A global scientific research programme has been launched in China to examine the unintended consequences of urban policies on human health and wellbeing.
The Urban Health & Wellbeing Programme aims to better understand what makes a "healthy urban environment".
People living in cities face a number of health risks, such as air pollution.
The majority of people now live in towns and cities and the global urban population is growing by an estimated one million people each week.
The launch of the programme comes amid a growing body of research that links urbanisation with growing health risks.
"Historically, a lot of the focus in health has been on rural health," explained Prof Anthony Capon, director of the UN University's International Institute for Global Health, based in Kuala Lumpur, Malaysia.
But since 2008, more people live in towns and cities than rural areas. Currently, an estimated 3.9bn people live in urban areas.
This total is projected to increase to in excess of six billion people by the middle of this century.
Prof Capon told BBC News: "When we take an overview, urban areas are very important determinates of health.
"The way we live on a day-to-day basis in cities affects our health in so many ways, whether it is the air that we breath, or the fact that many people in cities around the world are very sedentary (sitting at a desk in an office or sitting in a car to get to and from work) - and many people are also eating very unhealthy foods.
"We are facing global epidemics of non-communicable diseases - heart disease, diabetes and so on - and mental health problems. We are also seeing the health impact of climate change, such as heat-stress in cities and changes in the distribution of infectious vector-borne diseases."
But he added that the programme offered hope: "Now that most people live within cities, we have got the opportunity to rethink the way that we live in cities and the way we plan and develop cities.
"The essence of this programme is about scientists working with urban decision makers. It is about identifying problems together, and how we might better understand those problems and developing better ways of responding to rapid urban population growth. Much of it is happening in low- to middle-income countries and that is why the United Nations is particularly concerned about the issue.
"I think the key is understanding that cities are really about people. We are attracted to cities for economic, educational and social opportunities. When we live in cities, they need to work for us. It is not just about the economic efficiencies of these cities."
Commenting on the establishment of the programme, Dr Franz Gatzweiler of the International Council for Science (ICSU) said: "One of the questions we need to address in this programme is: 'How many health risks are people willing to take for the benefits that come with urban lives?'
"Citizens and policymakers need to be able to make that decision and become active agents of urban change."
The consortium behind the Urban Health and Wellbeing Programme, which will provide a hub for "interdisciplinary scientific knowledge", include the International Council for Science, the InterAcademy Medical Panel and the United Nations University.
The programme's secretariat will be hosted by the Chinese Academy of Sciences' Institute of Urban Environment in Xiamen, China.