Indoor Pollution Levels Research Articles

Sources and determinants of exposure to indoor air pollutants in schools and hospitals: a review

Abstract Background Indoor Air Quality (IAQ) is an important determinant of health. This study aimed to review the available scientific evidence about indoor pollutants and determinants of exposure in several settings, in the scope of the K-HEALTHinAIR project. Methods The systematic review was performed for the sources, concentrations, and determinants of pollutants in schools in the European region for 2013-2023. Articles were selected for data extraction if they were epidemiological studies, reported primary data for indoor air and pollutant levels, and, identified sources and determinants of exposure. Results The main pollutants affecting IAQ in schools and hospitals were carbon dioxide, volatile organic compounds (e.g., formaldehyde, terpenes), particulate matter, nitrogen dioxide, radon, ozone, and carbon monoxide. Besides the outdoor environment, several important indoor sources of emissions were identified such as occupancy, resuspension, cleaning products. Ventilation was the main determinant influencing the indoor levels of pollutants, stressing the importance of good planning, installation, and maintenance of mechanical ventilation systems in buildings. Other determinants were the number of occupants and their activities, and the building characteristics (e.g., type of floor, location, etc). Conclusions Results revealed indoor air quality as a public health concern since several pollutants are present in indoor settings. The identification of sources and determinants of exposure is fundamental for determining preventive measures in a public health perspective. Acknowledgments: K-HEALTHinAIR team for screening and data extraction: Mariana Corda, Jose Fermoso, Alicia Aguado, Sandra Rodriguez, Hanns Moshammer, Mireia Ferri, Belén Costa, Leticia Pérez, Wojciech Hanke, Artur Badyda, Piotr Kepa, Katarzyna Affek, Nina Doskocz, Laura Martín, Oguz Mulayim, Cesar Mediavilla Martinez, Alba Gómez, Ruben González, Isaac Cano, Josep Roca, Simon de Leede.

Indoor Air Quality at an Urban Primary School in Madrid (Spain): Influence of Surrounding Environment and Occupancy.

Monitoring indoor air quality (IAQ) in schools is critical because children spend most of their daytime inside. One of the main air pollutant sources in urban areas is road traffic, which greatly influences air quality. Thus, this study addresses, in depth, the linkages of meteorology, ambient air pollution, and indoor activities with IAQ in a traffic-influenced school situated south of Madrid. The measurement period was from 22 November to 21 December 2017. Simultaneous measurements of indoor and outdoor PM1, PM2.5, and PM10 mass concentrations, ultrafine particle number concentration (PNC) and equivalent black carbon (eBC) were analyzed under different meteorological conditions. PNC and eBC outdoor concentrations and their temporal trend were similar among the sampling points, with all sites being influenced in the same way by traffic emissions. Strong correlations were found between indoor and outdoor concentrations, indicating that indoor pollution levels were significantly affected by outdoor sources. Especially, PNC and eBC had the same indoor/outdoor (I/O) trend, but indoor concentrations were lower. The time delay in indoor vs. outdoor concentrations varied between 0.5 and 2 h, depending on wind speed. Significant differences were found between different meteorological conditions (ANOVA p-values < 2.14 × 10-6). Atmospheric stability periods led to an increase in indoor and outdoor pollutant levels. However, the highest I/O ratios were found during atmospheric instability, especially for eBC (an average of 1.2). This might be related to rapid changes in the outdoor air concentrations induced by meteorology. Significant variations were observed in indoor PM10 concentrations during classroom occupancy (up to 230 µg m-3) vs. non-occupancy (up to 19 µg m-3) days, finding levels higher than outdoor ones. This was attributed to the scholarly activities in the classroom. Conversely, PNC and eBC concentrations only increased when the windows of the classroom were open. These findings have helped to establish practical recommendations and measures for improving the IAQ in this school and those of similar characteristics.

Evaluating Indoor Air Quality in Schools: Is the Indoor Environment a Haven during High Pollution Episodes?

