Indoor exposure to bioaerosol particles: levels and implications for inhalation dose rates in schoolchildren

Children spend most of their time inside schools and bioaerosol particles are part of their everyday environment. Although bioaerosol particles are considered to be a potential risk factor for various health concerns, information concerning the indoor exposures and inhalation doses is still limited. This study aimed (i) to quantify bacterial and fungal particles levels in indoor and outdoor air of public primary schools, (ii) to assess the influence of ambient air on bacteria and fungi presence indoors, and (iii) to estimate the inhalation dose rates for respective children (8–10 years old) in comparison with adult staff. Air samples were collected in 20 primary schools in a total of 71 classrooms during heating season with a microbiological air sampler. The results showed that indoor bacterial and fungal concentrations were higher than outdoor levels (p?<?0.05), which could be explained by differences in density of occupation, occupant’s activities, and inadequate ventilation. CO₂ levels were significantly correlated with indoor bacteria concentrations. Moreover, mean indoor bacteria concentrations were above national limit values in all the evaluated Porto primary schools, from two to nine times higher. Regarding fungi concentrations, indoor levels were above the reference value in 75% of the schools and overall indoor levels registered a 3-fold increase compared with outdoor values. Children had two times higher inhalation dose rates to bioaerosol particles when compared to adult individuals. Thus, due to their susceptibility, special attention should be given to educational settings in order to guarantee the children healthy development.     

Microbiological indoor air quality in an office building in Gliwice,Poland: analysis of the case study

Bioaerosols play a significant role in indoor air quality (IAQ) as they can be the cause of several health problems, including acute allergies and infectious diseases. This study aimed to characterize and compare the microbial air quality of air-conditioned (AC) and naturally ventilated (NV) office rooms in the Upper Silesia region of Poland. The bacterial samples were collected during the late spring season. Culturable bacteria were deposited on the nutrient media on Petri dishes to investigate the viable-culturable count (VCC) of bacteria and bacterial community structure using a Biolog GEN III system. In total, 12 species of bacteria were identified, with the most isolated Macrococcus equipercicus, Micrococcus luteus D, Staphylococcus xylosus (indoor), and Bacillus species (outdoor). The indoor mean concentrations of bacterial aerosol ranged from 10² to 10³ CFU m^?3, below Polish proposals for threshold limit standards in office buildings. The indoor-to-outdoor (I/O) ratios indicated that studied air pollutants in the office rooms originated from the indoor air. These results, together with community composition of bacteria, indicate that most of the bacteria present in the studied office building were relatively fresh and of human origin. Multi-antibiotic resistance (MAR) tests showed that the most antibiotic-resistant features were present in Macrococcus species. The office building exposure dose (OBED) and mass median aerodynamic diameter (MMAD) of bacteria aerosol were estimated. The highest value of OBED over the study period was obtained for staff working in offices with natural ventilation (141 CFU kg^?1), in contrast to the value for staff working in offices equipped with air conditioning (about 100 CFU kg^?1). The MMAD of viable airborne bacteria was higher in AC offices (2.4 μm) than in NV offices (2.2 μm).     

Polycyclic aromatic hydrocarbons and their nitro derivatives from indoor biomass-fueled cooking in two rural areas of Thailand: a case study

