Characterization and source profiling of volatile organic compounds in indoor air of private residences in Selangor State, Malaysia

The association between clustering based on composition of volatile organic compound in indoor air and building-related symptoms

Volatile organic compounds (VOCs) have been suspected to cause building-related symptoms (BRSs). Although some studies investigated the association between BRSs and VOCs in indoor air, those results were inconsistent. This study investigated the contamination status of VOCs in the indoor air of 154 houses in Japan. Additionally, these samples were grouped by hierarchical clustering analysis based on the VOC composition, and the relationship between a VOC cluster and the BRSs was investigated. The median concentration of the sum of VOCs (ΣVOCs) was 140 μg m-3 (range: 18-3500 μg m-3). The levels of acetaldehyde in four samples and p-dichlorobenzene in one sample exceeded the guideline value. As a result of the hierarchical clustering analysis, the samples in this study were divided into six characteristic clusters based on the VOC composition. The ΣVOCs in cluster 1 were significantly lower than those in other clusters. In cluster 2, acyclic and aromatic hydrocarbons were dominant. Cluster 3 had a relatively high proportion of limonene. In cluster 4, the concentrations and composition ratios of α-pinene were higher than those of other clusters. In cluster 5, p-dichlorobenzene accounted for 42 %-72 % of the total VOCs. Cluster 6 had a relatively high proportion of decamethyl cyclopentasiloxane. This clustering likely depended on the construction of houses and lifestyles. As a result of logistic regression analysis, cluster 5 was associated with the cough symptoms of the BRSs. The results of the present study suggest that investigating the association between VOCs and BRSs is necessary to consider not only total concentrations such as TVOC and ΣVOCs but also VOC composition.

A novel low sampling rate and cost-efficient active sampler for medium/long-term monitoring of gaseous pollutants

Active sampling is a dependable approach for gaseous pollutants monitoring, offering high accuracy and precision that is unaffected by environmental factors such as wind and temperature in comparison to passive sampling. To measure long-term average concentrations while minimizing the use of materials, a reduced sampling rate is necessary. Thus, this study aims to develop a novel low sampling rate (down to 1 mL/min) and cost-efficient active sampler (LASP) for medium/long-term monitoring of gaseous pollutants. The LASP mainly consisted of a syringe pump, a Y-shaped fitting with two one-way valves, and a control unit for intermittent operation. Results showed that LASP can obtain a sampling rate of less than 1 mL/min and sampling rate exhibited a high level of stability. Daily average concentrations measurements for nitrogen dioxide and formaldehyde by LASP had normalized mean biases of 2.8% and 5.2%, respectively. These numbers were - 5.8% and 6.1% for weekly-average samplings. This study demonstrated applications of LASP in real outdoor (daily-average) and indoor (weekly-average) air quality measurements. It worked well with low noise levels, and without interfering with occupants' daily activities. LASP can assist in improving our ability to monitor air quality and pollutants emissions, thereby supporting health research and policy development. ENVIRONMENTAL IMPLICATION: Gaseous air pollution is an important hazardous factor threatening human health. Medium/long-term air quality monitoring is essential for outdoor and indoor air quality assessment and control. However, air sampler for medium/long-term sampling is lacking. This study developed a novel low sampling rate and cost-efficient active sampler and applied it to medium/long-term air sampling. The sampler can work at a sampling rate of less than 1 mL/min. This technology provides a feasible strategy for medium/long-term monitoring of gaseous air pollutants in both environments and emission hotspots.

A scientometric analysis of indoor air pollution research during 1990-2019

Indoor air pollution (IAP) is one of the leading risk factors for various adverse health outcomes including premature deaths globally. Even though research related to IAP has been carried out, bibliometric studies with particular emphasis on this topic have been lacking. Here, we investigated IAP research from 1990 to 2019 retrieved from the Web of Science database through a comprehensive and systematic scientometric analysis using the CiteSpace 5.7.R2, a powerful tool for visualizing structural, temporal patterns and trends of a scientific field. There was an exponential increase in publications, however, with a stark difference between developed and developing countries. The journals publishing IAP related research had multiple disciplines; 'Indoor Air' journal that focuses solely on IAP issues ranked fifth among top-cited journals. The terms like 'global burden', 'comparative risk assessment,' 'household air pollution (HAP)', 'ventilation', 'respiratory health', 'emission factor', 'impact,' 'energy', 'household', 'India' were the current topical subject where author Kirk R. Smith was identified with a significant contribution. Research related to rural, fossil-fuel toxicity, IAP, and exposure-assessment had the highest citation burst signifying the particular attention of scientific communities to these subjects. Overall, this study examined the evolution of IAP research, identified the gaps and provided future research directions.

Assessing BTEX concentrations emitted by hookah smoke in indoor air of residential buildings: health risk assessment for children

Hookah smoke is one of the major indoor sources of Volatile Organic Compounds (VOCs), including Benzene, Toluene, Ethylbenzene, and Xylenes (BTEX). The present study aimed to investigate potential exposure to BTEX compounds among primary school children whose parents smoked hookah at home. BTEX concentrations in indoor air were measured in 60 residential buildings of Khesht, southwestern Iran (case = 30 and control = 30). Target compounds were sampled by charcoal tubes, and the samples were then analyzed by GC-FID. Monte Carlo simulation was used to assess the carcinogenic and non-carcinogenic risks of BTX exposure for the children aged 7-13 years. The concentrations of benzene (7.19 ± 3.09 vs. 0.82 ± 0.5 μg/m³), toluene (1.62 ± 0.69 vs. 0.3 ± 0.22 μg/m³), and xylenes (2.9 ± 1.66 vs. 0.31 ± 0.22 μg/m³) were considerably higher in the indoor air of the case houses compared with the control houses (p < 0.05). The Incremental Lifetime Cancer Risk (ILCR) of benzene for non-smoking and smoking houses were estimated 1.8 × 10^-6 and 15 × 10^-6, respectively, exceeding the recommendations of the World Health Organization (WHO) and the Environmental Protection Agency (EPA) (1 × 10^-6). Moreover, Hazard Quotients (HQs) of all BTX compounds were < 1. The indoor benzene concentration was significantly influenced by the floor at which families lived and type of the kitchen. In order to prevent children's exposure to BTX emitted by hookah, banning indoor smoking is the only way to eliminate these compounds in the indoor air.

