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Article

Sources of Indoor Air Pollution in Schools in Kosovo

by
Antigona Ukëhaxhaj
1,2,
Naser Ramadani
2,
Hanns Moshammer
3,4,* and
Drita Zogaj
5
1
Faculty of Medicine, University Fehmi Agani, 50000 Gjakove, Kosovo
2
National Institute of Public Health, 10000 Pristina, Kosovo
3
Department of Environmental Health, ZPH, Medical University of Vienna, 1090 Wien, Austria
4
Department of Hygiene, Medical University of Karakalpakstan, Nukus 230100, Uzbekistan
5
UBT College, 10000 Pristina, Kosovo
*
Author to whom correspondence should be addressed.
Buildings 2023, 13(3), 668; https://doi.org/10.3390/buildings13030668
Submission received: 7 February 2023 / Revised: 27 February 2023 / Accepted: 1 March 2023 / Published: 2 March 2023
(This article belongs to the Special Issue Indoor Air Environment for Large-Scale Public Buildings)
Browse Figures
Versions Notes

Abstract

:
There is increasing scientific evidence of the adverse health effects of indoor exposure to a collective mixture of chemicals in children. People spend 80–90% of their time indoors, breathing air that is often even more polluted than the air outside. This study presents results of school inspection and sampling of selected chemical pollutants—formaldehyde, benzene, and nitrogen dioxide—in classrooms and outdoors in ten schools in Kosovo, conducted by the National Institute of Public Health and the WHO. Nitrogen dioxide and benzene were most affected by outdoor concentrations and were too high in at least one school (NO2: >80 µg/m3, benzene: 1–2 µg/m3). Formaldehyde was significantly higher indoors than outdoors and higher in newer schools than older ones, but overall levels were not alarming (maximum around 20 µg/m3). CO2 levels during class indicated insufficient ventilation. The temperatures were occasionally too high during the cold season. This not only results in unnecessary energy wastage but also too low relative humidity. Improvements in air circulation and temperature control, as well as the identification and elimination of certain sources of pollution would improve the health and learning of school children.

