Global Alliance against Chronic Respiratory Diseases Demonstration Project: Aerosol Pollution and Its Seasonal Peculiarities in Primary Schools of Vilnius
The growing public health concern caused by non-communicable diseases (NCDs) in urban surroundings cannot be solved by healthcare alone; therefore, a multidisciplinary approach is mandatory. This study aimed to evaluate the airborne aerosol pollution level in primary schools as a possible factor influencing the origin and course of diseases in children. The research was conducted in the Lithuanian capital, Vilnius, as a model of a middle-sized Eastern European city.
Health promotion and prevention should start at conception and continue across the life cycle for healthy lungs and active and healthy aging. They form the basis of the goals of the Europe 2020 strategy of healthy and active aging, the United Nations’ Sustainable Development Goals for 2030, and the World Health Organization (WHO) strategy on NCDs. The growing public health concern caused by NCDs in urban surroundings must be solved within the framework of multidisciplinary studies, paying special attention to air pollution levels.
According to WHO, ambient particulate matter is responsible for an increased number of respiratory and cardiovascular diseases and deaths. For each 10 µg/m3 increase in particle mass concentrations (PMC) of particles less than or equal to 10 µm (PM10), respiratory mortality increases by 3.4% and cardiovascular mortality increases by 1.4%. Children are more susceptible to air pollution than adults. Studies have shown that in assessing the impact on human health and respiratory diseases, the sub-micron aerosol fraction (<1 µm) becomes more important, and both the mass and number concentrations should be considered. However, parallel studies of both aerosol number and mass concentrations in schools are scarce, especially those evaluating the influence of outdoor aerosol pollution affecting indoor air.
The aim of this survey was to evaluate the main seasonal aerosol pollution levels and their sources in primary schools of Vilnius, with about 570,000 inhabitants, as a model of a middle-sized Eastern European city. Seasonal indoor and outdoor aerosol particle number and mass concentrations were measured and estimated in Lithuania as a Global Alliance against Chronic Respiratory Diseases demonstration project.
Vilnius, situated at 54°41’17.00″ N, 25°15’58.00″ E, is located between two rivers, the Neris and the Vilnia, in a heavily hilly area. Invitations were sent to all 107 Vilnius schools to participate in the study, and 25 of them agreed. Every second school on the list was included in the study, resulting in 11 randomly selected schools. These schools were located in areas of different outdoor air pollution levels, with some in the downtown area, others in the peripheral part of the city, and a few in the suburbs.
A condensation particle counter (CPC; TSI model 3007) and an optical particle sizer (OPS, TSI model 3330) were used to measure total aerosol particle number concentration (PNC) in the size range of 0.01 to >1.0 µm and aerosol PNC and its distribution by sizes in the range of 0.3–10.0 µm, respectively. The PMC was calculated by OPS software, with the pre-defined particle density of 1 g/cm3. Before measurements, the instruments were checked for contamination by using high-efficiency particulate arrestance filters.
Indoor aerosol pollution in the classrooms, corridors, and nearby cafeterias of the primary schools was measured. Outdoor aerosol concentrations were measured in late autumn and winter, usually for 6–7 minutes in rooms in an induced draught. In spring, outdoor measurements were carried out near schools for 10 minutes. Indoor measurements were carried out during lessons from 9 AM until 2 PM in four or five classrooms on different floors for 10 minutes each. The devices were placed on the last desk of the classroom. Indoor measurements were also carried out near the cafeterias and in the corridors during the lesson breaks. The data collection period lasted from the start of the heating season in October 2017 until May 2018.
During all seasons, local cafeterias in the absence of ventilation were the main sources of the elevated levels of indoor PMC and PNC (up to 97,500 particles/cm3). The other sources of airborne particulates were the children’s activity during the lesson breaks with PMC up to 586 µg/m3. Soft furniture, carpets in the classrooms, and corridors were responsible for PMC up to 200 µg/m3. Outdoor aerosol pollution (up to 18,170 particles/cm3) was higher for schools in the city center. Elevated air pollution in classrooms also resulted from intermittent sources, such as construction work during classes (200–1000 µg/m3) and petrol-powered lawn trimmers (up to 66,400 particles/cm3).