Household fuel combustion for cooking is a major source of hazardous pollutants, including polycyclic aromatic hydrocarbons (PAHs) and their nitro derivatives (NPAHs). These pollutants impact indoor air quality and human health. In this study of two rural households in Chiang Mai, Thailand, PM_2.5 samples were collected both inside and outside the houses during cooking and noncooking periods. Real-time monitoring of indoor PM_2.5 was also conducted. The concentrations of PAHs, NPAHs, levoglucosan (LG), and carbon fractions in the PM_2.5 fractions were quantified. The most severe contamination was observed inside the house during cooking with mean concentrations of 9980 ng/m³ and 18,700 pg/m³ for PAHs and NPAHs, respectively. The composition profiles of PAHs and NPAHs showed that benz[a]anthracene, benzo[k]fluoranthrene, and benzo[a]pyrene made the greatest contribution to total PAHs, while 9-nitroanthracene made the greatest contribution to total NPAHs. The correlation coefficient (p < 0.01) of PAHs and NPAHs, using LG as a tracer, confirmed that the main source of PAHs and NPAHs was biomass burning. This was further confirmed by the indoor to outdoor ratios and diagnostic ratios using PAHs and NPAHs and carbonaceous fractions. During cooking periods, the carcinogenic risks exceeded the WHO guideline values and would be classified as “definite risks.” This suggest that biomass burning inside houses poses serious health risks through inhalation, which is the main route of exposure and may increase the incidence of cancer. Upgradation of residential environments is needed to improve indoor air quality, especially, in rural areas of Thailand.     

Concentrations of PM<Subscript>10</Subscript> and airborne bacteria in daycare centers in Seoul relative to indoor environmental factors and daycare center characteristics

The purpose of this study was to measure concentrations of PM₁₀ and airborne bacteria (AB) to determine how each one of them correlated with particular indoor environmental factors and characteristics of daycare centers in Seoul, South Korea.PM₁₀ and AB were sampled in 330 daycare centers in the middle of a classroom, along with measurements of temperature and relative humidity. Spearman’s correlation and Mann-Whitney analyses were used to examine the relationship among and differences between PM₁₀ concentration, AB concentration, indoor environmental factors, and daycare center characteristics.There were significant correlations between PM₁₀ concentration and AB concentration (r?=?0.128, p?<?0.05), temperature (r?=?0.153, p?<?0.01), and relative humidity (r?=?0.185, p?<?0.01). PM₁₀ concentrations with two or more windows; a heating, ventilation, and air conditioning (HVAC) system; and the use of air purifier were lower than concentrations with one window, window ventilation only, and no air purifier. AB concentrations were significantly higher when daycare centers had only one window and used only window ventilation (p?<?0.05).Though there are many uncontrollable outdoor environmental factors that influence air quality, we demonstrated that using an HVAC system and an air purifier significantly reduces PM₁₀ concentrations and is a practical change that could be implemented to improve the indoor air quality of daycare centers.     

Influence of Number of Visitors and Weather Conditions on Airborne Particulate Matter Mass Concentrations at The Plitvice Lakes National Park,Croatia During Summer and Autumn

We investigated the influence of local meteorological conditions and number of visitors on ambient particulate matter (PM) mass concentrations and particle fraction ratios at the Plitvice Lakes National Park between July and October 2018. Outdoor mass concentrations of particles with aerodynamic diameters of less than 1, 2.5, and 10 μm (PM₁, PM_2.5, and PM₁₀, respectively) and indoor PM₁ were measured with two light-scattering laser photometers set up near the largest and most visited Kozjak Lake. Our findings suggest that the particles mainly originated from background sources, although some came from local anthropogenic activities. More specifically, increases in both indoor and outdoor mass concentrations coincided with the increase in the number of visitors. Indoor PM₁ concentrations also increased with increase in outdoor air temperature, while outdoor PMs exhibited U-shaped dependence (i.e., concentrations increased only at higher outdoor air temperatures). This behaviour and the decrease in the PM₁/PM_2.5 ratio with higher temperatures suggests that the production and growth of particles is influenced by photochemical reactions. The obtained spectra also pointed to a daily but not to weekly periodicity of PM levels.Key words: anthropogenic PM sources, bivariate polar plot, light-scattering laser photometry, weighted overlapped segment averaging     

Analysis of the photochemical production of ozone using Tropospheric Ultraviolet-Visible (TUV) Radiation Model in an Asian megacity