1. Introduction

As the Healthy Environments for Children Alliance (HECA) states in its introduction, “Today’s children are tomorrow’s adults. You deserve to inherit a safer and healthier world. There is no more important task than protecting their environment” [1].
Children’s health is influenced by the quality of the indoor and outdoor environment [2]. They belong to the most affected part of the population, since their organism reacts particularly sensitively to all external factors during the developmental phase [3]. They spend most of their time indoors, be it at home, kindergarten or school, which makes them more exposed to indoor air pollution. Environmental factors in the classroom, such as air quality and climate, play an important role in teaching and learning [4].
Studies in this area show that air quality in classrooms is of particular concern as children are more vulnerable to poor indoor air quality (IAQ) while indoor air quality issues can be hidden and not always have easily identifiable health and well-being effects [5,6].
School children spend more of their working days and up to 4–6 h a day indoors at school. The air they breathe in their school can be more polluted than the air outside. Poor indoor air quality can increase rates of asthma, allergies, and infectious and respiratory diseases, and affect student performance on mental tasks such as concentration, arithmetic, and memory. Symptoms associated with poor indoor air quality include headache, fatigue, shortness of breath, coughing, sneezing, eye and nose irritation, and dizziness [1,7].
Children’s environment is of particular importance for three reasons: First, the environment in general is one of the most important determinants of children’s growth and development.
Second, children can be more vulnerable than adults to the adverse health effects of chemical, physical, biological, and other hazards. Lower immunity, immaturity of organs and functions, and rapid growth and development can make children more vulnerable than adults to the toxic effects of environmental hazards. In relation to their body weight, they breathe more air, eat more food, and drink more water than adults.
Third, children’s behavior patterns differ significantly from adults, putting them at risk of exposure to environmental threats that adults may not be exposed to [1]. In schools in both developed and developing countries, indoor air pollution can be the most pervasive of all environmental hazards.
There are many mobile and stationary outdoor sources that affect the air inside the building through the ventilation system or through infiltration (permeability of the building envelope). Building materials and furnishings (wall and floor coverings, paints, insulating materials, etc.) as well as processes within the building (combustion processes, heating, ventilation, and air conditioning systems, etc.) but also the residents themselves and their activities (tobacco smoke, cleaning products, plants, pets, drugs, cooking, etc.), and last but not least, water and soil (air pollutants brought in through water supplies and contaminated soil) contribute to indoor pollution [8].
A study by Nur Aida et al. [9] showed that pre-school children in urban areas are more exposed to particulate matter in the indoor air compared to those from rural areas. Faulty heating, ventilation, and air conditioning systems can exacerbate air quality problems, which manifest themselves as headaches, nervous system effects, respiratory problems, allergic sensitivity, and asthma, but also lung cancer, chronic obstructive pulmonary disease, and airborne respiratory infections and irritation [10]. Indoor air quality in schools affects students’ respiratory health [11,12,13] as well as their cognitive performance [14].
Surveys in many European countries on various pollutants have found strong and consistent associations between exposure to indoor air pollution and respiratory diseases [7,15]. Scientific knowledge gathered through a number of recent projects, such as the WHO Regional Office for Europe-led school survey, the Schools Indoor Pollution and Health Observatory Network in Europe (SINPHONIE) project and the School Environment and Respiratory Health of Children (SEARCH) project, has provided a solid basis for the development of guidelines and the planning and implementation of measures to reduce the health risks associated with poor indoor climate quality in schools and other buildings for children [16,17,18].
According to the introduction to the summary of the SINPHONIE final report [17], in Europe more than 64 million pupils and almost 4.5 million teachers spend many hours every school day in pre-primary, primary, and secondary schools. The authors conclude that a variety of indoor pollutants with potentially adverse health effects can be found in school environments, either originating from the ambient air or produced by indoor materials, products, or activities. The prevalence of bronchial asthma varies greatly worldwide [19] and is on the rise in the industrialized world, as the comparison of the different ISAAC waves documents [20]. The increase has been most notable among children, and asthmatic children are known to be particularly sensitive to the effects of poor air quality.
It is already known that exposure to a variety of physical, chemical, and biological stressors in the school environment increases the potential for short- and long-term health problems in students and staff and adversely affects learning performance [21].
Kosovo faces serious environmental problems and has inherited a large number of environmental problems accumulated over decades of uncontrolled use of natural and mineral resources and industrial production, with high levels of pollution. The general environmental situation in Kosovo has deteriorated in recent years with increasing construction together with traffic and industrial pollution.
Kosovo has the youngest population in Europe, where 28% are under 15 years old and the median age of the population is 30.2 years [22]. According to the statistics of the Education Strategy in Kosovo, currently a quarter of the total population is of school age [23].
Unfortunately, there is a lack of data and research on the importance of environmental factors in schools in Kosovo. This is the first research in this regard, and it was carried out by a team of specialists from the National Institute of Public Health (NIPH) in three municipalities of Kosovo (in Pristina, Fushë Kosovë, and Obiliq) during the heating season.
The indoor air quality is not only influenced by the outdoor air quality, but also by building-specific hazards that emanate for example from the building material. In addition, the sanitary situation in the school environment has a major impact on health in all school buildings in Kosovo. The lack of suitable school buildings, where the existing ones are often old and dilapidated, leads to overcrowding of the classrooms (60–100 students in one classroom), with some rooms even being used in two or even three shifts.
As is commonplace everywhere in the world, attending primary school in Kosovo is compulsory. It is important for children’s health that they have clean drinking water, sufficient water for hygiene, adequate sanitation, clean air to breathe, safe and nutritious food, and a safe place to study and play. A contaminated environment can cause or worsen health problems. These include short-term and long-term health effects such as infectious diseases, respiratory infections or asthma, which can affect school attendance and the ability to learn.
Exposure to CO, CO2, benzene, formaldehyde and NO2, as well as humidity and mold in classrooms are indicators of inadequate classroom air quality and can have a direct and very negative impact on children’s health, particularly regarding respiratory and cardiovascular health. Indoor air climate, CO2, and several volatile organic carbons, are among the indicators of indoor air quality that are most often used in schools [24].
Unfortunately, the health institutions in Kosovo have not established a systematic plan to monitor the school environment. Therefore, we set out to demonstrate the feasibility of such a monitoring program in a kind of pilot study. The results obtained from this study may become the baseline data for following studies that may appear in the near future. Primarily this project, encouraged and supported by the WHO Office in Pristina, serves to inform local policy makers at the Department of Health, Department of Education, and local departments of education, as well as school management, to implement new plans, policies, procedures, or guidelines for indoor air quality in schools.
This paper describes part of the research conducted in schools in Kosovo. Here we present the main indoor and outdoor pollutants in and near schools in Kosovo. Its main goal is to evaluate the measured concentrations of pollutants, compare these values to results from comparable studies from South-Eastern Europe, and examine possible sources of the pollutants.

