Indoor climate in low-ventilated day-care institutions

Measurements of indoor atmospheric environment were carried out in a day nursery and a kindergarten, in which natural air infiltration supplied the rooms with only 1–2 m³ fresh air per person and hour under the prescribed occupancy. The exposure situation from the field was duplicated under controlled conditions in a climate chamber. The results indicate unacceptably high concentrations of carbon dioxide, and emphasize the need for more elaborate building design in airtight buildings.     

Decreased influenza virus pathogenesis by infection with germicidal UV-irradiated airborne virus

Respiratory infections are acquired by the inhalation of airborne microorganisms. To evaluate the effect of germicidal UV-irradiation on airborne contagion, infectious clouds of influenza A/PR8/34 virus were generated and exposed to known intensities of UV. Thereafter, the airborne virus was used to infect mice wherein the pathogenesis of the viral pneumonia was evaluated. Increasing doses of UV inactivated infectious airborne virus in a dose-dependent manner and reduced the mortality rates as compared to an infectious cloud of untreated virus. When a sublethal cloud of infectious virus was used, UV-irradiation modified the viral infection, as quantitated by pulmonary virus titers, from a severe pneumonitis to a milder form of the disease. These data demonstrate the efficacy of germicidal UV-irradiation in disinfection of air by reducing the concentration of viable organisms which, in turn, reduces the severity of respiratory infection when transmitted to the susceptible host.     

Variations of airborne and waterborne Rn-222 in houses in Maine

Concentrations of airborne radon ranging from 0.05 to 135 pCi/L were found in houses in Maine. Tracketch cups were placed in five positions for 100 houses to determine integrated average radon concentrations over the period October 1980–May 1981. To investigate the association between elevated radon concentrations in well water and the indoor airborne radon concentrations, the radon in the water supplies of these houses was measured by liquid scintillation. Monitors of airborne radon, recording in intervals of 10 min for periods of 5–7 days, were used for dynamic studies in 18 houses, determining the component of airborne radon associated with major water uses, such as showers, laundry, and dishwashing, which liberate radon in bursts. House residents kept logs noting the time of major water uses. For some of the houses, ventilation rates ranging from 0.3 to 2 air changes per hour were determined by analysis of the dynamic data. The component of airborne radon associated with water sources was found to vary inversely with ventilation rate and directly with waterborne radon concentration, with 0.8 ± 0.2 pCi Rn/L air per nCi Rn/L water at a ventilation rate of 1.0 air change per hour. The data are pertinent to a study which has revealed significant correlations between county averages, from the National Cancer Institute, or age-adjusted cancer mortality rates in Maine and average values of radon concentrations in water for the counties.     

Review of bioaerosols in indoor environment with special reference to sampling,analysis and control mechanisms

Several tiny organisms of various size ranges present in air are called airborne particles or bioaerosol which mainly includes live or dead fungi and bacteria, their secondary metabolites, viruses, pollens, etc. which have been related to health issues of human beings and other life stocks. Bio-terror attacks in 2001 as well as pandemic outbreak of flue due to influenza A H1N1 virus in 2009 have alarmed us about the importance of bioaerosol research. Hence characterization i.e. identification and quantification of different airborne microorganisms in various indoor environments is necessary to identify the associated risks and to establish exposure threshold. Along with the bioaerosol sampling and their analytical techniques, various literatures revealing the concentration levels of bioaerosol have been mentioned in this review thereby contributing to the knowledge of identification and quantification of bioaerosols and their different constituents in various indoor environments (both occupational and non-occupational sections). Apart from recognition of bioaerosol, developments of their control mechanisms also play an important role. Hence several control methods have also been briefly reviewed. However, several individual levels of efforts such as periodic cleaning operations, maintenance activities and proper ventilation system also serve in their best way to improve indoor air quality.     