A study of surface layer ozone (O₃) and its primary precursors (NO _x ?=?NO?+?NO₂) was carried out at Kolkata (22° 33′ N, 88° 30′ E), an urban site in eastern India from October 2010 to April 2011. A simple NO _x cycle-based photochemical model for the net rate of production of tropospheric ozone was studied. Photolytic rate constants for NO₂ (\( {j}_{{\mathrm{NO}}_2} \)) were estimated using the Tropospheric Ultraviolet and Visible (TUV) Radiation Model-Version 4.1. Relationships between predicted and measured ozone data were found to be sensitive with respect to time of the day. A correlation between the observed ozone and \( {j}_{{\mathrm{NO}}_2} \) during some case study days in the morning (R ² range, 0.34 to 0.96) and the late afternoon (R ² range, 0.79 to 0.99) implies that the NO _x chemistry is predominant due to enhanced automobile emissions during the peak traffic hours. VOCs and some peroxy radicals play a vital role in the chemistry of ozone production (net). Computed air mass backward trajectories using HYSPLIT model established the source and transport pathways of the trace gases. The results obtained on different days indicate the importance of advection of gases from both continental as well as marine air mass on case-specific circumstances. Tropospheric columnar NO₂ outputs were also compared to ground-based measurements, and these point towards a good regional contribution of NO₂.     

Respiratory health effects associated with indoor particulate matter (PM<Subscript>2.5</Subscript>) in children residing near a landfill site in Durban,South Africa

Landfill sites are known for their potential for generating particulate matter (PM) which can pose respiratory health problems for people residing in the adjacent communities. As PM_2.5 have health impacts on children residing close to landfill sites, it is important to understand the extent to which they are affected. In this investigation, PM_2.5 measurements in an indoor environment were conducted to assess its concentration levels and its association with the lung function patterns in children aged between 6 and 12 years residing within a 2-km radius from the Bisasar Road landfill site, the largest formal landfill site in Africa. The study was conducted between November 2013 and January 2014 in the Clare Estate community in Durban, South Africa. Spirometry was conducted in children (n = 23) to obtain respiratory data. The mean forced expiratory volume in 1 s (FEV₁) was 82%, mean forced vital capacity (FVC) was 75%, and mean FEV₁/FVC was 115%. Furthermore, the study involved indoor PM_2.5 measurements from households (n = 23). The 24-h indoor PM_2.5 sampling was conducted using a real-time particulate monitor (HAZ-Dust EPAM-5000, Plaistow, USA) in each household. The mean PM_2.5 concentration of 76.5 μg m^?3 and the range of 202 μg m^?3 were observed. A regression model was computed to determine the association between PM_2.5 and lung function patterns. A strong statistically significant relationship (p < 0.002) between indoor PM_2.5 concentration levels and FVC was observed. The results suggest that residing near the landfill site is associated with an increased likelihood of respiratory effects among children.     

Skin cancer risk perception and sun protection behavior at work,at leisure,and on sun holidays: a survey for Danish outdoor and indoor workers

Background

To prevent occupational skin cancer, it is essential that the sun-protective behavior of outdoor workers is adequate. The aim is to study the sun-protective behavior of Danish outdoor workers at work, at leisure, and on sun holiday and compare it to that of indoor workers.

Methods

This is a cross-sectional study, based on a 53-item survey completed by Danish outdoor (n?=?380) and indoor workers (n?=?119) in 2016–2017. Status as outdoor or indoor worker was decided based on self-report and behavioral differences were tested using (paired) t tests and multiple regression adjusted for age, sex, educational level, history of smoking, and skin type.

Results

Danish outdoor workers at work use sun protection less than they do at leisure and on sun holiday (α?<?.05) where their sun protection behavior is similar to that of indoor workers. The proportion of Danish outdoor workers that always/often use sun protection at work is for shade seeking around noon 4.2%, sunscreen 34.5%, wide-brimmed hat 25.3%, and long trousers and shirt with sleeves 42.4%. Of Danish outdoor workers, 49.5% do not think about the risk of occupational skin cancer and 11.8% think the risk is insignificant, 32.4% think that the use of sun protection is of low or no importance, 84.2% consider sunburn important as skin cancer risk factor still 88.9% have a history of sunburn at work, >?80.0% agree that risk of skin cancer is reduced by the use of sun protection, and only 4.0% dismiss the possibility of sun protection use at work.

