Epidemiological and toxicological studies have consistently associated exposure to air pollutants to diverse negative health outcomes, most of them focusing in respiratory and cardiovascular effects as well as some type of cancers (such as lung cancer; WHO, 2013). Therefore, assessing air quality is important in order to be aware to what pollutants and in which concentrations we are exposed to. Not only the outdoor environment should be considered, since is in the indoor one where we spend most of our time and can have its own particular sources.
The BREATHE project (BRain dEvelopment and Air polluTion ultrafine particles in scHool children, www.creal.cat/projectebreathe) has its aim in determining if air pollution (focusing especially in road traffic emissions) has any detrimental effect in neurodevelopment of schoolchildren. Few previous studies have focused on the role of air pollution on brain development, but a growing body of research indicates that exposure to air pollution may be associated with an increased risk of neurodevelopmental disorders and cognitive impairments (Guxens and Sunyer, 2012). Children constitute a particularly vulnerable population, not only because it is a sensitive period for the central nervous system, but also because of their physiological and behavioural characteristics. They are characterised by having higher ventilation rates and higher levels of physical activity than adults (Trasande and Thurston, 2005), with the result that their inhaled dose of air pollutants is also higher. Children spend a large part of their time at school both indoors (in classrooms) and outdoors (at playgrounds).
In order to be able to find out if air pollution has any effect in neurodevelopment, an intensive campaign was carried out in 2011 and 2012 to assess air quality in indoor (classroom) and outdoor (playground) environments in 39 schools of Barcelona and Sant Cugat del Vallès. Various pollutants were monitored and the results showed high concentrations of fine particulate matter (PM2.5, particles with an aerodynamic diameter <2.5 µm), nitrogen dioxide (NO2), Black Carbon (BC, mainly emitted by incomplete combustion and especially related to diesel vehicles), ultrafine particle number concentration (UFP) and trace metals related to road traffic emissions (Rivas et al., 2014). In fact, PM2.5 concentration almost doubled the urban background levels, but it was due to high contributions from school activities instead of being mainly influenced by traffic emissions. For instance, in the classrooms, PM2.5 levels were importantly affected by an indoor source which was mainly composed of organic carbon (Amato et al., 2014, Figure 1). This points out how schools are a very complex microenvironment that needs to be further investigated. This organic carbon might have its origin in organic textile fibres from clothing, in cooking and other organic emissions. Other important components of this indoor source were calcium and strontium carbonates, from the chalk used for writing in the blackboards. Moreover, in those schools which had sandy playgrounds (instead of paved ones), the mineral source fraction was importantly increased in PM2.5 (both in the indoor and outdoor environments) due to the resuspension of mineral particles cause by children playing there (Amato et al., 2014; Rivas et al., 2014). Consequently, owing to the influence of school sources of PM2.5, it cannot be considered a good tracer of traffic emissions in schools.

BREATHE fonts indoor
Figure 1. Average source contributions to the indoor school environment. Source: Amato et al., 2014.

On the other hand, NO2, BC, ultrafine particles and antimony (Sb) were good indicators of traffic emissions (Reche et al., 2014; Rivas et al., 2014). The concentrations of NO2 were 1.2 times higher at schools than at the urban background, suggesting the proximity of some schools to road traffic. The spatial variation showed higher levels of traffic tracers in the schools located in the centre of Barcelona than in the outskirts, highlighting the influence of traffic emissions (Figure 2).

BREATHE mapes desest
Figure 2. Spatial Distribution of NO2, PM2.5, BC and UFP levels in BREATHE schools. Perimeters are based on the outdoor BC highest tercile (red) and lowest tercile (green). Source: Rivas et al., 2014.

It is worth mentioning that the indoor concentration of these pollutants was similar to the one found outdoors. In fact, the 75% of outdoor BC (which is mainly related to road traffic emissions) infiltrated indoors in the abovementioned schools when windows were closed (if windows were opened, the entry of this pollutant increased to 92%; Rivas et al., 2015). Although BC was one of the pollutants with the highest infiltration, other pollutants had also significant infiltration into the indoor environment. We expected to have different infiltration rates depending on windows material (wooden or PVC/Aluminium framed windows), however, no significant differences were found (except for NO2).
Health effects from the exposure to PM2.5 and other pollutants depend on their chemical composition (and size, in the case of PM). The high levels of mineral matter and organic carbon (generated by local school activities) might not have any negative health effect. In the BREATHE project, we are working to determine the effect of the exposure to all this air pollutants in neurodevelopment. However, levels of air pollutants related to road traffic are high in some schools, which added to the easy infiltration to indoor environments that is associated with many of them, makes our children to be exposed to considerable levels of air pollutants. Therefore, policies focused on reducing traffic intensities around schools should be implemented and taking into account in future urban planning.
Ioar Rivas Lara

REFERENCES
Amato, F., Rivas, I., Viana, M., Moreno, T., Bouso, L., Reche, C., Alvarez-Pedrerol, M., Alastuey, A., Sunyer, J., Querol, X., 2014. Sources of indoor and outdoor PM2.5 concentrations in primary schools. Sci. Total Environ. 490, 757–765.
Guxens, M., Sunyer, J., 2012. A review of epidemiological studies on neuropsychological effects of air pollution. Swiss Med. Wkly. 141, w13322.
Reche, C., Viana, M., Rivas, I., Àlvarez-Pedrerol, M., Alastuey, A., Sunyer, J., Querol, X., 2014. Outdoor and Indoor UFP in primary schools across Barcelona. Sci. Total Environ. 493, 943–953.
Rivas, I., Viana, M., Moreno, T., Bouso, L., Pandolfi, M., Àlvarez-Pedrerol, M., Forns, J., Alastuey, A., Sunyer, J., Querol, X., 2015. Outdoor infiltration and indoor contribution of UFP and BC, OC, secondary inorganic ions and metals in PM2.5 in schools. Atmos. Environ. 106, 129–138.
Rivas, I., Viana, M., Moreno, T., Pandolfi, M., Amato, F., Reche, C., Bouso, L., Àlvarez-Pedrerol, M., Alastuey, a., Sunyer, J., Querol, X., 2014. Child exposure to indoor and outdoor air pollutants in schools in Barcelona, Spain. Environ. Int. 69, 200–212.
Trasande, L., Thurston, G.D., 2005. The role of air pollution in asthma and other pediatric morbidities. J. Allergy Clin. Immunol. 115, 689–99.
WHO, 2013. Review of evidence on health aspects of air pollution – REVIHAAP Project.

Published by Ioar Rivas Lara

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