Variation in residential radon levels in new Danish homes

Radon‐222 gas arises from the radioactive decay of radium‐226 and has a half‐life of 3.8 days. This gas percolates up through soil into buildings, and if it is not evacuated, there can be much higher exposure levels indoors than outdoors, which is where human exposure occurs. Radon exposure is classified as a human carcinogen, and new Danish homes must be constructed to ensure indoor radon levels below 100 Bq/m³. Our purpose was to assess how well 200 newly constructed single detached homes perform according to building regulations pertaining to radon and identify the association between indoor radon in these homes and municipality, home age, floor area, floor level, basement, and outer wall and roof construction. Median (5–95 percentile) indoor radon levels were 36.8 (9.0–118) Bq/m³, but indoor radon exceeded 100 Bq/m³ in 14 of these new homes. The investigated variables explained nine percent of the variation in indoor radon levels, and although associations were positive, none of these were statistically significant. In this study, radon levels were generally low, but we found that 14 (7%) of the 200 new homes had indoor radon levels over 100 Bq/m³. More work is needed to determine the determinants of indoor radon.     

Associations between evaporative cooling and dust‐mite allergens,endotoxins, and β‐(1 → 3)‐d‐glucans in house dust: A study of low‐income homes

Recent work suggests that evaporative coolers increase the level and diversity of bioaerosols, but this association remains understudied in low‐income homes. We conducted a cross‐sectional study of metropolitan, low‐income homes in Utah with evaporative coolers (n = 20) and central air conditioners (n = 28). Dust samples (N = 147) were collected from four locations in each home and analyzed for dust‐mite allergens Der p1 and Der f1, endotoxins, and β‐(1 → 3)‐d ‐glucans. In all sample locations combined, Der p1 or Der f1 was significantly higher in evaporative cooler versus central air conditioning homes (OR = 2.29, 95% CI = 1.05‐4.98). Endotoxin concentration was significantly higher in evaporative cooler versus central air conditioning homes in furniture (geometric mean (GM) = 8.05 vs 2.85 EU/mg, P < .01) and all samples combined (GM = 3.60 vs 1.29 EU/mg, P = .03). β‐(1 → 3)‐d ‐glucan concentration and surface loads were significantly higher in evaporative cooler versus central air conditioning homes in all four sample locations and all samples combined (P < .01). Our study suggests that low‐income, evaporative cooled homes have higher levels of immunologically important bioaerosols than central air‐conditioned homes in dry climates, warranting studies on health implications and other exposed populations.     

Radon measurement studies in workplace buildings of the Rawalpindi region and Islamabad Capital area, Pakistan

A survey concerning measurement of the indoor radon levels has been carried out in 105 workplaces of the Rawalpindi region and Islamabad Capital Territory using CR-39 based radon detectors. The main objective of this study was to assess the health hazard due to the indoor radon. CR-39 based NRPB type detectors were installed in offices/rooms located on first floors, ground floors and basements and were exposed to indoor radon for six months. The measured indoor radon concentration in the buildings surveyed ranged from 12 ± 5 to 293 ± 19 Bq m⁻³ with an overall mean value of 64 ± 32 Bq m⁻³. The highest mean radon concentration (113 ± 48 Bq m⁻³) was observed in the offices located in basements of the Rawalpindi city. The overall average annual effective dose in the studied workplaces was estimated to be 0.61 ± 0.30 mSv. The mean annual effective doses in basements, ground floor and first floor were found to be 0.87 ± 0.34 mSv, 0.55 ± 0.28 mSv, and 0.47 ± 0.29 mSv, respectively. These values are less than the action level recommended by International Commission on Radiological Protection.     

Modeling microbial growth in carpet dust exposed to diurnal variations in relative humidity using the “Time-of-Wetness” framework

Resuspension of microbes in floor dust and subsequent inhalation by human occupants is an important source of human microbial exposure. Microbes in carpet dust grow at elevated levels of relative humidity, but rates of this growth are not well established, especially under changing conditions. The goal of this study was to model fungal growth in carpet dust based on indoor diurnal variations in relative humidity utilizing the time-of-wetness framework. A chamber study was conducted on carpet and dust collected from 19 homes in Ohio, USA and exposed to varying moisture conditions of 50%, 85%, and 100% relative humidity. Fungal growth followed the two activation regime model, while bacterial growth could not be evaluated using the framework. Collection site was a stronger driver of species composition (P = 0.001, R² = 0.461) than moisture conditions (P = 0.001, R² = 0.021). Maximum moisture condition was associated with species composition within some individual sites (P = 0.001-0.02, R² = 0.1-0.33). Aspergillus, Penicillium, and Wallemia were common fungal genera found among samples at elevated moisture conditions. These findings can inform future studies of associations between dampness/mold in homes and health outcomes and allow for prediction of microbial growth in the indoor environment.     