Pollution data were collected at five schools in Hong Kong using low-cost, sensor-based monitors both indoors and outdoors during two consecutive high pollution episodes. The pollutants monitored included NO2, O3, PM2.5, and PM10, which were also used as input to a health risk communication protocol known as Air Quality Health Index (AQHI). CO2 was also measured simultaneously. The study aimed to assess the relationship between indoor pollutant concentrations and AQHI levels with those outdoors and to evaluate the efficacy of building operating practices in protecting students from pollution exposure. The results indicate that the regular air quality monitoring stations and outdoor pollutant levels at schools exhibit similar patterns. School AQHI levels indoors were generally lower than those outdoors, with PM10 levels showing a larger proportional contribution to the calculated values indoors. NO2 levels in one school were in excess of outdoor values. CO2 monitored in classrooms commonly exceeded indoor guidelines, suggesting poor ventilation. One school that employed air filtration had lower indoor PM concentrations compared to other schools; however, they were still similar to those outdoors. O3 levels indoors were consistently lower than those outdoors. This study underscores the utility of on-site, sensor-based monitoring for assessing the health impacts of indoor and community exposure to urban air pollutants. The findings suggest a need for improved ventilation and more strategic air intake placement to enhance indoor air quality.

Effectiveness of the recirculation air cleaner in real conditions at variation of the air flow and PM2.5 content

Technical data on the effectiveness of air purifiers are usually obtained in laboratory conditions in special aerosol stands with test chambers or boxes of a small volume, while in real conditions the purifiers are used in rooms with a volume of at least 40-60 m3 with a permanent presence of people (distribution respiratory diseases emitted with breathing) and entry of PM2.5..PM10 particles into the room from working equipment (printers, chargers, power tools, etc.). There are already enough scientific materials on this matter, which prove that the actual efficiency of air purifiers in real conditions is much lower than the data given by the manufacturers. Therefore, there is a need to determine the optimal performance of the air purifier in real conditions in order to achieve the WHO recommended levels of safe indoor pollution with a maximum time interval of 1 hour, besides, taking into account that the air outside has a higher level of pollution with particles of PM 2.5. In this study, we strive to obtain a PM 2.5 value of 5 μg/m3 with a PM2.5 level in the air outside of 16.7 μg/m3. The calculated value of CADR for light pollution should be at least half of the power of the air purifier for the projected cleaning duration of no more than 1 hour. A smaller value of CADR leads to further accumulation of pollutants, which reduces the work of the cleaner. In this study, the value of CADR was at L=100 m3/hour the value of CADR= 59 m3/hour with the efficiency of filter inserts in 73% and natural sedimentation of particles in 25%, and at L=310 m3/hour the value of CADR= 59 m3/hour at efficiency of filter inserts in 94% and natural sedimentation of particles in 18%. The process of natural deposition and the amount of external pollution do not allow to clean the air without the use of mechanical filtration for any of the pollutants specified in the study.

Numerical Analysis of the Effects of Different Window-Opening Strategies on the Indoor Pollutant Dispersion in Street-Facing Buildings

The idling of automobiles at street intersections can lead to pollutant accumulation which impacts the health of residents in street-facing buildings. Previous research focused on pollutant dispersion within street canyons and did not consider the coupling of indoor and outdoor pollutants. This paper employs the computational fluid dynamics (CFD) method to simulate the dispersion characteristics of vehicle emission pollutants in street canyons, primarily investigating the indoor and outdoor pollutant dispersion patterns under various window opening configurations (single-sided ventilation, corner ventilation, and different positions of the glass under corner ventilation). Additionally, the study considers the impacts of the aspect ratio and ambient wind speed. Studies have shown that corner ventilation is effective in reducing indoor pollutant levels. When the two window glass positions are far away from the center of the intersection, the average CO mass fraction in the single-sided ventilation room is reduced by 87.1%. The average indoor CO mass fraction on the leeward side decreases with the increasing wind speed and aspect ratio. At a wind speed of 8 m/s, the average indoor CO mass fraction on the leeward side decreases to 2.45 × 10−8. At an aspect ratio of 2, the indoor CO mass fraction on the leeward side decreases with increasing floors before stabilizing at approximately 4.77 × 10−9. This study suggests optimal window opening strategies to reduce indoor pollutant levels in street-facing buildings at street intersections, offering guidance to indoor residents on window ventilation practices.

