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Ninety-nine percent of the global population — practically everyone in the entire world — is exposed to harmful air pollutants known as PM 2.5, according to a massive study recently published in the journal The Lancet Planetary Health.

Conversely, it found that only 0.001 percent of the global population live in areas with levels of PM 2.5 below the safe threshold recommended by the World Health Organization (WHO), which accounts for less than 0.18 percent of available land on the planet.

"Almost no one is safe from air pollution," study lead author Yuming Guo, a professor at the Monash University School of Public Health and Preventive Medicine, told The Washington Post. "The surprising result is that almost all parts of the world have annual average PM 2.5 concentrations higher than air quality guidelines recommended by the World Health Organization."

PM 2.5 is a fine air particulate that's no more than 2.5 microns in width — over thirty times smaller than a grain of sand — allowing it to easily invade our lungs and bloodstream. Lung cancer is an obvious fear, but PM 2.5's potential to cause and exacerbate heart disease should not be overlooked, either.

According to research by the US Environmental Protection Agency (EPA), exposure to PM 2.5 as brief as a few hours can be enough to trigger "cardiovascular disease-related heart attacks and death." Long-term exposure can lead to an "increased risk of cardiovascular mortality and decreases in life expectancy."

In 2021, the WHO revised its air quality guidelines, bringing the PM 2.5 threshold down from ten micrograms per cubic meter to just five, in response to new understandings of how air pollution affected the human body. The next year, the UN agency conducted similar research to Guo's and also found that 99 percent of the global population is exposed to high PM 2.5 levels, exceeding its guidelines.

Unlike the WHO's study, however, Guo's is the first to provide insights on the daily levels of the pernicious particulate worldwide. His team accomplished this by combining ground data from countries across the globe, satellite-based meteorological data, as well as "an innovative machine learning approach" to integrate all of the above, Guo explained in a press release.

He and his team found that while daily levels have dropped in North America and Europe over the past two decades, it continues to climb in other regions, including Southern Asia, Latin America, and Australia.

The researchers also found that the global average level of PM 2.5 was extremely high between 2000 and 2019 at 32.8 micrograms per cubic meter, over six times the recommended threshold.

Such an alarmingly pervasive presence echoes the ominous death tolls found in other studies, such as a 2022 study published in The Lancet that determined air pollution was responsible for nine million premature deaths in 2015.

In spite of these deaths, many environmental bodies around the world, including the EPA, maintain PM 2.5 thresholds that still exceed the WHO's.

Guo hopes that armed with the information learned in his study, "policymakers, public health officials, and researchers can better assess the short-term and long-term health effects of air pollution and develop air pollution mitigation strategies," he said in the release.

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