Conclusions

Skin cancer risk and use of sun protection at work are largely neglected in Danish outdoor workers, more so than at leisure and on sun holiday where their risk behavior resembles that of indoor workers. This indicates an untapped workplace preventive potential.

     

Study of metals in radical-mediated toxicity of particulate matter in indoor environments of Pune,India

The concentration of coarse and fine indoor particulate matter (PM) was measured along with that of metals (Fe, Cu, Zn, Mn, Pb, Cd, Co, Ni, and Cr) collected from rural and urban residential environments of Pune City with the purpose of examining their free radical generation and its related toxicity. The average mass concentration of indoor PM₁₀ and PM_2.5 was ～3.3 and ～4.5 times higher than the threshold limits of the Indian National Ambient Air Quality Standards (NAAQS) at urban and rural sites, respectively. The concentration of metals was found to be higher in the fine fraction of PM collected from the rural site. Metal analysis revealed the dominance of Fe concentrations in both PM₁₀ and PM_2.5 followed by Zn, Ni, and Cu. Electron paramagnetic resonance (EPR) was used to evaluate the presence of free radicals in samples collected from both the sites. EPR spectra for these particles were attributed to both Fe³⁺ (g = 1.99～2.0) and free radicals (g = 2.0023 and g = 2.003) in PM samples. Dithiothreitol (DTT) assay was also performed which supports the presence of higher redox activity in the fine fraction of PM at the rural site. Significant DNA damage was observed by both fractions of PM when tested in the controlled experiment, with averages of 43 and 30.9 % for PM₁₀ and 55.3 and 40.5 % for PM_2.5 at the rural and urban sites, respectively. This study articulates a significant amount of evidence to understand the importance of size and composition (especially metals) of indoor PM in the toxicological mechanism.     

Evaluation of the toxicity of a Kosa (Asian duststorm) event from view of food poisoning: observation of Kosa cloud behavior and real-time PCR analyses of Kosa bioaerosols during May 2011 in Kanazawa,Japan

Kosa (Asian duststorm) is a well-known phenomenon where particles are transported from Mongolia and northwestern China via Eastern Asia to the American continent. Kosa bioaerosols (airborne microorganisms within Kosa) were frequently found during Kosa event, and there is concern that they may affect human health. For biological observation and evaluation of Kosa events, we made sampling of aerosols in Kosa events on May 2 (KOSA1) and May 13 (KOSA2), 2011, at Kanazawa, Japan. From the data of lidar from Toyama, SPRINTARS simulation model and the backward trajectories of air masses, both events were originated in desert area of Mongolia. KOSA episode 1 was stronger than KOSA episode 2 above the surface boundary layer, and KOSA episode 2 contained the particles from the local source such as soil, sea salt, and various particles formed in the polluted atmosphere. The DNA to total suspended particle matter (SPM) ratios in KOSA1 and KOSA2 were 0.012 and 0.00978, respectively. Bacterial species compositions were identified qualitatively. Many Gammaproteobacteria were cloned and identified from both KOSA. Quantitative toxicity observations to assess the risk of food poisoning were performed by real-time PCR of food poisoning bacteria, Bacillus and Staphylococcus spp. The ratios of the concentrations of Bacillus and Staphylococcus spp. relative to SPM in KOSA1 and KOSA2 were 33.1 and 43.1 copies μg-SPM^?1, respectively. The results of toxicity evaluations by the mathematical simulations suggested that compared with KOSA1, KOSA2 had a 1.35 times higher risk of causing food poisoning.     