Soil radium, soil gas radon and indoor radon empirical relationships to assist in post-closure impact assessment related to near-surface radioactive waste disposal

Least squares (LS), Theil’s (TS) and weighted total least squares (WTLS) regression analysis methods are used to develop empirical relationships between radium in the ground, radon in soil and radon in dwellings to assist in the post-closure assessment of indoor radon related to near-surface radioactive waste disposal at the Low Level Waste Repository in England. The data sets used are (i) estimated ²²⁶Ra in the <2 mm fraction of topsoils (eRa226) derived from equivalent uranium (eU) from airborne gamma spectrometry data, (ii) eRa226 derived from measurements of uranium in soil geochemical samples, (iii) soil gas radon and (iv) indoor radon data. For models comparing indoor radon and (i) eRa226 derived from airborne eU data and (ii) soil gas radon data, some of the geological groupings have significant slopes. For these groupings there is reasonable agreement in slope and intercept between the three regression analysis methods (LS, TS and WTLS). Relationships between radon in dwellings and radium in the ground or radon in soil differ depending on the characteristics of the underlying geological units, with more permeable units having steeper slopes and higher indoor radon concentrations for a given radium or soil gas radon concentration in the ground. The regression models comparing indoor radon with soil gas radon have intercepts close to 5 Bq m⁻³ whilst the intercepts for those comparing indoor radon with eRa226 from airborne eU vary from about 20 Bq m⁻³ for a moderately permeable geological unit to about 40 Bq m⁻³ for highly permeable limestone, implying unrealistically high contributions to indoor radon from sources other than the ground. An intercept value of 5 Bq m⁻³ is assumed as an appropriate mean value for the UK for sources of indoor radon other than radon from the ground, based on examination of UK data. Comparison with published data used to derive an average indoor radon: soil ²²⁶Ra ratio shows that whereas the published data are generally clustered with no obvious correlation, the data from this study have substantially different relationships depending largely on the permeability of the underlying geology. Models for the relatively impermeable geological units plot parallel to the average indoor radon: soil ²²⁶Ra model but with lower indoor radon: soil ²²⁶Ra ratios, whilst the models for the permeable geological units plot parallel to the average indoor radon: soil ²²⁶Ra model but with higher than average indoor radon: soil ²²⁶Ra ratios.     

Suspended particulate matter in dwellings — the impact of tobacco smoking

The indoor concentration of suspended particulate matter (SPM) was measured in forty-four retrofitted and tight dwellings, which had electric cooking and were central heated and where the basic ventilation rate in median amounted 0.23 air changes per hour as measured with a tracer dilution method. The indoor concentration of SPM was in median 230 μg/m³ with a strong correlation to the tobacco consumption (r_s=0.716), but with no correlation to the frequency of airing or the basic ventilation rate. Tobacco smoking seems to be the main indoor source of SPM in contemporary dwellings. The importance of these findings is underlined by epidemiologic studies on passive smoking and health. Air quality standards for the ambient air are based on certain risk groups such as infants, children, persons with chronic obstructive lung disorders, and indoor air standards should be based on the same concepts of health protection.     

Flame retardants in indoor dust and air of a hotel in Japan

Occurrence of flame retardants (FRs) in the indoor environment of highly flame-retarded public facilities is an important concern from the viewpoint of exposure because it is likely that FRs are used to a greater degree in these facilities than in homes. For this study, brominated flame-retardants (BFRs) and organophosphate flame-retardants and plasticizers (OPs), and brominated dibenzo-p-dioxins/furans (PBDD/DFs) were measured in eight floor dust samples taken from a Japanese commercial hotel that was assumed to have many flame-retardant materials. Concentrations of polybrominated diphenylethers (PBDEs) and hexabromocyclododecanes (HBCDs) varied by about two orders of magnitude, from 9.8–1700 ng/g (median of 1200 ng/g) and from 72–1300 ng/g (median of 740 ng/g), respectively. Concentrations of the two types of BFRs described above were most dominant among the investigated BFRs in the dust samples. It is inferred that BFR and PBDD/DF concentrations are on the same level as those in house and office dust samples reported based on past studies. Regarding concentrations of 11 OPs, 7 OPs were detected on the order of micrograms per gram, which are equivalent to or exceed the BFR concentrations such as PBDEs and HBCDs. Concentrations of the investigated compounds were not uniform among dust samples collected throughout the hotel: concentrations differed among floors, suggesting that localization of source products is associated with FR concentrations in dust. Passive air sampling was also conducted to monitor BFRs in the indoor air of hotel rooms: the performance of an air cleaner placed in the room was evaluated in terms of reducing airborne BFR concentrations. Monitoring results suggest that operation of an appropriate air cleaner can reduce both gaseous and particulate BFRs in indoor air.     

