The effects of paints and moisture content on the indoor air emissions from pinewood (Pinus sylvestris) boards.

The emissions of volatile organic compounds (VOCs) from building materials may significantly contribute to indoor air pollution, and VOCs have been associated with odor annoyance and adverse health effects. Wood materials together with coatings are commonly used indoors for furniture and large surfaces such as walls, floors, and ceilings. This leads to high surface-to-volume ratios, and therefore, these materials may participate remarkably to the VOC levels of indoor environment. We studied emissions of VOCs and carbonyl compounds from pinewood (Pinus sylvestris) boards of 10% and 16% moisture contents (MC) with three paints using small-scale test chambers (27 L). The emissions from uncoated pinewood and paints (on a glass substrate) were tested as references. The 28-day experiment showed that the VOC emissions from uncoated pinewood were lower from sample with 16% MC. Painted pinewood samples showed lower emissions compared to paints on glass substrate. Additionally, paints on 16% MC pinewood exhibited lower emissions than on drier 10% MC wood. The emissions from painted pinewood samples were dominated by paint-based compounds, but the share of wood-based compounds increased over time. However, we noticed differences between the paints, and wood-based emissions were clearly higher with the most permeable paint.

Human exposure to air contaminants in sports environments.

The aim of this review was to investigate human exposure to relevant indoor air contaminants, predictors affecting the levels, and the means to reduce the harmful exposure in indoor sports facilities. Our study revealed that the contaminants of primary concern are the following: particulate matter in indoor climbing, golf, and horse riding facilities; carbon dioxide and particulate matter in fitness centers, gymnasiums, and sports halls; Staphylococci on gymnasium surfaces; nitrogen dioxide and carbon monoxide in ice hockey arenas; carbon monoxide, nitrogen oxide(s), and particulate matter in motor sports arenas; and disinfection by-products in indoor chlorinated swimming pools. Means to reduce human exposure to indoor contaminants include the following: adequate mechanical ventilation with filters, suitable cleaning practices, a limited number of occupants in fitness centers and gymnasiums, the use of electric resurfacers instead of the engine powered resurfacers in ice hockey arenas, carefully regulated chlorine and temperature levels in indoor swimming pools, properly ventilated pools, and good personal hygiene. Because of the large number of susceptible people in these facilities, as well as all active people having an increased respiratory rate and airflow velocity, strict air quality requirements in indoor sports facilities should be maintained.

Emissions of DEHP-free PVC flooring.

Degrading 2-ethylhexyl-containing PVC floorings (eg DEHP-PVC floorings) and adhesives emit 2-ethylhexanol (2-EH) in the indoor air. The danger of flooring degradation comes from exposing occupants to harmful phthalates plasticisers (eg DEHP), but not from 2-EH as such. Since the EU banned the use of phthalates in sensitive applications, the market is shifting to use DEHP-free and alternative types of plasticisers in PVC products. However, data on emissions from DEHP-free PVC floorings are scarce. This study aimed at assessing the surface and bulk emissions of two DEHP-free PVC floorings over three years. The floorings were glued on the screed layer of concrete casts at 75%, 85%, and 95% RH. The volatile organic compounds (VOCs) were actively sampled using FLEC (surface emissions) and micro-chamber/thermal extractor (µ-CTE, bulk emissions) onto Tenax TA adsorbents and analyzed with TD-GC-MS. 2-EH, C9-alcohols, and total volatile organic compound (TVOC) emissions are reported. Emissions at 75% and 85% RH were similar. As expected, the highest emissions occurred at 95% RH. 2-EH emissions originated from the adhesive. Because the two DEHP-free floorings tested emitted C9-alcohols at all tested RH, it makes the detection of flooring degradation harder, particularly if the adhesive used does not emit 2-EH.

An atypical Bacillus anthracis infection in a bull-A potential occupational health hazard.