Impacts of weatherization on indoor air quality: A field study of 514 homes

Residential energy efficiency retrofits continue to be common in the United States, especially through governmental and utility programs. Because of the potential for reduced air exchange, there have been concerns raised regarding the potential for negative impacts on health and safety of residents when air sealing occurs. To address this concern, a study was undertaken in 2009‐2010 to evaluate the indoor air quality impacts of weatherization performed through the U.S. Department of Energy's Weatherization Assistance Program. Testing was conducted on 514 homes throughout the United States. The results show that weatherization, as performed at the time of the study, could result in small but statistically significant increases in some indoor contaminants such as radon and humidity, while also reducing exposures to elevated carbon monoxide in some homes.     

Indoor fine particulate matter and demographic,household, and wood stove characteristics among rural US homes heated with wood fuel

Household heating using wood stoves is common practice in many rural areas of the United States (US) and can lead to elevated concentrations of indoor fine particulate matter (PM_2.5). We collected 6-day measures of indoor PM_2.5 during the winter and evaluated household and stove-use characteristics in homes at three rural and diverse study sites. The median indoor PM_2.5 concentration across all homes was 19 µg/m³, with higher concentrations in Alaska (median = 30, minimum = 4, maximum = 200, n = 10) and Navajo Nation homes (median = 29, minimum = 3, maximum = 105, n = 23) compared with Montana homes (median = 16, minimum = 2, maximum = 139, n = 59). Households that had not cleaned the chimney within the past year had 65% higher geometric mean PM_2.5 compared to those with chimney cleaned within 6 months (95% confidence interval [CI]: −1, 170). Based on a novel wood stove grading method, homes with low-quality and medium-quality stoves had substantially higher PM_2.5 compared to homes with higher-quality stoves (186% higher [95% CI: 32, 519] and 161% higher; [95% CI:27, 434], respectively). Our findings highlight the need for, and complex nature of, regionally appropriate interventions to reduce indoor air pollution in rural wood-burning regions. Higher-quality stoves and behavioral practices such as regular chimney cleaning may help improve indoor air quality in such homes.     

Stenotrophomonas,Mycobacterium, and Streptomyces in home dust and air: associations with moldiness and other home/family characteristics

Respiratory illnesses have been linked to children's exposures to water‐damaged homes. Therefore, understanding the microbiome in water‐damaged homes is critical to preventing these illnesses. Few studies have quantified bacterial contamination, especially specific species, in water‐damaged homes. We collected air and dust samples in twenty‐one low‐mold homes and twenty‐one high‐mold homes. The concentrations of three bacteria/genera, Stenotrophomonas maltophilia, Streptomyces sp., and Mycobacterium sp., were measured in air and dust samples using quantitative PCR (QPCR). The concentrations of the bacteria measured in the air samples were not associated with any specific home characteristic based on multiple regression models. However, higher concentrations of S. maltophilia in the dust samples were associated with water damage, that is, with higher floor surface moisture and higher concentrations of moisture‐related mold species. The concentrations of Streptomyces and Mycobacterium sp. had similar patterns and may be partially determined by human and animal occupants and outdoor sources of these bacteria.     