Detection of fluorotelomer alcohols in indoor environments and their relevance for human exposure

Fluorotelomer alcohols (FTOH) are important precursors of perfluorinated carboxylic acids (PFCA). These neutral and volatile compounds are frequently found in indoor air and may contribute to the overall human exposure to per- and polyfluorinated alkyl substances (PFAS). In this study air samples of ten workplace environments and a car interior were analysed. In addition, extracts and emissions from selected outdoor textiles were analysed in order to establish their potential contribution to the indoor levels of the above-mentioned compounds.Concentrations of FTOHs measured in air ranged from 0.15 to 46.8, 0.25 to 286, and 0.11 to 57.5 ng/m³ for 6:2, 8:2 and 10:2 FTOHs, respectively. The highest concentrations in air were identified in shops selling outdoor clothing, indicating outdoor textiles to be a relevant source of FTOH in indoor workplace environments. Total amounts of FTOH in materials of outdoor textiles accounted for < 0.8–7.6, 12.1–180.9 and 4.65–105.7 μg/dm² for 6:2, 8:2 and 10:2 FTOHs, respectively. Emission from selected textiles revealed emission rates of up to 494 ng/h.The measured data show that a) FTOHs are present in indoor textiles (e.g. carpets), b) they are released at ambient temperatures and c) indoor air of shops selling outdoor textiles contains the highest levels of FTOH. Exposure of humans to perfluorooctanoic acid (PFOA) through absorption of FTOH and subsequent degradation is discussed on the basis of indoor air levels. Calculation of indoor air-related exposure using the median of the measured air levels revealed that exposure is on the same order of magnitude as the recently reported dietary intakes for a background-exposed population. On the basis of the 95th percentile, indoor air exposure to PFOA was estimated to exceed dietary exposure. However, indoor air-related intakes of FTOH are far below the tolerable daily intake (TDI) of PFOA, indicating that there is no risk to health, even when assuming an unrealistic complete degradation of FTOH into PFOA.     

Guidelines for Nordic building regulations regarding indoor air quality

A subcommittee of the Nordic Committee for Building Codes has released guidelines for building regulations regarding indoor air quality, especially concerning ventilation. The main features of the guidelines, such as acceptable outdoor air quality for ventilation and minimum outdoor air flows for dwellings and offices, are presented and discussed. Mechanical ventilation is, in principle, required in all buildings including dwellings, due to the requirement of a minimum outdoor air change of 0.5 h⁻¹ and the normal highly airtight nature of new buildings. The guidelines are a basis for designing energy-efficient buildings while maintaining an indoor air quality which provides acceptable comfort and does not impair health.     

Oxidative potential and chemical composition of PM2.5 in office buildings across Europe – The OFFICAIR study

In the frame of the OFFICAIR project, indoor and outdoor PM_2.5 samples were collected in office buildings across Europe in two sampling campaigns (summer and winter). The ability of the particles to deplete physiologically relevant antioxidants (ascorbic acid (AA), reduced glutathione (GSH)) in a synthetic respiratory tract lining fluid, i.e., oxidative potential (OP), was assessed. Furthermore, the link between particulate OP and the concentration of the PM constituents was investigated.The mean indoor PM_2.5 mass concentration values were substantially lower than the related outdoor values with a mean indoor/outdoor PM_2.5 mass concentration ratio of 0.62 and 0.61 for the summer and winter campaigns respectively. The OP of PM_2.5 varied markedly across Europe with the highest outdoor OP^AA m⁻³ and OP^GSH m⁻³ (% antioxidant depletion/m³ air) values obtained for Hungary, while PM_2.5 collected in Finland exhibited the lowest values. Seasonal variation could be observed for both indoor and outdoor OP^AA m⁻³ and OP^GSH m⁻³ with higher mean values during winter. The indoor/outdoor OP^AA m⁻³ and OP^GSH m⁻³ ratios were less than one with 4 and 17 exceptions out of the 40 cases respectively. These results indicate that indoor air is generally less oxidatively challenging than outdoors. Correlation analysis revealed that trace elements play an important role in determining OP, in particular, the Cu content. Indoor air chemistry might affect OP since weaker correlations were obtained for indoor PM_2.5. Our findings also suggest that office workers may be exposed to health relevant PM constituents to a different extent within the same building.     

