Outdoor Dust Research Articles

Occurrence, distribution and human exposure to 20 organophosphate esters in air, soil, pine needles, river water, and dust samples collected around an airport in New York state, United States

Organophosphate esters (OPEs) are used in aircraft lubricating oil and hydraulic fluids, and, thus, airplane emissions are thought to be an important source of these chemicals in the environment. In this study, concentrations of 20 OPEs, comprising seven alkyl-OPEs, three chlorinated (Cl)-OPEs, seven aryl-OPEs, and three oligomeric-OPEs, were determined in outdoor air, soil, pine needles, river water, and outdoor dust samples collected around an airport in Albany, New York, in 2018. Elevated ∑OPE concentrations were found in outdoor air, soil, pine needles, outdoor dust, and river water in the ranges of 1320–20,700 pg/m3 (median: 3880), 1.16–73.1 (14.3) ng/g dry weight (dw), 23.2–534 (102) ng/g (dw), 153–2140 (824) ng/g (dw), and 174–24,600 (1250) ng/L, respectively. The total OPE concentrations in air, soil, water, and outdoor dust samples in the study area were dominated by Cl-OPEs, whereas those in pine needles were dominated by aryl-OPEs. The spatial distribution of OPEs in air, soil, and pine needles showed a gradual decreasing trend with increasing distance from the airport. A significant correlation was observed between ∑OPE concentrations in air and soil, and the fugacity ratio showed the flux of OPEs from air to soil. The spatial distribution of OPEs between air and pine needles was similar and highly correlated, suggesting that pine needles are suitable indicators of atmospheric OPE concentrations. In addition to urban activities, aircraft hydraulic/lubricant oils are a major source of OPEs in the vicinity of the airport. The average daily intake of OPEs via air inhalation and outdoor dust ingestion in the vicinity of the airport was up to 1.53 ng/kg bw/day for children and 0.73 ng/kg bw/day for adults.

Occurrence, distribution and health risk assessment of organophosphate esters in outdoor dust in Nanjing, China: Urban vs. rural areas

With increasing use of organophosphate esters (OPEs) largely due to the phasing out of various brominated flame retardants, much more attention has been paid to their occurrence, distribution and potential health risks. In this study, we investigated the occurrence and distribution characteristics associated to their potential health risks of selected 13 OPEs in outdoor dust with a comparison between urban and rural areas in Nanjing, China as well as seasonal variations. Ten out of 13 OPEs showed higher concentrations in urban dust than those in rural dust (p < 0.05). Six OPEs congeners exhibited significantly different concentrations with seasonal variations (p < 0.01) in rural dust. Halogenated OPEs were the dominant group in both urban (median: 56.8%) and rural (median: 45.9%) dust, and tris(2-chloroisopropyl) phosphate (TCPP) was found to be the most abundant OPE in both urban (median: 48.7%) and rural (median:26.4%) dust. Principal component analysis with multiple linear regression (PCA-MLR) and spearman correlations showed the different sources of OPEs in urban and rural dust. The non-carcinogenic (Hazard Index, HI < 1.62 × 10−5) and carcinogenic risks (CR < 2.28 × 10−9) of ΣOPEs were much lower than the theoretical threshold of risk, revealing a negligible risk to local residents from the exposure of OPEs in outdoor dust.

Characteristics and health risk assessment of heavy metals in indoor dust from different functional areas in Hefei, China

Metals in indoor dust pose potential health risks to humans. Dust deposition on air conditioner filters can represent the resuspended particulate matter in indoor air. However, few studies have examined this until now. This study investigated the total concentrations and different chemical fractionations of Cd, Cr, Mn, Ni, Pb, Sb, V, and Zn in indoor dust from three different functional zones (the Chief District, Commercial District (CmD), and Industrial District) in Hefei. The mean metal concentrations in indoor dust decreased in the following order: Zn > Mn > Pb > Cr > Ni > V > Cd > Sb. Cd, Pb, and Zn mainly existed in the mobile fraction. Cr and V mainly existed in the residual fraction. The enrichment factor and geo-accumulation index values of heavy metals were all ranked in the order of Cd > Zn > Pb > Sb > Ni > Cr > V, and these values in indoor dust were larger than those in outdoor dust. In addition, the enrichment patterns of these elements were similar in the three functional areas. The orders of non-carcinogenic risk (hazard index; HI) for the different functional areas for children were roughly the same, but there were clear differences for adults. In general, all the HIs were less than 1, which were within the internationally recognized safe range. The total carcinogenic risk (TR) was in the order of Cr > Pb > Cd for both children and adults in the three functional zones. The TRs from Cr exposure were not negligible. The TRs were significantly higher in the CmD.

