A Proposal of IAQ Standards for Turkish Schools: Professor Sofuoglu and the Turkish Limit Values Working Group
The Indoor Air Quality Committee of the Turkish Climatisation Assembly which is part of the Union of Chambers and Commodity Exchanges of Türkiye (TOBB), recently established a Limit Values Working Group (LVWG) consisting of indoor air scientists. The task of the working group was to cover a wide list of pollutants to recommend pollutant limit values that would be applicable to indoor air quality in schools by reviewing the relevant literature and limit and guide values. For this purpose, group members identified the indoor air pollutants that should be included in the study, conducted a literature review, and presented their compilations and limit value recommendations in a book (Sofuoglu et al., 2023). The information compiled by the LVWG and the proposed values were presented to HVAC sector stakeholders in a two-day workshop (19-21 September 2023, Ankara, Türkiye) entitled International Indoor Air Quality of Schools and Student Living Areas Summit. This work was also announced to the European stakeholders by publishing an executive summary of the book in the REHVA Journal (Sofuoglu et al. 2024), from which this piece was adapted.
Indoor air pollutants examined by LVWG cover inorganic and organic gases, particulate matter (PM) and biological pollutants. In this context, an evaluation was made for a total of 19 pollutants / pollutant groups, which included carbon dioxide, carbon monoxide, nitrogen dioxide, ozone, radon, volatile organic compounds, formaldehyde, trihalomethanes, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, brominated flame retardants, organophosphate esters, phthalate esters, PM, bioaerosols (bacteria, fungi, viruses), microbial pollutants and allergens.
Nitrogen dioxide (NO2), carbon monoxide (CO), and ozone (O3), are discussed together because their source in schools is generally the outdoor air and these pollutants have been governed by ambient air quality legislation for many years now. Therefore, the health effects are well known, and the limit values in concerned legislation are based on potential health effects. Of these gaseous pollutants, NO2, and CO are mainly emitted from motor vehicles in an urban setting among other combustion sources. O3 is a secondary pollutant that at ground level forms as a result of atmospheric chemical reactions of traffic emissions in the presence of sunlight, therefore, its formation is the highest in traffic-dense areas. For these reasons, children are exposed to high levels of all three pollutants in urban schools, especially in high-traffic areas. Due to the health effects summarised in the book, it was deemed appropriate to recommend limit values for all three pollutants.
Respiration is the main source of carbon dioxide in indoor environments. Its indoor air concentrations may significantly increase in crowded places such as schools. CO2 was not considered an indoor air pollutant until recently and was used as an indicator of ventilation effectiveness. At levels observed in classrooms, health effects are in the form of symptoms of sick building syndrome such as headaches and fatigue, while cognitive effects and reduced academic performance are plausible. It was therefore deemed necessary to find a limit value for CO2 both as an indicator of ventilation effectiveness and because of its cognitive effects.
Radon has been studied for many years and its health effects are well known. It is a gas regulated by legislation in Türkiye in homes and workplaces. According to both the data from World Health Organisation and the Ministry of Health, smoking ranks first among the main causes of lung cancer, while cancers caused by the effects of radon gas rank second. Radon pollution is more common in radon-contaminated areas due to its geological origin. It was therefore found to be important to recommend a limit value to be applicable in these regions.
Volatile Organic Compounds (VOCs), which include a wide range of compounds, are organic vapours that can cause various adverse health effects that volatilise at room temperature, especially cancer, as a result of long and short-term exposure. They are very important pollutants to consider given their impact on indoor air quality in homes, public buildings, offices, schools and other indoor environments. VOCs collectively threaten human health causing issues such as building related symptoms, especially for sensitive individuals in the short term, and as a result of continuous exposure lead to chronic-toxic and carcinogenic health effects in long term. It is therefore considered crucial to recommend limit values for VOCs with carcinogenic and toxic effects, for schools where school-age children, a susceptible population, spend a significant part of their daily lives.
Although well known for a long time, formaldehyde is still one of the most important indoor air pollutants. There are standards to limit emissions from building and furnishing materials and consumer products. However, a limit is still needed to keep indoor exposures below non-safe levels. The effects of formaldehyde on human health include acute, chronic-toxic (non-cancer), and carcinogenic effects. Therefore, it is very important to recommend an indoor air limit value for schools.