2. Materials and Methods

2.1. Study Locations

This cross-sectional study was conducted in 2020 at ten randomly selected primary schools from urban and rural areas in Kosovo. Three municipalities were chosen that represent different environmental situations in Kosovo. Pristina Municipality is the capital of Kosovo and home to the highest number of inhabitants. The total number of school children in Pristina is 29,840 (14,540 female and 15,300 male children). The schools selected in Pristina are located near to busy residential areas in the city, large parking lots at 100 m, and busy roads. Fushë Kosova Municipality represents a suburban area with heavy traffic but is also close to the coal-fired power plants Kosovo A and B. It has a total of 6970 school children, of whom 3346 are female and 3624 are male. Obiliq Municipality represents a more rural area with a smaller population number. The total number of school children is 3081, of which 1514 are female and 1567 are male [22].
Six schools were selected from Pristina with a total of 11,241 students or 37.7% of the total student population. Two schools from Fushë Kosova hosted 2179 students or 31.3% and two schools from Obiliq with 1524 students or 49.5% were also surveyed.

2.2. Study Survey

One responsible person from each school management was interviewed using a predefined questionnaire. This included general information about the school (property, type and number of classes, number of students and teachers, and timetable), information about the school building (including age of construction, number of floors, building materials, water and sanitation infrastructure, ventilation, and heating system), and hygiene (use of various chemicals and biological agents in the school buildings for cleaning purposes, toilets and washroom infrastructure, moisture and mold problems observed).
The experts on the inspection team examined the school’s surroundings for signs of local sources of pollution. In particular, they noted the location of the school whether in a busy residential area of the city or in an industrial area, in the presence of a parking lot, a gas station or a busy road, all less than 100 m away, and a coal-fired power plant within a radius of 3 km.

2.3. Instruments and Procedures

Benzene, formaldehyde, and NO2 were measured at an outdoor site in front of the school building and in three classrooms per school. The classrooms were intended to represent the entire school building and were therefore chosen from different floors or blocks of each school. Unfortunately, because of constraint of resources, CO2, CO, temperature (T), and relative humidity (RH) were measured in only one classroom on the ground floor of each school. This was conducted following the advice of the WHO experts who were mostly interested in the temperature as an indicator of comfort conditions for the children. While the temperature in a single room might be representative of the whole building, the CO2 concentration depends on the number of persons in the room and on the air exchange rate. Had we known both CO2 concentration and number of children per classroom, we could have estimated the air exchange rate. This would have offered a valuable hint as to the main source (indoor or outdoor) of the other pollutants. The sampling took place during a single school week (Monday morning before school until Friday evening after school) in the heating period.
The classrooms were inspected by the expert team and described in detail regarding possible sources of indoor air pollution. The data description of three classrooms included information about the classrooms, information about the type of ventilation of the classroom (natural/mechanical), type of heating, humidity and mold in the classroom, information about the type of construction material of floors, ceilings and walls, type of writing materials, type of electronic equipment in the classroom (TV, beamer, computer, etc.), type of furniture material, daily occupancy of the classroom, renovation of the classroom in the last 12 months, maintenance of classroom hygiene, and type of classroom disinfectants. The information was further augmented by input of the teachers responsible for each classroom. In addition, the location and state of each sensor were documented.

