Emissions of VOCs, SVOCs, and mold during the construction process: Contribution to indoor air quality and future occupants' exposure

Emissions of Semi-Volatile Organic Compounds from Architectural Coatings and Polyvinyl Chloride Floorings: Microchamber Method

Semi-volatile organic compounds (SVOCs) are modern chemical substances that are present in large quantities in indoor environments. Understanding the emission of SVOCs from building materials is essential to identify the main sources of indoor SVOCs and to improve indoor air quality. In this study, a reference method employing custom-designed microchambers (630 mL) was optimized by improving the structure of the gas path and adding polytetrafluoroethylene inner coating to the chamber. After optimization, the recoveries of the microchamber method were significantly improved (75.4-96.7%), and the background in the microchamber was greatly reduced (<0.02 μg/h). By using the microchamber method, 33 SVOCs (including two alkanes, one aromatic, one nitrogen compound, and twenty-nine oxygenated compounds) and 32 SVOCs (including seven alkanes, eight aromatics, and seventeen oxygenated compounds) were detected in the emissions of the architectural coating and the PVC flooring samples, respectively. The area-specific emission rates (SERa) of total SVOCs emitted from architectural coatings and PVC floorings were in the range of 4.09-1309 μg/m2/h) (median: 10.3 μg/m2/h) and 0.508-345 μg/m2/h (median: 11.9 μg/m2/h), respectively. Propanoic acid had the highest SERa (3143 μg/m2/h) in architectural coatings, while methylbenzene (345 μg/m2/h), 2-methylnaphthalene (65.2 μg/m2/h), and naphthalene (60.3 μg/m2/h) were main SVOCs emitted from PVC floorings. Meanwhile, the average second-stage (adsorbed phase) emission mass of the total SVOCs accounts for 66.3% and 47.3% in architectural coatings and PVC floorings, respectively, suggesting that the SVOCs emitted from building materials have a strong tendency to be absorbed on the surface of the room, e.g., the interior wall, the desk or even the skin.

Indoor cooking and cleaning as a source of outdoor air pollution in urban environments

Indoor sources of air pollution, such as from cooking and cleaning, play a key role in indoor gas-phase chemistry. The focus of the impact of these activities on air quality tends to be indoors, with less attention given to the impact on air quality outside buildings. This study uses the INdoor CHEmical Model in Python (INCHEM-Py) and the Advanced Dispersion Modelling System (ADMS) to quantify the impact cooking and cleaning have on indoor and outdoor air quality for an idealised street of houses. INCHEM-Py has been developed to determine the concentrations of 106 indoor volatile organic compounds at the point they leave a building (defined as near-field concentrations). For a simulated 140 m long street with 10 equi-distant houses undertaking cooking and cleaning activities, the maximum downwind concentration of acetaldehyde increases from a background value of 0.1 ppb to 0.9 ppb post-cooking, whilst the maximum downwind chloroform concentrations increase from 1.2 to 6.2 ppt after cleaning. Although emissions to outdoors are higher when cooking and cleaning happen indoors, the contribution of these activities to total UK emissions of volatile organic compounds is low (less than 1%), and comprise about a quarter of those emitted from traffic across the UK. It is important to quantify these emissions, particularly as continued vehicle technology improvements lead to lower direct emissions outdoors, making indoor emissions relatively more important. Understanding how indoor pollution can affect outdoor environments, will allow better mitigation measures to be designed in the future that can take into account all sources of pollution that contribute to human exposure.