Determination of aniline and related mono-aromatic amines in indoor air in selected Canadian residences by a modified thermal desorption GC/MS method

A modified thermal desorption method to determine low levels of aniline and other related mono-aromatic amines (MAAs) in residential air is described. The method was successfully applied to the determination of levels of these chemicals in residential air from 69 selected homes in two Canadian regions. Instrument detection limits of between 0.02 and 0.06 ng per thermal desorption tube were achieved for aniline and other MAAs. In the absence of environmental tobacco smoke (ETS) the mean concentrations of aniline in both indoor air and outdoor air were similar, at about 0.01 microgram/m3 after correction with field blanks. There was however a statistically significant difference in aniline concentrations between field blanks and indoor or outdoor air samples. No significant difference of aniline levels in the two study regions was observed. A clear link between aniline concentrations in indoor air and smoking activities inside homes was evident. Analysis of cigarette leaves indicated that aniline was most likely formed due to combustion during smoking. Shoe polishing was identified as another source of aniline in indoor air.     

Pollutant emission rates from indoor combustion appliances and sidestream cigarette smoke

Particulate and gaseous emissions from indoor combustion appliances and smoking can elevate the indoor concentrations of various pollutants. Indoor pollutant concentrations resulting from operating one of several combustion appliances, or from sidestream tobacco smoke, were measured in a 27-m³ environmental chamber under varying ventilation rates. The combustion appliances investigated were gas-fired cooking stoves, unvented kerosene-fired space heaters, and unvented natural-gas-fired space heaters. Results showed elevated levels of carbon dioxide, carbon monoxide, nitric oxide, nitrogen dioxide, formaldehyde, and suspended particles from one or more of the pollutant sources investigated. Our findings suggest that, of the sources examined in this study, nitrogen dioxide from combustion appliances and particles from sidestream cigarette smoke are the most serious contaminants of indoor air, if we use existing standards and guidelines as the criteria. An emission rate model was used to quantify the strengths of the pollutant sources, which are reported in terms of the mass of pollutant emitted per energy unit of fuel consumed (in the case of gas and kerosene appliances) and per mass of tobacco combusted (in the case of smoking).     

Short-term dynamics of indoor and outdoor endotoxin exposure: Case of Santiago,Chile, 2012

Indoor and outdoor endotoxin in PM_2.5 was measured for the very first time in Santiago, Chile, in spring 2012. Average endotoxin concentrations were 0.099 and 0.094 [EU/m³] for indoor (N = 44) and outdoor (N = 41) samples, respectively; the indoor–outdoor correlation (log-transformed concentrations) was low: R = − 0.06, 95% CI: (− 0.35 to 0.24), likely owing to outdoor spatial variability.A linear regression model explained 68% of variability in outdoor endotoxins, using as predictors elemental carbon (a proxy of traffic emissions), chlorine (a tracer of marine air masses reaching the city) and relative humidity (a modulator of surface emissions of dust, vegetation and garbage debris). In this study, for the first time a potential source contribution function (PSCF) was applied to outdoor endotoxin measurements. Wind trajectory analysis identified upwind agricultural sources as contributors to the short-term, outdoor endotoxin variability. Our results confirm an association between combustion particles from traffic and outdoor endotoxin concentrations.For indoor endotoxins, a predictive model was developed but it only explained 44% of endotoxin variability; the significant predictors were tracers of indoor PM_2.5 dust (Si, Ca), number of external windows and number of hours with internal doors open. Results suggest that short-term indoor endotoxin variability may be driven by household dust/garbage production and handling. This would explain the modest predictive performance of published models that use answers to household surveys as predictors. One feasible alternative is to increase the sampling period so that household features would arise as significant predictors of long-term airborne endotoxin levels.     

