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Long-term exposure to particulate matter (PM) 2.5 is associated with higher blood pressure in adolescents, a new study that analysed the data of 3,284 adolescents aged 11-16 in London found.
The association was stronger in girls, the findings showed. The research was published February 8, 2023 in PLOS One journal by researchers from the Faculty of Life Sciences & Medicine, King’s College London.
PM2.5, tiny pollutants in the air that car exhaust fumes and building and industry materials contain, were associated with higher blood pressure across all ages in people studies, the report noted. “Every microgram per cubic metre increase in PM2.5 was associated with 1.34 millimetre of mercury increase in systolic blood pressure for girls and 0.57 mmHg increase in systolic BP for boys.”
Higher blood pressure can raise the risk of hypertension, heart attacks and strokes in adulthood, the authors of the study highlighted.
The period between 11-16 years of age is specifically of importance since adolescents continue to grow and develop, the scientists wrote. “Negative effects on their organs at this stage could lead to life-long complications.”
The study researchers also found that adolescents from ethnic minority groups were exposed to higher annual average concentrations of pollution at home against their white UK peers. “However, impact of pollutants on blood pressure did not vary according to ethnicity, BMI or economic status.”
The researchers measured the systolic and diastolic blood pressure of adolescents from 51 participant schools across the United Kingdom Capital.
A 2021 study had found that 3.1 million children across England go to schools in areas exceeding World Health Organization (WHO) limits on PM2.5 and 98 per cent of schools in London are in areas exceeding WHO pollution limits.
More than 1 million people under the age of 18 live in neighbourhoods where air pollution is higher than the recommended health standards, noted the study’s senior author Seeromanie Harding, head of department of population health sciences, King’s College London.
“This longitudinal study provides a unique opportunity to track exposures of adolescents living in deprived neighbourhoods,” she added.
Exposure to high levels of nitrogen dioxide, however, was associated with lower blood pressure in this group, according to the report. “Interestingly, nitrogen dioxide (NO2), a pollutant which in London is predominately due to diesel traffic, was associated with lower blood pressure.”
Systolic BP decreased by ~around 5 mmHg for boys and 8 mmHg for girls when NO2 almost doubled from a low to a high concentration, the study showed.
“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,” said report co-author Dr Andrew Webb, clinical senior lecturer in the School of Cardiovascular Medicine & Sciences.
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, he added.
“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 adolescents over the years,” he explained.