Indoor Contaminants Research Articles

Quantitative PCR analysis of fungal DNA in Swedish day care centers and comparison with building characteristics and allergen levels

Abstract Sweden has had allergen-avoidance day care centers (AADCs) since 1979. The aim of this study was to measure fungal DNA by quantitative polymerase chain reaction (qPCR), a new method, in AADCs and ordinary day care centers (ODCs) and examine associations between allergen levels and building characteristics. Dust samples were collected by swabbing doorframes, vacuum-cleaning, and using Petri dishes. In total, 11 AADCs and 11 ODCs were studied (70 rooms). Total fungal DNA, measured by qPCR in the swab dust, was detected in 89%, Aspergillus or Penicillium (Asp/Pen) DNA in 34%, and Stachybotrys chartarum DNA in 6% of the rooms. Total fungal DNA was significantly higher in rooms with linoleum floor (P = 0.02), textile carpets (P = 0.03), reported dampness/molds (P = 0.02) and reported odor (P < 0.001) in the buildings, and significantly lower in wooden facade buildings (P = 0.003). Reported odor was related to the amount of sieved fine dust, reported dampness/molds and type of building construction. Total fungal DNA was related to cat, dog, horse and total allergen levels (P = 0.003) in the day care centers. In conclusion, total fungal DNA is related to reported dampness/molds, reported odor, and type of wall construction. The association between fungal and allergen contamination indicated a general 'hygiene factor' related to biological contaminants. Practical Implications The associations between fungal DNA, reported dampness/molds, and odor support the view that buildings with odor problems should be investigated for possible hidden fungal growth. There is a need to measure fungal biomass in different types of building constructions by monitoring fungal DNA. Analysis of fungal DNA with quantitative PCR can be a fast and practical way to study indoor fungal contamination. Swabbing dust from the doorframe of the main entrance to the room can be a convenient method of sampling dust for fungal DNA analysis. The high prevalence of reported dampness/molds and the common occurrence of fungal DNA indicate the need to improve the indoor environment of Swedish day care centers.

PBDEs in US and German clothes dryer lint: A potential source of indoor contamination and exposure

Polybrominated diphenyl ethers (PBDEs) are emerging persistent organic pollutants (POPs). Since the 1970s, PBDEs have been widely used as additive flame retardants in furniture and electronic equipment. Due to their wide use and persistent nature, these chemicals are found in the environment, human blood, breast milk and other tissues in increasing levels in recent decades. PBDEs are similar to polychlorinated biphenyls (PCBs) in structure and toxicity. However, unlike PCBs and PCDDs/PCDFs, the route of PBDE exposure is not almost exclusively through food. PBDE levels in US food are not markedly higher than in Europe, although US human blood and milk levels are an order of magnitude higher. For these reasons, other possible routes of PBDE exposure have been investigated to understand PBDE intake into humans. PBDE contaminated clothes dryer lint and household dust are indicators of indoor contamination and may be sources of human exposure through hand-to-mouth contact or dermal absorption. There are very few publications about PBDEs in US or European lint. Household dryer lint from 12 US and seven German homes were analyzed for PBDEs by gas chromatography coupled to high-resolution mass spectrometry. We found the median US total PBDE levels were more than 10 times higher than median German levels and the mean US levels were two times higher than mean German levels. The US levels ranged from 321 to 3073ngg−1 (median: 803ngg−1, mean: 1138ngg−1) and the German levels were from 330 to 2069ngg−1 (median: 71ngg−1, mean: 361ngg−1). PBDE contamination of lint was found in all samples; the source of the PBDEs may be from dryer electrical components and/or dust deposition onto clothing.

Potential Risk of Indoor Semivolatile Organic Compounds Indoors to Human Health

The concerns on indoor contamination by semivolatile organic compounds (SVOCs) are increasing. Because of the high boiling points in the range of 260-380 degrees C, SVOCs are considered to vaporize poorly under living conditions. However, a wide variety of SVOCs were detected in indoor air and house dust in previous studies. Indeed, we found SVOCs frequently in both air and dusts of residential dwellings in Sapporo city in 2006. Among SVOCs, there are a number of findings indicating that phthalates and pesticides use associated with allergy or bronchial obstruction. The adjuvant effect of phthalates, particularly monoesters, was shown in animal experiments and the association between allergy prevalence and exposure to phthalates or indoor materials containing plasticizers was observed in previous epidemiological studies. Regarding pesticides involving organophosphates and pyrethroids among others, the association of pesticide use with asthma or chronic bronchitis was observed in commercial pesticide applicators or farmers. Because SVOCs were often found in air and house dust of residential dwellings, the risk of SVOC exposure should be assessed in the Japanese general population.