Characterization of coarse particulate matter in school gyms

We investigated the mass concentration, mineral composition and morphology of particles resuspended by children during scheduled physical education in urban, suburban and rural elementary school gyms in Prague (Czech Republic). Cascade impactors were deployed to sample the particulate matter. Two fractions of coarse particulate matter (PM_10−2.5 and PM_2.5−1.0) were characterized by gravimetry, energy dispersive X-ray spectrometry and scanning electron microscopy. Two indicators of human activity, the number of exercising children and the number of physical education hours, were also recorded. Lower mass concentrations of coarse particulate matter were recorded outdoors (average PM_10−2.5 4.1–7.4 μg m⁻³ and PM_2.5−1.0 2.0–3.3 μg m⁻³) than indoors (average PM_10−2.5 13.6–26.7 μg m⁻³ and PM_2.5−1.0 3.7–7.4 μg m⁻³). The indoor concentrations of coarse aerosol were elevated during days with scheduled physical education with an average indoor–outdoor (I/O) ratio of 2.5–16.3 for the PM_10−2.5 and 1.4–4.8 for the PM_2.5−1.0 values. Under extreme conditions, the I/O ratios reached 180 (PM_10−2.5) and 19.1 (PM_2.5−1.0). The multiple regression analysis based on the number of students and outdoor coarse PM as independent variables showed that the main predictor of the indoor coarse PM concentrations is the number of students in the gym. The effect of outdoor coarse PM was weak and inconsistent. The regression models for the three schools explained 60–70% of the particular dataset variability. X-ray spectrometry revealed 6 main groups of minerals contributing to resuspended indoor dust. The most abundant particles were those of crustal origin composed of Si, Al, O and Ca. Scanning electron microscopy showed that, in addition to numerous inorganic particles, various types of fibers and particularly skin scales make up the main part of the resuspended dust in the gyms. In conclusion, school gyms were found to be indoor microenvironments with high concentrations of coarse particulate matter, which can contribute to increased short-term inhalation exposure of exercising children.     

High Blood Pressure and Long-Term Exposure to Indoor Noise and Air Pollution from Road Traffic

Background: Traffic noise has been associated with prevalence of hypertension, but reports are inconsistent for blood pressure (BP). To ascertain noise effects and to disentangle them from those suspected to be from traffic-related air pollution, it may be essential to estimate people’s noise exposure indoors in bedrooms.Objectives: We analyzed associations between long-term exposure to indoor traffic noise in bedrooms and prevalent hypertension and systolic (SBP) and diastolic (DBP) BP, considering long-term exposure to outdoor nitrogen dioxide (NO₂).Methods: We evaluated 1,926 cohort participants at baseline (years 2003–2006; Girona, Spain). Outdoor annual average levels of nighttime traffic noise (L_night) and NO₂ were estimated at postal addresses with a detailed traffic noise model and a land-use regression model, respectively. Individual indoor traffic L_night levels were derived from outdoor L_night with application of insulations provided by reported noise-reducing factors. We assessed associations for hypertension and BP with multi-exposure logistic and linear regression models, respectively.Results: Median levels were 27.1 dB(A) (indoor L_night), 56.7 dB(A) (outdoor L_night), and 26.8 μg/m³ (NO₂). Spearman correlations between outdoor and indoor L_night with NO₂ were 0.75 and 0.23, respectively. Indoor L_night was associated both with hypertension (OR = 1.06; 95% CI: 0.99, 1.13) and SBP (β = 0.72; 95% CI: 0.29, 1.15) per 5 dB(A); and NO₂ was associated with hypertension (OR = 1.16; 95% CI: 0.99, 1.36), SBP (β = 1.23; 95% CI: 0.21, 2.25), and DBP (β⊇= 0.56; 95% CI: –0.03, 1.14) per 10 μg/m³. In the outdoor noise model, L_night was associated only with hypertension and NO₂ with BP only. The indoor noise–SBP association was stronger and statistically significant with a threshold at 30 dB(A).Conclusion: Long-term exposure to indoor traffic noise was associated with prevalent hypertension and SBP, independently of NO₂. Associations were less consistent for outdoor traffic L_night and likely affected by collinearity.Citation: Foraster M, Künzli N, Aguilera I, Rivera M, Agis D, Vila J, Bouso L, Deltell A, Marrugat J, Ramos R, Sunyer J, Elosua R, Basagaña X. 2014. High blood pressure and long-term exposure to indoor noise and air pollution from road traffic. Environ Health Perspect 122:1193–1200; http://dx.doi.org/10.1289/ehp.1307156     

