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, and some indoor/outdoor ratios greater than unity, suggest that indoor sources and building conditions might have negative effects on air indoors. Increasing ventilation rates and use of low-emission materials would contribute towards improving indoor air quality.

Analysis of indoor air quality (IAQ) in schools usually reveals higher levels of pollutants than in outdoor environments. The aims of this study are to measure indoor and outdoor concentrations of NO(2), speciated volatile organic compounds (VOCs) and carbonyls at 14 elementary schools in Lisbon, Portugal. The investigation was carried out in May-June 2009. Three of the schools were selected to also measure comfort parameters, such as temperature and relative humidity, carbon dioxide (CO(2)), carbon monoxide (CO), total VOCs, and bacterial and fungal colony-forming units per cubic metre. Indoor concentrations of CO(2) in the three main schools indicated inadequate classroom air exchange rates. The indoor/outdoor (I/O) NO(2) ratio ranged between 0.36 and 0.95. At the three main schools, the total bacterial and fungal colony-forming units (CFU) in both indoor and outdoor air were above the advised maximum value of 500 CFU/m(3) defined by Portuguese legislation. The aromatic compounds benzene, toluene, ethylbenzene and xylenes, followed by ethers, alcohols and terpenes, were usually the most abundant classes of VOCs. In general, the indoor total VOC concentrations were markedly higher than those observed outdoors. At all locations, indoor aldehyde levels were higher than those observed outdoors, particularly for formaldehyde. The inadequate ventilation observed likely favours accumulation of pollutants with additional indoor sources.

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The aim of this study was to evaluate the indoor (I) and outdoor (O) levels of NO₂, speciated volatile organic compounds (VOCs) and carbonyls at fourteen primary schools in Lisbon (Portugal) during spring, autumn and winter. Three of these schools were also selected to be monitored for comfort parameters, such as temperature and relative humidity, carbon dioxide (CO₂), carbon monoxide (CO), total VOCs, and both bacterial and fungal colony-forming units per cubic metre. The concentration of CO₂ and bioaerosols greatly exceeded the acceptable maximum values of 1800 mg m⁻³ and 500 CFU m⁻³, respectively, in all seasons. Most of the assessed VOCs and carbonyls occurred at I/O ratios above unity in all seasons, thus showing the importance of indoor sources and building conditions in indoor air quality. However, it has been observed that higher indoor VOC concentrations occurred more often in the colder months, while carbonyl concentrations were higher in the warm months. In general, the I/O NO₂ ratios ranged between 0.35 and 1, never exceeding the unity. Some actions are suggested to improve the indoor air quality in Lisbon primary schools.

Previous studies performed by the National Aeronautics Space Administration (NASA) indicated that plants and associated soil microorganisms may be used to reduce indoor pollutant levels. This study investigated the ability of plants to improve indoor air quality in schools. A 9-wk intensive monitoring campaign of indoor and outdoor air pollution was carried out in 2011 in a primary school of Aveiro, Portugal. Measurements included temperature, carbon dioxide (CO₂), carbon monoxide (CO), concentrations of volatile organic compounds (VOC), carbonyls, and particulate matter (PM₁₀) without and with plants in a classroom. PM₁₀ samples were analyzed for the water-soluble inorganic ions, as well for carbonaceous fractions. After 6 potted plants were hung from the ceiling, the mean CO₂ concentration decreased from 2004 to 1121 ppm. The total VOC average concentrations in the indoor air during periods of occupancy without and with the presence of potted plants were, respectively, 933 and 249 μg/m³. The daily PM₁₀ levels in the classroom during the occupancy periods were always higher than those outdoors. The presence of potted plants likely favored a decrease of approximately 30% in PM₁₀ concentrations. Our findings corroborate the results of NASA studies suggesting that plants might improve indoor air and make interior breathing spaces healthier.

Airborne particulate matter (PM 10 ) samples were collected daily, indoors and outdoors, in a primary school at Aveiro, Portugal, from February 28 to May 27, 2011. The carbonaceous content (organic and elemental carbon) was determined by a thermo-optical technique. The organic speciation of PM 10 was performed by gas chromatography-mass spectrometry. Mean PM 10 levels of 107 and 36 µg/m 3 were obtained in the schoolroom and outdoors, respectively. On average, organic carbon accounted for 30.0% of the mass of PM 10 indoors, whereas a lower mass fraction of 21.3% was found outdoors. The lack of correlation between indoor and outdoor organic carbon and the much higher indoor levels suggest significant contributions by indoor sources. The most abundant organic compound classes were acids, sugars, polyols and n-alkanes. Infiltration of outdoor particles leads to contamination of the schoolroom with vehicle emissions, as well as emissions related to the burning of biofuel in nearby restaurants and bakeries. However, the much higher indoor concentrations than in the outdoor air for the majority of compounds suggest that the origin of much of the particulate matter is from within the school building (due to school activities and materials, skin debris, microorganisms, and so on), and this also includes the formation of secondary organic aerosols. Based on the concentrations of polycyclic aromatic hydrocarbons, a negligible cancer risk was estimated in relation to the air within the school.

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