ong-term exposure to polluted air has been linked to higher blood pressure in London teenagers, according to a new study.

Researchers from Kings College London (KCL) found that exposure to PM2.5 was associated with an increase in blood pressure in children aged 11 to 16. The pollutant is contained in exhaust fumes, building and industry materials.

Air pollution particles are inhaled into the body and can get into the bloodstream, causing damage to blood vessels and airways. Damage to organs when children are aged between 11 to 16 could lead to lifelong complications, clinicians have warned.

More than a million under 18s in the UK live in neighbourhoods where air pollution is higher than the recommended health standards.

The paper examined the possible effects of long-term exposure to air pollution in children attending 51 schools across the capital.

Researchers analysed data from 3,284 adolescents and followed up from ages 11-13 and 14-16 years old. They measured systolic and diastolic blood pressure at participants in schools.

The results showed that exposure to PM2.5 was associated with higher blood pressure across all ages, with particular increases seen in girls.

For girls, a μg/m3 increase in PM2.5 was associated with a 1.34 mmHg increase in systolic blood pressure – while boys saw a 0.57 mmHg rise.

Higher blood pressure can raise the risk of hypertension, heart attacks and strokes in adulthood.

Researchers also found adolescents from ethnic minority groups were exposed to higher annual average concentrations of pollution at home than white participants, but the impact of pollutants on blood pressure did not vary according to ethnicity, BMI, or economic status.

Corresponding author Dr Alexis Karamanos, from King’s College London, said: “The findings highlight the potential detrimental role of exposure to higher concentrations of particulate matter on adolescents' blood pressure levels.

"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.”

Mayor of London Sadiq Khan has made reducing air pollution one of his key policy priorities and will expand the ultra low emission zone to all 32 of the capital’s boroughs from August this year.

Last year, the Standard backed “Ella’s Law”, a bill that will enshrine the human right to clean air in law. It is named after Ella Adoo-Kissi-Debrah, the first person in the UK to have air pollution listed as a cause of death

The KCL study also found that exposure to nitrogen dioxide (NO2), a separate pollutant which in London is linked to diesel traffic, was associated with lower blood pressure.

It follows a recent study which found that sitting next to a lit gas cooker – which emits NO2 – acutely lowered blood pressure in healthy adult volunteers by around 5 mmHg.

That effect was explained by a rapid increase in circulating nitrite (NO2) concentration in the blood.

Co-author Dr Andrew Webb from King’s College London said: “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.

“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.”

The paper was published on Monday in the PLOS One journal.

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