INMA: “Short- and medium-term air pollution exposure, plasmatic protein levels and blood pressure in children”
Air pollution is one of the well-known key contributors to the global burden of mortality and disease. Nowadays, approximately 91% of the worldwide population lives in places where the levels of air quality exceed the guideline limits established by the WHO (World Health Organization, 2021).
Among the different harmful air pollutants affecting human health, some have been highlighted given their potential direct effects in the incidence of cardiovascular disease; such as particulate matters (PMs) of different sizes (PM2.5 and PM10), nitrogen dioxide (NO2), sulphur dioxide (SO2), carbon monoxide (CO) and ozone (O3). According to recent evidences gathered in adults, the effects of these pollutants on cardiovascular health could be mediated through the elevation of blood pressure levels. However, not much is known about the exact underlying biological and molecular mechanisms. Additionally, evidence regarding to which extent the harmful effects of air pollutants on blood pressure levels occur during early stages of life is still scarce. On the other hand, this type of knowledge is of critical importance since exposure to environmental hazards during childhood might permanently change the body’s structure, metabolism, and physiology, marking the cardiovascular health of future populations.
In order to shed some light to these open questions, INMA researchers have conducted what is one of the first studies evaluating the influence of air pollution exposure on blood pressure, and attempted to elucidate the most plausible biological mechanisms underlying such connections, all in the context of early childhood.
To do so, different time windows of exposure to various air pollutants (1-day, 1-week, and 1-year) and the levels of thirty-six different cytokines, apolipoproteins, adipokines, and other proteins were measured in 1170 children aged 6–11 years (in which INMA represents one among five other cohorts), mapping their relationship with blood pressure alterations.
Among the most remarkable results, they found a potential effect of exposure to some of the analyzed pollutants (NO2, PM10, or PM2.5) on the levels of proteins such as the hepatocyte growth factor (HGF) and interleukin 8 (IL8), showing higher concentrations in those children living in more polluted environments. These findings are in line with previous evidence in adults showing that the adverse health effects of air pollution could come from the exacerbation of harmful molecular processes such as oxidative stress and systemic inflammation.
Interestingly, this study could further connect the exposure to NO2 with higher levels of systolic blood pressure, reaffirming in children what previous investigations have shown in adults. Furthermore, the mediation study suggested that HGF could explain 19% of the short-term effects of NO2 on blood pressure, thereby proposing specific molecular mechanisms that could underly the air pollutants-blood pressure relationship.
Despite the interest and novelty of these results, they have to be interpreted with caution, since, for example, the relationship between HGF and BP is still uncertain. HGF is not usually considered as an inflammatory marker, and was first described as a liver-regenerative circulating factor. It could possibly be a downstream product of increased blood pressure or a molecule excreted by the body in response to air pollution exposure to counteract the endothelial damage induced by hypertension. In any case, further studies are needed to continue investigating these hypotheses.
Overall, the findings presented in this study reinforce the idea of increased adverse cardiovascular effects as a result of air pollution exposure in children. Moreover, considering that elevated blood pressure during childhood has an impact on health across the lifespan, reducing the exposure to this environmental risk factor can be an important prevention strategy.
INMA-article summary written by Augusto Anguita-Ruiz, INMA researcher.
Reference: de Prado-Bert P, Warembourg C, Dedele A, Heude B, Borràs E, Sabidó E, Aasvang GM, Lepeule J, Wright J, Urquiza J, Gützkow KB, Maitre L, Chatzi L, Casas M, Vafeiadi M, Nieuwenhuijsen MJ, de Castro M, Grazuleviciene R, McEachan RRC, Basagaña X, Vrijheid M, Sunyer J, Bustamante M. Short- and medium-term air pollution exposure, plasmatic protein levels and blood pressure in children. Environ Res. 2022 Aug;211:113109.
Link to scientific article: https://pubmed.ncbi.nlm.nih.gov/35292243/