Influence of humidity on accuracy of QCM - IR780-based GUMBOS sensor arrays

Herein, hydrophobic coating materials are reported for QCM detection of VOCs under dry and humid conditions. In this study, IR780-based GUMBOS ([IR780][OTf] and [IR780][NTf2]) were synthesized using an ion exchange reaction and the anions trifluoromethanesulfonimide ([OTf]) and bisperfluoromethanesulfonimide ([NTf2]). The parent iodide salts and GUMBOS ([IR780][I]), [IR780][OTf], and [IR780][NTf2]) were characterized using several analytical techniques. These salts were then employed as sensor coatings on quartz crystal resonators using an electrospray coating method. These sensors were exposed to four flow ratios of five common VOCs in the absence and presence of 10 vol% water. Fundamental frequency responses were recorded and further employed as input variables to develop highly accurate multi-sensor arrays (MSAs). Accuracy was better than 78.3% without water, and better than 91.7% in the presence of water. When multi-harmonic responses were evaluated as input variables to assess discrimination ability for each sensor, highly accurate virtual sensor arrays (VSAs) were developed using each GUMBOS coating. In the case of [IR780][NTf2], a slight improvement in discrimination was achieved in the presence of water (95%) versus the absence of water. Moreover, this study highlights development of readily synthesized hydrophobic coatings of IR780-based GUMBOS for potential detection and discrimination of VOCs in aqueous systems.

Intermediate volatile organic compounds in Canadian residential air in winter: Implication to indoor air quality

Intermediate volatile organic compounds (IVOCs) have recently been characterized for their contributions to the formation of secondary organic aerosol in atmospheric air. However, IVOCs in air in various indoor environments have not been characterized yet. In this study, we characterized and measured IVOCs, volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs), in residential indoor air in Ottawa, Canada. IVOCs, including n-alkanes, branched-chain alkanes (b-alkanes), unspecified complex mixtures (UCM) IVOCs, and oxygenated IVOCs (such as fatty acids), were found to have a large impact on indoor air quality. The results indicate that the indoor IVOCs behave differently from those in the outdoor environment. IVOCs in the studied residential air ranged from 14.4 to 69.0 μg/m³, with a geometric mean of 31.3 μg/m³, accounting for approximately 20% of the total organic compounds (IVOCs, VOCs and SVOCs) in indoor air. The total b-alkanes and UCM-IVOCs were found to have statistically significant positive correlations with indoor temperature but have no correlations with airborne particulate matter less than 2.5 μm (PM_2.5) as well as ozone (O₃) concentration. However, indoor oxygenated IVOCs behaved differently from b-alkanes and UCM-IVOCs, with a statistically significant positive correlation with indoor relative humidity but no correlation with other indoor environmental conditions.

Evaluation of VOCs from fungal strains, building insulation materials and indoor air by solid phase microextraction arrow, thermal desorption-gas chromatography-mass spectrometry and machine learning approaches

Solid phase microextraction Arrow and thermal desorption-gas chromatography-mass spectrometry allowed the collection and evaluation of volatile organic compounds (VOCs) emitted by fungal cultures from building insulation materials and in indoor air. Principal component analysis, linear discriminant analysis and supported vector machine were used for visualization and statistical assessment of differences between samples. In addition, a screening tool based on the soft independent modelling of class analogies (SIMCA) was developed for identification of fungal contamination of indoor air. Ten different fungal strains, incubated under ambient and microaerophilic conditions, were analyzed for time period ranging from 5 to 29 days after inoculation resulting in a total of 140 samples. In addition, the effect of additives on the fungal growing media was studied. The total number of compounds and concentration values were used for the evaluation of the results. Clear differences were observed for VOC profiles emitted by different fungal strains by exploiting long chain alcohols (3-octanol, 1-hexanol and 2-octen-1-ol) and sesquiterpenes (farnesene, cuprene). The analysis of glass-wool and cellulose based building insulation materials (3 samples) gave clear differences, mainly for oxygenated compounds (ethyl acetate and hexanal) and benzenoids (benzaldehyde). Moreover, the comparison of indoor air and insulation materials collected from a house with fungal indoor air problems indicated that 42% of the VOCs were found in both samples. The analysis of 52 indoor air samples demonstrated clear differences in their VOC profiles, especially for hydrocarbons, and between control (44 samples) and indoor air problem houses (8 samples). Finally, the SIMCA model enabled to recognize differences between control and fungi contaminated houses with a prediction capacity over 84%.