Adsorption and Regeneration on Activated Carbon Fiber Cloth for Volatile Organic Compounds at Indoor Concentration Levels

There are increasing concerns about indoor volatile organic compounds (VOCs) regarding their health effects and frequent occurrence. Adsorption using granular activated carbon (GAC) is a safe methodology for removing VOCs from indoor air. Although GAC has been widely used to remove VOCs from indoor air, the use of activated carbon fiber cloth (ACFC) is a promising substitute to the conventional activated carbon because of its regenerative properties; hence, this paper provides promising results for the application of ACFC as a regenerative adsorbent for the removal of VOCs from indoor air. The impacts of operating variables on the adsorption/regeneration performance of the ACFC were assessed. A single-layer ACFC exhibited remarkable adsorption and regenerative properties using 100 parts per billion by volume (ppbv) toluene as the indoor contaminant. The use of Joule heating regeneration technique showed that the ACFC was rapid and efficient in removing the low initial loading of toluene. Even after continuous adsorption/regeneration cycles the ACFC showed very good performance. After over 300 heating and cooling cycles the ACFC showed excellent durability and adsorption capacity

Analysis of indoor air pollution trends and characterization of infiltration delay time using a cross-correlation method

High-density housing in close proximity to freeways in conjunction with high concentrations of traffic emissions may contribute to significant degradation of indoor air quality. Densely populated areas may also be targeted for intentional releases of biological or chemical agents because an urban release could result in higher morbidity and mortality from the attack. Since people tend to spend the majority of their time indoors, it is paramount to explore the relationships between outdoor and indoor air quality and, specifically, the time scales that characterize transport of airborne contaminants from outdoors to indoors. In the Brooklyn Traffic Real-Time Ambient Pollutant Penetration and Environmental Dispersion (B-TRAPPED) study, a three-story row house with a flat face and roof and multiple rooms was used to investigate outdoor-to-indoor contaminant time scales. The building was located in the Sunset Park neighborhood of Brooklyn, NY, USA, in the vicinity of a major expressway and a heavily trafficked arterial road. It was found that the building shell has a profound impact on the indoor concentrations. A strong hourly periodicity (see Eisner et al., this issue, DOI: 10.1039/b907132f) in concentration outside the building during the morning "rush hour" was used as evidence to suggest that indoor contaminants originated from outdoor air penetration. Although the indoor concentrations followed a similar pattern, indoor concentrations were found to be more persistent than outdoor concentrations. Stronger persistency is used here to describe the tendency of the indoor concentration to continue to rise even if the outdoor concentration has started to drop, or vice versa. This may be an important factor in assessing negative health risks to inhabitants or first responders. A cross-correlation technique was employed to study the correlation between outdoor and indoor time series. In the high-density housing residential building used in the study, it was found that a long lag time exists (11 min) before indoor and outdoor concentrations reach maximal correlation.

Indoor contaminants from newspapers: VOCs emissions in newspaper stands

Mean volatile organic compound (VOC) concentrations in 16 newspaper stands and in two printing shops were monitored for the purpose of quantifying the various VOCs in these areas and to relate the results. In each site halogenated, oxygenated, aliphatic, and aromatic compounds were monitored during one workweek. They were sampled with diffusive samplers for thermal desorption and analysed by GC–MS. The results showed that in all newspaper stands the indoor levels of toluene were much higher than the outdoor levels; some sites had toluene indoor concentrations 100 times higher than their correspondent outdoor levels. The investigations in two printing shops confirmed that newspapers, in particular the inks, are the main sources of toluene in the newspaper stands.