Organic Emissions of Volatile Chemical Products in Canada: Emission Inventories, Indoor-to-Outdoor Transfer, and Regional Impacts.

The contribution of volatile chemical products (VCPs) to ambient air pollution has increased following decades of regulating combustion sources. There is a research gap concerning the impact of indoor physicochemical phenomena on VCP emissions. In this work, a bottom-up speciated VCP emission inventory with indoor-outdoor resolution was developed for Canada, an industrialized country with low air pollution levels, whose major cities are among the largest urban areas in North America. VCPs were estimated to account for about 290 kilotons of gaseous organic emissions for a typical year in the 2010s, with more than 60% of emissions occurring indoors. Coatings and cleaners were the most emissive VCP categories. Oxygenated species and saturated aliphatics dominated the chemical profiles of most emissions. Less than 5% of VCP emissions were impacted by indoor physicochemical phenomena. VCP emissions were predicted to account for 0.8-3.2 s-1 of OH reactivity and 0.22-0.52 μg/m3 of secondary organic aerosol formation potential in major urban areas in Canada. Our predictions aligned with previous measurements concerning indoor and outdoor organic pollutant levels, underscoring the important air quality impacts of VCPs relative to other sources. Our results provide helpful insights for future research regarding VCP emissions, especially from indoor spaces.

Wildfires exacerbate inequalities in indoor pollution exposure

Wildfires lead to dramatic increases in fine particulate matter pollution concentrations. Based on the premise that higher-income households purchase more defensive investments to reduce the degree to which outdoor pollution infiltrates indoors, in this study, we investigate how income contributes to outdoor–indoor pollution infiltration rates during wildfire events. Using crowd-sourced data from the PurpleAir Real-Time Air Quality Monitoring Network and econometric models that explore variations in monitor readings over time, we find increases in outdoor pollution lead to significant increases in indoor pollution, but disproportionately so in lower-income areas. The results highlight a new inequality in pollution exposure: not only are outdoor pollution levels higher for lower-income individuals, but indoor pollution levels are higher even for similar outdoor pollution levels.

Implications of Exposure to Air Pollution on Male Reproduction: The Role of Oxidative Stress.

Air pollution, either from indoor (household) or outdoor (ambient) sources, occurs when there is presence of respirable particles in the form of chemical, physical, or biological agents that modify the natural features of the atmosphere or environment. Today, almost 2.4 billion people are exposed to hazardous levels of indoor pollution, while 99% of the global population breathes air pollutants that exceed the World Health Organization guideline limits. It is not surprising that air pollution is the world's leading environmental cause of diseases and contributes greatly to the global burden of diseases. Upon entry, air pollutants can cause an increase in reactive oxygen species (ROS) production by undergoing oxidation to generate quinones, which further act as oxidizing agents to yield more ROS. Excessive production of ROS can cause oxidative stress, induce lipid peroxidation, enhance the binding of polycyclic aromatic hydrocarbons (PAHs) to their receptors, or bind to PAH to cause DNA strand breaks. The continuous and prolonged exposure to air pollutants is associated with the development or exacerbation of pathologies such as acute or chronic respiratory and cardiovascular diseases, neurodegenerative and skin diseases, and even reduced fertility potential. Males and females contribute to infertility equally, and exposure to air pollutants can negatively affect reproduction. In this review, emphasis will be placed on the implications of exposure to air pollutants on male fertility potential, bringing to light its effects on semen parameters (basic and advanced) and male sexual health. This study will also touch on the clinical implications of air pollution on male reproduction while highlighting the role of oxidative stress.