Biomonitoring of Indoor Air Fungal or Chemical Toxins with Caenorhabditis elegans nematodes

Bad indoor air quality due to toxins and other impurities can have a negative impact on human well-being, working capacity and health. Therefore, reliable methods to monitor the health risks associated with exposure to hazardous indoor air agents are needed. Here, we have used transgenic Caenorhabditis elegans nematode strains carrying stress-responsive fluorescent reporters and evaluated their ability to sense fungal or chemical toxins, especially those that are present in moisture-damaged buildings. Liquid-based or airborne exposure of nematodes to mycotoxins, chemical agents or damaged building materials reproducibly resulted in time- and dose-dependent fluorescent responses, which could be quantitated by either microscopy or spectrometry. Thus, the C. elegans nematodes present an easy, ethically acceptable and comprehensive in vivo model system to monitor the response of multicellular organisms to indoor air toxicity.

Fractional diffusion model for emission and adsorption prediction of TXIB from wallpaper

Mercury injection test shows that wallpaper is a porous building material with a complex fractal mass transfer channel. Therefore, fractional Fick's law is employed to investigate sub-diffusion of 2,2,4 trimethy1-1,3-pentanediol diisobutyrate (TXIB) from wallpaper. In view of the fact that a small amount of TXIB has been released from the wallpaper before the environmental chamber experiment, the non-uniform initial concentration is introduced. Based on fractional Fick's law, both fractional convective mass transfer equation and fractional mass balance equation have been firstly proposed. Combining the finite difference method and L1 algorithm, the fractional diffusion model is solved numerically. Numerical simulation results show that the present model matches well with the experimental data. Compared with the previous model based on Fick's law, the present model is in better agreement with experimental data of di-2-ethylhexyl phthalate (DEHP) released from polyvinyl chloride (PVC) flooring. The influence of key parameters on the concentration of TXIB is analyzed graphically. In addition, the absorption amount and absorption rate of TXIB on the environmental bulkhead are numerically simulated for the first time.

Latest Trends in Pollutant Accumulations at Threatening Levels in Energy-Efficient Residential Buildings with and without Mechanical Ventilation: A Review

Improving the energy efficiency of buildings is a major target in developed countries toward decreasing their energy consumption and CO₂ emissions. To meet this target, a large number of countries have established energy codes that require buildings to be airtight. While such a retrofitting approach has improved health outcomes in areas with heavy traffic, it has worsened the health outcomes in Nordic countries and increased the risk of lung cancer in areas with high levels of radon emissions. This review highlights the importance of adapting the characteristics of energy-efficient residential buildings to the location, age, and health of inhabitants to guarantee healthy indoor pollutant levels. The implementation of mechanical ventilation in new energy-efficient buildings has solved some of these problems; however, for others, a decrease in the level of outdoor pollutants was still required in order to achieve a good indoor air quality. A good balance between the air exchange rate and the air humidity level (adapted to the location) is key to ensuring that exposure to the various pollutants that accumulate inside energy-efficient buildings is low enough to avoid affecting inhabitants′ health. Evidence of the protective effect of mechanical ventilation should be sought in dwellings where natural ventilation allows pollutants to accumulate to threatening levels. More studies should be carried out in African and Asian countries, which, due to their rapid urbanization, use massive volumes of unproven/unrated building materials for fast-track construction, which are frequent sources of formaldehyde and VOC emissions.

Toxicological transcriptome of human airway constructs after exposure to indoor air particulate matter: In search of relevant pathways of moisture damage-associated health effects

BACKGROUND

Multiple health effects are associated with moisture damage in buildings. Studies explaining these associations and cell-level mechanisms behind the observed health effects are urgently called for.

OBJECTIVES

We focused on characterizing gene expression in human airway epithelium after exposure to indoor air particulate matter (PM) sampled from houses with and without moisture damage, alongside determination of general toxicological markers.

METHODS

We performed detailed technical building inspections in 25 residential houses and categorized them based on the detection of moisture damages and the probability of occupant exposure. PM sampling was complemented by microbiological and volatile organic compound assessment. We exposed human airway constructs to three dilutions (1:16, 1:8, 1:4) of collected PM from moisture-damaged (index) and non-moisture-damaged (reference) houses and imaged selected constructs with electron microscopy. We analyzed general toxicological markers and the RNA of exposed constructs was sequenced targeting genes associated with toxicological pathways. We did groupwise comparisons between index and reference houses and pairwise comparisons in matched index/reference houses.

