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Smog. To effectively fight air pollution, we should know their composition

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Understanding the chemical composition of smog can make it easier to fight air pollution. American scientists analyzed data from 2006-2020 on PM2.5 suspended dust and found that their concentration had decreased and the composition of pollutants had also changed locally. Understanding these relationships may influence the creation of regional air quality improvement strategies.

PM2.5 suspended dust is not homogeneous – it is a mixture of many chemical compounds with a diameter of less than 2.5 microns that can penetrate deep into the human body. Pollutants may include sulfates, ammonium, nitrates, organic carbon compounds and other trace elements. Particulate matter has been linked to many adverse effects on human health, including premature death. According to research published in “Atmospheric Environment”, knowledge of the composition smog can be a valuable asset in the fight for better air quality.

Local results

Using data from the U.S. Air Quality System of the federal Environmental Protection Agency (EPA), a research team from the University of North Carolina at Chapel Hill analyzed air quality improvements and changes in pollutant composition in 48 states. The research covered the period from 2006 to 2020 – during this time, numerous ordinances to combat smog were introduced in the United States.

The greatest improvements were seen in areas with the worst baseline air quality, including the Ohio Valley and Southeast. At the beginning of the period under study, these regions were among the main emitters of sulfur dioxide, the release of which into the atmosphere is related to the level of sulfates. Thanks to regulations on emission sources, emissions of this compound by power plants have decreased by 91.5 percent over the years, and the industrial and transport sectors have also recorded significant reductions.

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The researchers also noticed one relationship – during the period under study, the emission of specific pollutants, for example sulphates, was mainly reduced, but other pollutants still remained at a high level. Results also varied by region.

– Different chemical components of PM2.5 are associated with different emission sources, therefore the development of an emission control strategy should take into account the analysis of changes in the chemical composition of PM2.5 – explained Bin Cheng, the main author of the analysis.

In the face of change

Although sulfate and ammonium levels have dropped, scientists noted that the next important step will be to look at reducing carbon emissions – its percentage of PM2.5 measurements is rising. There are fewer and fewer days of high pollution in the United States, but during the winter months these compounds often become trapped in the atmosphere – low temperatures prevent them from escaping.

Scientists emphasized that such regional differences show how important a local, targeted approach to combating air pollution is. Creating anti-smog strategies based on the characteristics of a given region may be more effective than federal recommendations alone. As co-author of the analysis Saravanan Arunachalam added, the study results were published at an important moment – in February, the EPA announced a reduction of the annual standard for PM2.5 from 12 µg/m3 to 9 µg/m3.

– States with old monitoring stations operating under old standards will seek to understand the chemical composition of PM2.5 and how it has changed over time. This will be of key importance for developing an emission reduction policy, the researcher explained.

UNC Chapel Hill, New York Times

Main photo source: Shutterstock

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