When to wear a
There is a growing consensus that pollution is a global problem, especially since China declared a war on pollution. This has resulted in more transparent reporting, as well as increased availability of data from sources all over the world. However, neither has resulted in improved understanding of pollution for people living in polluted areas such as China, India, as well as large cities around the world. This is mainly because there are different ways to measure pollution, as well as different ways to interpret it. This article aims to give clarity to the subject.
First things first, what determines the Air Quality Index (AQI) level? The answer is simple: outdoor pollutants, specifically 6 that are monitored. However, the one pollutant that can really hike up the danger level to humans is called fine particulate matter, or PM2.5. This pollutant is not easily digestible in the human body and can penetrate deep into our bloodstream. When this level gets too high it is recommended that individuals should wear a mask.
Now, on to the not so simple answer, at what AQI score should an individual wear a mask? This can depend on a few different things, and to make it even more complicated, these scores also vary from country to country. However, The World Health Organization has found that the safest dosage of PM2.5 in a 24-hour time period is approximately 25 ug/m3. This is an AQI score of roughly 30 according to Chinese standards. Any more exposure than this in a 24-hour period can lead to serious lung or respiratory issues, and even cancer.
According to the Chinese government, wearing a mask is recommend when the AQI score exceeds 200, or a PM2.5 concentration of 150 ug/m3. This scale is allowing 6 times more PM2.5 ug/m3 exposure in a 24-hour period than is recommended for healthy standards set by the World Health Organization.
For example, the average AQI in 2014 in Beijing was a 109. This is a PM2.5 concentration level of approximately 80 ug/m3, which is described as “Lightly Polluted”. Meanwhile, according to the stricter U.S. scale, an AQI score of 109 is an approximate PM2.5 concentration of 37 ug/m3 and is described as “Unhealthy for Sensitive Groups”.
Basically, The World Health Organization, the United States government, and the Chinese government each have different AQI scales that differ greatly on the amount of pollution allowed in a 24-hour period before deeming it hazardous to human health. The World Health Organization says a PM2.5 exposure of 25 ug/m3 is the safest, the U.S. EPA says 35 ug/m3, and China says 75 ug/m3. So, which scale should you follow and when should you wear a mask?
The best approach would be to follow the World Health Organization’s strict standards. Their research has found that long-term exposure to PM2.5, even in low concentration levels can lead to serious and fatal conditions. This means wearing a mask before the AQI score (based on Chinese standards) exceeds 50. Sadly, for many cities in China, this means citizens should be wearing a mask anytime they are outdoors. If these standards are too strict, the U.S. scale is a bit more flexible, recommending a mask when the AQI reaches a score of 101. Either way, stay healthy and wear a mask much sooner than the currently recommended AQI score of 200.
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You may also enjoy reading our blog on indoor air quality and ways to improve it!