Chemical risk factors and childhood leukaemia: a review of recent studies

The search for chemical risks factors as determinants of childhood leukaemia has been ongoing for over two decades. Results of epidemiological studies, published from 1998 to the present, evaluating parental smoking, outdoor sources of pollution, indoor contaminants and chemicals from drinking water are reported. Overall, results were mostly negative. This may be due to the relatively small study sizes to detect environmental effects, usually measured imprecisely. Another reason may be that such effects, which may be revealed among the genetically susceptible, have rarely accounted for genetic susceptibility. The few studies that have are also reported here. Suggestions are made for work in the immediate future, which include pooling of data and of analyses, as well as carrying out in-depth reviews of studies with the goal of understanding the reasons for discrepant results.

Prompt tracking of indoor airborne contaminant source location with probability-based inverse multi-zone modeling

Indoor air quality (IAQ) has a significant influence on occupants' comfort, health, productivity, and safety. Existing studies show that the primary causes of many IAQ problems are various airborne contaminants that either are generated indoors or penetrate into indoor environments with passive or active airflows. Accurate and prompt identification of contaminant sources can help determinate appropriate IAQ control solutions, such as, eliminating contaminant sources, isolating and cleaning contaminated spaces. This study develops a fast and effective inverse modeling method for identifying indoor contaminant source characteristics. The paper describes the principles of the probability-based adjoint inverse modeling method and formulates a multi-zone model based inverse prediction algorithm that can rapidly track contaminant source location with known source release time in a building with many compartments. The paper details the inverse modeling procedure with modification of an existing multi-zone airflow and contaminant transport simulation program. The application of the method has been demonstrated with two case studies: contaminant releases in a multi-compartment residential house and in a complex institutional building. The numerical experiments tested the source identification capability of the program for various contaminant sensing scenarios. The investigation verifies the effectiveness and accuracy of the developed method for indoor contaminant source tracking, which will be further explored to identify more complicated indoor contamination episodes.

Association between indoor contamination and respiratory diseases in children living in Temuco and Padre Las Casas, Chile

Indoor air pollution, is the main cause of population exposure to polluting agents. To establish an environmental profile of indoor contamination emission sources in families of children under 5 years that assist to kindergartens in Temuco and Padre Las Casas. To associate respiratory disease episodes in children with indoor contamination. Cross sectional analysis of 355 family groups subjected to questionnaires about indoor contamination and number of respiratory disease episodes. Forty six percent of mothers or caregivers smoked, 37% smoked at home and 93% smoked one to two cigarettes per day. There was a significant association between respiratory diseases in children and drying clothes in the kitchen, using firewood for heating and the presence of humidity in the dwelling. Mothers identified as indoor contaminants the use of braziers in 76% of cases and firewood stoves in 24%. Ninety seven percent considered that these appliances were detrimental for respiratory health. The lack of awareness about indoor contamination among subjects of low socioeconomic status should prompt educational campaigns to modify behaviors in their dwellings.

Outdoor ozone and building-related symptoms in the BASE study

Reactions between ozone and indoor contaminants may influence human health and indoor air quality. The U.S. EPA Building Assessment Survey and Evaluation (BASE) study data were analyzed for associations between ambient ozone concentrations and building-related symptom (BRS) prevalence. Multiple logistic regression (MLR) models, adjusted for personal, workplace, and environmental variables, revealed positive relationships (P < 0.05) between ambient ozone concentrations and upper respiratory (UR), dry eyes, neurological and headache BRS (odds ratios ranged from 1.03 to 1.04 per 10 mug/m(3) increase in ambient ozone concentrations). Other BRS had marginally significant relationships with ambient ozone (P < 0.10). A linear dose-response in UR symptoms was observed with increasing ambient ozone (P = 0.03); most other symptoms showed similar but not statistically significant trends. Ambient ozone correlated with indoor concentrations of some aldehydes, a pattern suggesting the occurrence of indoor ozone chemistry. Coupled with the MLR ambient ozone-BRS analysis, this correlation is consistent with the hypothesis that ozone-initiated indoor reactions play an important role in indoor air quality and building occupant health. Replication with increased statistical power and with longitudinal data is needed. If the observed associations are confirmed as causal, ventilation system ozone removal technologies could reduce UR BRS prevalence when higher ambient ozone levels are present. This paper provides strong statistical evidence that supports (but does not prove) the hypothesis that ozone entrained into buildings from the outdoor air is involved in increasing the frequency that occupants experience and a range of upper and lower respiratory, mucosal and neurological symptoms by as much as a factor of 2 when ambient ozone levels increase from those found in low-ozone regions to those typical of high-ozone regions. Although replication is needed, the implication is that reducing the amount of ozone entrained into building ventilation systems, either by ambient pollution reduction or engineered gas-phase filtration, may substantially reduce the prevalence of these symptoms experienced by occupants.

