Blood pressure in teens linked to air pollution

Air pollution is known to be a major public health issue, and is associated with cardio-respiratory disease incidence, hospitalizations and deaths. However, most of the previous studies have focused on adults. It is possible that adolescents, with their rapid growth rates, may be even more susceptible to the long-term effects of air pollution, but few studies involving teens have been conducted. 

In a new study led by King’s College London, researchers have investigated the associations between the blood pressure of 3,284 adolescents living in London, and the levels of nitrogen dioxide (NO₂) and particulate matter (PM_2.5) in the air where they live. The data were collected as part of the Determinants of Adolescent Social Well-Being and Health (DASH) study, which tracks the well-being of thousands of ethnically diverse London schoolchildren over time. 

The participants came from 51 different secondary schools in London, and were mostly (80 percent) from ethnic minority backgrounds. The students were recruited during the periods 2003–2004 and 2005–2006, when their blood pressure, height, and weight were measured.

Each participant completed a questionnaire that included details on ethnicity, residential area and socio-economic status. Levels of NO₂ and particulate matter were derived from annual models of pollution levels in London for the relevant time periods. The results of the study are published in the journal PLOS ONE. 

The analysis showed a link between greater estimated exposure to NO₂ and lower systolic blood pressure in the adolescent participants. In addition, the researchers found that increased estimated exposure to PM_2.5 was associated with higher systolic blood pressure. No evidence of a relationship was observed between diastolic blood pressure and levels of NO₂ or PM_2.5.These associations were stronger in girls than in boys.

For example, a 1μg/m³ increase in nitrogen dioxide was associated with a 0.30 mmHg (95% CI 0.18 to 0.40) decrease in systolic blood pressure for girls and a 0.19 mmHg (95% CI 0.07 to 0.31) decrease in systolic blood pressure for boys. Meanwhile, a 1μg/m³ increase in PM_2.5 was associated with a 1.34 mmHg (95% CI 0.85 to 1.82) increase in systolic blood pressure for girls and a 0.57 mmHg (95% CI 0.04 to 1.03) increase in systolic blood pressure for boys. 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 the pollutants than were their white peers.

The researchers call 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 PM_2.5 in London remain well above World Health Organization Guidelines, suggesting opportunities to reduce pollution and improve lifelong health for adolescents in the city.

“This longitudinal study provides a unique opportunity to track exposures of adolescents living in deprived neighborhoods,” said study co-author Seeromanie Harding. “Given that more than 1 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.”

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By Alison Bosman, Earth.com Staff Writer

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