Photocatalytic purification of contaminated air in intensive care units by ZnSn(OH)6 nanoparticles

The air purification in intensive care units (ICU) involving the removal of smog and volatile organic compounds (VOCs), disinfection, and sterilization are closely linked to important health issues. The environmental photocatalysis technology that could decompose gaseous pollutants into small molecular inorganic substances provides the potential solution. In a chamber of 30-m³ simulated ICU, photocatalytic purifier with ZnSn(OH)₆ nanoparticles photocatalyst is set up to treat 10 VOCs with concentration below 2 ppm. Compared with regular purifiers of plasma and activated carbon, the present photocatalytic purifier can completely eliminate 10 varieties of low-concentration irritating VOCs without CO production. The continuous tests show that loading of 600 g ZnSn(OH)₆ has capacity to treat large volumes of VOCs and remains high removal efficiencies up to 600-h operation. The results suggest that the photocatalytic purifier could be potentially applied for the treatment of contaminated indoor air particularly ICU. The mechanism of ZnSn(OH)₆ photocatalysis is proposed to interpret the high performance and mineralization of the degradation process.

Biomarkers of Low-Level Environmental Exposure to Benzene and Oxidative DNA Damage in Primary School Children in Sardinia, Italy

Background: The main anthropic sources of exposure to airborne benzene include vehicular traffic, cigarette smoke, and industrial emissions. Methods: To detect early genotoxic effects of environmental exposure to benzene, we monitored environmental, personal, and indoor airborne benzene in children living in an urban area and an area near a petrochemical plant. We also used urinary benzene and S-phenylmercapturic acid (S-PMA) as biomarkers of benzene exposure and urinary 8-hydroxydeoxyguanosine (8-OHdG) as a biomarker of early genotoxic effects. Results: Although always below the European Union limit of 5 μg/m³, airborne benzene levels were more elevated in the indoor, outdoor, and personal samples from the industrial surroundings compared to the urban area (p = 0.026, p = 0.005, and p = 0.001, respectively). Children living in the surroundings of the petrochemical plant had urinary benzene values significantly higher than those from the urban area in both the morning and evening samples (p = 0.01 and p = 0.02, respectively). Results of multiple regression modelling showed that age was a significant predictor of 8-OHdG excretion, independent of the sampling hour. Moreover, at the low exposure level experienced by the children participating in this study, neither personal or indoor airborne benzene level, nor personal monitoring data, affected 8-OHdG excretion. Conclusions: Our results suggest the importance of biological monitoring of low-level environmental exposure and its relation to risk of genotoxic effects among children.

Adsorption of VOCs on reduced graphene oxide

A modified Hummer's method was adopted for the synthesis of graphene oxide (GO) and reduced graphene oxide (rGO). It was revealed that the modified method is effective for the production of GO and rGO from graphite. Transmission electron microscopy (TEM) images of GO and rGO showed a sheet-like morphology. Because of the presence of oxygenated functional groups on the carbon surface, the interlayer spacing of the prepared GO was higher than that of rGO. The presence of OH and CO groups in the Fourier transform infrared spectra (FTIR) spectrum and G-mode and 2D-mode in Raman spectra confirmed the synthesis of GO and rGO. rGO (292.6m²/g) showed higher surface area than that of GO (236.4m²/g). The prepared rGO was used as an adsorbent for benzene and toluene (model pollutants of volatile organic compounds (VOCs)) under dynamic adsorption/desorption conditions. rGO showed higher adsorption capacity and breakthrough times than GO. The adsorption capacity of rGO for benzene and toluene was 276.4 and 304.4mg/g, respectively. Desorption experiments showed that the spent rGO can be successfully regenerated by heating at 150.0°C. Its excellent adsorption/desorption performance for benzene and toluene makes rGO a potential adsorbent for VOC adsorption.

Assessment of the Endocrine-Disrupting Effects of Trichloroethylene and Its Metabolites Using in Vitro and in Silico Approaches

Trichloroethylene (TCE) is a ubiquitous environmental contaminant, which may have effects on both ecosystem and human health. TCE has been reported to cause several toxic effects, but little effort has been made to assess the ecological risks of TCE or its major metabolites: trichloroethanol (TCOH), trichloroacetic acid, and oxalic acid (OA). In this study, the endocrine-disrupting potential of TCE and its metabolites were investigated using in vitro and in silico approaches. We examined alterations in the steroidogenesis pathway using the NCI-H295R cell line and utilized receptor-mediated luciferase reporter cell lines to identify effects on estrogen and androgen receptors. Molecular docking was also used to explore chemical interactions with these receptors. All test chemicals except OA significantly increased 17β-estradiol production which can be attributed to an up-regulation of 17β-hydroxysteroid dehydrogenase. Moreover, TCOH exhibited significant antiestrogenic activity with a RIC20 (20% relative inhibitory concentration) of 3.7 × 10-7 M. Molecular docking simulation supported this finding with lower docking scores for TCOH, indicating that hydrogen bonds may stabilize the interaction between TCOH and the estrogen receptor binding pocket. These findings suggest that TCE contamination poses an endocrine-disrupting threat, which has implications for both ecological and human health.