2.4. Sampling Devices, Sensors, Laboratory Analysis

The sensors were sealed after 5 days and brought to the central laboratory of the NIPH and analyzed. The following sensors were used:
  • Benzene-Radiello Code 130, passive sampler, according to ISO 16000-1 (2004) protocol, samples collected were analyzed by GC-MS.
  • Formaldehydes-Radiello Code 165, passive sampler, according to ISO protocol 16000-2 (2004), were analyzed by HPLC.
  • NO2—Radiello code 166, passive sampler, according to ISO 16000-15 (2008) protocol.
  • CO2, temperature, relative humidity, and CO were measured with the HD21AB instrument using the Delta Log 10 program version 0.1.5.3—Reference standards: ASHRAE 62.1-2004, Legislative Decree 81/2008.
For completing the questionnaires used in schools and for the way sensors for indoor and outdoor air parameters are placed and labeled, we relied on standard WHO documents described in: “School environment: Policies and current status” [15], “Methods for monitoring indoor air quality in schools” [10] and “Methods for sampling and analyzing chemical pollutants in indoor air” [25], “Guidelines for indoor air quality” [26] and “WHO Indoor Air Quality Guidelines: Selected Pollutants” [27].

2.5. Data Analysis

Data were collected and compiled in Excel sheets. Descriptive figures were produced in Excel while analytical statistics were performed in STATA vers. 17 [28]. This analysis was mostly concerned with the identification of possible sources of the pollutants. therefore, possible influencing factors on pollutant concentrations were examined in multiple linear regression. Two models were initially created for each pollutant (benzene, formaldehyde, and NO2). The first model included the outdoor air pollution level and the characteristics of the school (age, heating source, ventilation) and room (floor), the second replaced the outdoor air pollution with the list of possible nearby pollutant sources and compared suburban and urban schools with rural schools. In all models, non-influential factors were omitted, starting with the factor with the highest p-value, until only significant factors remained (p < 0.05) or the coefficients of the remaining factors changed by more than 10% by removing the insignificant factor.
The time courses of carbon dioxide (CO2), relative humidity, and temperature were examined visually and representative examples were presented for illustration. A more in-depth statistical analysis of these values was unfortunately not possible because of the paucity of the data (only one measurement point per school, no information on outdoor concentrations).
The findings are presented and discussed for each parameter separately and the discussion also focuses on comparison with other studies’ findings from the same region of South-East Europe.

3. Results and Discussion

3.1. Characteristics of School Facilities

The indoor and outdoor concentrations of chemical pollutants were measured at all schools. School buildings vary in location and as such it was expected that they would provide different indoor air quality, particularly between urban and rural locations. Only one school was younger than 10 years, two schools 11 to 30 years, and four schools 31 to 50 years. Three schools were even older than 50 years (Figure 1).
Of the ten schools, only one has assisted ventilation, refrigeration, and air conditioning. Natural ventilation makes less sense for windows on the street side, as otherwise harmful particles from the air and other harmful pollutants could enter the school building.
In the area of heating, three schools are connected to the central district heating network. Among the remaining seven schools, the main heat source is wood for five of the schools, while only two schools are heated with oil (Figure 1).
In three schools, administrators indicated that there had been water leaks or flooding in the past 12 months. In addition, there is an odor of mold in two schools and signs of mold growth, dampness, water ingress or moisture damage in the building are visible in three schools. The places where mold is most clearly seen are classrooms and hallways and stairways. Mold was less common in toilets, washrooms, and other rooms within the school building than in classrooms and corridors.
Five of the schools are located in the urban area, four of which are in the most densely populated areas of the city, four in the outskirts of the city, one of which is also in an industrial area, and only one in a rural area. The only rural school is in the oldest age category (over 50 years old). The four suburban schools are the newest (from category 1–10 and category 31–50 years). The five municipal schools are older and in the 31–50 year old and over 50 year old categories).
According to the assessors of the inspection team, six schools (five urban and one suburban according to zoning) were located in a busy urban area, eight near a large parking lot, two near a busy road, two near a gas station, one in an industrial area, and two (one suburban and one rural) near a coal-fired power plant. Overall, each school had between zero (a suburban school) and three nearby sources of pollution. The average number of pollution sources per school was 2.1.

3.2. Nitrogen Dioxide, Formaldehyde, and Benzene

Many pollutants are considered harmful in school environments, including radon, particulate matter, and mold [24]. The pollutants examined in this study represent only a small part of these but serve as indicators for various sources of pollutants and are therefore valuable indicators of indoor air quality.