RESULTS

In groupwise comparison, gene Cytochrome P450 Family 1 Subfamily A Member 1 (CYP1A1) was statistically significantly over-expressed in index houses at all dilutions of collected PM and Nuclear Factor Kappa B Subunit 1 (NFKB1) at dilution 1:4 of collected PM. In pairwise index/reference house comparison, several genes related to multiple toxicological pathways were activated, largest expression differences seen for CYP1A1. However, none of the genes was consistently expressed in all the matched pairs, and general toxicological markers did not differentiate index and reference houses.

DISCUSSION

The exposure to PM from index houses activated toxicology -related genes in airway constructs. Differential expression was not consistent among all the index/reference pairs, possibly due to compositional differences of bioactive particles. Our study highlights CYP1A1 and NFKB1 as potential targets in moisture damage -associated cellular responses.

Identification of key volatile organic compounds in aircraft cabins and associated inhalation health risks

The identification of key VOCs during flights is important in creating a satisfactory aircraft cabin environment. Two VOC databases for the building indoor environment (from 251 occupied residences) and the aircraft cabin environment (from 56 commercial flights) were compared, to determine the common compounds (detection rate (DR) > 70%) in the two environments and the characteristic VOCs (only those with high DR during flights) in aircraft cabins. Possible VOC emission sources in flights were also discussed. As TVOC is usually viewed as a general indicator of air quality, the prediction of TVOC concentration was carried out using BP neural network algorithm, and the average error between the predicted and measured values was 55.35 μg/m³ (R² = 0.80). Meanwhile, the VOCs' inhalation cancer/non-cancer risks to crew members and passengers were calculated on the basis of detection rates, exposure concentrations, and health risk assessments. Six compounds (i.e., formaldehyde, benzene, tetrachloroethylene, trichloromethane, 1,2-dichloroethane, and naphthalene) were proposed as the key VOCs in the existing aircraft cabin environment, presenting a risk to crew members that is higher than the US EPA proposed acceptable level (evaluated mean value > 1E-06). The estimated lifetime excess cancer/non-cancer risks for passengers were all below the assessment criteria. Based on a summary of various VOC limits in five built environments, hierarchical design of VOC concentration limits is recommended for the aircraft environment.

Emissions and toxic units of solvent, monomer and additive residues released to gaseous phase from latex balloons

This study describes the VOCs emissions from commercially available latex balloons. Nine compounds are determined to be emitted from 13 types of balloons of different colors and imprints in 30 and 60 °C. The average values of total volatile organic compounds (TVOCs) emitted from studied samples ranged from 0.054 up to 7.18 μg g^-1 and from 0.27 up to 36.11 μg g^-1 for 30 °C and 60 °C, respectively. The dataset is treated with principal component analysis (PCA) and multiple curve resolution (MCR) to characterize its internal patterns. Here two groups on compounds are recognized - the first one related to balloon material, the second one being emissions of compounds previously adsorbed on balloon material. The toxicity assessment of MCR modeled balloons' emissions was performed by toxic unit (TU) approach. The obtained TUs were summed to give toxicity emission assessment. The incorporation of TUs allows to identify the balloons with the most toxic emissions- imprinted ones in 60 °C. The compounds of the highest TUs are hexanal and benzene. FTIR analysis shows that all balloons are made of the same polymeric material - isoprene, so all differences in emissions are related to different additives like pigments, imprints or these responsible for opaqueness. Analyzing the obtained research results it was noticed that latex balloons might be considered as an important source of emission of aliphatic and monoaromatic hydrocarbons to the gaseous phase.

Factor analysis of the influence of environmental conditions on VOC emissions from medium density fibreboard and the correlation of the factors with fitting parameters

RH has positive effects on the initial VOC emissions and ACR has negative effects on VOC emissions. a₁ has a power relationship with ACR and a polynomial relationship with RH and b₁ has a polynomial relationship with both ACR and RH.