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Global Daily Air Pollution Study Says Only 0.001% Of People On Earth Live Below WHO-safe Levels

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99.999% of people on Earth live in areas with air quality below WHO safety standards, according to a new study.

Just 0.18 percent of the world’s geographical area and 0.001 percent of the world’s population are exposed to levels of PM2.5 below thresholds of safety recommended by the World Health Organization (WHO), according to a study conducted by researchers at Monash University.

In the last two decades up to 2019, daily levels of air pollution have decreased in Europe and North America. However, in Southern Asia, Australia, New Zealand, Latin America, and the Caribbean, pollution levels have increased. Alarmingly, more than 70 percent of days worldwide have recorded pollution levels exceeding safe limits.

The inadequate availability of pollution monitoring stations worldwide has resulted in insufficient data on local, national, regional, and global exposure to PM2.5 pollution.

Now, thanks to research led by Professor Yuming Guo of Melbourne, Australia’s Monash University School of Public Health and Preventive Medicine and published in the peer-reviewed journal Lancet Planetary Health, we have a global picture of how PM2.5 has evolved over the past few decades in every region of the world.

In order to more precisely estimate PM2.5 concentrations worldwide, the study team used conventional air quality monitoring data, satellite-based meteorological and air pollution detectors, and statistical, and machine learning approaches, according to Professor Guo.

The researcher stated that their study utilized an innovative machine learning approach to incorporate multiple meteorological and geological data to estimate daily surface-level PM2.5 concentrations globally with a high spatial resolution of about 10km × 10km for global grid cells from 2000-2019. The study focused on areas exceeding the safe limit of 15 μg/m³ according to WHO (although this threshold remains a subject of debate).

The findings of the study indicate that annual PM2.5 concentration and the number of high PM2.5 exposure days decreased in Europe and North America during the two decades analyzed. In contrast, Southern Asia, Australia, New Zealand, Latin America, and the Caribbean experienced increases in PM2.5 exposures.

The study also found the following:

  • Globally, high PM2.5 exposure days have somewhat decreased, but by 2019, more than 70 percent of days still had PM2.5 concentrations more than 15 μg/m³.
  • More than 90 percent of days in southern and eastern Asia had daily PM2.5 values more than 15 μg/m³.
  • 2019 saw a noticeable rise in the number of days with high PM2.5 concentrations in Australia and New Zealand.
  • From 2000 to 2019, the yearly average PM2.5 level globally was 32.8 μg/m³.
  • The locations with the greatest PM2.5 concentrations were Eastern Asia (50.0 μg/m³), Southern Asia (37.2 μg/m³), and Northern Africa (30.1 μg/m³).
  • The lowest annual PM2.5 values were found in Australia and New Zealand (8.5 μg/m³), other Oceanian countries (12.6 μg/m³), and southern America (15.6 μg/m³).
  • Based on the new WHO guideline limit for 2021, only 0.18 percent of the world’s land area and 0.001 percent of the world’s population were exposed to an annual average of 5 μg/m³ in 2019.

Northeast China and North India saw high PM2.5 concentrations during their winter months (December, January, and February), whereas eastern regions of northern America experienced high PM2.5 levels during their summer months (June, July, and August), according to Professor Guo.

“We also recorded relatively high PM2.5 air pollution in August and September in South America and from June to September in sub-Saharan Africa.”

According to him, this study holds significant importance as it offers a comprehensive understanding of the present condition of outdoor air pollution and its impacts on human health. This information can assist policymakers, public health officials, and researchers in evaluating both short-term and long-term health effects of air pollution and developing effective strategies to mitigate air pollution.

Image Credit: Indranil Aditya/NurPhoto via Getty Images

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