3.2.1. Nitrogen Dioxide

Nitrogen dioxide (NO2) is clearly an outdoor pollutant in the environments studied. Indoor levels correlated strongly with outdoor measurements. Indoor concentrations decreased with increasing number of floors or distance from the ground. Interestingly, school age was even more closely associated with NO2 concentrations (Table 1). Although classrooms heated with oil (+2.3 µg/m3) or wood (+6.2 µg/m3) showed slightly higher NO2 values than classrooms supplied with district heating, this difference was not significant and had no influence on the coefficients of the other factors. Among the possible outdoor sources, only one gas station nearby (<100 m) remained significant. If, in addition to the outdoor concentration, only the number of floors is considered, the indoor concentrations drop significantly by approx. 6.5 µg/m3 per floor. The latter relationship is not linear: rooms on the ground floor have a 10.4 µg/m3 lower concentration than on the ground floor, on the second floor 16.4 and on the third floor 18.3 µg/m3 less than on the ground floor. The steepest gradient is between the ground floor and the first floor.
Road traffic is the main urban source of outdoor NO2. The main indoor sources include tobacco smoke and gas, wood, oil, kerosene, and coal-fired appliances such as stoves, ranges, room and hot water boilers—particularly appliances that are not linked to a chimney or poorly maintained [29]. Outdoor nitrogen dioxide from natural and anthropogenic sources also affects indoor concentrations. The distance between buildings and roads has an influence on the indoor NO2 concentration [12]. Asthmatics and patients with chronic obstructive pulmonary disease are sensitive to the effects of NO2. Direct eye contact can cause eye irritation [30].
The maximum indoor concentrations of NO2 in the schools studied were found in schools in urban areas where the school buildings are located in dense residential areas and ranged from 70.7 to 102.6 μg/m3, while in rural areas NO2 concentrations ranged from 7.0 to 85.1 μg/m3. In schoolyards, the concentrations were between 13.5 and 106.7 μg/m3 (Figure 2). With the exception of one school that heats with wood, indoor concentrations were of the same order of magnitude as outdoors.
The urban values in particular are high compared to the results of various studies [31] from the same region. For example, NO2 in Serbia was between 12 and 22 μg/m3. If the outdoor values are viewed as representative for a whole year, they exceeded the annual limit value of 40 µg/m3 according to European legislation in several places [32].

3.2.2. Formaldehyde

Formaldehyde is found in the environment and comes from natural sources and anthropogenic activities. Secondary formaldehyde formation in air results from the oxidation of volatile organic compounds and the reaction between ozone and alkenes. The main sources of indoor air are from building materials and consumer goods: Furniture and wood products contain formaldehyde resin such as chipboard, plywood, and insulating materials, urea foams, textiles, paints, adhesives, varnishes, cleaning agents such as detergents, disinfectants, fabric softeners, and carpet and shoe cleaners such as liquid soaps, shampoos, nail polishes, electronic devices including computers and photocopiers, insecticides and paper products [33,34]. The maximum formaldehyde concentrations found were between 5.4 and 21.0 µg/m3 in schools and between 1.9 and 6.8 µg/m3 in the schoolyard (Figure 3). The formaldehyde concentrations in all the rooms examined remained well below the indoor air guideline value of 100 µg/m3 proposed by the WHO [35].
The outdoor concentration of formaldehyde is not a predictor of the indoor concentration (in the first model the coefficient is small and negative and p is 0.412, e.g., when controlling for age group and heating system. The type of heating system also has no significant impact on indoor formaldehyde concentrations, although levels are slightly higher in schools not connected to district heating (+2.1 µg/m3) (p = 0.177). Only the age category has a clear and significant effect (Table 2).
Compared to the youngest buildings (1–10 years), the second category (11–30 years) has 3.8 µg/m3 lower formaldehyde values (p = 0.162), the next category (31–50 years) 8.4 µg/m3 less (p < 0.001), and the oldest category (51 years and older) 7.4 µg/m3 less (p = 0.002). These estimates change slightly after accounting for specific outdoor sources (Table 2).
There are not many outdoor sources that explain the formaldehyde concentration. Only “parking lot” is positively and significantly associated with formaldehyde. All other possible sources, as far as they approach significance, are negatively associated. After removing these implausible factors from the model, the parking lot loses its significant effect (Table 2).