Detection of metallic iron in urban dust by using high-temperature measurements supplemented with microscopic observations and Mössbauer spectra

This paper presents a thermomagnetic study of fresh, unheated indoor dust, outdoor dust, street dust and dust from the cabin air filters of cars. Detailed analysis of thermomagnetic curves clearly indicated the presence of two magnetic transitions: the first identified at the Curie temperature TC ~ 585 °C for magnetite; the second TC detected at about ~765 °C, indicating the presence of metallic iron and/or iron-based alloys. The ‘tail,’ i.e., the substantial decreasing of κ visible on the heating curves of κ(T) between 600 °C and 700 °C, was attributed to the metallic iron or iron-based alloys. The presence of a high-temperature Fe-phase is not dependent on the types of urban dust or the sampling method, as variable amounts of metallic iron were detected in material collected from different environments: both indoor dust and outdoor dust, and dust gathered by sweeping indoor floor surfaces as well as dust collected with a vacuum cleaner.The presence of metallic iron in different types of dust was confirmed by non-magnetic methods. Electron microscopic observations with Energy-Dispersive X-ray Spectroscopy revealed elongated shaving-like particles comprised of metallic iron. A component with a magnetic hyperfine field of Bhf ~ 33 T and an almost zero value for isomeric shift as well as zero quadrupole splitting typical of metallic α-Fe at micrometer size or Fe-based alloys was recognized in all the Mössbauer spectra.Additional measurements of hysteresis properties at high temperatures (up to 750 °C) and after step-wise annealing indicated the process of oxidation of iron to magnetite. This has a strong effect on the run of κ(T) and M(T) curves during heating and cooling because M and κ are strongly dependent on the apparent concentration of both ferromagnetic phases (magnetite and metallic iron).

Widespread distribution of PET and PC microplastics in dust in urban China and their estimated human exposure

Dust is a fate of many contaminants and may be an important medium for the human exposure to these contaminants. Microplastics (MPs) have been observed in dust in previous studies. However, the mass concentrations of dominant MPs in dust and the exposure risk to human remain unclear. In this study, indoor and outdoor dust samples were collected from 39 major cities of China. The mass concentrations of polyethylene terephthalate (PET) and polycarbonate (PC) MPs were determined through alkali-assisted thermal depolymerization-liquid chromatography-tandem mass spectrometry, and the shape and component distribution of MPs were analyzed by optical microscopy and micro-Fourier transform infrared spectroscopy. PET MPs were detected in all the samples at high concentrations of 1550–120,000 mg/kg (indoor) and 212–9020 mg/kg (outdoor) and PC MPs were detected in approximately 70% of the samples, with median concentrations of 4.6 mg/kg (indoor) and 2.0 mg/kg (outdoor). Fiber was the main shape of suspected MPs, and polyester (including PET) was identified as an important component in MPs from dust. Indoor dust is a non-negligible source of human exposure to MPs, accounting for a geomean daily intake of 17,300 ng/kg-bw of PET MPs in children.

Waterproof-breathable PTFE nano- and Microfiber Membrane as High Efficiency PM2.5 Filter.

This study shows the feasibility of using electrospinning technique to prepare polytetrafluoroethylene/poly (vinyl alcohol) (PTFE/PVA) nanofibers on PTFE microfiber membrane as substrate. Then, PVA in the fiber membrane was removed by thermal treatment at about 350 °C. Compared to PTFE microfiber substrates, the composite PTFE fiber membranes (CPFMs) have improved filtration efficiency by 70% and water contact angle by 23°. Experimental test data showed that the water contact angle of the sample increased from about 107° to 130°, the filtration efficiency of PM2.5 increased from 44.778% to 98.905%, and the filtration efficiency of PM7.25 increased from 66.655% to 100% due to the electrospun PTFE nanofiber layer. This work demonstrates the potential of CPFMs as a filter for the production of indoor or outdoor dust removal and industrially relevant gas filtration.

Distribution, sources and pollution status of Pb in indoor and outdoor dusts of Kerman City, SE Iran

The aims of this study were to explore the status of pollution and the temporal/spatial distribution of indoor and outdoor dust-Pb in the city of Kerman (SE Iran), located in a dry playa and arid climatic zone. Flat panes were laid at appropriate locations, in the indoor and the outdoor spaces of selected one-story houses in different areas of the city, to collect dust samples. Forty-two samples were taken and analyzed using the ICP-MS method. The measurements have shown that the outdoor dust-Pb concentrations varied from 23.7 to 275.2 mg kg−1, with a mean value of 71.8 mg kg−1, and indoor dust-Pb concentrations ranged from 47.6 to 150.2 mg kg−1, with a mean value of 89.6 mg kg−1. Based on these measurements, Pb was enriched in the outdoor and the indoor dust samples up to 48.8 and 29.4 times, respectively. Dilution, as a result of prevalence of geogenic dust in the outdoor space, is expected to be the main cause of the temporal differences. This study has shown that the eastern part of the city is more polluted compared to the other parts, and, because of the stable air conditions, the concentration of Pb in the summer dust is higher than the other seasons.

