The study conducted by researchers from the University of Toronto is the first of its kind, looking at the grime covering buildings, statues and outdoor surfaces in cities as a potential source of the toxic pollution.
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According to Dr. Donaldson, urban grime can be defined as a compound of thousands of chemical elements that are scattered in the air by factories, traffic and other sources.
Scientists used to think that once nitrous oxides get caked and locked onto surfaces as grime, they no longer contribute to air pollution.
APTo test this further, Donaldson collaborated with researchers in Germany and set up a 6-week field study in Leipzig.
When these nitrogen oxides react with other compounds in the atmosphere, they transform into volatile organic compounds which are produced in the ozone and ground level producing the major ingredient of smog.
Grime-covered buildings in cities are not only aesthetically unpleasant, but can also inflict significant damage on the environment, according to the findings of a new study presented Monday at a conference of the American Chemical Society in Boston. “If our suspicions are correct, it means that the current understanding of urban air pollution is missing a big chunk of information”.
After analyzing the situation in a real-world environment through field studies, researchers concluded that this phenomenon is very much happening.
Research released by the American Lung Association last year found that nearly half Americans live in areas where air pollution levels are often dangerously high.
To test that hypothesis, Donaldson and his colleagues put out grime collectors containing small glass beads-the same sort of glass as windows-the cities. In lab based studies, Donaldson and his team had found that nitrate anions disappeared from grime at faster rates than could be explained by wash-off due to rainfall. Among these compounds is nitrogen oxides, which when exposed to light split the molecules into nitric oxide and an oxygen atom.
This was not it! in yet another study, they exposed grime to either artificial sunlight or kept it in the dark. Results showed that more nitrates escaped from the exposed grime, suggesting that light has the chemical ability of reactivating nitrogen compounds, which then return in the air.
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“In our work, we are showing that there is the potential for significant recycling of nitrogen oxides into the atmosphere from grime, which could give rise to greater ozone creation”, Donaldson said in the statement. This difference could have a significant influence on the city’s air quality. But in Leipzig, the researchers found that grime in shaded areas contained 10 percent more nitrates than grime exposed to natural sunlight, which was consistent with the team’s laboratory findings. The latter showed 20 times the amount of grime, suggesting locals might be breathing in larger amounts of ozone, which can cause chest pain and wheezing and aggravate bronchitis and emphysema.
