More than 90% of the world’s population is exposed to air pollutant concentrations exceeding World Health Organisation guideline levels. Having air that is healthy to breathe is one of the greatest challenges of the 21st Century. Some of this is unfinished business from the last 60 years, but as more and more of us live in cities, more of us are living close to pollution sources. Europe is wrestling with air pollution from diesel transport and in China and India they are facing air pollution problems that they have never met before. The air pollution that we breathe every day is largely invisible to us but it is having a significant impact on our health and that of our children. The Invisible Killer will take you on a journey from London to Los Angeles to Beijing, challenging our ideas of what creates air pollution and how we measure it, and introducing us to incredible individuals whose groundbreaking research paved the way to today’s understanding, often at their own detriment. Dr Fuller argues that to change the future of our planet and collective global health, city and national government action is essential. It is not for lack of evidence that air pollution harm persists. Instead it remains in place due to a lack of political will to make changes to our urban lives, to persuade the public and to make polluters bear the full cost of the harm that they do.