Indoor Air Quality in Homes

Indoor air pollution is an international health concern because people spend a majority of their time indoors. Children are at a higher risk of health problems from pollutant exposure, especially because air in the child breathing zone is more polluted than it is in the adult breathing zone. Pollutants of concern include biological contaminants, combustion pollutants, volatile organic compounds, and radon and other soil gases. Humans have a history with lead and asbestos that goes back thousands of years to the ancient Romans and Egyptians. These two pollutants are still problems in older homes and apartments. All of these toxicants can be minimized or abated. Awareness of these issues is a critical first step in improving air quality in places where people live. These factors are of particular concern when examining indoor air quality because most people in the U.S. spend about 90% of their time indoors with some groups such as infants, the elderly, and infirm persons spending nearly all of their time indoors [1]. A number of conditions contribute to typically higher levels of indoor pollutants than corresponding levels outdoors [2]. The U.S. Environmental Protection Agency has reported that pollutant levels can be higher indoors than outdoors. By one estimate, pollutant levels can be 10 to 100 times higher inside than outside [3].

Determinants of manual window control for natural ventilation in homes

Understanding energy-related occupant behavior can improve the energy efficiency of homes. Natural ventilation is one of the energy-related complex occupant behavior which influences both the thermal environment and indoor pollutants levels. The objective of the present study is to find determinant parameters of occupant behavior related to the manual control of windows for natural ventilation in homes. The field monitoring was carried out in thirteen sample homes from December 7, 2017, to December 31, 2022. The importance of twenty outdoor and indoor physical parameters was calculated by the Random Forest algorithm from the data set of the sample homes. The importance of the parameters changed from sample home to sample home and from season to season. And there was also a clear difference between the driving parameters for opening and closing windows in the sample homes. The Random Forest algorithm predicted both window opening and closing behavior with high accuracy when the outdoor and indoor seven parameters were applied. The results of the present study could be applied to develop occupant behavior models that can be implemented in energy simulation tools.

Applying Natural Ventilation for Commercial Buildings With Atrium: Indoor Environment Prediction and Outdoor Pollutant Impact

Abstract The use of natural ventilation for commercial buildings becomes ever attractive due to the potential for economic savings and increased occupant satisfaction. However, it has proven to be particularly challenging to predict the indoor air temperature and airflow distribution from natural ventilation in more complex building geometries such as those with an atrium. This study used the energy-simulation-coupled computational fluid dynamics (CFD) method to predict the indoor temperatures of a typical multi-story, open-floorplan office building with a central atrium. The prediction accuracy using CFD was slightly improved for the periods with extreme outdoor conditions, where large temperature disparities often occur between simulation and experiment. For the tested cases, adjustment of window opening sizes seems to have marginal impacts on the simulation results. This paper further explores the impacts of outdoor gas-phase pollutants on indoor air quality of such a naturally ventilated commercial building with an atrium. A few architectural features such as window blockers and double skin façade (DSF) designs were numerically investigated for their performance to lower the indoor pollution levels while still maintaining adequate building ventilation rates. The results reveal that the features affecting the wind patterns around and above the building have a strong influence on the contamination rates on each floor of the building. DSF can not only reduce indoor pollution levels but also reduce the ventilation rate. When a pollutant source is not close to the building, a conventional central atrium design is preferred for better ventilation rates.

Geospatial Mapping of Indoor Air Quality and Respiratory Illnesses in an Urban Slum.

Introduction Air pollution is a well-recognized determinant of health. The general perception has focused primarily on outdoor pollution, and indoor pollution which may be due to smoking, biomass use, an extension of outdoor pollution, etc. has been neglected. It is therefore imperative to understand the levels of indoor pollution and find out if these are associated with high rates of illnesses, particularly, respiratory diseases. Material and methods This was a cross-sectional study involving 300 houses and 727 participants in an urban slum, selected through simple random sampling. Indoor air quality was assessed using the Prana C -Air Plus air quality monitor (Prana Air, New Delhi, India). The instrument detected formaldehyde, air quality index (AQI), temperature, humidity, PM2.5, PM10 particles, and total volatile organic (TVO) compounds. Socio-demographic details were noted, and geospatial mapping was done using Q-GIS software (www.qgis.org). A questionnaire was used to survey the residents of those houses. Ethical committee clearance was obtained before starting the project. Results The mean distribution of pollution parameters over the entire study area wasAQI - 67.4±65.48, PM 2.5 - 37.6±35.82 μg/m3, formaldehyde - 0.09±0.37 mg/m3, PM 10 - 43.9±38.59 μg/m3, TVO compounds - 0.43±2.13 mg/m3, CO2 - 1128.9±323.86 ppm, temperature - 23.7±21.2 degree Celsius, and PM 1 - 24.3±20.5 μg/m3;2.6% of the participants had respiratory diseases, and a significant association was found between the AQI, TVO compounds and ventilation, and respiratory diseases (p<0.05). Conclusion Indoor air pollutionnot unlike outdoor pollution can have dramatic health effects and needs to be addressed to lower the overall respiratory disease burden. The AQI, TVOC, and poor ventilation/cross-ventilation are associated with respiratory illnesses. Geospatial mapping shows a concentration of cases in areas of high pollution.

