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Our Invisible Enemy: Particulate Matter

Author: Grace Enjia Xu

Editors: Junyu Zheng and Kevy Chen

Artist: Grace Enjia Xu 

Air is one of the fundamental needs and resources humanity shares to survive. Yet, when people see warnings and posters about smog and haze, most people will ignore these warnings because they assume air pollution only exists when they can see it - a seemingly reasonable but dangerous oversight. 

Although the most pervasive air pollution, smog, reduces the visibility of what we see in the distance, the air consists of a dangerous pollutant called particulate matter. These particles are invisible to the naked eye and are capable of entering your body, which can be harmful. Through every breath you take, no matter where you are, these particles will move through your bloodstream. Particulate matter comes in varying sizes, from up to 90 micrometers in diameter, equivalent to a piece of fine beach sand, to 2.5 or less micrometers in diameter, thirty times smaller than a single string of hair and only visible under an electron microscope. Prolonged exposure to PM 10 (particulate matter 10 micrometers in diameter) can induce severe asthma attacks and can also lead to several lung diseases like chronic bronchitis and lung cancer in the future. Even finer particulate particles, like PM 2.5 or smaller, can pose significant health risks when they enter the alveolus in the lungs, causing fatal myocardial injuries, damage to the cells in the heart, or reducing lifespan. It is through unclean air that solid particles and liquid droplets of particulate matter can enter your body and lead to health complications, even if you can’t see them.

So, where exactly do these particulate matters come from? In 2015, famous reporter Chai Jing answered this question in her documentary “Under the Dome.” When giving birth to her daughter, Chai Jing’s daughter was diagnosed with a benign tumor in the womb. As a mother, she was concerned, which led her to investigate how air pollution affected her daughter’s health. Through her research, she learned that particulate matter pollution never originated from one source but from multiple sources. Much of the pollution comes from the combustion of fossil fuels, carbon emissions from diesel cars and traffic, construction sites, burning of unclean coal (lignite), etc., all contributing to the formation of particulate matter in the atmosphere. To make matters worse, when particulate matter is emitted into the air, it also reacts with other primary pollutants, such as nitrogen oxide, to create even more particulate matter. They contain several carcinogens, like benzopyrene, that have caused an increase in lung cancer regardless of smoking status. For example, the documentary showed the surgery of an early-stage lung cancer patient at Beijing Cancer Hospital. This patient was not a smoker but was still affected by the exposure to particulate matter that accumulated in her lungs, causing her immune system to weaken. Her case is only one of the many documented cases worldwide that are caused by poor air quality. 

With the rise of industrialization, exposure to dangerous particulate matter is ubiquitous, but it doesn’t have to be that way. Many countries and governments have taken action to mitigate and prevent more deaths caused by pollution by enforcing policies and limits on the emission of particulate matter. In California, air resource boards have enforced regulations for installing diesel particulate filters on diesel trucks to help mitigate PM2.5 emissions from trucks. Meanwhile, Germany has taken action to create clean and renewable sources for power plants and generators. While these changes may make us feel comfortable, let it be known that individual contribution still matters if we want to resolve this issue permanently. Despite the current situation, efforts from governments and citizens alike can go a long way in reducing particulate matter and improving our quality of life.



Edwards, Rob. “Clean-Coal Debut in Germany.” MIT Technology Review, MIT Technology

“Particulate Matter (PM) Basics.” EPA, Environmental Protection Agency, 11 July 2023,

“National Ambient Air Quality Standards (NAAQS) for PM.” EPA, Environmental

Protection Agency, 15 Feb. 2024,

Chai, Jing. “Under the Dome (English Subtitle,Complete) by Chai Jing: Air Pollution in

China.” YouTube, Jiahua Guo, 9 Mar. 2015,

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