Emergence of Aspergillus fumigatus azole resistance in azole‐naïve patients with chronic obstructive pulmonary disease and their homes

Azole‐resistant Aspergillus fumigatus (ARAF) has been reported in patients with chronic obstructive pulmonary disease (COPD) but has not been specifically assessed so far. Here, we evaluated ARAF prevalence in azole‐naïve COPD patients and their homes, and assessed whether CYP51A mutations were similar in clinical and environmental reservoirs. Sixty respiratory samples from 41 COPD patients with acute exacerbation and environmental samples from 36 of these patient's homes were prospectively collected. A. fumigatus was detected in respiratory samples from 11 of 41 patients (27%) and in 15 of 36 domiciles (42%). Cyp51A sequencing and selection on itraconazole medium of clinical (n = 68) and environmental (n = 48) isolates yielded ARAF detection in 1 of 11 A. fumigatus colonized patients with COPD (9%) and 2 of 15 A. fumigatus‐positive patient's homes (13%). The clinical isolate had no CYP51A mutation. Two environmental isolates from two patients harbored TR₃₄/L98H mutation, and one had an H285Y mutation. Coexistence of different cyp51A genotypes and/or azole resistance profiles was detected in 3 of 8 respiratory and 2 of 10 environmental samples with more than one isolate, confirming the need for a systematic screening of all clinically relevant isolates. The high prevalence of ARAF in patients with COPD and their homes supports the need for further studies to assess the prevalence of azole resistance in patients with Aspergillus diseases in Northern France.     

Usage and impacts of the Envirofit HM‐5000 cookstove

Burning solid fuels to fulfill daily household energy needs results in chronic exposure to household air pollution (HAP), which is among the world's greatest health risks. This paper presents the results of a cross‐sectional study of cookstove usage, fuel consumption, and indoor PM_2.5 concentrations in rural and urban Honduran homes cooking with the Envirofit HM‐5000 metal plancha stove (n = 32) as compared to control households using baseline cooking technologies (n = 33). Temperature‐based stove usage measurements showed high HM‐5000 acceptance, with significant displacement of the traditional cookstoves at both the urban (99%, P < .05) and rural study sites (75%, P < .05). However, longer‐term usage data collected in peri‐urban households showed that participants cooked on the HM‐5000 more frequently during the 3‐day monitoring period than during the following 3 weeks. Average indoor PM_2.5 was 66% lower in HM‐5000 households as compared to control households (P < .05). Lower indoor PM_2.5 concentrations observed in participant homes as compared to control households, supported by high usage and traditional stove displacement, suggest the potential for the HM‐5000 to yield health improvements in adopting Honduran households.     

Polybrominated diphenyl ethers and polychlorinated biphenyls in indoor dust in Durban,South Africa

Polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) were measured in indoor dust of three microenvironments in Durban, South Africa. The sum of eight PBDEs and three PCBs were quantified by gas chromatography with mass spectral detection. The mean concentrations of ∑_n = 8 PBDEs and ∑_n = 3 PCBs in 10 homes, 11 offices, and 13 university students’ computer laboratories were 1710, 1520, and 818 ng/g, and 891, 923, and 1880 ng/g for PBDEs and PCBs, respectively. The concentration of PCBs found in homes was independent (P = 0.0625) of building construction year. Similarly, no relationship was observed between PCB concentrations and floor type. The concentrations of PBDEs correlated (r = 0.60) with PCB concentrations in homes, thus assuming similar sources. The elevated concentrations of PBDEs and PCBs may have significant implications for human exposure.     

Microbial secondary metabolites in homes in association with moisture damage and asthma

We aimed to characterize the presence of microbial secondary metabolites in homes and their association with moisture damage, mold, and asthma development. Living room floor dust was analyzed by LC‐MS/MS for 333 secondary metabolites from 93 homes of 1‐year‐old children. Moisture damage was present in 15 living rooms. At 6 years, 8 children had active and 15 lifetime doctor‐diagnosed asthma. The median number of different metabolites per house was 17 (range 8–29) and median sum load 65 (4–865) ng/m². Overall 42 different metabolites were detected. The number of metabolites present tended to be higher in homes with mold odor or moisture damage. The higher sum loads and number of metabolites with loads over 10 ng/m² were associated with lower prevalence of active asthma at 6 years (aOR 0.06 (95% CI <0.001–0.96) and 0.05 (<0.001–0.56), respectively). None of the individual metabolites, which presence tended (P < 0.2) to be increased by moisture damage or mold, were associated with increased risk of asthma. Microbial secondary metabolites are ubiquitously present in home floor dust. Moisture damage and mold tend to increase their numbers and amount. There was no evidence indicating that the secondary metabolites determined would explain the association between moisture damage, mold, and the development of asthma.     