Efficient degradation of formaldehyde based on DFT-screened metal-doped C3N6 monolayer photocatalysts: performance evaluation and mechanistic insights.

Photocatalytic oxidation is an efficient and promising technology for reducing indoor pollution levels of formaldehyde (HCHO). However, developing efficient and low-cost photocatalysts for the removal of HCHO remains challenging due to the time-consuming and expensive nature of traditional "trial and error" and "directed research" approaches. To achieve this goal, first-principles density functional theory (DFT) calculations were conducted to high-throughput screen candidate TM-C3N6 photocatalysts for high-performance degradation of HCHO. The results revealed that Zr-C3N6 and Hf-C3N6 in functionalizing C3N6 with 28 transition metals showed excellent adsorption energy of HCHO, boosting the highly effective capture of HCHO. Meanwhile, an excellent adsorption performance mechanism was further elicited by the electric structure-property relationship. In addition, reaction mechanisms for HCHO degradation and three potential reaction pathways for HCHO degradation were systematically evaluated. Our findings indicated that hydroxyl-assisted dehydrogenation and oxygen-assisted dehydrogenation are the most favorable pathways, with rate-limiting steps involving the formation of ˙OH and ˙O radicals. Overall, this study may provide new insights into a high-throughput screening of novel photocatalysts that are both high-performing and low-cost for the removal of formaldehyde. This, in turn, can accelerate the experimental development process and reduce the associated costs and time consumption.

Health impact of indoor air pollution in the gulf region: A review

Factors such as unfavorable meteorological conditions within the Gulf region force citizens to spend a considerable amount of time in their homes. Indoor air quality in the Arabian Gulf is rapidly becoming an issue of vital concern that requires urgent governmental intervention and control measures as well as increased in-depth research on likely health consequences. In this review, we surveyed the current literature on the potential health impact of daily household activities in Gulf Cooperation Council (GCC) countries like Qatar where practiced traditions such as burning incense and scented candles are commonplace. These may increase indoor pollution levels, and worsen the health conditions of residents. The main goal of this review is to assess the extent of common indoor pollutants and suggest strategies of pollution control that may alleviate pollution concentration in an indoor environment. Creating awareness about the most common sources of indoor air pollution in the GCC may help improve health promotion and lifestyle changes, especially with respect to reproductive health that is a major concern in the region. The government may also explore recommendations for more environmentally friendly incense and organic candles.

Cooking, Heating, Insulating Products and Services (CHIPS) for Mongolian ger: Reducing energy, cost, and indoor air pollution

This project sought to answer three related questions about the Mongolian ger (ger are called yurt in Russian) assembled in the highly polluted, informal settlement areas called ger-districts. (1) Can replacing coal stoves with electric heaters in ger reduce indoor PM2.5 concentration? (2) What are the major causes of indoor PM2.5 concentration in ger? (3) Is it cost effective to heat ger with electric heaters? A year of testing insultation protocols in Ulaanbaatar was followed in the second year by the deployment of a package of “Cooking, Heating, Insulating Products and Services” (CHIPS) to nearly 183 ger in Bayankhongor, Mongolia. The results demonstrated that a better sealed and insulted ger could be heated with electricity less expensively than heating a typical ger with wood and coal. However, the use of electric heaters did not reduce indoor air pollution. The results showed that indoor pollution levels closely followed outdoor levels, with a small delay for air to infiltrate. The study suggests that to reduce indoor air pollution, enough ger in a district would need to be heated with electricity to significantly reduce the outdoor air pollution.

