Ambient air pollution is the greatest environmental risk factor for premature mortality according to the World Health Organization (WHO)1 and a leading cause of global disease burden.2 Increased exposures have been linked to an elevated risk of cardiovascular diseases (CVD), high blood pressure (BP), respiratory infections and lung cancer, leading to reduced life expectancy, mortality, and morbidity.2 Gaseous air pollutants (Nitrogen Dioxide – NO2, Sulphur Dioxide – SO2, Carbon Monoxide – CO, Ozone – O3) and particulate matter (PM2.5, PM10) have been associated with adverse health effects, with the majority of published studies focusing on PM2.5 and NO2.3,4

Evidence has demonstrated that elevations in ambient air pollution are associated with the induction of oxidative stress, systemic inflammation, endothelial dysfunction, and an imbalance in the autonomous nervous system, all of which are consistent with increased BP.5, 6, 7 Several epidemiological studies of adults have reported increased BP levels and visit to the hospitals due to hypertension for short-term exposures (a few hours to days) to several air pollutants (SO2, O3, NO2, PM.2.5, and PM10)7, 8, 9, 10, 11, 12, 13 and significant positive associations in hypertension risk for long-term exposures (several months to years) to ambient air pollution (PM2.5, PM10, NO2, and SO2).9,12,14,15 Acute and chronic exposures to ambient air pollution are significantly associated with CVD.16 The most extensive review conducted in 2018 with 100 studies and 0.7 million participants found significant associations for long-term exposures to 3 air pollutants (PM10, PM2.5, and NO2) and for short-term exposures to 2 air pollutants (PM2.5, SO2) with diastolic blood pressure (DBP) and systolic blood pressure (SBP), respectively.7

Elevated BP in adolescence is associated to hypertension and poor cardiovascular health in adulthood.17,18 Adolescents, defined by the WHO as those 10-19 years of age,19 are more vulnerable to ambient air pollution as they spend more time outdoors.20,21 Studies so far in children and adolescents have reported inconsistent findings. Cross-sectional studies in China generally show positive associations between short and long-term exposures and BP.22, 23, 24, 25, 26, 27, 28, 29 Other epidemiological studies reported either positive6,30, 31, 32, 33 or no associations with BP.34,35 A California-based study reported higher maternal long-term NO2 exposures during the third trimester of pregnancy was linked with elevated BP in adolescents aged 11 years.36

Exposure to ambient air pollution differs by gender,37, 38, 39, 40, 41, 42 ethnicity,42, 43, 44, 45 and residential deprivation.45,46 Studies documenting varying socio-economic circumstances (SEC) and air pollution have been inconclusive so far, due to variable settings, methodological diversity,47, 48, 49, 50 and lack of adjustments for confounding. Populations living in lower SEC are more likely to be exposed to poor air quality, as well as other factors linked to poor health status (such as smoking, drinking, obesity).51,52 Intersectionality of these influences is increasingly recognized in health inequalities research and, there is limited evidence about how these factors intersect with pollution to affect inequalities in outcomes. Treating social characteristics separately – mainly age, gender, ethnicity, and SEC - does not match the reality of people's lives as they experience multiple exposures simultaneously.

This review aims to identify and collate evidence for exposure to short- and long-term exposures to ambient air pollution and its association with BP in adolescents. Where data are available, we will use an intersectional approach to examine how age, gender, ethnicity, and SEC combine to affect adolescent BP.