Towards zero-pollution cities

Urban infrastructure transformations can produce resource-efficient, inclusive and healthy cities.
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A compact city limits both urban land expansion and motorized travel with its pollution.
50 per cent: the reduction in energy use in well-designed green buildings.

Air pollution is a global killer and predominantly an urban one. Worldwide, about 7 million premature deaths are associated with indoor and outdoor air pollution by fine particulate matter. Most occur in urban areas where a majority of people now live, breathing air that can cause asthma, respiratory infections, high blood pressure, heart and lung disease, and cancer. Diverse cities – rich, poor, small, large, developed and developing – are reporting airborne levels of these particles that exceed the World Health Organization’s clean air guidelines: some of the most polluted air, and the heaviest toll on human lives, occur in Asia.

End-of-pipe pollution controls are important, and have reduced air pollution in the past, but they alone cannot keep up with urbanization's current massive scale and pace. Eventually, a transformation of urban land, buildings, transportation, energy, water, waste management and food systems will be needed, both to reduce pollution and to sustainably and inclusively support the 6 billion urban dwellers expected by the year 2050.

Such transformation is urgently needed. The 2.5 billion new urban residents expected in Asia and Africa by 2050 require supporting infrastructure in their new cities, while existing cities in advanced economies must repair or replace aging infrastructure. Once put in place, these systems will then last for 40 more years. This presents a once-in-a-lifetime opportunity for infrastructure transformation worldwide. Focusing on inclusive and resource-efficient infrastructure offers win-win strategies that can advance human health and wellbeing by reducing air pollution, in line with Sustainable Development Goal 3. It can also achieve additional Goals related to inequality, clean energy, climate change, sustainable cities and communities, and sustainable production and consumption. Such strategies include:

• Sustainable urban land expansion with inclusive rural-urban interactions. Urban areas worldwide are taking over prime agricultural land (often destroying farmers’ livelihoods), and depleting valuable ecosystem services. Meanwhile, agricultural waste-burning greatly contributes to urban particulate air pollution. New urban-rural arrangements can address these issues systemically. Urban development agencies are coordinating land-pooling programs with farmers to guide urban infrastructure expansions so as to preserve critical ecological functions, while offering rural land-owners a stake. Novel arrangements are converting agricultural crop residues to valuable products – like electricity generated from rice husks – for sale in urban areas, thus preventing uncontrolled crop-waste burning. This reduces air pollution, and improves health, resilience and livelihoods in both rural and urban areas;

• Compact and inclusive urban form. A compact city limits both urban land expansion and motorized travel with its pollution. Compact city planning around the principles of density, diversity of uses, multi-modal design, short distances to transit, and easy access to destinations (primarily jobs), have reduced motorized travel by up to 40 per cent in diverse cities. The urban poor are fully integrated in the city core, rather than being relocated on the periphery, enabling them to walk, cycle or use public transport to access nearby jobs. This has been demonstrated through inclusive approaches for in situ slum rehabilitation in Indian cities. The popularity of car-sharing, the revival of walking and cycling, and the emergence of new smart technologies for on-demand transit, together give hope for achieving resource-efficient and low polluting urban mobility for all;

• Resource-efficient multi-storey buildings with low-polluting construction materials. Structurally-sound, resource-efficient high-rise and mid-rise buildings are essential for compact cities. Well-designed green buildings can reduce energy demand by about 50 per cent, thus cutting electricity generation from polluting fossil fuels. Multi-storey buildings also use about 30 per cent less construction materials than single-storey concrete ones, reducing polluting cement and brick manufacture. Alternative low-polluting construction materials – such as slag cements and “smokeless bricks” – are being main-streamed in China and Bangladesh to help conserve resources, create local livelihoods, and reduce air pollution. Linking sustainable building codes in cities with clean industry policies simultaneously achieves market transformation and pollution reduction;

• Synergies using circular economy principles. Cities present powerful opportunities to exchange “waste” energy and materials across sectors. Low grade “waste heat” from industries can, for example, be transmitted efficiently for 30 kilometres for reuse in advanced district energy systems that heat and cool homes and offices, thus displacing inefficient coal-fired boilers. Such cross-sectoral strategies – already being piloted in many cities in the United States, the European Union and China – realize greater energy efficiencies in urban systems than could be achieved within single sectors, like buildings or transport. Applying such strategies in all China's cities would, it is estimated, reduce national carbon emissions by about 4 per cent and avoid 47,000 premature deaths each year;

• Municipal solid waste management to prevent air pollution. Open burning of garbage in the streets of developing world cities is a major source of particulate pollution. Innovative solutions are emerging in many cities, including employing the informal sector, which is skilled in recycling and reusing diverse waste streams, and segregating and converting food waste into biogas, thus providing clean cooking fuel and stimulating a virtuous cycle toward a zero-pollution city;

• Resources for more inclusive and equitable cities. The urban poor are also exposed to air pollution indoors, where the use of dirty cooking fuels contributes to more than 4 million annual deaths worldwide. Providing clean cooking fuels and electricity is essential for inclusive development. Household consumption data, available in many world cities, are being used to both identify resource needs for the under-served, and to design innovative behavioural campaigns that promote energy efficiency among high consumers;

Implemented together, these strategies can significantly reduce air pollution while advancing health, equity, inclusion, resource efficiency, carbon mitigation, and sustainable consumption and production patterns in cities worldwide. Such transformations in urban infrastructure – paired with end-of-pipe pollution control technologies – can pave the way to zero-pollution cities. Case studies exemplifying these strategies are summarized in the "Weight of Cities" report that UN Environment’s International Resource Panel will present at the World Urban Forum in February 2018. Many strategies save resources and hence are cost-neutral and can be implemented though well-designed partnerships among public and private sectors and civil society.

Isn’t it time to say “No to air pollution” through transforming urban infrastructure systems?