A study has found long-term exposure to airborne PM2.5 particles in increasing the blood pressure of teenagers in the UK.
Researchers also found a link between high levels of nitrogen dioxide exposure and lower blood pressure in teenagers. The study examined the possible effects of long-term exposure to air pollution in children and teenagers across 51 schools in London.
“This longitudinal study provides a unique opportunity to track exposures of adolescents living in deprived neighbourhoods. Given that more than one million under 18s live in neighbourhoods where air pollution is higher than the recommended health standards, 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,” said senior author, Professor Seeromanie Harding, from King’s College London.
PM2.5 can cause life-long damage
Pollutant air particles are inhaled into the body and can enter the bloodstream, causing damage to blood vessels and airways. The effects of air pollution on adult blood pressure have been well-researched; however, there have been few longitudinal studies on the effects of air pollution on adolescents.
Between the ages of 11-16 years, the body is particularly vulnerable to internal damage as adolescents grow and develop. Damage to their organs at this stage could lead to life-long complications.
The researchers analysed data of 3,284 adolescents and measured each participant’s systolic and diastolic blood pressure.
Results showed that tiny pollutants in the air, known as PM2.5, were associated with higher blood pressure across all ages, and were especially damaging to girls. PM2.5 is frequently emitted from car exhaust fumes, building and industry materials. Higher blood pressure caused by PM2.5 can raise the risk of hypertension, heart attacks and strokes in adulthood.
Some pollutants can lower blood pressure
The researchers were surprised to find that nitrogen dioxide (NO2), a pollutant which is prominent in London due to diesel traffic, was associated with lower blood pressure. Systolic blood pressure decreased by ~5 mmHg for boys and ~8 mmHg for girls when rates NO2 doubled in concentration.
Previous research has shown that NO2 can damage the respiratory system, but it’s impact on the cardiovascular system is unclear. However, a recent study from the same team found that sitting next to a lit gas cooker, which emits NO2, can actually lower blood pressure in healthy adults. This is due to a rapid increase in the circulation of NO2 in the bloodstream.
“The effect of NO2 on blood pressure is similar to what we and other researchers have observed previously after ingesting green leafy vegetables or beetroot juice. These are rich in dietary nitrate (NO3–) which increases circulating nitrite (NO2–) concentration in the blood and lowers blood pressure, an effect which may also be sustained over weeks or months with continued ingestion of nitrate-rich vegetables,” said Dr Andrew Webb from King’s College London.
“As NO2 also increases circulating nitrite (NO2–) concentration, this provides a potential explanation as to why elevated NO2 appears to be associated with lower blood pressure in the adolescents over years,” he added.
The study also revealed that ethnic minority groups were exposed to higher average concentrations of pollution at home than non-minority groups. However, the impact of pollutants on blood pressure did not vary according to ethnicity, BMI, or economic status.
In 2021, a study found that 3.1m children in England were exposed to levels of PM2.5 that exceeded limits set by the World Health Organization (WHO). In addition to this, 98% of schools in London are located in areas exceeding WHO’s pollution limits.
“The findings highlight the potential detrimental role of exposure to higher concentrations of particulate matter on adolescents’ blood pressure levels,” said corresponding author. Dr Alexis Karamanos.
“Further studies following the same adolescents over time in different socio-economic contexts are needed to understand whether and how exposure to higher pollutant concentrations may affect differently the cardiovascular health of children and adolescents,” he concluded.