Bacillus anthracis infecting cattle is usually identified based on the typical symptom: sudden death. Bacillus anthracis causing atypical symptoms may remain undiagnosed and represent a potential occupational health hazard for, that is veterinarians and producers, butchers and tanners. In the year 2004, one case of sudden death in a dairy farm in southern Finland was diagnosed as bovine anthrax. Four years later 2008, an atypical case of anthrax was diagnosed in the same holding. The bull was taken to the Production Animal Hospital of the Faculty of Veterinary Medicine, University of Helsinki because of fever, loss of appetite and a symmetrically swollen scrotal sac. Penicillin treatment cured the fever but not the swollen scrotum. Before the intended therapeutic castration, a punctuate consisting of 10 ml fluid collected into a syringe from the scrotal sac was cultivated on blood agar at 37°C. After 24 hr, an almost pure culture of a completely non-hemolytic Bacillus cereus-like bacteria was obtained. The strain was identified as B. anthracis using Ba-specific primers by the Finnish Food Safety Authority (RUOKAVIRASTO). After the diagnosis, the bull was euthanized and destroyed, the personnel were treated with prophylactic antibiotics and the clinic was disinfected. In this particular case, treatment with water, Virkon S and lime seemed to be effective to eliminate endospores and vegetative cells since no relapses of anthrax have occurred in 10 years. This case is the last reported anthrax case in Finland.

Cleaning products: Their chemistry, effects on indoor air quality, and implications for human health.

The use of cleaning and disinfecting products both at work and at home increased during the COVID-19 pandemic. Those products often include surfactants, acids/bases, carcinogens such as chloroform, and endocrine-disrupting chemicals, such as cyclosiloxanes, phthalates, and synthetic fragrances, which may cause harmful health effects among professional cleaners as well as among people exposed at home or in their workplaces. The aim of this study was to synthesize the effects of the commonly used chemical, surface cleaning and disinfecting products on indoor air quality, focusing on chemical and particulate matter pollutants, exposure, and human health in residential and public buildings. We also provide a summary of recommendations to avoid harmful exposure and suggest future research directions. PubMed, Google Scholar, Scopus, and Web of Science (WoS) were used to search the literature. Analysis of the literature revealed that the use of cleaning products and disinfectants increase occupants' exposure to a variety of harmful chemical air contaminants and to particulate matter. Occupational exposure to cleaning and disinfectant products has been linked to an increased risk of asthma and rhinitis. Residential exposure to cleaning products has been shown to have an adverse effect on respiratory health, particularly on asthma onset, and on the occurrence of asthma(-like) symptoms among children and adults. Efforts to reduce occupants' exposure to cleaning chemicals will require lowering the content of hazardous substances in cleaning products and improving ventilation during and after cleaning. Experimentally examined, best cleaning practices as well as careful selection of cleaning products can minimize the burden of harmful air pollutant exposure indoors. In addition, indirect ways to reduce exposure include increasing people's awareness of the harmfulness of cleaning chemicals and of safe cleaning practices, as well as clear labelling of cleaning and disinfecting products.

Toxicity Screening of Fungal Extracts and Metabolites, Xenobiotic Chemicals, and Indoor Dusts with In Vitro and Ex Vivo Bioassay Methods.

It is controversial how useful bioassays are for identifying the in vivo toxicity of hazardous environmental exposures. In this study, fruiting bodies of forest mushrooms (n = 46), indoor mold colonies (n = 412), fungal secondary metabolites (n = 18), xenobiotic chemicals such as biocides and detergents (n = 6), and methanol extracts of indoor dusts from urban buildings (n = 26) were screened with two different bioactivity assays: boar sperm motility inhibition (BSMI) and inhibition of cell proliferation (ICP) tests. For the forest mushrooms, the toxicity testing result was positive for 100% of poisonous-classified species, 69% of non-edible-classified species, and 18% of edible-classified species. Colonies of 21 isolates of Ascomycota mold fungal species previously isolated from water-damaged buildings proved to be toxic in the tests. Out of the fungal metabolites and xenobiotic chemicals, 94% and 100% were toxic, respectively. Out of the indoor dusts from moldy-classified houses (n = 12) and from dry, mold-free houses (n = 14), 50% and 57% were toxic, respectively. The bioassay tests, however, could not differentiate the samples from indoor dusts of moldy-classified buildings from those from the mold-free buildings. Xenobiotic chemicals and indoor dusts were more toxic in the BSMI assay than in the ICP assay, whereas the opposite results were obtained with the Ascomycota mold colonies and fungal secondary metabolites. The tests recognized unknown methanol-soluble thermoresistant substances in indoor settled dusts. Toxic indoor dusts may indicate a harmful exposure, regardless of whether the toxicity is due to xenobiotic chemicals or microbial metabolites.