Influence of different complexity levels of road traffic models on air quality modelling at street scale

Urban mobility accounts for 38 and 19% of nitrogen oxide (NO_x) and particulate matter (PM) emissions at European urban areas, respectively. Despite of all the technological development around automobile industry, urban areas are still facing problems related to exposure to high levels of air pollutants. Increasing the accuracy of both emissions and air quality modelling from road traffic is a key-issue for the management of air pollution in road transport sector. This study assessed the influence of using different road traffic emission models on the accuracy of air quality modelling with street-level resolution, having as a case study an urban area located on the centre region of Portugal. Two emission models, with different complexity levels regarding the ability to characterise the traffic dynamics were analysed, namely, transport emission model for line sources (TREM) and vehicle-specific power (VSP), based on data obtained in an experimental campaign. To perform the air quality simulations, the pollutant dispersion in the atmosphere under variable wind conditions (VADIS) model was used and two pollutants were analysed: NO_x and PM10. The results showed that the magnitude of PM10 and NO_x concentrations were result of a conjoint influence of traffic dynamics and meteorological conditions. Comparison between measured and modelled data showed that the VADIS model could track the evolution of NO_x levels, for both emission models considered, displaying a high correlation (>?0.8) between traffic-related NO_x emissions and NO_x concentrations. For PM10, VADIS model is more sensitive to the differences in the emissions calculation; however, it was observed that the traffic-related PM10 emissions accounts 1.3–8.4% to the PM10 concentration levels at the study area.     

Green wall technology for the phytoremediation of indoor air: a system for the reduction of high CO<Subscript>2</Subscript> concentrations

Along with the growing requirement to reduce building carbon emissions, a need has arisen to find energy efficient means of improving the quality of indoor air. Indoor plants have been shown to be capable of reducing most air pollutants; however, practical numbers of potted plants will not have the capacity to control many forms of air pollution, especially CO₂. Green walls are space-efficient means of increasing the density of indoor plants. We assessed an active green wall for its potential to reduce CO₂ in chambers and a test room. Chlorophytum comosum and Epipremnum aureum were both effective cultivars for CO₂ removal at light densities greater than 50 μmol m^?2 s^?1. Substrate ventilation increased the rate of CO₂ draw down from chambers, possibly due to increased leaf gas exchange rates. Green walls were then tested in a 15.65-m³ sealed simulation room, allowing the calculation of clean air delivery rate (CADR) and air changes per hour (ACH) equivalents based on CO₂ draw down. Rates of CO₂ draw down were modest under typical brightly lit indoor conditions (50 μmol m^?2 s^?1); however, when light intensity was increased to relatively bright levels, similar to indoor conditions next to a window or with the addition of supplementary lighting (250 μmol m^?2 s^?1), a 1-m² green wall was capable of significant quantifiable reductions of high CO₂ concentrations within a sealed room environment. Extrapolating these findings indicates that a 5-m² green wall containing C. comosum could balance the respiratory emissions of a full-time occupant.     

The effect of outdoor air and indoor human activity on mass concentrations of PM(10), PM(2.5), and PM(1) in a classroom