The purpose of disinfection applied to water used in swimming pools is to prevent swimmers from being exposed to waterborne infections caused by microbial pathogens originating from the water that feeds the pool water or from swimmers in the water. Disinfectants dosed into water to prevent microbial activity react with organic and nitrogenous compounds (urine, sweat, hygiene and cosmetic products, etc.) in swimming pool water and form disinfection by-products (DBPs). Generally chlorinated disinfectants are preferred. Trihalomethanes are known as the most dominant group of DBPs. THM intake occurs through dermal contact, accidental oral ingestion, and inhalation exposures. Considering that THMs are volatile compounds, volatilisation from the pool water results in their accumulation in indoor air, if the air exchange rate does not sufficiently replenish the indoor environment with fresh air. There is no limit value for DBPs in indoor air around the world other than the value determined for indoor pools in Germany. In light of the available information, a THM limit value(s) for indoor pools would be significantly beneficial for the health of swimmers, coaches and staff, as well as in particular for children.
Polycyclic aromatic hydrocarbons (PAHs) may be considered as persistent organic pollutants (POPs) due to their ability to resist environmental degradation through biological, chemical, and photolytic processes. PAHs occur as products of incomplete combustion and their major anthropogenic sources include emissions from traffic, coal combustion processes, power plants, waste treatment, biomass and wood combustion. PAHs in indoor air arise from activities such as smoking, cooking, burning various fuels, candle burning, building materials, and infiltration of outdoor air. Unless there is a specific source indoors, the main source of PAH compounds is outdoor air. It is considered important to recommend limit values for these compounds due to their carcinogenic and chronic-toxic effects, but having an outdoor air quality standard is deemed currently sufficient.
PM2.5 and PM10 are generally the monitored size fractions in schools while measurements are mostly carried out in classrooms. Studies on PM1 and particle count concentrations are limited in the literature. PM levels in schools are affected by factors such as location of the school, its proximity to traffic, number of students, proximity of the classroom to the cafeteria, number of classroom windows, frequency of classroom cleaning, and ventilation type and rate, but most of the studies have emphasised that outdoor air is the main source of PM in classrooms. Additionally, the movement of children is found to be important as it results in outdoor-to-indoor transport and re-entrainment of settled dust into indoor air, which especially is significant for larger particles, i.e. PM10. PM is a well-known contaminant categorised as a carcinogen by WHO, and it is an important component of indoor air pollution in schools that have adverse effects on children’s health. PM exposure is associated with diseases such as asthma, allergic diseases, acute and chronic respiratory diseases, changes in blood pressure and lung functions, obesity and slowing of cognitive development in children. Therefore, limit values should be recommended for PM.
Bioaerosols (especially bacteria and fungi) are commonly found in the environment, including indoors. They have a wide range of health effects, from mild symptoms such as coughing and sneezing to serious infections and diseases that could result in death. Although the observed health effects depend on the concentration and species composition in indoor environments, they generally cause respiratory and skin diseases but they have also been linked to sick building syndrome among other issues. Therefore, it was considered important to have a limit value for bacteria and fungi.
In conclusion, the list of recommendations emerged from the existing sufficient scientific basis composed of the indoor air pollutant levels, pollutant health effects, time period students spend in schools, prevalence of existing limit/guideline values and the known health effects of eleven pollutants/groups (CO2, CO, NO2, O3, radon, VOC, formaldehyde, trihalomethanes, PM, bacteria, fungi). However, no recommendation was made for eight pollutant groups (polycyclic aromatic hydrocarbons, polychlorinated biphenyls, brominated flame retardants, organophosphate esters, phthalate esters, microbiological contaminants and allergens). The compiled information on all the pollutants and proposed limit values are available in the referenced book (Sofuoglu et al., 2023). Although the book is in Turkish, an executive summary in English is available by Sofuoglu et al. (2024) and a shortened, English version of the report is to be submitted to a scientific journal in English.
Note: This article, authored by Professor Sait C. Sofuoglu from the Izmir Institute of Technology, Department of Environmental Engineering, and EDIAQI Advisory Board Member, has been published on his behalf.
References
Sofuoglu, SC, Toksoy, M, Ari, A, Civan, M, Dumanoglu, Y, Gullu, G, Mentese, S, Onat, B, Alver Sahin, U. “Okullarda İç Hava Kirliliği, Sağlık Etkileri ve Sınır Değerler”. Editors: Sofuoglu, SC and Toksoy, M., Türkiye Odalar Borsalar Birliği, ISBN: 978-605-137-984-5, E-ISBN: 978-605-137-987-6. Ankara, Türkiye, 2023. (in Turkish).
Sofuoglu, SC, Ari, A, Civan, M, Dumanoglu, Y, Gullu, G, Mentese, S, Onat, B, Alver Sahin, U., Toksoy, M. “To be or not to be regulated: indoor air pollution in Turkish schools. REHVA Journal, 61(4), 21-26, 2024.