Air Pollution Dangerously High in Hundreds of World Cities

air pollutionDirty air is a fact of life for most city dwellers around the world. Research on the true scale of urban air pollution problem is still necessary for policy reasons. A study by the World Health Organization (WHO), released on Thursday, shows that air pollution levels are dangerously high in hundreds of world cities.

The WHO collected PM2.5 particulate data from 1600 cities in 91 countries. PM2.5 is the diameter in microns of particulates of ammonia, carbon, nitrates, and sulfate that are small enough to pass into the bloodstream through the lungs and cause diseases, including cancer and emphysema.

The news isn’t good for people living in the 1600 cities that submitted data. Only 12 percent of the people living in those cities are breathing air that meets WHO guidelines. About 50 percent of the people are exposed to air pollution at least 2.5 times higher than what the WHO considers safe. Those people are at increased risk of long-term health problems because of that air pollution.

The survey found that air quality in most cities that monitor their air pollution is higher than the WHO considers safe. The WHO collected data on particulate matter, known as PM2.5 from the size of the particles. PM2.5 is considered the most dangerous to human health.

Half of the 20 dirtiest cities are India. Delhi, India came out the worst in the survey, with the highest level of particulate pollution with 153 micrograms per cubic meter of air. Patna, India was in second place with 149 micrograms. Both figures are approximately six times the 25 micrograms that the WHO considers a “safe” level of PM2.5 exposure.

India’s Center for Science and Environment, a public interest organization, cites weak enforcement of pollution control laws as one reason for Delhi’s air pollution.

Twenty-four of the 32 cleanest cities, with a PM2.5 reading of five or less, were in Canada, including Vancouver. Seven of the cleanest cities were in the United States. Hafnarfjordur, Iceland also made the list. Still, air pollution is dangerously high in hundreds of world cities, including cities in China.

No Chinese cities were in the top 20 list, in spite of the famous pollution issues in cities like Beijing. Beijing’s city government started publishing hourly PM2.5 numbers in January 2012. Beijing’s government reported a PM2.5 concentration of 89.5 micrograms in 2013, which is 156 percent higher than China’s standard. That reading would put Beijing in 17th place in the WHO report.

Maria Neira, Director for Public Health, Environmental and Social Determinants of Health at the WHO said that the study was meant as a “challenge” to cities. She thought the results would help cities become more open about air pollution, which comes from a combination of traffic, coal-burning power plants and heavy industries. Burning wood, dung, and charcoal for heat and cooking also contributes to urban air pollution in the world’s cities.

She did not think China might be cheating, saying that Chinese authorities were becoming better at collecting air pollution data.

This new WHO studies points to major air quality issues for most of the world’s city dwellers. The lack of data on China’s huge cities does not undermine the conclusion that particulate air pollution is dangerously high in hundreds of world cities

By Chester Davis

World Health Organization




2 Responses to "Air Pollution Dangerously High in Hundreds of World Cities"

  1. hjjhg   June 3, 2015 at 1:07 am

    Air Pollution Is Killing Millions
    India air pollution ‘cutting crop yields by almost half’
    Agriculture hit by both urban and rural pollution as wheat and rice yield decrease significantly, study finds

    Air pollution in India has become so severe that yields of crops are being cut by almost half, scientists have found.
    Researchers analysed yields for wheat and rice alongside pollution data, and concluded significant decreases in yield could be attributed to two air pollutants, black carbon and ground level ozone. The finding has implications for global food security as India is a major rice exporter.
    Black carbon is mostly caused by rural cookstoves, and ozone forms as a result of motor vehicle exhaust, industrial emissions, and chemical solvents reacting in the atmosphere in the presence of sunlight. Both are “short-lived climate pollutants” that exist locally in the atmosphere for weeks to months, with ozone damaging plants’ leaves and black carbon reducing the amount of sunlight they receive.
    The study looked at both the effects of climate change and the two pollutants on crop yields.
    “While temperature’s gone up in the last three decades, the levels of smog and pollution have changed much more dramatically,” says Jennifer Burney, an environmental scientist at University of California, San Diego, and co-author of the paper, published in the journal PNAS. “But this was the first time anyone looked at historical data to show that these pollutants are having tremendous impacts on crops.”
    Comparing crop yields in 2010 to what they would be expected to be if temperature, rainfall and pollution remained at their 1980 levels, the researchers showed that crop yields for wheat were on average 36%lower than they otherwise would have been, while rice production decreased by up to 20%. In some higher population states, wheat yields were as much as 50% lower.
    Using modelling to account for the effects of temperature increase and precipitation changes in that time, they were able to show that 90% of this loss is attributable to the impact of the two pollutants.
    The results are specific to India’s seasonal patterns, the crops, and its high pollution levels, but may extend to other places with similar problems, such as China. Chinese scientists warned in February that severe air pollution is slowing photosynthesis in plants, with effects “somewhat similar to a nuclear winter”.
    Previous studies had used experimental data looking at the impacts of ozone on plants to extrapolate potential losses, but this is the first ever study to use actual historical agricultural and emissions data to account for lower crop yields.
    “Overall I think it’s a great paper,” says Stanford agricultural ecologist David Lobell. “I think in both India and China there is growing recognition of the toll that poor air quality has on agriculture. This study will certainly add to that recognition.”
    Lobell and Burney both point out that because black carbon and ozone are short-lived pollutants, they present a clear opportunity for tackling climate change. While long-lived greenhouse gases like carbon dioxide and nitrous oxide can persist in the atmosphere for decades to centuries, addressing sources of the short-lived pollutants will have more immediately perceptible effects.
    Measures such as improved cookstove technology for rural areas, or cleaner coal consumption and diesel filters on trucks in urban ones, could go a long way to improving the impacts on agricultural yields.
    “Our thought is that these are more politically tractable points of entry for making meaningful change in climate,” says Burney. “There’s a really local benefit for taking on some sort of costly action.”
    Burney also points out that because of India’s key role in exporting rice, such efforts could play a critical role in helping global food security.

  2. Fia   May 8, 2014 at 3:11 pm

    Children in Delhi have lungs of chain-smokers!

    Thought Beijing air was bad? Delhi’s no better

    And the deadly soot also melts the Himalayan glaciers and effects climate change, weather systems and agriculture

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