3.2.3. Benzene

Indoor sources of benzene are building materials and furniture. Benzene is also carried in from garages, from heating and cooking systems, from various human activities, including air transport from industrial plants. The materials used in the construction, remodeling and decoration of the buildings are the main source of indoor benzene [36]. Newly built or newly renovated buildings usually have benzene concentrations from furniture and fixtures. However, the level of benzene emissions from these sources decreases significantly over the course of several weeks or months to a year [21]. Due to the exchange of indoor and outdoor air, the indoor concentrations are influenced by the outdoor values. Outdoor benzene concentrations stem primarily from motorized traffic and are affected by season and meteorology.
In our study, most benzene concentrations in classrooms were found at levels of 0.2 to 0.3 μg/m3. The highest value was found at 2.3 μg/m3 in a school near the industrial area and in classrooms on the 1st floor of a school (Figure 4). In all other schools, the variation in concentration between rooms was small and the indoor concentrations were very similar to the outdoor values. We have no clear explanation as to why concentrations were so much higher indoors in this one school.
For benzene we also see a relationship between indoor and outdoor concentrations, but no effect of floor number. This is not surprising given that outdoor sources of these pollutants can often be industrial point sources, which are further away and offer a more homogeneous distribution. However, the indoor/outdoor association is not as strong as with NO2.
Among the possible outdoor sources, only “Industry” gives a clear signal in the multiple regression. Surprisingly, a nearby gas station had no effect on benzene levels. Building and room properties do not provide any information about the indoor concentration (Table 3). A single school showed higher values in all three examined rooms than outdoors. A clear reason for this observation could not be determined. Benzene is a genotoxic human carcinogen, and no safe exposure level can be recommended. Therefore, we recommend continuing to use the same unit risk factors calculated from the Pliofilm cohort studies. According to the WHO indoor air quality guidelines [37], there is no safe threshold for benzene and a concentration of 1.7 µg/m3 would result in a lifetime cancer risk of 1/100,000.

3.3. CO, CO2, Temperature and Relative Humidity

3.3.1. Carbon Monoxide (CO)

At all times and in all schools, CO concentrations were close to the detection limit and certainly far from any guideline values. Measured values ranged from below limit of detection (LOD) up to 2 ppm or about 2.3 mg/m3. Average values per classroom (when LOD was set to zero), were always well below 1 ppm. The 24-h guideline value of WHO is set at 7 mg/m3 [38]. Therefore, CO is not discussed further here.

3.3.2. Carbon Dioxide

The carbon dioxide (CO2) concentration is clearly influenced by the occupancy. Therefore, the concentrations differ between the times when lessons take place, usually weekdays during the day and especially in the morning hours, and the rest of the time, including weekends and nights. Figure 5 shows two examples from two schools, demonstrating the passage of time over these two periods. During lessons, CO2 concentrations peak at 2000 ppm and even slightly higher. Even with the windows open during breaks, the concentrations only drop to around 1000 ppm. The humidity also increases during the lessons and drops slightly when the windows are open. At night, the CO2 levels fall below 500 ppm and the relative humidity is also rather low. This is also due to the unnecessarily high temperature at this time. Better temperature control in this school would not only improve the indoor climate, but also save on heating costs.
Elevated levels of CO2 in classrooms impact student health as they serve as an important indicator of adequate ventilation. Poor ventilation, especially in the cold season, affects the lungs, especially in chronically ill and allergic patients. For this reason, it is preferable to air the classrooms after each lesson. Good air exchange also reduces the risk of the students being infected by respiratory germs and reduces other pollutants from indoor sources [39]. The CO2 concentration in the schools studied ranged from 596 ppm to 1382.53 ppm in two city schools, where this value should not exceed 1000 ppm according to standards [40,41,42,43]. Based on the investigations of the SINPHONIE project, the concentration of CO2 levels in schools in Albania and Greece ranged from 1433 to 4960 ppm [17,18].
The task of indoor ventilation is to constantly replace the polluted air with fresh air from the outside atmosphere in order to maintain the necessary hygienic conditions for a healthy and comfortable stay of children in these rooms. Ventilation also plays a role in eliminating excess moisture, mold, and harmful gases in classrooms and controlling heat and humidity, which helps improve air quality and thereby reduces the negative impact on children’s health.
The adverse health effects of poor classroom ventilation are a cause of frequent headaches and respiratory infections in children as well as memory problems, leading to more absenteeism and reduced academic education [44].