The exposure of children to PM2.5 and dust in indoor and outdoor school classrooms in Kuala Lumpur City Centre

It is important to assess indoor air quality in school classrooms where the air quality may significantly influence school children's health and performance. This study aims to determine the concentrations of PM2.5 and dust chemical compositions in indoor and outdoor school classroom located in Kuala Lumpur City Centre. The PM2.5 concentration was measured from 19th September 2017–16th February 2018 using an optical PM2.5 sensor. Indoor and outdoor dust was also collected from the school classrooms and ion and trace metal concentrations were analysed using ion chromatography (IC) and inductively couple plasma-mass spectrometry (ICP-MS) respectively. This study showed that the average indoor and outdoor 24 h PM2.5 was 11.2 ± 0.45 µg m−3 and 11.4 ± 0.44 µg m−3 respectively. The 8 h PM2.5 concentration ranged between 3.2 and 28 µg m−3 for indoor and 3.2 and 19 µg m−3 for outdoor classrooms. The highest ion concentration in indoor dust was Ca2+ with an average concentration of 38.5 ± 35.0 µg g−1 while for outdoor dust SO42- recorded the highest ion concentration with an average concentration of 30.6 ± 9.37 µg g−1. Dominant trace metals in both indoor and outdoor dust were Al, Fe and Zn. Principle component analysis-multiple linear regression (PCA-MLR) demonstrated that the major source of indoor dust was road dust (69%), while soil dominated the outdoor dust (74%). Health risk assessment showed that the hazard quotient (HQ) value for non-carcinogenic trace metals was < 1 while the total cancer risk (CR) value for carcinogenic elements was below the acceptable limit for both indoor and outdoor dust through dermal and inhalation pathways, but not the ingestion pathway. This study suggests indoor contributions of PM2.5 concentrations are due to the activities of the school children while the compositions of indoor and outdoor dust are greatly influenced by the soil/earth source plus industrial and traffic contribution.

Organophosphate flame retardants in the indoor and outdoor dust and gas-phase of Alexandria, Egypt

Little is known about the presence of organophosphate flame retardants (OPFRs) as a substitute for polybrominated diphenyl ethers in developing countries. This study investigated - for the first time - concentrations, sources and exposure levels of OPFRs in the indoor and outdoor environments of Alexandria, Egypt, in dust and gas-phase samples. Passive samplers were deployed (n = 78) to determine gaseous concentrations, and various dust samples were collected from apartments (n = 25), working places (n = 14), cars (n = 18), and outdoors (OD, n = 30). Indoor concentrations (air: 7.0–64 pg/m3; dust: 150–1850 ng/g) were significantly higher than outdoor (2.0–16 pg/m3 and 83–475 ng/g) concentrations. Tris-1,3-dichloropropyl phosphate (TDCIPP), tris(1-chloro-2-propyl) phosphate (TCIPP), tri (2-butoxyethyl) phosphate (TBOEP) and triphenyl phosphate (TPHP) dominated in all samples with more indoor variabilities. Profiles of OPFRs in OD and floor dust (collected from carpets and floors) were similar but differed from elevated fine dust (collected 1 m above the floor from all available surfaces), possibly due to the influence of carryover of OD by shoes. Despite the high uncertainty in dust – air partitioning coefficients, log transformed values showed significant linear relationships with log octanol – air-partitioning coefficients in all microenvironments, indicating an equilibrium partitioning between dust and vapor. Exposure assessment indicated the importance of the dermal exposure route for adults and ingestion route for children.

Grain size distribution and exposure evaluation of organophosphorus and brominated flame retardants in indoor and outdoor dust and PM10 from Chengdu, China.

To investigate overall pollution and potential risk of 32 targets (11 PBDEs, 8 NBFRs, and 13 OPFRs) in indoor and outdoor environments, dust and PM10 samples were sampled from non-occupational and occupational zones in Chengdu, China. ∑Cl-OPFRs, BDE-209, and DBDPE were the dominant constitutes in both the non-occupational and occupational dust. Regarding the PM10, no significant differences were found between the kitchen and the living room for studied OPFRs except TDCIPP, and TCEP, TCPP, TEHP, and TCP displayed significant correlation among the kitchen, the living room and personal samples. Profiles of the OPFRs in the PM10 from occupational areas presented great variation and ranked as: ∑Aryl-OPFRs < ∑Alkyl-OPFRs < ∑Cl-OPFRs. The estimated daily intakes (EDIs) of the investigated FRs via dust suggested dust ingestion and inhalation were the main exposure route to FRs, and the total of EDIs were at least one order of magnitude lower than reference data, indicating a low risk for the general public in Chengdu. However, with increasing usage of FRs in daily goods, a long-term monitoring should be conducted.