Air Distribution Effectiveness for Different Mechanical Ventilation Systems

The purpose of ventilation is to dilute indoor contaminants that an occupant is exposed to. In a multi-zone environment such as a house, there will be different dilution rates and different source strengths in every zone. Most US homes have central HVAC systems, which tend to mix conditions between zones. Different types of ventilation systems will provide different amounts of dilution depending on the effectiveness of their air distribution systems and the location of sources and occupants. This paper will report on work being done to model the impact of different systems and to outline measurements using a new multi-tracer measurement system that has the capacity to measure not only the flow of outdoor air to each zone, but zone-to-zone transport. The ultimate objective of this project is to determine the effectiveness of different systems so that appropriate adjustments can be made in residential ventilation standards such as ASHØ Standard 62.2.

Prevalence of allergic sensitization to indoor fungi in West Virginia

Exposure to indoor fungi is of growing concern in residential and occupational environments in the United States. The purpose of this study was to determine the prevalence of sensitization to common indoor fungal species in an atopic population. We evaluated 102 patients (73 female and 29 male patients) for immunoglobulin E (IgE) reactivity to a panel of skin-prick test (SPT) reagents used for routine allergy testing. Patients also were tested for six additional fungi that are common indoor contaminants. All patients had symptoms consistent with allergic rhinitis or asthma. The presence of specific IgE against the fungal species was determined using immunoblotting. Of the 102 eligible patients, 68% had at least one positive skin test. The most prevalent positive SPTs were to dust mites, cats, vernal grass, and short ragweed. Overall, 21/102 (21%) patients with asthma or allergic rhinitis were skin test positive to at least one fungal extract. Of the patients with a positive SPT to fungi, 12/21 (58%) showed sensitivity to one or more of the newly tested species; most notably Trichoderma viride (8%), Chaetomium globosum (7%), Paecilomyces variotii (7%), and Acremonium strictum (6%). Immunoblotting revealed specific IgE against a number of protein bands belonging to these fungal species. The prevalence of fungal sensitization was common, particularly for indoor fungal contaminants that are not routinely included in SPT panels. Cross-reactivity with other fungi may partially explain our results; however, skin testing for these indoor fungi may provide useful diagnostic information.

Location identification for indoor instantaneous point contaminant source by probability-based inverse Computational Fluid Dynamics modeling

Indoor pollutions jeopardize human health and welfare and may even cause serious morbidity and mortality under extreme conditions. To effectively control and improve indoor environment quality requires immediate interpretation of pollutant sensor readings and accurate identification of indoor pollution history and source characteristics (e.g. source location and release time). This procedure is complicated by non-uniform and dynamic contaminant indoor dispersion behaviors as well as diverse sensor network distributions. This paper introduces a probability concept based inverse modeling method that is able to identify the source location for an instantaneous point source placed in an enclosed environment with known source release time. The study presents the mathematical models that address three different sensing scenarios: sensors without concentration readings, sensors with spatial concentration readings, and sensors with temporal concentration readings. The paper demonstrates the inverse modeling method and algorithm with two case studies: air pollution in an office space and in an aircraft cabin. The predictions were successfully verified against the forward simulation settings, indicating good capability of the method in finding indoor pollutant sources. The research lays a solid ground for further study of the method for more complicated indoor contamination problems. The method developed can help track indoor contaminant source location with limited sensor outputs. This will ensure an effective and prompt execution of building control strategies and thus achieve a healthy and safe indoor environment. The method can also assist the design of optimal sensor networks.