3.3.3. Temperature and Relative Humidity

Classroom temperatures averaged 15.8 to 32.4 °C, so we can say that four schools we visited had classroom temperatures above the recommended 17 to 20 °C.
The indoor relative humidity values according to IAQ standards [45] should be 30–50%. In our case, relative humidity was exceeded in two urban and suburban schools, which had values of 49.3% and 59.1%. The relative humidity in the studies carried out in Albania, Malta, and Portugal ranged from 6 to 98% [17,18].

3.4. Limitations of This Study

This study was only a pilot study with limited resources. Therefore, only a small number of schools and classrooms could be included. The main aim was to prove the feasibility of such a program, to train local public health experts on the monitoring devices, and to provide a baseline for further monitoring campaigns in schools in Kosovo. Therefore, the results are difficult to generalize, and they are not necessarily representative for all schools in that country. Nevertheless, valuable results, although not very unexpected, could be demonstrated: The schools are often old in age with poor heating and ventilation systems, signs of water damage, and mold growth. Indoor air quality is often affected by outdoor sources, but also indoor sources, as in the case of formaldehyde and partially also for benzene, could be demonstrated, although the actual source for the high benzene levels in one school could not be found. Indeed, these findings should trigger further detailed examinations.

4. Conclusions

School environments should be health-promoting and support the learning process. This means schools must be clean and safe, with appropriate lighting, indoor air temperature, and relative humidity, be adequately ventilated and present as comfortable classrooms. Such environments not only reduce student exposure to toxic substances, but also prevent disease.
Nitrogen dioxide, an important indicator of outdoor air quality [46], is still high in many urban areas in Kosovo, including in the vicinity of schools. Indoor air quality is also negatively affected by this pollutant. Benzene levels were surprisingly high in one school while the source of this exposure could not be determined. Ventilation rate was poor during classes considering the large number of pupils per room.
At all levels, national and local, policies should be developed, and legislation strengthened as follows: a municipal level indoor air management requirement should be included; indoor air regulation should be improved at national level; building regulations should be updated; there should be requirements for planning and building such as school site selection, cleaning, and building maintenance procedures; a tobacco ban should be enforced; allergen avoidance and health-based ventilation should be paramount in the school. It is also important that the level of education in Kosovo promotes awareness campaigns and training on a healthy school environment, aimed at school children and their families, school staff, professionals, policy makers, and the general public. Nationwide monitoring programs are needed to provide information to assess the collective health risks from indoor pollution.
This is the first research of this kind to be carried out in Kosovo, so other studies should be implemented in different locations in Kosovo to further research and develop sustainable measures aimed at improving indoor air quality in the school environment as well as related ones to achieve public health benefits with low-cost and technological approaches to the building environment for each student.

Author Contributions

Conceptualization, A.U. and N.R.; methodology, D.Z.; formal analysis, H.M.; investigation, A.U., N.R., and D.Z.; data curation, A.U.; writing—original draft preparation, H.M.; writing—review and editing, A.U.; visualization, H.M. All authors have read and agreed to the published version of the manuscript.

Funding

This study was funded by the WHO Office in Pristina, United Nation Development Progamme (UNDP) and the National Institute of Public Health (NIPH) (Project “Healthier Kosovo”, (2017–2020), project code 00109215.

Data Availability Statement

Raw and anonymized data are available upon request. Contact Hanns Moshammer (hanns.moshammer@meduniwien.ac.at).

Acknowledgments

The authors would like to express their thanks to the staff of the examined schools.

Conflicts of Interest

The authors declare no conflict of interest.