Endotoxins in indoor air and settled dust in primary schools in a subtropical climate.

Endotoxins can significantly affect the air quality in school environments. However, there is currently no reliable method for the measurement of endotoxins, and there is a lack of reference values for endotoxin concentrations to aid in the interpretation of measurement results in school settings. We benchmarked the "baseline" range of endotoxin concentration in indoor air, together with endotoxin load in floor dust, and evaluated the correlation between endotoxin levels in indoor air and settled dust, as well as the effects of temperature and humidity on these levels in subtropical school settings. Bayesian hierarchical modeling indicated that the concentration in indoor air and the load in floor dust were generally (<95th percentile) <13 EU/m(3) and <24,570 EU/m(2), respectively. Exceeding these levels would indicate abnormal sources of endotoxins in the school environment and the need for further investigation. Metaregression indicated no relationship between endotoxin concentration and load, which points to the necessity for measuring endotoxin levels in both the air and settled dust. Temperature increases were associated with lower concentrations in indoor air and higher loads in floor dust. Higher levels of humidity may be associated with lower airborne endotoxin concentrations.

Composition of Culturable Microorganisms in Dusts Collected from Sport Facilities in Finland during the COVID-19 Pandemic.

Sport facilities represent extreme indoor environments due to intense cleaning and disinfection. The aim of this study was to describe the composition of the cultivated microbiota in dust samples collected in sport facilities during the COVID-19 pandemic. A dust sample is defined as the airborne dust sedimented on 0.02 m2 within 28 d. The results show that the microbial viable counts in samples of airborne dust (n = 9) collected from seven Finnish sport facilities during the pandemic contained a high proportion of pathogenic filamentous fungi and a low proportion of bacteria. The microbial viable counts were between 14 CFU and 189 CFU per dust sample. In seven samples from sport facilities, 20-85% of the microbial viable counts were fungi. Out of 123 fungal colonies, 47 colonies belonged to the potentially pathogenic sections of Aspergillus (Sections Fumigati, Nigri, and Flavi). Representatives of each section were identified as Aspergillus fumigatus, A. flavus, A. niger and A. tubingensis. Six colonies belonged to the genus Paecilomyces. In six samples of dust, a high proportion (50-100%) of the total fungal viable counts consisted of these potentially pathogenic fungi. A total of 70 isolates were considered less likely to be pathogenic, and were identified as Aspergillus section Nidulantes, Chaetomium cochliodes and Penicillium sp. In the rural (n = 2) and urban (n = 7) control dust samples, the microbial viable counts were >2000 CFU and between 44 CFU and 215 CFU, respectively, and consisted mainly of bacteria. The low proportion of bacteria and the high proportion of stress tolerant, potentially pathogenic fungi in the dust samples from sport facilities may reflect the influence of disinfection on microbial communities.

Aspergillus Was the Dominant Genus Found during Diversity Tracking of Potentially Pathogenic Indoor Fungal Isolates.

Viable airborne pathogenic fungi represent a potential health hazard when exposing vulnerable persons in quantities exceeding their resilience. In this study, 284 indoor fungal isolates from a strain collection of indoor fungi were screened for pathogenic potential through the ability to grow in neutral pH at 37 °C and 30 °C. The isolates were collected from 20 locations including 14 problematic and 6 non-problematic ordinary buildings. Out of the screened isolates, 170 isolates were unable to grow at 37 °C, whereas 67 isolates growing at pH 7.2 at 37 °C were considered as potential opportunistic pathogens. Forty-seven isolates growing at 30 °C but not at 37 °C were considered as less likely pathogens. Out of these categories, 33 and 33 strains, respectively, were identified to the species level. The problematic buildings included known opportunistic pathogens: Aspergillus calidoustus, Trichoderma longibrachiatum, Rhizopus arrhizus and Paecilomyces variotii, as well as less likely pathogens: Aspergillus versicolor, Chaetomium cochliodes, Chaetomium globosum and Chaetomium rectangulare. Opportunistic pathogens such as Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger and Aspergillus tubingensis and less likely pathogens such as Aspergillus westerdijkiae, Chaetomium globosum and Dichotomopilus finlandicus were isolated both from ordinary and from problematic buildings. Aspergillus was the dominant, most diverse genus found during screening for potentially pathogenic isolates in the indoor strain collection. Studies on Aspergillus niger and Aspergillus calidodoustus revealed that tolerance to cleaning chemicals may contribute to the adaptation of Aspergillus species to indoor environments.

