I told you about what's happening in London, but what's happening in countries where industrialization is still taking place? Well, China is an interesting and important example of where vehicular emissions are comparatively less important to matters of [inaudible] and particular to emissions overall. In China, industrial processes in coal based power generation account for between 40 and 60 percent of all emissions. Over the last decade, the government has reduced industrial emissions to a very significant degree, predominantly by a process of increased regulation and scrutiny. The 2008 Beijing Olympics, or industry around the Olympic Games venues, shut down for short periods before the events. During and since then in Beijing, alternate day entry for automobiles, based on number plates has also been used to discourage private transportation. At the same time, there's been huge investment in mass transit systems across many of China's largest cities. But much of the improvement has been driven by a central government push to phase out outdated industrial capacity, improve environmental standards, and alter the power generation blend, predominantly away from coal, towards natural gas. But I want to discuss the idea of visibility in social norms, and identify some of the risks that we face when pushing the public health agenda. If you've watched any international news, or if you've visited industrialized cities in East Asia, you'll be aware that it's not uncommon to see people wearing face masks when outside. Now, while these masks are worn for a number of reasons. One of the main reasons that they use, is to prevent inhalation of air pollution. The evidence for these is relatively mixed, but what does wearing them say? Well, we have to be really careful about the social norms that they create. While Beijing is a rather extreme example of masks, if they work, may be useful, they are a very powerful message to everyone that going outside is dangerous. In Beijing and in other polluted cities, people are warned not to jog or take strenuous activity outside. I certainly advocate jogging along busy roads in London. But advice such as this, can create powerful social norms about exercise being dangerous. This can end up protecting a population from one hazard while opening them up to another. This is a photograph I took a few years ago, that shows an air quality index in a public park, in this case in Shanghai. For me, there's a danger in such an approach. Do we discourage people from undertaking behaviors that are physically and mentally beneficial by underlining the risks? This is a particularly challenging issue when dealing with politicians who will tend to want to do something. Always be careful about what you intervention might do in terms of unintended consequences. We don't cover exposure assessment in this specialization, but I want you to be aware that there's a whole area of environmental science, that looks at exposure to pollution and other hazards. Exposure assessment can be a very complicated and unpredictable science, merely by walking on the inside of the pavement and being taller, rather than a child, can substantially reduce your exposure. I'm telling you this because your role in health protection or in public health will be to analyze all of this evidence, and to synthesize recommendations. Think carefully about what you recommend, and what unintended consequences your recommendations might precipitate. Yet rapidly industrializing countries offer huge opportunities to build health into urban environments, as cities expand, a new urban settlement arises. In 2019 Public Health England published an evidence review, highlighting how municipal government can consider air quality in the development of urban infrastructure. I draw your attention to three of their recommendations. Promoting and enabling low emission vehicle uptake by providing charging points. Boosting investment in public transport and active travel enablers, such as psychopaths in foot ways, and designating residential zoning to areas set back from busy roads. I've told you about both tactical and more strategic responses to health protection threat, in this case air pollution. By now I hope you can see just how broad and potentially complex the policy issues are arising from challenges such as these. Yet at the same time, I hope you can see a huge opportunity for public health practitioners to engage and influence decision making.