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Buildings 13 00668 g001 550
Figure 1. School building age and type of heating (x: mechanical ventilation).
Figure 1. School building age and type of heating (x: mechanical ventilation).
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Buildings 13 00668 g002 550
Figure 2. Concentration of nitrogen dioxide (in µg/m3) in the classrooms (minimum—arithmetic mean—maximum, in red) and in front of the school (one sampling point per school, in green).
Figure 2. Concentration of nitrogen dioxide (in µg/m3) in the classrooms (minimum—arithmetic mean—maximum, in red) and in front of the school (one sampling point per school, in green).
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Buildings 13 00668 g003 550
Figure 3. Formaldehyde concentrations (in µg/m3) in the classrooms (minimum—arithmetic mean—maximum, in red) and in front of the school (one sampling point per school, in green).
Figure 3. Formaldehyde concentrations (in µg/m3) in the classrooms (minimum—arithmetic mean—maximum, in red) and in front of the school (one sampling point per school, in green).
Buildings 13 00668 g003
Buildings 13 00668 g004 550
Figure 4. Benzene concentrations (in µg/m3) in the classrooms (minimum—arithmetic mean—maximum, in red) and in front of the school (one sampling point per school, in green).
Figure 4. Benzene concentrations (in µg/m3) in the classrooms (minimum—arithmetic mean—maximum, in red) and in front of the school (one sampling point per school, in green).
Buildings 13 00668 g004
Buildings 13 00668 g005 550
Figure 5. Time course of CO2, temperature, and relative humidity. Scale for temperature (in °C) and for relative humidity (in %) is on the left, for CO2 (in ppm) on the right axis. (A): example from a school on a week-day from 10 a.m. until 6 p.m. (B): example from another school at night from 7 p.m. till 3 a.m.
Figure 5. Time course of CO2, temperature, and relative humidity. Scale for temperature (in °C) and for relative humidity (in %) is on the left, for CO2 (in ppm) on the right axis. (A): example from a school on a week-day from 10 a.m. until 6 p.m. (B): example from another school at night from 7 p.m. till 3 a.m.
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Table
Table 1. Building associated factors and outdoor sources relevant for NO2 levels. Coefficients in µg/m3.
Table 1. Building associated factors and outdoor sources relevant for NO2 levels. Coefficients in µg/m3.
FactorCoefficient95% Confidence Intervalp-Value
Outdoor level0.850.63; 1.07<0.001
Age category (20 years)−13.16−18.92; −7.40<0.001
Floor−4.24−8.96; 0.470.076
Constant42.0929.07; 55.10<0.001
Outdoor level0.710.43; 1.00<0.001
Floor−6.47−12.67; −0.270.042
Constant22.079.15; 35.000.002
Age category (20 years)−11.27−20.95; −1.580.024
Petrol station35.4013.75; 57.050.002
Constant46.5926.19; 66.98<0.001
Table
Table 2. Building factors and outdoor sources relevant for formaldehyde levels. Coefficients in µg/m3.
Table 2. Building factors and outdoor sources relevant for formaldehyde levels. Coefficients in µg/m3.
FactorCoefficient95% Confidence Intervalp-Value
Age category (20 years)−2.31−3.79; 0.820.004
Constant14.3811.12; 17.64<0.001
11–30 years−3.83−9.11; 1.450.148
31–50 years−7.88−12.01; −3.740.001
More than 50 years−6.57−11.00; −2.140.036
Car park2.58−0.50; 5.660.097
Constant13.999.15; 18.83<0.001
Table
Table 3. Building factors and outdoor sources relevant for benzene levels. Coefficients in µg/m3.
Table 3. Building factors and outdoor sources relevant for benzene levels. Coefficients in µg/m3.
FactorCoefficient95% Confidence Intervalp-Value
Outdoor levels2.030.93; 3.130.001
Constant−0.21−0.58; 0.150.247
Industrial area1.180.95; 1.41<0.001
Constant0.310.23; 0.38<0.001
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Ukëhaxhaj, A.; Ramadani, N.; Moshammer, H.; Zogaj, D. Sources of Indoor Air Pollution in Schools in Kosovo. Buildings 2023, 13, 668. https://doi.org/10.3390/buildings13030668

AMA Style

Ukëhaxhaj A, Ramadani N, Moshammer H, Zogaj D. Sources of Indoor Air Pollution in Schools in Kosovo. Buildings. 2023; 13(3):668. https://doi.org/10.3390/buildings13030668

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Ukëhaxhaj, Antigona, Naser Ramadani, Hanns Moshammer, and Drita Zogaj. 2023. "Sources of Indoor Air Pollution in Schools in Kosovo" Buildings 13, no. 3: 668. https://doi.org/10.3390/buildings13030668

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