Melinacidin-Producing Acrostalagmus luteoalbus, a Major Constituent of Mixed Mycobiota Contaminating Insulation Material in an Outdoor Wall.

Occupants may complain about indoor air quality in closed spaces where the officially approved standard methods for indoor air quality risk assessment fail to reveal the cause of the problem. This study describes a rare genus not previously detected in Finnish buildings, Acrostalagmus, and its species A. luteoalbus as the major constituents of the mixed microbiota in the wet cork liner from an outdoor wall. Representatives of the genus were also present in the settled dust in offices where occupants suffered from symptoms related to the indoor air. One strain, POB8, was identified as A. luteoalbus by ITS sequencing. The strain produced the immunosuppressive and cytotoxic melinacidins II, III, and IV, as evidenced by mass spectrometry analysis. In addition, the classical toxigenic species indicating water damage, mycoparasitic Trichoderma, Aspergillus section Versicolores, Aspergillus section Circumdati, Aspergillus section Nigri, and Chaetomium spp., were detected in the wet outdoor wall and settled dust from the problematic rooms. The offices exhibited no visible signs of microbial growth, and the airborne load of microbial conidia was too low to explain the reported symptoms. In conclusion, we suggest the possible migration of microbial bioactive metabolites from the wet outdoor wall into indoor spaces as a plausible explanation for the reported complaints.

Chaetomium and Chaetomium-like Species from European Indoor Environments Include Dichotomopilus finlandicus sp. nov.

The genus Chaetomium is a frequently occurring fungal taxon world-wide. Chaetomium and Chaetomium-like species occur in indoor environments, where they can degrade cellulose-based building materials, thereby causing structural damage. Furthermore, several species of this genus may also cause adverse effects on human health. The aims of this research were to identify Chaetomium and Chaetomium-like strains isolated from indoor environments in Hungary and Finland, two geographically distant regions of Europe with drier and wetter continental climates, respectively, and to study their morphological and physiological properties, as well as their extracellular enzyme activities, thereby comparing the Chaetomium and Chaetomium-like species isolated from these two different regions of Europe and their properties. Chaetomium and Chaetomium-like strains were isolated from flats and offices in Hungary, as well as from schools, flats, and offices in Finland. Fragments of the translation elongation factor 1α (tef1α), the second largest subunit of RNA polymerase II (rpb2) and ß-tubulin (tub2) genes, as well as the internal transcribed spacer (ITS) region of the ribosomal RNA gene cluster were sequenced, and phylogenetic analysis of the sequences performed. Morphological examinations were performed by stereomicroscopy and scanning electron microscopy. Thirty-one Chaetomium sp. strains (15 from Hungary and 16 from Finland) were examined during the study. The most abundant species was Ch. globosum in both countries. In Hungary, 13 strains were identified as Ch. globosum, 1 as Ch. cochliodes, and 1 as Ch. interruptum. In Finland, 10 strains were Ch. globosum, 2 strains were Ch. cochliodes, 2 were Ch. rectangulare, and 2 isolates (SZMC 26527, SZMC 26529) proved to be representatives of a yet undescribed phylogenetic species from the closely related genus Dichotomopilus, which we formally describe here as the new species Dichotomopilus finlandicus. Growth of the isolates was examined at different temperatures (4, 15, 20, 25, 30, 37, 35, 40, and 45 °C), while their extracellular enzyme production was determined spectrophotometrically.

Detection of Chaetomium globosum, Ch. cochliodes and Ch. rectangulare during the Diversity Tracking of Mycotoxin-Producing Chaetomium-Like Isolates Obtained in Buildings in Finland.