Pet cats, the better sentinels for indoor organic pollutants

Pets are the most intimate companions of humans, as pets and people share most of their lives indoors. Based on the connections between pet animals, humans, and the environment, pet cats and dogs are often recommended as sentinels for the detection of environmental contaminants and for comorbidity tracking. However, their suitability as sentinels is yet to be established. Persistent organic pollutants and environmental hormones have replaced particulate matter (PM2.5) and volatile organic compounds (VOCs) in causing indoor air pollution. This review summarises the differences in the types and concentrations of indoor organic environmental pollutants detected in pet dogs and cats. This includes an analysis of the main exposure routes of different types of pollutants. To identify which of the two pet species are better sentinels, cats and dogs were compared based on their metabolic capacities of various indoor organic pollutants. In addition to PM2.5, a range of organic compounds including polychlorinated biphenyls, polybrominated diphenyl ethers (PBDEs), bromophenols, perfluoroalkyl substances, organochlorine pesticides, fungicides, polycyclic aromatic hydrocarbons, phthalic acid esters, organophosphate pesticides, organophosphorus flame retardants, and melamine have been detected in both dogs and cats. Pets often accumulate PBDEs from dust; however, traces of PBDEs are present in their diet. The indoor pollutant contamination levels in internal cats were generally higher than those in dogs. Cats accumulate organic pollutants associated with indoor environments, but they are sensitive to their toxicity because, unlike dogs, cats cannot metabolise most of the accumulated pollutants. Moreover, cats share similar clinical symptoms of thyroid diseases in humans. Based on the above observations of detection of indoor organic pollutants, it could be said that cats are better sentinels than dogs.

Indoor Air Pollution and the Health of Vulnerable Groups: A Systematic Review Focused on Particulate Matter (PM), Volatile Organic Compounds (VOCs) and Their Effects on Children and People with Pre-Existing Lung Disease

Air pollution affects health, but much of the focus to this point has been on outdoor air. Higher indoor pollution is anticipated due to increasingly energy-efficient and less leaky buildings together with more indoor activities. Studies of indoor air pollution focusing on children and people with respiratory disease from the database Web of Science (1991–2021) were systemically reviewed according to the PRISMA guidelines, with 69 studies included in the final selection. Emissions from building materials affected indoor air quality, and ventilation also had an influence. The main indoor air pollutants are Volatile Organic Compounds (VOCs) and Particulate Matter (PM). PM sources included smoking, cooking, heating, candles, and insecticides, whereas sources of coarse particles were pets, housework and human movements. VOC sources included household products, cleaning agents, glue, personal care products, building materials and vehicle emissions. Formaldehyde levels were particularly high in new houses. Personal exposure related to both indoor and outdoor pollutant levels, highlighting home characteristics and air exchange rates as important factors. Temperature, humidity, educational level, air purifiers and time near sources were also related to personal exposure. There was an association between PM and Fractional exhaled Nitric Oxide (FeNO), lung function, oxygen saturation, childhood asthma and symptoms of chronic obstructive pulmonary disease (COPD) patients. High VOCs were associated with upper airways and asthma symptoms and cancer. Effective interventional studies for PM in the future might focus on human behavior together with air purifiers and increased ventilation, whereas VOC interventions might center more on building materials and household products, alongside purification and ventilation.

