CNN
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Scientists know that air pollution can make it difficult to breathe and may ultimately cause serious health problems like cancer, but a new study shows that it might also have a negative impact on teens’ blood pressure.

Exposure to higher levels of nitrogen dioxide was associated with lower blood pressure in teens, according to the study, published Wednesday in the journal PLOS One. Exposure to particulate matter 2.5, also known as particle pollution, was associated with higher blood pressure.

The researchers say the impact is “considerable.”

Other studies have found a connection between blood pressure changes and pollution, but much of that work focuses on adults. Some research has also found negative associations with pollution exposure and younger children, but little has focused on teens.

Generally, low blood pressure can cause immediate problems like confusion, tiredness, blurred vision and dizziness. High blood pressure in adolescence can lead to a lifetime of health problems including a higher risk of stroke or heart attack. It’s a leading risk factor for premature death worldwide.

The study did not look at whether the teens had symptoms or health effects from the change in blood pressure.

The scientists saw this association between pollution and blood pressure in data from the Determinants of Adolescent Social Well-Being and Health study, which tracks the health of a large and ethnically diverse group of children in London over time.

The researchers took data from more than 3,200 teens and compared their records to their exposures to pollution based on annual pollution levels where they lived.

Nitrogen dioxide pollution is most commonly associated with traffic-related combustion byproducts. Nitrogen may help plants grow, but it can impair a person’s ability to breathe and may cause damage to the human respiratory tract. In this study, the nitrogen was thought to be coming predominantly from diesel traffic.

The particle pollution in the study is so tiny – 1/20th of a width of a human hair – that it can travel past the body’s usual defenses. Instead of being carried out when a person exhales, it can get stuck in the lungs or go into the bloodstream. The particles cause irritation and inflammation and may lead to a whole host of health problems.

Particle pollution can come from forest fires, wood stoves, power plants and coal fires. It can also come from traffic and construction sites.

In this study, the link between pollution exposure and changes in blood pressure was stronger in girls than in boys. The researchers can’t determine why there is a gender difference, but they found that 30% of the female participants got the least amount of exercise among the group and noted that that can have an effect on blood pressure.

“It is thus imperative that air pollution is improved in London to maximise the health benefits of physical exercise in young people,” the study says.

Although the study also can’t pinpoint why teens’ blood pressure changed with pollution exposure, others have found that exposure to air pollution may affect the central nervous system, causing inflammation and damage to the body’s cells. Additionally, exposure to particle pollution can disrupt a person’s circadian rhythms, which could affect blood pressure. Particle pollution exposure may also reduce the kidneys’ ability to excrete sodium during the day, leading to a higher nighttime blood pressure level, the study says.

When it came to nitrogen dioxide pollution, the researchers had previously done a crossover study that involved the blood pressure of 12 healthy teen participants who were exposed to nitrogen oxide from a domestic gas cooker with lit burners. Their blood pressure fell compared with participants exposed to only room air.

In the new study, the associations between pollution and blood pressure were consistent. Body size, socieoecomonic status and ethnicity didn’t change the results.

However, it looks only at teens in London, and only 8% of them were people of color. Those children were exposed to higher levels of pollution than White children, the study found.

Levels of pollution in London are also well above what World Health Organization guidelines suggest is safe for humans. However, the same could be said for most any area in the world. In 2019, 99% of the world’s population lived in places that did not meet WHO’s recommended air quality levels.

Earlier work has shown that pollution can damage a young person’s health and may put them at a higher risk for chronic diseases like heart problems later in life. Studies in adults found that exposure to air pollution can affect blood pressure even within hours of exposure.

Pollution caused 1 in 6 deaths worldwide in 2019 alone, another study found.

Some experts suggest that one way to reduce a teen’s risk of pollution-related health problems is to invest in portable air cleaners with HEPA filters that are highly effective at reducing indoor air pollution. However, the filters can’t remove all of the problem, and experts say communitywide solutions through public policy are what’s needed.

Dr. Panagis Galiatsatos, an assistant professor in pulmonary and critical care medicine at Johns Hopkins Medicine, said research like this is important to generate a hypothesis about what these pollutants are doing to people. Galiatsatos, a volunteer medical spokesperson with the American Lung Association, was not involved with the new study.

“A lot of these air pollutions tend to cluster in economically disadvantaged neighborhoods, so it’s one of the big reasons we want to always keep a close eye on this, as it disproportionately impacts certain populations more than others,” he said.

Blood pressure is an important marker to track for health because it is a surrogate to understand the more complex processes that might be happening in the body.

“My big takeaway is that these toxins clearly seem to have some physiological impact on the cardiovascular system, and any manipulation should be taken into the context of a concern,” Galiatsatos said.

Study co-author Dr. Seeromanie Harding, a professor of social epidemiology at King’s College London, said she hopes it will lead to more research on the topic.

“Given that more than 1 million under 18s live in [London] neighborhoods where air pollution is higher than the recommended health standards,” she said in a news release, “there is an urgent need for more of these studies to gain an in-depth understanding of the threats and opportunities to young people’s development.”