Today, there are 23 cities giant with a population of over 10 million people. In all probability, their number will grow. Meanwhile, urbanization poses a threat to our health. It is reported by the report prepared by the world meteorological organization (WMO) and the International project to study the chemistry of the atmosphere (IGAC).

The document was launched at the Open science conference IGAC on atmospheric chemistry in the anthropocene, held recently in Beijing (PRC). Now lives in cities little more than half the world's population, and by 2050 the share of the urban population, according to experts, should be close to 70 percent. "Almost all of this growth will come from developing countries" - said the head of research of the atmosphere WMO Fox, Jalkanen.

"The city-the giants are able to offer better jobs and education and a well-planned, densely populated areas can reduce the need for development of new lands and to use energy more efficiently" - believes the President Malinovskogo of the center for strategic studies on energy and environment (USA), Luisa Molina.

But not all so good. "Many cities in developing countries are expanding rapidly and are planned poorly, and measures to reduce pollution are rarely accepted. This has serious impacts on the environment and health" - says a colleague of Jalkanen and Molina, researcher atmosphere Zhu Tong from Beijing University (China).

This is not a horror story, it confirmed the undeniable facts. Thus, only in Asia, according to a recent report by the Asian Bank of development, air pollution leads to half a million deaths a year. At the same time in more than two thirds of Asian cities the air does not meet the quality standards for the number of particles is determined by the European Union.

"Part of the problem is the speed of development," said Zhu Tong. According to him, since 1950, the urban population in China has increased almost five times. Accordingly increased energy consumption and the number of vehicles. And the famous Beijing smog has become the byword.

In turn, David Parrish of the National Board of oceanic and atmospheric research (USA) stated that over the last 30 years, the concentration of ozone in Beijing at ground level has increased six times, and now it is twice higher than the level defined by the U.S. Department of environmental protection (EPA). The concentration of aerosols in the air of Beijing exceeds the norm by 6-10 times.

"The health impact can be enormous" - said the ecologist Andre Nelson of the University of California in Los Angeles (USA). He added that, according to one expert estimates, the death rate in cities is directly proportional to the growth of air concentrations of aerosol particles PM2.5.

In February of this year, the State Council passed a law limiting the levels of ozone and PM2.5, and other polluting emissions. These standards are planned to come by 2016, they have much in common with the American and European counterparts. However, as said Shao Ming from Beijing University, in 1996 were introduced instructions that limit emissions from vehicles and encourage the use of natural gas and low-sulfur coal, which helped significantly reduce emissions of sulphur dioxide and carbon monoxide.

"In order to meet the new standards (particularly for ozone and PM2.5), will require strategic changes measures to reduce pollution" - said Shao Ming. He noted that, unlike sulfur dioxide and carbon monoxide, ozone and PM2.5 are not created directly by sources and are the product of chemical reactions between different substances in the atmosphere. "This means that we have to throw a wider network instead of focusing on several predecessors" - adds the researcher.

Although atmospheric emissions in Beijing are tightly controlled, a significant portion of contaminants coming into town from the surrounding areas, says Zhu Tong. So, he says, during the Olympic games of 2008 the share of air masses from the South, containing elevated concentrations of ozone, reached 34-88 percent.

"The quality of the Beijing air can be increased only in the case if it will be possible to overcome the administrative border" - believes Zhu Tong.

Meanwhile, we should not think that such a catastrophic situation is observed only in Beijing. Monitoring of atmospheric emissions is required in other major cities - is the main recommendation made by the conference participants. "Otherwise town giants will be the main source of global pollution, warns Luisa Molina. - How governments cope with the problems of rapid urbanization, will determine the future quality of life".