CFD Studies of Indoor Airflow and Contaminant Particle Transportation

This article presents a numerical study of indoor airflows and contaminant particle transportation in three ventilated rooms. The realizable k − ϵ model is employed to model the air-phase turbulence, while the Lagrangian particle tracking model is utilized for the particle-phase simulation. The predicted air-phase velocities and contaminant particle concentrations are validated against the experimental data obtained from the literature. In the first case, the realizable k − ϵ model successfully captures the flow trend and reasonably predicts the airflow velocity. The realizable k − ϵ model under-predicts the vertical air velocities along the vertical inlet jet axis by 11% at x = 0.219 m, which is slightly better than the standard k − ϵ model error of 17%. In a two-zone room case, the realizable k − ϵ model, combined with a Lagrangian particle tracking model, predicts the particle concentration decay with the highest normalized difference being 24%. In the third case, the influence of particle size, location of particle resource, and particle-wall collision on the particle concentrations is investigated by the realizable k − ϵ model and the Lagrangian model. It is found that for relatively small particles (diameter ≤ 10 μm), the particle concentration may be insensitive to the particle diameter. In addition it has been observed that the particle-collision model may have considerable effect on the particle concentration prediction.

Indoor and outdoor air carbonyl compounds correlation elucidated by principal component analysis

In this study indoor and outdoor air carbonyl compounds concentrations data are processed by means of principal component analysis (PCA). The analysis pointed to the carbonyl compounds sources as well as to their mutual interrelations. A global six sources (components) solution, accounting for the joint variability of the measured variables, was obtained. The existence of a linear function connecting outdoor and indoor components allowed for an exchange model between indoor and outdoor carbonyl compounds to be outlined. The different sources of carbonyl compounds were tentatively identified. Overall, this work demonstrates the presence of a delicate balance between indoor and outdoor carbonyl compounds contamination with the two compartments (indoor and outdoor) engaged in a close relationship.

Numerical analysis of two contaminants removal from a three-dimensional cavity

This paper reports the results of a numerical study on removal of two contaminants from a three-dimensional enclosure with one inlet, one exhausting port and one returning port. In the formation of the problem, use is made of Reynolds stress model (RSM). The governing equations are solved by means of the SIMPLE algorithm. Lots of cases have been studied for the sensitivity analysis, including more practical cases from the total fresh air supplying to the total recirculation situations. The influence of inlet velocity, fresh air ratio, recirculating air filtered removal efficiency and contaminant property is investigated. The indoor contaminant is studied parametrically as a function of governing dimensionless numbers (Reynolds number and Schmidt number). The results show the above parameters have complex influence to indoor contaminant removal.

Hollow fiber membrane contactor for hydrogen sulfide odor control

AbstractHollow fiber membrane modules are extensively used as gas–liquid contactors for acid gas removal from waste gas streams. Hydrogen sulfide is an important indoor and outdoor contaminant, but, given its toxicity, a limited number of experimental results have been reported for this compound. Moreover, chemical absorption has been exclusively investigated. In this study, hydrogen sulfide odor control by absorption in water thanks to a hollow fiber contactor has been studied both experimentally and theoretically. The scrubbing of hydrogen sulfide from air gas mixture is investigated in two porous polypropylene (PP) hollow fiber modules of different contact area and fiber packing fraction. The gas phase is circulated in the lumen of the fiber bore and the liquid phase in the shell in a nonwetted mode, i.e. the membrane pores being filled with gas. The gas phase was run in countercurrent contact with the liquid phase at constant pressure. A laminar parabolic velocity has been employed to describe the convective diffusive mass transport equation which has been solved analytically and numerically. The calculated extents of hydrogen sulfide depletion reasonably compare with the generated experimental results for both membrane modules. Up to 85% of acid gas could be removed at gaseous flowrates of 200 cm3/min for the large module and removals as high as 89% at 10 cm3/min have been observed for the smaller one. The overall mass transfer coefficients calculated from the experimental data, agree satisfactorily with those generated by the mathematical model. The relation of the dimensionless Sherwood number to the Graetz number is in a good agreement with the Levêque semianalytical solution. © 2007 American Institute of Chemical Engineers AIChE J, 54: 122–131, 2008

Estimates of Hourly Dust and Soil Ingestion Rates for Children and Adults In- and Outdoors