The diversity of Chaetomium-like isolates in buildings in Finland is poorly documented. This paper describes a set of methods for rapid diversity tracking of 42 indoor Chaetomium-like isolates. These isolates were categorized based on their fluorescence emission, ascomatal hair morphology, responses in three bioassays and resistance/sensitivity to the wetting agent Genapol X-080. Thirty-nine toxigenic isolates were identified [Ch. globosum (n = 35), Ch. cochliodes (n = 2) and Ch. rectangulare (n = 2)]. These isolates were identified down to the species level by tef1α gene sequencing. The major toxic substances in the ethanol extracts of the Ch. globosum and Ch. cochliodes strains were chaetoglobosin, chaetoviridin A and C, chaetomugilin D and chaetomin, identified based on HPLC-UV and mass spectrometry data (MS and MS/MS). Ethanol extracts from pure Ch. globosum cultures exhibited a toxicological profile in the boar sperm motility inhibition assay (BSMI), sperm membrane integrity damage assay (SMID) and inhibition of cell proliferation (ICP) assay, similar to that exhibited by pure chaetoglobosin A. Overall, differences in fluorescence, morphology, toxicity profile, mycotoxin production and sensitivity to chemicals were consistent with those in tef1α sequencing results for species identification. The results indicate the presence of Ch. cochliodes and Ch. rectangulare in Finnish buildings, representing a new finding.

Bioreactivity, Guttation and Agents Influencing Surface Tension of Water Emitted by Actively Growing Indoor Mould Isolates.

The secretion of metabolites in guttation droplets by indoor moulds is not well documented. This study demonstrates the guttation of metabolites by actively growing common indoor moulds. Old and fresh biomasses of indoor isolates of Aspergillus versicolor, Chaetomium globosum, Penicillium expansum, Trichoderma atroviride, T. trixiae, Rhizopus sp. and Stachybotrys sp. were compared. Metabolic activity indicated by viability staining and guttation of liquid droplets detected in young (<3 weeks old) biomass were absent in old (>6 months old) cultures consisting of dehydrated hyphae and dormant conidia. Fresh (<3 weeks old) biomasses were toxic more than 10 times towards mammalian cell lines (PK-15 and MNA) compared to the old dormant, dry biomasses, when calculated per biomass wet weight and per conidial particle. Surfactant activity was emitted in exudates from fresh biomass of T. atroviride, Rhizopus sp. and Stachybotrys sp. Surfactant activity was also provoked by fresh conidia from T. atroviride and Stachybotrys sp. strains. Water repealing substances were emitted by cultures of P. expansum, T. atroviride and C. globosum strains. The metabolic state of the indoor fungal growth may influence emission of liquid soluble bioreactive metabolites into the indoor air.

Corrigendum: Structural Diversity and Bioactivities of Peptaibol Compounds From the Longibrachiatum Clade of the Filamentous Fungal Genus Trichoderma.

[This corrects the article DOI: 10.3389/fmicb.2019.01434.].

Exposure to indoor air contaminants in school buildings with and without reported indoor air quality problems.

Reported indoor air quality (IAQ) complaints are common even in relatively new or renovated school buildings in Finland. However, detecting the causes for complaints with commonly used indoor air measurements is difficult. This study presents data on perceived and measured IAQ in six comprehensive school buildings in Finland. The aim of this study was to discover the possible differences of perceived and measured IAQ between schools with reported IAQ complaints and schools without reported IAQ complaints. The initial categorisation of schools with ('problematic schools') and without ('comparison schools') complaints was ensured via a validated indoor climate survey and a recently developed online questionnaire, which were completed by 186 teachers and 1268 students from the six schools. IAQ measurements of physical parameters, gaseous pollutants, particulate matter and bioaerosols were conducted in four problematic school buildings (26 classrooms) and two comparison school buildings (12 classrooms). Using air sampling as well as exhaust air filters and classroom settled dust to detect the presence of elevated concentrations of airborne cultivable microbes and pathogenic, toxigenic and mycoparasitic Trichoderma strains were the most indicative methods in distinguishing problematic schools from comparison schools. Other IAQ-related measurements did not detect clear differences between problematic and comparison schools, as the concentration levels were very low. The results indicate that the complaints reported by occupants could have been related to excess moisture or mould problems that had not been found or repaired. Ventilation pressure condition investigations and simultaneous exhaust and supply air filter dust culture should be addressed precisely in future studies.

Renovation of a "sick building": the challenge of attaining the confidence of occupants.