An overview of indoor air pollution in the Malaysian kindergarten environment

Abstract The components of indoor air determine the quality of the indoor environment, which affects the health and well-being of inhabitants. Exposure to high levels of indoor air pollution in a kindergarten environment has a detrimental influence on children’s learning performance and increases the risk of respiratory problems that could lead to absenteeism. This paper explores and summarises the literature on indoor air pollution in kindergartens in the Malaysian environment. A review was done by analyzing papers taken from four electronic databases: Scopus, Science Direct, PubMed and Google Scholar. Information on indoor pollution levels and determinants sources were extracted from 17 studies. The most investigated pollutants were carbon dioxide (CO2), particulate matter (PM2.5 and PM10), volatile organic compounds (VOCs), carbon monoxide (CO), fungi and bacteria. Inadequate ventilation systems and overcrowded classrooms all contributed to excessive CO2 levels. Indoor PM2.5 sources are generated from cooking activities while cleaning, opening windows and movement activities of children were the primary sources of coarse particles. High concentrations of VOCs are emitted from a wide variety of indoor sources. Mobile vehicles and the proximity of kindergartens to busy roads were key contributors to higher CO concentrations. The findings highlight the importance of interventions to improve indoor air pollution in kindergarten premises in various settings.

Latest Trends in Pollutant Accumulations at Threatening Levels in Energy-Efficient Residential Buildings with and without Mechanical Ventilation: A Review.

Improving the energy efficiency of buildings is a major target in developed countries toward decreasing their energy consumption and CO2 emissions. To meet this target, a large number of countries have established energy codes that require buildings to be airtight. While such a retrofitting approach has improved health outcomes in areas with heavy traffic, it has worsened the health outcomes in Nordic countries and increased the risk of lung cancer in areas with high levels of radon emissions. This review highlights the importance of adapting the characteristics of energy-efficient residential buildings to the location, age, and health of inhabitants to guarantee healthy indoor pollutant levels. The implementation of mechanical ventilation in new energy-efficient buildings has solved some of these problems; however, for others, a decrease in the level of outdoor pollutants was still required in order to achieve a good indoor air quality. A good balance between the air exchange rate and the air humidity level (adapted to the location) is key to ensuring that exposure to the various pollutants that accumulate inside energy-efficient buildings is low enough to avoid affecting inhabitants′ health. Evidence of the protective effect of mechanical ventilation should be sought in dwellings where natural ventilation allows pollutants to accumulate to threatening levels. More studies should be carried out in African and Asian countries, which, due to their rapid urbanization, use massive volumes of unproven/unrated building materials for fast-track construction, which are frequent sources of formaldehyde and VOC emissions.

Environmental quality in primary schools and related health effects in children. An overview of assessments conducted in the Northern Portugal

Since children are far more vulnerable than adults to the effects of air pollution and spend about a third of their day in school, strict control of indoor environments in educational buildings is paramount to properly identify, manage and mitigate putative environmental risks for children. In this context, this work aimed to provide a holistic view on the outcomes obtained from the national ARIA project, which was focused on broadening the knowledge on the effects on children’s health of the exposure to schools’ indoor air. In particular, this work performed a comprehensive investigation of the indoor air quality (IAQ) in 20 public primary schools located in Porto (Northern Region, Portugal). This paper presents the results of the investigation along with the recently published main outcomes of ARIA on (1) the characteristics of the environment surrounding the surveyed buildings, and (2) the school’s environment-related health effects in school-age children from the studied classrooms. The investigation consisted in an extensive assessment plan conducted in 71 classrooms to assess temperature, relative humidity, carbon monoxide and dioxide, particulate matter (PM2.5, PM10, and ultrafine particles), nitrogen dioxide, ozone, volatile organic compounds, formaldehyde, acetaldehyde, airborne fungi, bacteria and endotoxins, and investigate their respective sources, during the cold seasons of 2014–2015. A series of studies was also launched to investigate school environment-related health detriments in 916 children. The results showed that comfort and ventilation issues and/or indoor pollutant levels that exceeded recommended limits were found in a substantial number of the classrooms surveyed. The high density of occupants, deficient ventilation, soil characteristics, presence of indoor pollution sources (e.g. classroom materials and consumer products) and outdoor pollution were some of the factors that seemed to explain the high air stuffiness and/or indoor pollution load identified in classrooms. In fact, some of indoor pollutants detected, even at low exposure levels, were associated with the development of respiratory symptoms in school-age children. Moreover, results from this work have also shown that the characteristics of the environment surrounding the schools, namely the presence of green spaces and species richness, can be major determinants of respiratory health among school-age children. Overall, the body of evidence generated from the ARIA project can support new evidence-based perspectives for promotion of health in educational buildings.