From Nature magazine

Rapid urbanization will take a heavy toll on public health if city planning and development do not incorporate measures to tackle air pollution, warns a report launched in Beijing last month.

The report, compiled by the World Meteorological Organization (WMO) in Geneva, Switzerland, and the International Global Atmospheric Chemistry (IGAC) project in Boulder, Colorado, was launched as part of the IGAC Open Science Conference on Atmospheric Chemistry in the Anthropocene. A striking point in the report, says Liisa Jalkanen, head of the WMO’s Atmospheric Environment Research Division, is how quickly megacities — metropolitan areas with populations of more than 10 million — are rising in developing countries.

There are now 23 megacities in the world, compared with just two 60 years ago. Just over half of the population currently dwells in cities, and with the urban population expected to nearly double by 2050, that proportion is projected to approach 70%. “Almost all this growth will take place in the developing world,” says Jalkanen.

Megacities “have better job and education opportunities, and well-planned, densely populated areas can reduce land conversion and use energy more efficiently”, says Luisa Molina, president of the Molina Center for Strategic Studies in Energy and Environment in La Jolla, California.

“But many cities in developing countries are expanding rapidly with poor planning and few pollution-reduction measures,” says Zhu Tong, an atmospheric scientist at Peking University in Beijing. “This is having serious consequences on the environment and public health.”

Asia, for instance, has more than half of the world’s most-polluted cities, and air pollution contributes to half a million deaths each year in the region, according to a recent report by the Asian Development Bank. More than two-thirds of Asian cities — compared with just one-fifth in the rest of the world — fail to meet the European Union’s air-quality standard for particulate pollutants.

“Part of the problem is the pace of development,” says Zhu. The population of city dwellers in China has risen almost five-fold since 1950, sending energy consumption skyrocketing and putting millions of cars on the roads, contributing to pollution hot-spots such as the notorious ‘Beijing smog’.

Levels of the air pollutants responsible for respiratory and heart diseases are high and rising in Beijing. Ground-level ozone concentrations have risen six-fold in the past three decades, with current levels typically twice the standard set by the US Environmental Protection Agency (EPA), according to David Parrish, an atmospheric scientist at the National Oceanic and Atmospheric Administration in Boulder, Colorado.

The concentrations of PM_2.5 — airborne particles 2.5 micrometres or less in diameter — typically range between 100 and 150 micrograms per cubic metre of Beijing's air, which is six to ten times higher than the EPA standard. “The health impact can be enormous,” says Andre Nel, an environmental scientist at the University of California, Los Angeles. By one estimate, mortality increases by 1% for every 10-microgram-per-cubic-metre increase of PM_2.5 in big cities, he says.

In February, China’s State Council introduced legislation aimed at curbing ozone and PM_2.5 levels, as well as other emissions. The standards, which must be implemented by 2016, are similar to, or in some cases higher than, their counterparts in the United States and the European Union. The move follows regulations introduced in 1996 that helped to significantly reduce emissions such as sulphur dioxide and carbon monoxide by adopting vehicle-emission standards and promoting the use of natural gas and low-sulphur coal, says Shao Min, an atmospheric scientist at Peking University.

6 Comments

1. 1. way2ec 03:30 AM 10/13/12

   Help me out here, isn't urban synonymous with city, (latin urbanus, city)? So how does the following work..." Just over half of the population currently dwells in cities, and with the urban population expected to nearly double by 2050, that proportion is projected to approach 70%. "? What am I missing here? Cities vs megacities? The suburbs? Urban "sprawl"? And finally, megacities are over 10 million but how are the megacity boundaries defined or set?

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2. 2. Kerome 04:08 AM 10/13/12

   The overall population is not set to double, but population in cities is, hence the proportion living in cities is likely to rise to 70%.
   
   It's not surprising, given the breakneck pace of development. One can guess at the effects on healthcare and the environment, as well as social development... I'm guessing it's a rerun of 1960's tower blocks.

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3. 3. Owl905 01:55 AM 10/14/12

   Yes, the overall population is set to double. And the mega-city is the quantitative answer. The quality is uncertain, and there will certainly be a wide and changing range of conditions. The two biggest things that will affect quality will be the planning and regulation of growth; and pollution.

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4. 4. EARTHARCHITECT 08:40 AM 10/14/12

   Moving from suburban sprawl to walkable community saves 60% energy use, so it is really a design problem. China's new cities are designed using 1950 planning models copying USA sprawl with superhighways and super traffic. Great design bringing green into high density places; such as Jefferson's checkerboard and linear parks and human powered infrastructure as pervasive as poison powered; and second glass envelopes around skyscrapers within which food is grow on conveyor belts will make the cities far less polluting and far more sustainable. All that is needed is to hire great architects like me to design the new ones and redesign the old; great design is also cost effective because it grows towards using our structures the full 168 hours in a week by combining mixed uses and designing flexible spaces.

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5. 5. gregore in reply to way2ec 08:33 AM 10/15/12

   today's urban population is 50% of 7 billion = 3.5 billion. by 2050 it should double to 7 billion = 70% of 10 billion.

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6. 6. greenhome123 05:19 PM 10/16/12

   I believe high rise vertical urban farms could substantially reduce pollution in these megacities by increasing oxygen levels in the cities and reducing the carbon footprint of food. Also, city planners should implement regulations on the type of vehicles that are allowed in these cities, like MPG restrictions, and even phase out of fossil fuel powered vehicles altogether by a near future date. Also, I believe that megacities should start using large scale solar or wind powered atmospheric water generators to provide supplemental water for the city. And, in regards to ground level ozone, it is my understanding that pollution from tailpipe emissions from cars/trucks interact with heat and sunlight to create ground level ozone. So, if cities were to add giant solar panels to the top of their high rise buildings then it will block a lot of the sunlight and heat from hitting the ground and thus reduce ground level ozone while creating energy at the same time.

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