Radon in indoor air of primary schools: a systematic survey to evaluate factors affecting radon concentration levels and their variability

In order to optimize the design of a national survey aimed to evaluate radon exposure of children in schools in Serbia, a pilot study was carried out in all the 334 primary schools of 13 municipalities of Southern Serbia. Based on data from passive measurements, rooms with annual radon concentration >300 Bq/m³ were found in 5% of schools. The mean annual radon concentration weighted with the number of pupils is 73 Bq/m³, 39% lower than the unweighted 119 Bq/m³ average concentration. The actual average concentration when children are in classrooms could be substantially lower. Variability between schools (CV = 65%), between floors (CV = 24%) and between rooms at the same floor (CV = 21%) was analyzed. The impact of school location, floor, and room usage on radon concentration was also assessed (with similar results) by univariate and multivariate analyses. On average, radon concentration in schools within towns is a factor of 0.60 lower than in villages and at higher floors is a factor of 0.68 lower than ground floor. Results can be useful for other countries with similar soil and building characteristics.     

Air exchange rates and migration of VOCs in basements and residences

Basements can influence indoor air quality by affecting air exchange rates (AERs) and by the presence of emission sources of volatile organic compounds (VOCs) and other pollutants. We characterized VOC levels, AERs, and interzonal flows between basements and occupied spaces in 74 residences in Detroit, Michigan. Flows were measured using a steady‐state multitracer system, and 7‐day VOC measurements were collected using passive samplers in both living areas and basements. A walk‐through survey/inspection was conducted in each residence. AERs in residences and basements averaged 0.51 and 1.52/h, respectively, and had strong and opposite seasonal trends, for example, AERs were highest in residences during the summer, and highest in basements during the winter. Airflows from basements to occupied spaces also varied seasonally. VOC concentration distributions were right‐skewed, for example, 90th percentile benzene, toluene, naphthalene, and limonene concentrations were 4.0, 19.1, 20.3, and 51.0 μg/m³, respectively; maximum concentrations were 54, 888, 1117, and 134 μg/m³. Identified VOC sources in basements included solvents, household cleaners, air fresheners, smoking, and gasoline‐powered equipment. The number and type of potential VOC sources found in basements are significant and problematic, and may warrant advisories regarding the storage and use of potentially strong VOCs sources in basements.     

Formaldehyde levels in FEMA‐supplied travel trailers,park models,and mobile homes in Louisiana and Mississippi

In 2006, area physicians reported increases in upper respiratory symptoms in patients living in U.S. Federal Emergency Management Agency (FEMA)‐supplied trailers following Hurricanes Katrina and Rita. One potential etiology to explain their symptoms included formaldehyde; however, formaldehyde levels in these occupied trailers were unknown. The objectives of our study were to identify formaldehyde levels in occupied trailers and to determine factors or characteristics of occupied trailers that could affect formaldehyde levels. A disproportionate random sample of 519 FEMA‐supplied trailers was identified in Louisiana and Mississippi in November 2007. We collected and tested an air sample from each trailer for formaldehyde levels and administered a survey. Formaldehyde levels among all trailers in this study ranged from 3 parts per billion (ppb) to 590 ppb, with a geometric mean (GM) of 77 ppb [95% confidence interval (CI): 70–85; range: 3–590 ppb]. There were statistically significant differences in formaldehyde levels between trailer types (P < 0.01). The GM formaldehyde level was 81 ppb (95% CI: 72–92) among travel trailers (N = 360), 57 ppb (95% CI: 49–65) among mobile homes (N = 57), and 44 ppb (95% CI: 38–53) among park models (N = 44). Among travel trailers, formaldehyde levels varied significantly by brand. While formaldehyde levels varied by trailer type, all types tested had some levels ≥100 ppb.     

