sense to move from these natural systems to a high-tech urban one? In answering these questions, we might consider that our current systems are capable of producing over 2kg of food a day for every person on the planet, but over 40% of this goes to waste. Perhaps we need to look beyond the technology of the zero-emission city and ask the people living in it for the answers. What do you think?