BACKGROUND: This case study focused on the renovation of a building with severe mold and HVAC problems. The users did not trust the success of the planned remedies, and the situation became conflict-prone. The aims of the study were to improve communication and cooperation between experts participating in the renovation process and the future users of the building and monitor the success of the remedies. METHODS: An intervention was implemented with the aim of making the renovation easily understood by the future users of the building and preventing the escalation of unnecessary concern among them. The follow-up methods comprised a questionnaire study, technical inspections, quality measurements of the indoor air, structural follow-up measurements, and interviews of key persons. RESULTS: The renovation itself seems to have been successful, and the model to improve communication and cooperation appears to be a promising one. The confidence of the future users was attained, and the relocation took place as planned. CONCLUSIONS: In order to succeed in the renovation of a "sick building," both technical expertise and investment in information and communication are needed.

Man-made vitreous fibers in office buildings in the Helsinki area.

Several sources of man-made vitreous fibers (MMVFs) may exist in an office environment causing irritation symptoms among occupants. In 258 office buildings, the occurrence and density of settled MMVFs on surfaces were measured by two sampling methods. Altogether, 1113 samples of settled dust were collected from surfaces with plastic bags and gelatine tape and were analyzed with a scanning electron microscope and a stereomicroscope, respectively. Tape samples from 68 buildings were collected from frequently cleaned (n = 162) and seldom cleaned (n = 57) room surfaces in 56 and 29 offices, respectively, and from supply air ducts (n = 24) in 10 offices. MMVFs longer than 20 microm were counted with a stereomicroscope. Irritation symptoms were recorded with a questionnaire. More than 60% of the surface dust and almost 90% of the samples collected from supply air ducts contained MMVFs. The density of MMVFs longer than 20 microm ranged from < 0.1 to 5 fiber cm(- 2). The mean density of the MMVFs was about two times higher on the seldom cleaned surfaces than on the frequently cleaned surfaces. The density was usually under 0.2 MMVF cm(- 2) in surface dust of offices without emission sources of MMVFs. The measurements combined with qualitative analysis of settled dust can help to localize relevant sources of fiber emissions. Altogether, in 40% of the buildings, several occupants had repeated irritation symptoms that were verified by occupational health care personnel.

Airborne concentrations of volatile organic compounds, formaldehyde and ammonia in Finnish office buildings with suspected indoor air problems.

A database of indoor air concentrations of volatile organic compounds (VOCs) (n = 528), formaldehyde (n = 76), and ammonia (n = 47) in office environments was analyzed to suggest interpretation guidelines for chemical measurements in office buildings with suspected indoor air problems. Indoor air samples were collected for VOCs from 176 office buildings, 23 offices for formaldehyde, and 14 office buildings for ammonia in 2001-2006. Although the buildings had reported indoor air complaints, a walk-through inspection by indoor air specialists showed no exceptional sources of indoor air pollutants. The measurements of chemical pollutants did not indicate any clear reason for the complaints. The geometric mean concentration of total volatile organic compounds (TVOC) was 88 microg m(-3) in office rooms and 75 microg m(-3) in the open plan offices. The mechanical supply and exhaust ventilation significantly (p < 0.004) decreased the indoor air concentration of TVOC. The highest mean concentration and frequency distributions were determined for the individual VOCs. The most common VOCs found in > or = 84% of the indoor samples include toluene, xylene (p,m), 1-butanol, nonanal, and benzene. According to concentrations, the most abundant VOCs were 2-(2-ethoxyethoxy)ethanol, acetic acid, 1,2-propanediol, and toluene. The geometric mean concentration of formaldehyde and ammonia in the office buildings was 11 microg m(-3) (3-44 microg m(-3) and 14 microg m(-3) (1-49 microg m(-3), respectively. On the basis of statistical analyses, the guideline value indicating a usual concentration of the pollutant in office buildings is 70 microg m(-3) for TVOC, 7 microg m(-3) for most individual VOCs, 10 microg m(-3) for formaldehyde, and 12 microg m(-3) for ammonia. The guidance value suggested for TVOC is 250 microg m(-3), for formaldehyde 15 microg m(-3), and for ammonia 25 microg m(-3). If the guidance value is exceeded, this may indicate the existence of an exceptional source and the need for additional environmental investigations. The levels should not be used for the evaluation of health risks. The guideline values are applicable in a subarctic climate for modern, urban office buildings.

Human exposure to NO2 in school and office indoor environments.