Air filtration and radon daughter levels

The authors investigate the effect of filtration and aerosol loading of the air on the level of short-lived air-borne daughter products of radon. By the use of a combination of filtration and aerosol loading, it is possible to shift the partitioning of the radon daughters in the room between the states: airborne, plated-out on the walls, and trapped by filters; the airborne fraction will shift between being attached to aerosol particles and existing as molecular-sized clusters. When the air filtered the equilibrium factor decreases with increasing filtration rate. At high aerosol concentrations the decrease can be explained solely as an effect of the filter removing the daughter products from the air passing through it. As the aerosol production and concentration is lowered, the decrease in equilibrium factor becomes larger. This is caused by an increase in the unattached fraction of the airborne activity and hence in the wall-deposited fraction of the total activity. At a given radon concentration, the dose delivered to a certain portion of the respiratory tract depends not only upon the equilibrium factor but also upon the fraction of, especially, ₈₄²¹⁸Po in the unattached state. It is further demonstrated that, according to the dose model of Harley and Pasternak, the dose to the basal cells of the epithelium of the bronchii will in general decrease with increasing filtration rate and increase with decreasing aerosol concentration.     

Comparison of indoor and outdoor air quality at two staff quarters in Hong Kong

The indoor and outdoor air quality of two staff quarters of Hong Kong Polytechnic University at Tsim Sha Tsui East (TSTE) and Shatin (ST) were investigated. The air sampling was carried out in winter for about two months starting from January to February of 1996. Fifteen flats from each staff quarter were randomly selected for indoor/outdoor air pollutant measurements. The pollutants measured were NO_x, NO, NO₂, SO₂, CO, and O₃. The variations of pollutant concentrations between indoor and outdoor air were investigated on weekday mornings, weekday evenings, weekend mornings, and weekend evenings. All indoor/outdoor pollutant concentrations measured did not exceed the ASHRAE/NAAQS standard. The carbon monoxide concentrations indoors were systemically higher than those outdoors at the TSTE and the ST quarters, both on weekdays and Sunday, which indicates there are CO sources indoors. Except for CO, the indoor levels of other pollutants (NO_x, NO, NO₂, SO₂, and O₃) are lower than those outdoors. There was a significant correlation (P < 0.05) between indoor and outdoor concentrations for SO₂ and O₃ at both the TSTE and the ST quarters. Except for O₃, the mean concentrations of all the pollutants in the TSTE quarters, both indoor and outdoor, were higher than that of the ST quarters in all sampling periods. All indoor and outdoor O₃ levels were lower at the TSTE quarters than those at the ST quarters. The O₃ ratios of TSTE/ST were 0.72 outdoor and 0.79 indoor. This can be explained by the NO titration reaction through NO conversion to NO₂.     

Indoor radon concentrations

The indoor air of 60 residences in and around a Maryland suburb of Washington, DC, was monitored in a pilot study to determine residential radon concentrations. In each residence, a radon grab sample was acquired in the living room, and, if possible, in the basement. Infiltration rates were determined by tracer gas dilution. To help standardize sampling conditions, each home remained closed up for 8 h prior to sampling and during analysis. Over 60% of the residences sampled showed air infiltration rates below 0.6 air changes per hour. Approximately 55% of all surveyed basements and 30% of all surveyed living areas displayed radon concentrations in excess of 4.0 nCi m⁻³. Assuming an equilibrium factor of 0.5, these radon levels may lead to working levels above the annual guidelines suggested by EPA for florida homes build on land reclaimed from phosphate mining.     

Indoor air quality and minimum ventilation rate

In a 30-m³ test chamber the air pollutants caused by man were measured. Variables were the number of persons and the rate of air change. During 2-h test sessions the temperature, relative humidity, carbon dioxide, and intensity of odors were measured. The relationship between the perceived odor intensities and the concentrations of carbon dioxide-independent of the number of persons and the air change rate—was observed. At air change rates of 12–15 m³/person/h, the carbon dioxide concentration was not higher than 0.15% and the odor intensity was evaluated only as a “slight annoyance.” Higher ventilation rates are necessary if smoking and increased physical activities are done in the rooms.     

