What Is the Relationship Between Air Pollution and Blood Pressure in Children?

[By predoctoral researcher Paula de Prado Bert and staff scientist Mariona Bustamante, both at ISGlobal.]

In April, the World Health Organisation (WHO) published an update of its global air quality database. According to the new data, 99% of the world’s population breathes air that exceeds WHO air quality limits.

In recent decades, various scientific studies have shed light on the adverse health effects of air pollution. For example, it has been shown that air pollution increases blood pressure and the risk of cardiovascular disease—one of the leading causes of death worldwide.

But what happens inside the human body that causes air pollution exposure to lead to these adverse effects?

Inflammation—both local and systemic—is one of the biological processes that is altered in response to air pollution

Multiple biological processes and functions coexist within our bodies. Any factor that affects these biological functions—whether environmental or genetic—can lead to alterations with varying degrees of clinical relevance. Inflammation—both local and systemic—is one of the biological processes that is altered in response to air pollution. This bodily response can be analysed by measuring certain proteins in plasma, a component of blood.

Previous studies have found that air pollution increases the levels of some proteins, such as cytokines and adipokines, which are related to inflammatory processes. However, these studies are limited to the adult population, to a few proteins and to a single window of exposure. In our latest study within the framework of the HELIX project, we assessed the effect of levels of different air pollutants (NO₂, PM_2.5, PM₁₀ and PM_abs), measured at home and at school in different time windows (1 day, 1 week, 1 year), in relation to blood pressure and levels of 36 proteins in 1,170 children from the HELIX project.

In line with previous studies in adults, our findings show that exposure to air pollution in children is associated with elevated blood pressure and an increase in the HGF and IL8 proteins

Our findings showed that exposure to NO₂ in the week prior to blood sampling was associated with higher systolic blood pressure. As for proteins, we observed an association between PM₁₀ levels in the week prior to blood sampling and the concentration of interleukin-8 (IL8), which promotes inflammatory processes. We also observed that high levels of exposure to NO₂, PM_2.5 or PM₁₀ were associated with high levels of hepatocyte growth factor (HGF), which is involved in tissue repair in various organs, including the heart, and has been linked to blood pressure. We showed, through a mediation analysis, that 19% of the effect of air pollution on systolic blood pressure could be mediated through HGF levels. However, the causal link between blood pressure and HGF (or vice versa) needs to be explored more fully in future studies.

In conclusion, in line with previous studies in adults, our findings show that exposure to air pollution in children is associated with elevated blood pressure and an increase in the HGF and IL8 proteins. Because elevated blood pressure in early childhood has health consequences later in life, reducing exposure to this environmental risk factor is an important preventive strategy.