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Air pollution, antenatal depression and anxiety, and foetus brain development

Periodic Reporting for period 1 - PRESSURE (Air pollution, antenatal depression and anxiety, and foetus brain development)

Reporting period: 2021-04-01 to 2023-03-31

Mental and substance use disorders (especially depressive disorders and anxiety) account for a considerable share of the burden of disease: 30% of years lived with disability. Environmental determinants of mental illnesses are yet to be adequately understood, however, it is essential to identify modifiable risk factors to put policies in place to reduce the incidence of these disorders. Recent epidemiological research suggests a likely link between air pollution (particularly Traffic-Related Air Pollutants, TRAPs) and psychological health. However, further studies are required to unravel inconsistencies and to fulfil the large numbers of gaps of knowledge identified by previous studies.
Prevalence of depression is greater among women, being around 20% for both anxio and depressive disorders. In the case of pregnant women, besides mother’s own well-being, anxiety or depression during pregnancy may result in abnormal cognitive and brain development of the offspring generation. Moreover, during its in-utero development, the brain is very sensitive to environmental factors through the mother, which could determine whether children would be able to reach their full neurodevelopmental potential at adulthood.
Traditionally in epidemiological studies in the field, subjects’ exposure has been based on ambient air pollutants concentrations estimated using geographical modelling at the residential address. However, this is a notable simplification: people usually spend their time in different microenvironments, and pollutant concentrations vary considerably between microenvironments (e.g. workplace and commuting). Moreover, the quantification of the inhaled dose, the total quantity of pollutant inhaled, is the product of pollutant concentration and a dosimetry factor (such as the minute ventilation, the total volume of air breathed in a minute), which is dependent on physical activity levels. Therefore, data on air pollutant concentrations, time-activity diaries and physical activity intensity is needed to determine the inhaled doses. Finally, noise has also been associated with depressive symptoms and, therefore, there is a need to evaluate the contribution of both exposures (air pollution and noise) to mental health.
Hence, the overall aim of the “Air pollution, antenatal dePRESSion and anxiety, and foetUs bRain dEvelopment” (PRESSURE) project is to assess the effect of air pollution and noise in mother’s antenatal depression and anxiety and to evaluate how mother’s depression and/or anxiety mediates the association between air pollution and the development of brain structures in the foetus. Specifically, the main research objectives are:
• To quantify the exposure and dose of pregnant women in the BiSC cohort (N=1080, to PM2.5 Black Carbon (BC), and NO2 in different time-windows of the pregnancy period.
• To assess the effect of the exposure and dose of urban air pollution during pregnancy on antenatal depression and anxiety in BiSC.
• To evaluate the mediating role of antenatal depression and anxiety in the possible association between prenatal exposure to TRAPs and changes in structures of the growing brain in the foetuses and new-borns.
The results obtained from this work will (i) contribute with a methodology to accurately quantify the exposure and dose, (ii) add insight on the effects of TRAPs on mental health, (iii) will explore the mediation of antenatal depression and anxiety in the association between prenatal air pollution exposure and brain development.
We have, for the first time, calculated the inhaled doses of air pollutants (PM2.5 BC and NO2) of pregnant women for the full pregnancy period using a combination of (1) real measurements of air pollution, physical activity levels and time spent in the different microenvironments (home, work, and commuting), (2) air pollution and time-activity modelling based on questionnaire and real measurement data, and (3) using literature-based information on minute ventilation for adult population. Final checks to the dataset for the full cohort is ongoing.
Based on a subsample of the cohort (N=370) with personal Black Carbon, physical activity and GPS (for microenvironment identification) measurements, we have observed that the highest proportion of the daily dose is received while being at home. This is due to the fact that the participants spent more than 60% in this microenvironment. It is worth highlighting that during commuting, for which participants spend the least of their time, they received more than 20% of their daily dose. Therefore, improving air quality during commuting (when closer to road traffic emissions) is of major importance.

This work is in progress. We have already evaluated maternal mental health during pregnancy and few months after delivery. Specifically we have evaluated:
• At week 20 of pregnancy: anxiety and depression symptoms using the Symptom Checklist-90-R.
• At week 32 of pregnancy and 2 months after birth: postpartum depression using the Edinburgh Postnatal Depression Scale.
We could conclude that in the BiSC cohort between 4.5 to 5.3 % (depending on the scale and time of assessment) of the participants were at risk of depression. Moreover, 5.7 % of the participants were at risk of an anxiety disorder.
We also evaluated the structural brains of fetuses (at week 32 through neurosonography, N=956) and Magnetic Resonance Imaging (MRI) in new-born babies (27 days after birth, N=132).

Our preliminary results indicate that pregnant women in Barcelona are exposed to wide ranges of air pollution and different levels of physical activity, and, thus have wide ranges of inhaled doses. Moreover, we also found that our participants had a wide range of anxiety and depression scoring. Brain imaging form the foetuses and babies also showed high variability.
We are currently performing the analyses to evaluate the potential associations between air pollution exposure/dose and maternal anxiety and depression and we will start in the upcoming weeks the mediation analysis to evaluate the mediation role of maternal mental health in the associations between TRAPs and brain structures in the fetuses and new-born babies.
We have quantified the exposure and doses received by pregnant women in the BiSC cohort in the different microenvironments in which they spent most of their time in their daily life. Indoor environments (mostly home) are the largest contributor to the exposure and dose because indoor, and particularly home, is where people spent most of their time. However, the largest intensity of dose is received during commuting periods, due to the combination of the larger air pollutant concentration and higher levels of physical activity (which means, larger breathing rates). To our knowledge, this is the first time that inhaled doses are quantified for pregnant women.
Our next step, which is already in progress, is to evaluate the potential link between air pollution and noise and the effect of these exposures on maternal mental health and brain development.
We believe the results from this work will have a high impact on European society as our results may have a crucial impact on the upcoming regulations of air quality for the protection of human health, particularly of vulnerable populations such as pregnant women and early infancy.
BiSC personal air pollution exposure measurements