That's the conclusion of a report on the "urban metabolism" model of megacities presented here today at the 238th National Meeting of the American Chemical Society (ACS).
Charles Kolb, Ph.D., reports that the concept of urban metabolism has existed for decades. It views large cities as living entities that consume energy, food, water, and other raw materials, and release wastes. The releases include carbon dioxide, the main greenhouse gas; air pollutants, sewage and other water pollutants; and even excess heat that collects in vast expanses of concrete pavement and stone buildings.
Humans directly produce a significant share of this waste, but emissions from industrial, power generation and transportation systems respire the largest quantities of greenhouse gases and other air pollutants. Other urban metabolizers include sewage systems, landfills, domestic pets and pests like rats, which in some cities outnumber people.
During the last five years, this body of knowledge has drawn into sharper focus the hazards of poor air quality in megacities, not just on the large local populations but also on population centers, agricultural activities and natural ecosystems located downwind from these sprawling areas, Kolb said. He is with the Center for Atmospheric and Environmental Chemistry and the Center for Aerosol and Cloud Chemistry of Aerodyne Research Inc. in Billerica, Mass.
"Carbon dioxide and other pollutants in megacities make them immense drivers of climate change," he said. "They impact climate on both a regional and global level because these long-lived greenhouse gases are dispersed around the world."
More than half the world's population today lives in cities, and the world's largest urban areas are growing rapidly. The number of megacities — metropolitan areas with populations exceeding 10 million — has grown from just three in 1975 to about 20 today.
Kolb said that the most highly polluted megacities are in developing countries. They include Dhaka, Bangladesh; Cairo, Egypt; and Karachi, Pakistan. Some megacities in less developed regions have recently mounted air quality management campaigns that have resulted in lower levels of pollution; they include Mexico City, Mexico; Beijing, China; Sao Paulo, Brazil; and Buenos Aires, Argentina. Even the cleanest megacities like Tokyo/Osaka in Japan and New York City and Los Angeles in the United States — all in the developed world — still have serious problems, Kolb said.
The hot weather and frequent atmospheric inversions in southern California, for instance, foster Los Angeles' legendary smog problem. Mexico City's high altitude/low latitude location produces high levels of solar ultraviolet radiation that drive photochemical smog production, and the even higher surrounding mountains trap the resulting pollutants in and over the city on most days.
"That causes a very serious situation for residents of Mexico City," he said. "You get very unhealthful levels of ozone and fine particle pollutants that produce large numbers of premature deaths each year. Studies show that for each increase of 10 micrograms per cubic meter of these particles, you get roughly a 10 percent increase in premature deaths, producing a decrease in average life expectancy of about 0.8 years. Hospital visits, including bronchitis and asthma cases, also rise."
Controlling urban growth in the developing world is key to improving the world's air quality, Kolb said. Urban pollutant levels in poor countries will remain high, with increased emissions expected as the city populations and economic activities increase. Until megacities are rich enough to devote significant funds to reduce their emissions, two factors will invariably increase the stresses on their environment — increasing vehicular traffic and industrial growth.
Southern California, however, has taken successful action to modify its urban metabolism, pioneering efforts to reduce motor vehicle emissions. Kolb noted that Mexico City — unlike most megacities in less-developed countries — has also taken successful steps to partially address poor air quality. In the past two decades, the Mexican Government has introduced policies to improve air quality, including requiring pollution control devices like catalytic converters on newer vehicles, reducing sulfur levels in gasoline and diesel fuel and relocating some large industrial emitters outside the Valley of Mexico. Kolb says that megacities in Asia and Africa urgently need to modify their urban metabolism in similar ways. A few fundamental changes could pay off quickly.
"We need to start with low-hanging fruit," he said. "In some cities in Asia and Africa, they still have lead in their gasoline. In the developed world, we can institute emissions controls on diesel vehicles, which create hazardous fine particles, and we can also reduce pollution by using more rail-based mass transport or setting up specialized bus routes."
The urban metabolism model can reveal how developed-world megacities, such as Tokyo, New York and Los Angeles, have improved their air quality despite a rise in population. The study also assesses how developing-world megacities are seriously grappling with the problem.
The American Chemical Society is a nonprofit organization chartered by the U.S. Congress. With more than 154,000 members, ACS is the world's largest scientific society and a global leader in providing access to chemistry-related research through its multiple databases, peer-reviewed journals and scientific conferences. Its main offices are in Washington, D.C., and Columbus, Ohio.
Michael Bernstein | EurekAlert!
Further reports about: > ACS > CHEMISTRY > Megacity > air pollutant > catalytic converter > city populations > economic activities > fine particle pollutants > greenhouse gas > industrial growth > poor air quality in megacities > premature death > raw materials > transportation system > unhealthful levels of ozone > urban metabolism > vehicular traffic
Diagnoses: When Are Several Opinions Better Than One?
19.07.2016 | Max-Planck-Institut für Bildungsforschung
High in calories and low in nutrients when adolescents share pictures of food online
07.04.2016 | University of Gothenburg
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.
In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...
'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.
Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
24.10.2016 | Power and Electrical Engineering
24.10.2016 | Life Sciences
24.10.2016 | Life Sciences