The 12-h mass concentration of PM₁₀, PM_2.5, and PM₁ was measured in a lecturing room by means of three co-located Harvard impactors. The filters were changed at 8 AM and at 8 PM to cover the periods of presence and absence of students. Concentrations were assessed by gravimetry. Ambient PM₁₀ data were available for corresponding 12-h intervals from the nearest state air-quality-monitoring network station. The data were pooled into four periods according to the presence and absence of students—Monday-Thursday day (workday daytime), Monday-Thursday night (workday night), Friday-Sunday day (weekend daytime), and Friday-Sunday night (weekend night). Average indoor workday daytime concentrations were 42.3, 21.9 and 13.7 μg m⁻³, workday night were 20.9, 19.1 and 15.2 μg m⁻³, weekend daytime were 21.9, 18.1 and 11.4 μg m⁻³, and weekend night were 24.5, 21.3, and 15.6 μg m⁻³ for PM₁₀, PM_2.5, and PM₁, respectively. The highest 12-h mean, median, and maximum (42.3, 43.0, and 76.2 μg m⁻³, respectively) indoor concentrations were recorded on workdays during the daytime for PM₁₀. The statistically significant (r=0.68,P<0.0009) correlation between the number of students per hour per day and the indoor coarse fraction calculated as PM_10−2.5 during daytime on workdays indicates that the presence of people is an important source of coarse particles indoor. On workdays, the daytime PM₁₀ indoor/outdoor ratio was positively associated (r=0.93) with an increasing indoor coarse fraction (PM_10-2.5), also indicating that an important portion of indoor PM₁₀ had its source inside the classroom. With the exception of the calculated coarse fraction (PM_10-2.5), all of the measured indoor particulate matter fractions were significantly highly correlated with outdoor PM₁₀ and negatively correlated with wind velocity, showing that outdoor levels of particles influence their indoor concentrations.     

Multi-zone measurement of particle concentrations in a HVAC building with massive printer emissions: influence of human occupation and particle transport indoors

Particle number (PN) and mass (PM) concentrations were measured in four offices in a HVAC building, one of them corresponding to a printer room. On-line monitoring of the indoor PM concentrations was accompanied with monitoring of the outdoor concentration. In addition, black carbon was measured in two of the selected offices. PN concentrations were measured with a variety of instruments (SMPS,NanoScan, P-Trak) covering a range between 10 nm and 9 μm, whereas PM₁₀ mass concentrations were measured with several DustTraks. Cleaning activities and printing were identified as the most significant indoor sources for ultrafine particles with the latter resulting in a substantial increase of indoor PN_<1 concentrations in the printer room during workdays. Moreover, indoor transport of fine particles from the printer room was found to have an important contribution to both indoor PN_<1 and PM₁₀ concentrations in two of the rest three offices. The physical presence of the occupants had an impact on particles >2.5 μm during workdays due to particle resuspension. However, when the offices were not occupied (night, weekend) the outdoor environment was a strong contribution to indoor concentrations. Lastly, black carbon preserved low concentrations in both under study offices and was not associated with printer emissions suggesting that black carbon is not an appropriate measure for assessing printer emissions.     

Air quality in a school with dampness and mould problems

An air quality monitoring campaign was carried out from the 13th to the 17th of January 2013 in a secondary school of the municipality of Anadia (Portugal) with dampness and mould problems. Continuous measurements of different particulate matter (PM) sizes [PM₁, PM_2.5, PM₄ and PM₁₀ and total suspended particles (TSP)], comfort parameters (temperature and relative humidity), CO, CO₂ and total volatile organic compounds were simultaneously carried out in a computer classroom, in the girl’s locker/shower room and outdoors. Low-volume samplers were used to collect PM₁₀ samples for subsequent determination of their carbonaceous content. Bacteria and fungi were collected by liquid impinger sampling and by direct scratching of surfaces. Temperature and relative humidity were far outside the comfort ranges in both rooms. Contrary to the locker/shower room, highly inefficient ventilation rates in the computer classroom, with occupancy always higher than 20 students, led to elevated CO₂ concentrations (>2250 mg m^?3). Much higher particle concentrations were observed in the locker room. Although not allowed, some smoking episodes in this indoor space may have contributed to particle concentrations up to 30 mg m^?3 and to indoor-to-outdoor ratios of 340. If the short smoking episodes are excluded, similar average PM₁₀ levels (<50 μg m^?3) are obtained for both rooms. Around 60 % of the total suspended particles are composed of submicrometric material. The concentrations of total culturable bacteria in the locker room, computer classroom and outdoors were, on average, 1038, 772 and 176 CFU m^?3, respectively. The corresponding fungi concentrations were 285, 542 and 125 CFU m^?3. In most cases, the concentrations of both, culturable bacteria and fungi, were above the legal limits (500 CFU m^?3). Fungi present in impinger samples and also those collected by direct scratching of surfaces were identified as belonging to the genera Alternaria, Aspergillus, Cladosporium and Penicillium, all of them potentially harmful to human health. A high degree of discomfort, insufficient ventilation in some microenvironments and the presence of allergenic bioaerosols at excessive levels indicate that the adoption of remedial actions is required.     