Levels and sources of volatile organic compounds in homes of children with asthma

Many volatile organic compounds (VOCs) are classified as known or possible carcinogens, irritants, and toxicants, and VOC exposure has been associated with the onset and exacerbation of asthma. This study characterizes VOC levels in 126 homes of children with asthma in Detroit, Michigan, USA. The total target VOC concentration ranged from 14 to 2274 μg/m³ (mean = 150 μg/m³; median = 91 μg/m³); 56 VOCs were quantified; and d‐limonene, toluene, p, m‐xylene, and ethyl acetate had the highest concentrations. Based on the potential for adverse health effects, priority VOCs included naphthalene, benzene, 1,4‐dichlorobenzene, isopropylbenzene, ethylbenzene, styrene, chloroform, 1,2‐dichloroethane, tetrachloroethene, and trichloroethylene. Concentrations varied mostly due to between‐residence and seasonal variation. Identified emission sources included cigarette smoking, solvent‐related emissions, renovations, household products, and pesticides. The effect of nearby traffic on indoor VOC levels was not distinguished. While concentrations in the Detroit homes were lower than levels found in other North American studies, many homes had elevated VOC levels, including compounds that are known health hazards. Thus, the identification and control of VOC sources are important and prudent, especially for vulnerable individuals. Actions and policies to reduce VOC exposures, for example, sales restrictions, improved product labeling, and consumer education, are recommended.     

Isolation of Aspergillus fumigatus from sputum is associated with elevated airborne levels in homes of patients with asthma

Indoor bioaerosols, such as mold spores, have been associated with respiratory symptoms in patients with asthma; however, dose–response relationships and guidelines on acceptable levels are lacking. Furthermore, a causal link between mold exposure and respiratory infections or asthma remains to be established. The aim of this study was to determine indoor concentrations of Aspergillus fumigatus and a subset of clinically relevant fungi in homes of people with asthma, in relation to markers of airways colonization and sensitization. Air and dust samples were collected from the living room of 58 properties. Fungal concentrations were quantified using mold‐specific quantitative PCR and compared with traditional microscopic analysis of air samples. Isolation of A. fumigatus from sputum was associated with higher airborne concentrations of the fungus in patient homes (P = 0.04), and a similar trend was shown with Aspergillus/Penicillium‐type concentrations analyzed by microscopy (P = 0.058). No association was found between airborne levels of A. fumigatus and sensitization to this fungus, or dustborne levels of A. fumigatus and either isolation from sputum or sensitization. The results of this study suggest that the home environment should be considered as a potential source of fungal exposure, and elevated home levels may predispose people with asthma to airways colonization.     

Higher measured moisture in California homes with qualitative evidence of dampness

Relationships between measured moisture and qualitative dampness indicators (mold odor, visible mold, visible water damage, or peeling paint) were evaluated using data collected from California homes in a prospective birth cohort study when the infants were 6 or 12 months of age (737 home visits). For repeated visits, agreement between observation of the presence/absence of each qualitative indicator at both visits was high (71–87%, P < 0.0001). Among individual indicators, musty odor and visible mold were most strongly correlated with elevated moisture readings. Measured moisture differed significantly between repeated visits in opposite seasons (P < 0.0001), and dampness increased with the number of indicators in a home. Linear mixed‐effect models showed that 10‐unit increases in maximum measured moisture were associated with the presence of 0.5 additional dampness indicators (P < 0.001). Bedroom (BR) walls were damper than living room (LR) walls in the same homes (P < 0.0001), although both average and maximum readings were positively correlated across room type (r = 0.75 and 0.67, respectively, both P < 0.0001). Exterior walls were significantly damper than interior walls (P < 0.0001 in both LRs and BRs), but no differences were observed between maximum wall readings and measurements at either window corners or sites of suspected dampness.     

Home interventions are effective at decreasing indoor nitrogen dioxide concentrations

Nitrogen dioxide (NO₂), a by‐product of combustion produced by indoor gas appliances such as cooking stoves, is associated with respiratory symptoms in those with obstructive airways disease. We conducted a three‐armed randomized trial to evaluate the efficacy of interventions aimed at reducing indoor NO₂ concentrations in homes with unvented gas stoves: (i) replacement of existing gas stove with electric stove; (ii) installation of ventilation hood over existing gas stove; and (iii) placement of air purifiers with high‐efficiency particulate air (HEPA) and carbon filters. Home inspection and NO₂ monitoring were conducted at 1 week pre‐intervention and at 1 week and 3 months post‐intervention. Stove replacement resulted in a 51% and 42% decrease in median NO₂ concentration at 3 months of follow‐up in the kitchen and bedroom, respectively (P = 0.01, P = 0.01); air purifier placement resulted in an immediate decrease in median NO₂ concentration in the kitchen (27%, P < 0.01) and bedroom (22%, P = 0.02), but at 3 months, a significant reduction was seen only in the kitchen (20%, P = 0.05). NO₂ concentrations in the kitchen and bedroom did not significantly change following ventilation hood installation. Replacing unvented gas stoves with electric stoves or placement of air purifiers with HEPA and carbon filters can decrease indoor NO₂ concentrations in urban homes.     

