The number and types of indoor air pollutants in schools is rising, however little is known about the impact of their potentially synergistic interactions, upon schoolchildren health. Among children, highly susceptible individuals to air pollution include allergy and asthma sufferers, and a low socioeconomic background, however no specific guidance is available.

The Syn-Air-G project will develop a comprehensive and responsive multipollutant monitoring system (in accessible and actionable formats) by constructing and deploying novel but validated and improved sensors of chemical and biological (allergens, microbes) pollutants) and advancing environmentally friendly interventions (including air purifiers). Health: A comprehensive multidisciplinary and exposome approach of health effects of multi-pollution in small children.

Exposure to indoor air pollutants is evidently a critical issue for human health. For the paediatric population, good indoor air quality in the school's environment is an important contributor to the overall and respiratory health, attendance, and academic performance , while poor air quality is associated to a high risk for adverse health outcomes, especially in the vulnerable asthmatic population . Viruses, microbes, allergens, and chemical pollutants exhibit a complex interaction with the human immune system, depending upon several factors such as the age, predisposition (e.g., atopy) and identity of the agent . Pollen exposure increases the risk of viral infections, such as those attributed to rhinoviruses (RVs) and SARS-Cov2 , while viruses and allergens have been shown to interact with pollutants such as ozone (O3) and fine particles (PM2.5), increasing their morbidity effects. Viral infections, especially RVs, impair anti-bacterial innate immune responses , thus affecting the overall microbiome homeostasis.

There are suggestions of potential synergies between different environmental factors, including gas and particulate chemical pollutants, allergens, and viral/microbial species, particularly in the sensitive younger ages, however, such synergies have not been addressed in a real-life epidemiological, systematic, longitudinal study.

The list of indoor air pollutants associated with significant burden on health disorders and increasing social and economic costs, is long and expanding, as current knowledge evolves, on this particular subject. The detrimental effects of air pollution on several health aspects have recently been reviewed. Additionally, a joint statement by the American Thoracic Society (ATS) and the European Respiratory Society (ERS) integrated the latest scientific evidence showing that air pollution affects almost all systems of the human body, including the respiratory, cardiovascular, central nervous, and endocrine systems Studies based on google trend models have shown significant impact of pollutants on respiratory symptoms, especially during increased pollen season in sensitized individuals . Children, one of the most susceptible subgroups in the population, spend a large proportion of their time indoors such as in the school environments, thus, raising the interest in characterizing the health relevant air pollutants in this microenvironment. Studies of air quality composition in classrooms, has shown that several pollutants' levels exceed the recommended air quality standards . The detrimental health effects of exposure to school-derived pollution have been shown for certain pollutants , while a disproportionate effect has been documented in asthmatics, more so in those born prematurely. Schools also act as accumulators of airborne threats, such as viruses or allergens, which are of particular importance to a large but quite vulnerable proportion of the paediatric population: those will allergies and asthma . Allergens are well known elicitors of respiratory symptoms in sensitized individuals, although the allergen effect is person-specific and non-linear , while associations between aeroallergen exposure in schools and increased asthma morbidity has been documented . Although there is evidence suggesting potential synergies between several different factors, health effects of pollutants are more frequently assessed individually, while results on studies assessing multiple pollutants provide divergent results . The cumulative and/or synergistic exposure between chemical and biological (allergens, microbes) pollutants and how these may affect respiratory symptoms, immune, and mental health and DNA damage is barely known. Moreover, school-based environmental interventions on health outcomes studies, are small and not adequately powered.

The SynAir-Child study, within the context of the EU SynAir-G project, is an epidemiological real-life observational study, aiming to assess if there's a possible association and synergy between indoor air pollutant variability and general, respiratory, immune, and mental health outcomes in school children, based on different socioeconomic backgrounds and on different settings, in different Countries.

Previous studies, such as the European SINPHONIE study, the CAMP study on the association Between Allergen Exposure in Inner-City Schools and Asthma Morbidity Among Students, assessed in real-life settings the composition of school air quality and the impact of certain environmental elements on different health outcomes. Although the indication and aim of the studies is similar, the design of the SynAir-Child study provides a unique setting to prospectively assess the synergistic effects of pollutants at school and outdoor on several health aspects in a large and diverse cohort. In addition, outcomes that constitute an adverse health effect of air pollution on humans' health, as stated in the joint ERS/ATS policy statement, will be evaluated and included in the study. Most importantly, the continuous nature of information provided by sentinel devices set in the schools, will provide an individualized baseline of specific indicators that will be monitored during the follow-up period, to identify personalized health alterations, instead of comparing to generalized standards. It is estimated that the use of a personalized physiological profile can more accurately detect subtle changes in an individual's health markers, leading to a greater likelihood of early detection, in relation to the cumulative environmental exposures. Health outcome data, including respiratory health, immune fitness and both mental and non-mental perspectives will contribute to pollution sensing in an iterative way.

Inclusion Criteria:

• Child attending CM1 level at the beginning of the school year
• Child in a classroom selected for the project
• Child and caregiver(s) willing to follow the study procedures.

Exclusion Criteria:

Child or child's parents/guardian's who:

• Refuse to participate to the project / to give informed consent
• Do not want to use the application to fill the questionnaire and follow the protocol procedures.
• Do not read or/and write in French
• Plan a long stay outside the region that does not allow them to follow the visit plan

A maximum of 500 schoolchildren at CM1 level (French education system), equally distributed between males and females, will derive from a maximum of eight primary schools and 2-3 classes of CM1 in each school, when available. Therefore, two-three classrooms per schools, in no more than 8 schools, each year, over 2 consecutive school years will be monitored, and children will be followed-up during 10 months.

The selection of schools will be based on socioeconomic and air pollution criteria (differences between different regions of the participating centres) and whenever possible on annual reports on air quality (if available) from the respectively Directorate of Climate Change and Atmospheric Quality of the Ministry of Environment.