The impact of patient table on size-specific dose estimate (SSDE)

The use of parameters water equivalent diameter (D _W ) and size-specific dose estimate (SSDE) are becoming increasingly established as a recognised method to relate patient dose from a CT examination to the dose indicator volume CT dose index (CTDI_VOL). However, the role of the attenuation due to the patient table in these estimations requires careful consideration and is the subject of this study. The aim of this study is to investigate the impact of a minimal part of the patient table when calculating the D _W and SSDE. We investigated 164 patients who had undergone CT examinations for the pelvis, abdomen, thorax and head. We subsequently calculated D _W and SSDE using two methods: one using a small circular region of interest (ROI) including a minimal part of the patient table and the other using a ROI fitted to the patient border alone. The results showed that the water equivalent diameter calculated with the table included in the ROI (D _W,t ) is greater, compared to that without the consideration of the patient table (D _W,nt ), by 1.5–6.2% depending on the anatomy being imaged. On the other hand, the SSDE calculated with inclusion of the patient table (SSDE_t) is smaller than otherwise (SSDE_nt) by 1.0–5.5% again depending on the anatomy being imaged. The effect of the patient table on D _W and SSDE in the thorax CT examination was statistically significant, but its effect on D _W and SSDE in the other examinations of head, pelvis and abdomen was relatively small and not statistically significant.     

Indoor air quality in urban and rural kindergartens: short-term studies in Silesia,Poland

More than 80% of people living in urban areas who monitor air pollution are exposed to air quality levels that exceed limits defined by the World Health Organization (WHO). Although all regions of the world are affected, populations in low-income cities are the most impacted. According to average annual levels of fine particulate matter (PM2.5, ambient particles with aerodynamic diameter of 2.5 μm or less) presented in the urban air quality database issued by WHO in 2016, as many as 33 Polish cities are among the 50 most polluted cities in the European Union (EU), with Silesian cities topping the list. The aim of this study was to characterize the indoor air quality in Silesian kindergartens based on the concentrations of gaseous compounds (SO₂, NO₂), PM2.5, and the sum of 15 PM2.5-bound polycyclic aromatic hydrocarbons (PAHs), including PM2.5-bound benzo(a)pyrene (BaP), as well as the mutagenic activity of PM2.5 organic extracts in Salmonella assay (strains: TA98, YG1024). The assessment of the indoor air quality was performed taking into consideration the pollution of the atmospheric air (outdoor). I/O ratios (indoor/outdoor concentration) for each investigated parameter were also calculated. Twenty-four-hour samples of PM2.5, SO₂, and NO₂ were collected during spring in two sites in southern Poland (Silesia), representing urban and rural areas. Indoor samples were taken in naturally ventilated kindergartens. At the same time, in the vicinity of the kindergarten buildings, the collection of outdoor samples of PM2.5, SO₂, and NO₂ was carried out. The content of BaP and the sum of 15 studied PAHs was determined in each 24-h sample of PM2.5 (indoor and outdoor). In the urban site, statistically lower concentrations of SO₂ and NO₂ were detected indoors compared to outdoors, whereas in the rural site, such a relationship was observed only for NO₂. No statistically significant differences in the concentrations of PM2.5, PM2.5-bound BaP, and Σ15 PAHs in kindergartens (indoor) versus atmospheric (outdoor) air in the two studied areas were identified. Mutagenic effect of indoor PM2.5 samples was twice as low as in outdoor samples. The I/O ratios indicated that all studied air pollutants in the urban kindergarten originated from the ambient air. In the rural site concentrations of SO₂, PM2.5 and BaP in the kindergarten were influenced by internal sources (gas and coal stoves).