Living near busy roads may increase risk of high blood pressure in children

By Mark Waghorn via SWNS

Living near a busy road increases the risk of high blood pressure in children, according to new research on kids in London, UK.

The life-threatening condition - dubbed the 'silent killer' as there are no symptoms - normally affects older people.

But a study found adolescents exposed to high levels of traffic fumes are also prone.

The phenomenon was most prevalent in girls and has alarming implications for public health.

Exposure to air pollutants is linked to a greater risk of cardio-respiratory disease, hospital visits and death.

Corresponding author Dr. Alexis Karamanos 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.”

Rapidly growing bodies may be particularly susceptible to long-lasting effects on hypertension - the medical term for high blood pressure.

It can lead to blocked arteries - triggering a heart attack or stroke. Most prior studies on air pollution and blood pressure have focused on adults.

The shock findings are based on 3,284 participants in DASH (Determinants of Adolescent Social Well-Being and Health) - a study tracking the well-being of ethnically diverse London schoolchildren over time.

The team from King's College London looked at annual average levels of nitrogen dioxide (NO2) and PM2.5s where the eleven to 16-year-olds lived. They underwent regular blood pressure tests at school.

The toxic particles come from the burning of fossil fuels to power vehicles and factories.

Co-author Prof Seeromanie Harding, of King's College London, said: "This longitudinal study provides a unique opportunity to track exposures of adolescents living in deprived neighborhoods.

"Given that more than one million under 18s live in neighborhoods 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."

Greater exposure to PM2.5s was associated with higher systolic blood pressure - the top number which is the pressure in the arteries when the heart beats.

For example, one microgram per cubic meter (μg/m3) increase was linked to a 1.34 and 0.57 millimeter of mercury (mmHg) increase for girls and 0.57 mmHg and boys, respectively.

Interestingly nitrogen dioxide (NO2) a pollutant which in London is predominately due to diesel traffic - was associated with lower blood pressure.

A 1 μg/m3 increase was associated with a 0.30 and 0.19 mmHg decrease in systolic blood pressure for girls and boys respectively.

Co-author Dr. Andrew Webb 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 which increases circulating nitrite 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 concentration, this provides a potential explanation as to why elevated NO2 appears to be associated with lower blood pressure in the adolescents over years."

Air pollution particles are inhaled into the body and can get into the bloodstream, causing damage to blood vessels and airways.

While the effect on adult blood pressure is well known, few longitudinal studies have examined adolescents.

Negative effects on their organs at this stage could lead to life-long complications.

Results show PM2.5s, tiny pollutants in the air that come from car exhaust fumes, building and industry materials, were associated with higher blood pressure across all ages - and were particularly felt among girls.

It can raise the risk of hypertension, heart attacks and strokes in adulthood.

The researchers also found adolescents from ethnic minority groups were exposed to higher annual average concentrations of pollution at home than their white peers.

But the impact of pollutants on blood pressure did not vary according to ethnicity, BMI (body mass index) or economic status.

A study in 2021 found that 3.1m children across England go to schools in areas exceeding WHO (World Health Organization) limits on PM2.5 and 98 percent of schools in London are in areas exceeding these.

Previous research has shown NO2 may have damaging effects on the respiratory system, but the impacts of the pollutant on the cardiovascular system are less clear.

A recent study by the same team found sitting next to a lit gas cooker - which emits NO2 - acutely lowers blood pressure in healthy adult volunteers by around 5 mmHg.

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

The associations between pollutants and blood pressure were consistent regardless of ethnicity, body size, or socioeconomic status.

Eighty percent of the adolescents studied were from ethnic minority groups, and the residential estimates suggest that these adolescents were exposed to higher levels of pollutants than their white peers.

The researchers called for further studies to help confirm and clarify these findings, particularly among young people from different socioeconomic backgrounds.

They also note that levels of nitrogen dioxide and PM2.5 in London remain well above World Health Organization Guidelines, suggesting opportunities to reduce pollution and improve lifelong health for adolescents in the city.

The study is published in the journal PLOS ONE.