Radon exhalation from building materials for decorative use

Long-term exposure to radon increases the risk of developing lung cancer. There is considerable public concern about radon exhalation from building materials and the contribution to indoor radon levels. To address this concern, radon exhalation rates were determined for 53 different samples of drywall, tile and granite available on the Canadian market for interior home decoration. The radon exhalation rates ranged from non-detectable to 312 Bq m⁻² d⁻¹. Slate tiles and granite slabs had relatively higher radon exhalation rates than other decorative materials, such as ceramic or porcelain tiles. The average radon exhalation rates were 30 Bq m⁻² d⁻¹ for slate tiles and 42 Bq m⁻² d⁻¹ for granite slabs of various types and origins. Analysis showed that even if an entire floor was covered with a material having a radon exhalation rate of 300 Bq m⁻² d⁻¹, it would contribute only 18 Bq m⁻³ to a tightly sealed house with an air exchange rate of 0.3 per hour. Generally speaking, building materials used in home decoration make no significant contribution to indoor radon for a house with adequate air exchange.     

Modeling indoor air pollution of outdoor origin in homes of SAPALDIA subjects in Switzerland

Given the shrinking spatial contrasts in outdoor air pollution in Switzerland and the trends toward tightly insulated buildings, the Swiss Cohort Study on Air Pollution and Lung and Heart Diseases in Adults (SAPALDIA) needs to understand to what extent outdoor air pollution remains a determinant for residential indoor exposure. The objectives of this paper are to identify determining factors for indoor air pollution concentrations of particulate matter (PM), ultrafine particles in the size range from 15 to 300 nm, black smoke measured as light absorbance of PM (PM_absorbance) and nitrogen dioxide (NO₂) and to develop predictive indoor models for SAPALDIA. Multivariable regression models were developed based on indoor and outdoor measurements among homes of selected SAPALDIA participants in three urban (Basel, Geneva, Lugano) and one rural region (Wald ZH) in Switzerland, various home characteristics and reported indoor sources such as cooking. Outdoor levels of air pollutants were important predictors for indoor air pollutants, except for the coarse particle fraction. The fractions of outdoor concentrations infiltrating indoors were between 30% and 66%, the highest one was observed for PM_absorbance. A modifying effect of open windows was found for NO₂ and the ultrafine particle number concentration. Cooking was associated with increased particle and NO₂ levels. This study shows that outdoor air pollution remains an important determinant of residential indoor air pollution in Switzerland.     

Two-year follow-up study of nonregulatory recommendations for better air quality in indoor ice arenas

A standardized questionnaire was used in a two-year follow-up study to test the effectiveness of non-regulatory recommendations to improve indoor air quality of 103 ice arenas in Finland. In addition, the performance of a state-of-the-art emission control technology (ECT) on propane-fueled resurfacers was evaluated by measuring the one-week average nitrogen dioxide (NO₂) concentration in a small sample of arenas. The number of retrofitted ECT on propane-fueled resurfacers increased from 6 to 37 (8% to 37% of ice arenas) and the number of electric resurfacers from 7 to 9 (both 9% of arenas) in 1994–1996. At the same time, the prevalence of inadequate ventilation increased among the most susceptible small arenas (volume <30 000 m³) from 11 (31%) to 19 (38%). Combustion-powered resurfacers (88%) and inadequate ventilation (24%) were prevalent also among the 17 new arenas built in 1994–1996. ECT resurfacers significantly decreased the mean indoor NO₂ concentration of eleven arenas from 650 μg/m³ to 147 μg/m³. Thus, retrofitting resurfacers with ECT seems to be a feasible mitigation option to improve indoor air quality in ice arenas, but the ultimate solution is an electric ice resurfacer. Non-regulatory recommendations seem to be partially effective in abatement against the air quality problems, but additional regulatory measures are needed for full compliance in all arenas.