In autumn, the highest PNC (CPC) values in classrooms were measured in schools No. 3 and No. 4 due to the respective high PNC values measured in cafeterias. Elevated outdoor PNC (OPS), which exceeded their maximum indoor values in the classrooms, were only measured near school No.1. Maximum PMC (OPS) estimated by OPS software in all classrooms in the studied schools varied in the range of 70 to 275 µg/m3 and exceeded the outdoor values. This means that in autumn, the cafeterias were the main source of fine (sizes up to 2.5 µm, PM2.5) and coarse particles in all studied schools.
During the winter of 2017 to 2018, the highest PNC (CPC) values in classrooms were determined in schools No. 1, 3, 4, 5, and 6. This was not only due to high PNC values measured in their cafeterias but also likely due to high outdoor PNC values. In the absence of ventilation, high PNC maximum values were measured in the cafeterias of schools No. 10 and No. 11. Outdoor data on PNC (OPS) exceeded the maximum values in classrooms in schools No. 1, 2, 4, 6, and 7 and possibly partially influenced the indoor situation. Due to the cafeterias, elevated maximum PMC values were estimated in classrooms in schools No. 1, 2, 3, 8, 10, and No. 11 in the range of 74 to 1348 µg/m3. In the classroom in school No. 5, the maximum PMC value (about 564 µg/m3) was related to the influence of construction works carried out on the unpopulated third floor. Also, the pupil activity during the lesson breaks in lodgements with the soft furniture induced elevated PMC values.
In spring of 2018, rather low outdoor PNC (CPC) values were measured in all studied schools. In schools without adequate ventilation, maximum PNC values in their cafeterias in the range of 20,849 to 95,535 particles/cm3 were determined. Elevated PNC median values (7107–9146 particles/cm3) were calculated only in the classrooms in schools No. 1 and No. 4. Outdoor data on PNC (OPS) values showed that they were significantly elevated in schools No. 1 and No. 10 and possibly influenced the maximum respective values in their classrooms. Estimated PMC (OPS) maximum values in the classrooms in studied schools varied in the range of 99 to 1037 µg/m3. The latter high value was caused by construction works, which were performed on the second floor in school No. 3. A significant indoor PMC value (about 227 µg/m3) was also estimated in the classroom in school No. 10 during a basketball game on the sport yard.
In addition to the already mentioned sources of indoor aerosol pollution (cafeterias, lesson break activity, soft furniture, and carpets), other occasional pollution sources may be present. The use of petrol-powered brush cutters or trimmers in the schoolyard during lessons induced a significant increase in fine particle number and coarse PMCs in some classrooms. Construction works during lessons also increased PMC in some classrooms on the first floor because of construction work on the second floor for almost a week. The use of sandblasting mechanisms for wall scraping near schools poses a serious hazard to pupils. The outdoor PNC and PMC values near the entrance of school No. 10 during a basketball game in the schoolyard showed that scraping the walls of a neighboring building with a sandblasting mechanism caused the surface of the schoolyard to be covered with a thin layer of scraped particles.
The results of this survey show that even in a relatively low polluted region of Eastern Europe, there are big differences in aerosol pollution within a city. Only in two suburban Vilnius schools could the situation be considered satisfactory with respect to indoor particle matter concentrations. In the other schools, in different seasons, maximum values of the aerosol number and mass concentrations in classrooms varied in the range of 2800 to 31,000 particles/cm3 and of 70 to 590 µg/m3, respectively. Aerosol mass concentrations in classrooms associated with construction works reached almost 1000 µg/m3. Outdoor aerosol mass concentrations during casual events such as the use of sandblasting mechanisms near the schools may reach several µg/m3. Therefore, carrying out such works should be restricted.
During all seasons, cafeterias were the main source of indoor air pollution in these schools due to the spoiled or inadequate ventilation. In winter, pupils spend most time indoors, and soft furniture, carpets, and pupil clothes could be an additional source of elevated PMC in classrooms and corridors. Therefore, frequent wet cleaning of the premises and monitoring of the ventilation systems will help improve air quality in school lodgements. Considering that indoor aerosol sources are mainly responsible for the pollution levels in school premises, the proposed method for assessing aerosol air pollution in schools, conducted in the frame of a pilot study, can be further used to collect statistics on air pollution and establish correlation with data on respiratory diseases of pupils.
doi.org/10.1097/CM9.0000000000000913
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