BACKGROUND: Although nitrogen dioxide (NO2) is one of the most common air pollutants encountered indoors, and extensive literature has examined the link between NO2 exposure and duration causing adverse respiratory effects in susceptible populations, information about global and local exposure to NO2 in different indoor environments is limited. To synthesize the existing knowledge, this review analyzes the magnitude of and the trends in global and local exposure to NO2 in schools and offices, and the factors that control exposure. METHODS: For the literature review, Web of Science, SCOPUS, Google Scholar, and PubMed were searched using 42 search terms and their combinations to identify manuscripts, reports, and directives published between 1971 and 2019. The search was then extended to the reference lists of relevant articles. RESULTS: The calculated median, as well as the mean, concentration of NO2 in school (median 21.1 µg/m3; mean 29.4 µg/m3) and office settings (median 22.7 µg/m3; mean 25.1 µg/m3) was well below the World Health Organization (WHO) guideline of 40 µg/m3 for the annual mean NO2 concentration. However, a large range of average concentrations of NO2 were reported, from 6.00 to 68.5 µg/m3 and from 3.40 to 56.5 µg/m3 for school and office environments, respectively, indicating situations where the WHO guidelines are exceeded. Outdoor levels of NO2 are a reliable predictor of indoor NO2 levels across seasons, with mean and median Indoor/Outdoor (I/O) ratios of 0.9 and 0.7 in school and 0.9 and 0.8 in office environments, respectively. The absence of major indoor NO2 emission sources and NO2 sinks, including chemical reactions and deposition, are the reasons for lower indoor NO2 concentrations. During the winter, outdoor NO2 concentrations are generally higher than during the summer. In addition, various building and indoor environment characteristics, such as type of ventilation, air exchange rates, airtightness of the envelope, furnishing and surface characteristics of the building, location of the building (urban versus suburban and proximity to traffic routes), as well as occupants' behavior (such as opening windows), have been statistically significantly associated with indoor NO2 levels in school and office environments. CONCLUSIONS: Indoor exposure to NO2 from the infiltration of ambient air can be significant in urban areas, and in the case of high traffic volume. Although reducing transportation emissions is challenging, there are several easier means to reduce indoor NO2 concentrations, including a ventilation strategy with suitable filters; location planning of new schools, classrooms, and ventilating windows or intakes; traffic planning (location and density); and reducing the use of NO2-releasing indoor sources.

Screening Mold Colonies by Using Two Toxicity Assays Revealed Indoor Strains of Aspergillus calidoustus Producing Ophiobolins G and K.

The occurrence and toxin production of the opportunistic pathogen Aspergillus calidoustus in Finnish buildings is not well documented in the literature. We tracked and identified four A. calidoustus colonies cultivated from indoor settled dusts and revealed the biological activities of crude biomass extracts. The toxic substances were identified as 6-epi-ophiobolin K, ophiobolin K, and ophiobolin G by high-performance liquid chromatography-mass spectrometry (HPLC-MS) based on chromatographic and mass spectrometry data (MS and MS/MS) on the crude extract of A. calidoustus strain MH34. A total of 29 fungal colonies collected from settled dust in an office room reported for indoor-air-related illnesses were screened for toxins that inhibited boar sperm motility in the BSMI (boar sperm motility inhibiting) assay and cell proliferation in the ICP (inhibition of cell proliferation) assays with PK-15 cells. Out of the 27 colonies tested as toxic, 12 colonies exhibiting conidiophores representative of the genera Chaetomium, Penicillium, and Paecilomyces were excluded from the study, while 13 colonies exhibited Aspergillus-like conidiophores. Biomass suspensions of these colonies were divided into two categories: Category 1 colonies (n = 4), toxic in the BSMI assay and the ICP assays, emitted blue fluorescence and grew at 37 °C; Category 2 colonies (n = 9), only toxic in the ICP assay, emitted orange fluorescence and exhibited limited or no growth at 37 °C. Colonies in Category 1 were pure-cultured, and the strains were named as MH4, MH21, MH34, MH36. Strain MH34 was identified as A. calidoustus by the internal transcribed spacer (ITS) sequences. Ethanol-soluble dry substances extracted from the biomass of the pure cultures exhibited a toxicological profile in the BSMI assay, SMID (sperm membrane integrity damage) assay, and ICP assay similar to that exhibited by pure ophiobolin A. Overall, the viable conidia of A. calidoustus in indoor settled dusts deserve attention when potentially hazardous mold species are monitored.