ISEE-217 Objective: Daily soil and dust ingestion rates are often estimated using tracer studies. Information on the contribution of dust in the total soil and dust ingestion is often lacking. However, in view of the large contribution of indoor contaminants in the total exposure, this information is essential. Therefore, a mathematical model was developed that uses estimates of daily soil and dust ingestion rates from tracer studies, the fractions spend in- and outdoors and the indoor/outdoor ingestion ratio as input variables. Material and Methods: The average (±SD) daily soil and dust ingestion rates calculated from published tracer studies ranged between 71.8 ± 12.01 and 41.67 ± 10.32 mg/d for children and adults, respectively. For the Monte-Carlo simulations (5000 iterations) soil and dust ingestion was assumed to be log-normally distributed. The indoor/outdoor ingestion ratio was assumed to be uniformly distributed between 0.1 and 1.0 for children and between 0.3 and 1.0 for adults. A triangular distribution between 1 and 6 hours, with a most likely value of 3 hours was chosen for the time spent outside, both for children and adults. Results: Average hourly soil ingestion rates [corresponding with a central tendency exposure scenario (CTE)] for children outdoors and indoors of 13.55 and 3.28 mg/h were calculated. The average hourly dust ingestion inside was estimated as 3.44 mg/h. Corresponding estimates under a reasonable maximal exposure scenario (RME = 95th percentiles from simulations) for soil outdoors, indoors, and dust indoors were 22.52, 5.48, and 6.94 mg/h, respectively. For adults, these values were 5.78 (soil outdoors), 1.78 (soil indoors), and 1.90 mg/h (dust indoors) under a CTE scenario and 12.94 (soil outdoors), 3.83 (soil indoors), and 4.69 mg/h (dust indoors) under an RME scenario. Conclusions: Hourly ingestion rates for soil and dust allow the risk assessor to predict exposure to soil-borne pollutants for a particular setting and duration, more accurately.

Isolation and attempts of biomolecular characterization of fungal strains associated to foxing on a 19th century book

Abstract The brownish spots known as foxing, commonly found on old paper artefacts contain sometimes structures, which look like filamentous fungi. Attempts to grow these structures in vitro have been always unsuccessful so far. In order to study the role of these biological elements in paper decay, it is essential to identify them. This study is aimed at the identification of isolates from these brownish areas by culture-independent approaches using molecular biology techniques. The two Internal Transcribed Spacers and the 5.8 S gene (ITS1-5.8S-ITS2) from the nuclear ribosomal DNA were amplified, cloned and sequenced. Following a preliminary treatment with cellulase from Trichoderma reesei , DNA extractions were successfully achieved directly from paper samples. From 22 selected stained spots from a book dating from the 19th century, 8 extracts of genomic DNA were entirely analysed, which yielded 145 sequenced clones. No DNA could be sampled in unstained areas. Multiple alignment of the ITS sequences and comparison with reference sequences published in the NCBI database allowed to identify 14 groups of fungi belonging mainly to the following genera: Aspergillus , Bjerkandera , Chaetomium , Gloeotinia , Penicillium , Polyporus , Saccharicola , Trichoderma and Ulocladium . Some of these fungi are cellulolytic species but are not commonly found as indoor contaminant in storage rooms of graphic documents. The majority of the foxing spots exhibited sequences identified as Penicillium minioluteum . Gloeotinia temulenta occurred also frequently. Few isolates such as Aspergillus japonicus , Aspergillus oryzae , Chaetomium globosum , Penicillium citrinum , Trichoderma citrinoviride , Ulocladium chartarum and Ulocladium cucurbitae were present in only 1 or 2 clones. One of the foxing spots produced only one type of sequence similar to both Cordyceps sinensis and Fusarium lateritium , which have identical sequences in this rDNA region. This molecular approach, simple and rapid, could provide additional data for further discussion on the origin of the phenomenon of biological foxing.

Reduced fungal contamination of the indoor environment with the Plasmair™ system (Airinspace)

Aspergillus spp. and other moulds cause life-threatening opportunistic infections in immunocompromised patients. Indoor contamination and construction work that liberate fungal spores are a major source of nosocomial aspergillosis. Dijon hospital is a tertiary care institution in northeast France undergoing construction work beside high-risk clinical units. To determine the impact of this activity, a surveillance programme was implemented one year before building work began in order to establish baseline levels of contamination. Air and surface fungal contamination in adult and paediatric haematology units were prospectively examined following use, or not, of a new air-treatment system with mobile Plasmair units (Airinspace). There were significant reductions in overall fungal contamination for the Plasmair treated rooms for air and surface samples in both clinical units. Plasmair treatment also significantly reduced A. fumigatus in the air. These data suggest that Plasmair units may provide an efficient method of reducing indoor fungal contamination in hospitals.