More than half of the world’s population would be exposed to particulate matter concentrations that exceed the new WHO air quality guidelines

MIT Technology Review Italy

Along with climate change, air pollution is one of the greatest environmental threats to human health. The tiny particles known as particulate matter or PM2.5 (named for their diameter of just 2.5 micrometers or less) are a particularly dangerous type of pollutant and are produced from a variety of sources, including fires and burning fossil fuels.

In response to their danger to human health, the World Health Organization recently updated its annual guidelines on air qualitylowering the PM2.5 exposure threshold by 50 per cent, from 10 micrograms per cubic meter to 5, in an attempt to help reduce anthropogenic emissions.

Published in Environmental Science and Technology Letters, a new study by researchers from MIT’s Department of Civil and Environmental Engineering wondered how realistic the WHO guidelines were. According to the research authors, Professors Colette Heald and Jesse Kroll, many areas are unable to achieve this due to the high contribution from natural sources of particulate matter, i.e. dust, sea salt and organic matter from vegetation.

According to the data available to them, over 90 percent of the world’s population is currently exposed to annual mean concentrations above recommended guidelines and more than 50 percent of the world’s population would still be exposed to higher concentrations of PM2.5, even in the absence of all anthropogenic emissions.

Using 2019 as the baseline year, the researchers conducted a series of model simulations that referred to different anthropogenic sources that could be turned on and off to study the single contribution. For example, they have shown that high concentrations of PM2.5 in the Amazon consist mainly of carbon-containing aerosols from sources such as deforestation fires while in Northern Europe nitrogen-containing aerosols are prevalent due to the general presence of vehicles and use of fertilizers. The two regions would therefore require very different policies and methods to improve air quality.

The study of the characteristics of the toxicity properties of different particles on human health indicates the need for a new generation of air quality parameters that pave the way for targeted decision-making. “Routine and global measurements of the chemical composition of PM2.5”, concludes Jesse Kroll, “would provide policy makers with information on which interventions can most effectively improve air quality in a given location.”

Image: Pixabay


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