What is the relationship between indoor air quality parameters and airborne microorganisms in hospital environments? A systematic review and meta-analysis

Airborne microorganisms in hospitals have been associated with several hospital-acquired infections (HAIs), and various measures of indoor air quality (IAQ) parameters such as temperature, relative humidity, carbon dioxide (CO₂), particle mass concentration, and particle size have been linked to pathogen survival or mitigation of pathogen spread. To investigate whether there are quantitative relationships between the concentration of airborne microorganisms and the IAQ in the hospital environment. Web of Science, Scopus and PubMed databases were searched for studies reporting airborne microbial levels and any IAQ parameter(s) in hospital environments, from database inception to October 2020. Pooled effect estimates were determined via random-effects models. Seventeen of 654 studies were eligible for the meta-analysis. The concentration of airborne microbial measured as aerobic colony count (ACC) was significantly correlated with temperature (r = 0.25 [95% CI = 0.06–0.42], p = 0.01), CO₂ concentration (r = 0.53 [95% CI = 0.40–0.64], p ˂ 0.001), particle mass concentration (≤5 µg/m³; r = 0.40 [95% CI = 0.04–0.66], p = 0.03), and particle size (≤5 and ˃5 µm), (r = 0.51 [95% CI = 0.12–0.77], p = 0.01 and r = 0.55 [95% CI = 0.20–0.78], p = 0.003), respectively, while not being significantly correlated with relative humidity or particulate matter of size >5 µm. Conversely, airborne total fungi (TF) were not significantly correlated with temperature, relative humidity, or CO₂ level. However, there was a significant weak correlation between ACC and TF (r = 0.31 [95% CI = 0.07–0.52], p = 0.013). Although significant correlations exist between ACC and IAQ parameters, the relationship is not definitive; the IAQ parameters may affect the microorganisms but are not responsible for the presence of airborne microorganisms. Environmental parameters could be related to the generating source, survival, dispersion, and deposition rate of microorganisms. Future studies should record IAQ parameters and factors such as healthcare worker presence and the activities carried out such as cleaning, sanitizing, and disinfection protocols. Foot traffic would influence both the generation of microorganisms and their deposition rate onto surfaces in the hospital environment. These data would inform models to improve the understanding of the likely concentration of airborne microorganisms and provide an alternative approach for real-time monitoring of the healthcare environment.     

Effects of energy retrofits on Indoor Air Quality in multifamily buildings

We assessed 45 multifamily buildings (240 apartments) from Finland and 20 (96 apartments) from Lithuania, out of which 37 buildings in Finland and 15 buildings in Lithuania underwent energy retrofits. Building characteristics, retrofit activities, and energy consumption data were collected, and Indoor Air Quality (IAQ) parameters, including carbon monoxide (CO), nitrogen dioxide (NO₂), formaldehyde (CH₂O), selected volatile organic compounds (benzene, toluene, ethylbenzene, and xylenes (BTEX), radon, and microbial content in settled dust were measured before and after the retrofits. After the retrofits, heating energy consumption decreased by an average of 24% and 49% in Finnish and Lithuanian buildings, respectively. After the retrofits of Finnish buildings, there was a significant increase in BTEX concentrations (estimated mean increase of 2.5 µg/m³), whereas significant reductions were seen in fungal (0.6‐log reduction in cells/m²/d) and bacterial (0.6‐log reduction in gram‐positive and 0.9‐log reduction in gram‐negative bacterial cells/m²/d) concentrations. In Lithuanian buildings, radon concentrations were significantly increased (estimated mean increase of 13.8 Bq/m³) after the retrofits. Mechanical ventilation was associated with significantly lower CH₂O concentrations in Finnish buildings. The results and recommendations presented in this paper can inform building retrofit studies and other programs and policies aimed to improve indoor environment and health.