New study finds that teens' blood pressure is affected by pollution

A study published in the journal PLOS ONE found that nitrogen dioxide pollution from vehicles correlates with lower blood pressure levels in teens. Photo courtesy of B137 via Wikimedia Commons.

By Shira Sadeh ’25

Global Editor

A study published on Feb. 8, 2023, in the journal PLOS One found that pollution affects teens’ blood pressure. While it was already known that pollution can affect people’s ability to breathe and can cause health problems such as cancer, this new study focuses on the effect of pollution on blood pressure, a CNN article about the new study reported. 

The study involved 3,200 teenagers, whose blood pressure data was compared to exposure rates based on annual pollution reports for the areas in which the teens lived, CNN said. While previous blood pressure studies have observed adults and many pollution studies have observed children, this study is unique due to its focus on teens.

According to a CNN summary of the study, lower blood pressure levels were associated with exposure to nitrogen dioxide, while higher blood pressure levels were correlated with exposure to particulate matter 2.5 — also known as particle pollution. Although the researchers did not look into the health effects of fluctuating blood pressure, low blood pressure is known to cause “confusion, tiredness, blurred vision and dizziness.” High blood pressure in youth can “lead to a lifetime of health problems including a higher risk of stroke or heart attack,” the article explained, adding that high blood pressure is “a leading risk factor for premature death worldwide.”

The Environmental Protection Agency website explains that nitrogen dioxide pollution is caused by burning fuel, and is often emitted by buses, cars, trucks and off-road equipment. The EPA states that exposure to nitrogen dioxide can irritate the respiratory system, causing breathing problems, and can cause asthma or respiratory infections. Additionally, when nitrogen dioxide interacts with water and other chemicals in the atmosphere, it can create acid rain that harms ecosystems and makes the air hazy. 

The EPA has created National Ambient Air Quality Standards that define the maximum concentrations of nitrogen dioxide permitted to be in the outside air. When an area does not meet this standard, the EPA works with regional authorities to lower nitrogen dioxide emissions.

Particulate matter is a type of pollution composed of a mixture of solid particles — such as smoke, dust, soot or dirt — and liquid droplets, the EPA website explained. PM 2.5 is a category of particulate matter made up of fine, inhalable particles with a diameter of 2.5 micrometers or smaller. In comparison, the EPA states that the average person’s hair has a diameter of approximately 70 micrometers, making the largest PM 2.5 particles 30 times smaller than the average human hair. 

PM is emitted from numerous different sources, the EPA says. Roads, construction sites, fields and fires are major sources, but many particles also form in the atmosphere as a result of chemical reactions, often after emission by automobiles and power plants. According to the EPA, the small size of the particles means that they are easily inhalable, and can pose a danger to humans if they get into the lungs or bloodstream. Studies have shown that PM 2.5 can cause “premature death in people with heart or lung disease, nonfatal heart attacks, irregular heartbeat, aggravated asthma, decreased lung function and increased respiratory symptoms, such as irritation of the airways, coughing or difficulty breathing,” the EPA said. PM 2.5 has also been linked to increased haziness in the air, increased acidity in rivers and lakes, changing nutrient balances in water and soil and affecting ecosystems. Similarly to nitrogen dioxide pollution, the EPA regulates PM emissions, but these regulations exclude particles with a diameter greater than ten micrometers.

According to the study, female participants reacted to PM 2.5 pollution more dramatically than male participants, while participants of both sexes had similar reactions to nitrogen dioxide pollution. The researchers also found that there were marginally higher exposures to both pollutants in Black Caribbeans, Black Africans and Pakistani/Bangladeshis compared to white participants. The researchers recommend further study into the different reactions caused by the two pollutants and how they affect participants differently based on their socioeconomic backgrounds. “Understanding the social and biological mechanisms linking air pollution exposure to BP [blood pressure] over the life course is [a] major research and clinical gap,” the study concluded.