Assessing the contributions of metals in environmental media to exposure biomarkers in a region of ferroalloy industry.

Residential proximity to ferroalloy production has been associated with increased manganese exposure, which can adversely affect health, particularly among children. Little is known, however, about which environmental samples contribute most to internal levels of manganese and other ferroalloy metals. We aimed to characterize sources of exposure to metals and evaluate the ability of internal biomarkers to reflect exposures from environmental media. In 717 Italian adolescents residing near ferromanganese industry, we examined associations between manganese, lead, chromium, and copper in environmental samples (airborne particles, surface soil, indoor/outdoor house dust) and biological samples (blood, hair, nails, saliva, urine). In multivariable regression analyses adjusted for child age and sex, a 10% increase in soil Mn was associated with increases of 3.0% (95% CI: 1.1%, 4.9%) in nail Mn and 1.6% (95% CI: −0.2%, 3.4%) in saliva Mn. Weighted-quantile-sum (WQS) regression estimated that higher soil and outdoor dust Mn accounted for most of the effect on nail Mn (WQS weights: 0.61 and 0.22, respectively, out of a total of 1.0). Higher air and soil Mn accounted for most of the effect on saliva Mn (WQS weights: 0.65 and 0.29, respectively). These findings can help inform biomarker selection in future epidemiologic studies and guide intervention strategies in exposed populations.

Legacy and alternative brominated flame retardants in outdoor dust and pine needles in mainland China: Spatial trends, dust-plant partitioning and human exposure

Concentrations of 26 brominated flame retardants (BFRs), including 19 polybrominated diphenyl ethers congeners (PBDEs), 3 isomers of hexabromocyclododecanes (HBCDs), and 4 alternative BFRs (alt-BFRs; hexabromobenzene, pentabromotoluene, 1,2-bis(2,4,6-tribromphenoxy)ethane, and decabromodiphenylethane) were determined in outdoor settled dust and pine needles collected across mainland China. BFRs were extensively found in the two matrices, with mean total concentrations at 4090 and 314 ng/g dry weight (dw), in dust and pine needles, respectively. The total BFRs concentrations in dust significantly varied among three mixed-land-use categories, with mean concentrations of 74.3, 1284, and 25,525 ng/g dw in rural, urban, and point source areas, respectively. For PBDE congeners, dust samples contained predominantly BDE-209 (69.2% of the total BFRs), whereas lower brominated PBDEs such as BDE-28 (19.7%), −47 (11.0%), and −99 (12.2%) accounted for higher proportions in pine needles. Spatial distribution of BFRs showed distinct geographical signatures with the highest levels found in South Central China. Application of McLachlan's framework to our data suggested that the uptake of BFRs in pine needles was controlled primarily by kinetically limited gaseous deposition and by particle-bound deposition. Assessment on human exposure to BFRs through outdoor dust ingestion revealed a low risk for Chinese adults and toddlers.

Secondary VOCs emission from used fibrous filters in portable air cleaners and ventilation systems

Previous research suggests that filters used in indoor portable air cleaners or ventilation systems may be an indoor pollutant source at some point of using when it is loaded with certain amount of particle or gas phase pollutants. To evaluate its influence on indoor air quality, both qualitative and quantitative analysis of the potential source is needed. This study aims at investigating secondary volatile organic compounds (VOCs) emission from used fibrous particle filters. Used filters from portable air cleaners used in real life were collected. HEPA fibrous filters challenged by outdoor dust were investigated to simulate its application in residential fresh air system. Filter samples were stored in room temperature and three different relative humidity settings before testing. The emitted VOCs species and emission rate were measured using a single-pass test system, with TENAX sorbent tubes sampling and GC-MS analysis method. The emitted TVOC concentration profile with time presented a single-peak curve. The data indicated that the TVOC emission rate of used filters were influenced by both dust loading amount and environmental VOCs level. With the same dust loading, TVOC emission rate of filters challenged by indoor dust was 2–10 times higher than filters challenged by outdoor dust. When the environmental VOCs concentration was stable, there is a liner relationship between TVOC emission rate and dust loading. The TVOC emission rate was in the range of 0.63mg/m2-3.46 mg/m2 for filters used in portable air cleaners. After exposure in humid environment, the total emitted TVOC generally decreased with the major decrease of Alkanes, Aromatics, Esters and Alcohols categories, while the emission rate of Aldehydes, Ketones and Olefins increased. Possible reason was discussed.

Pesticides in indoor and outdoor residential dust: a pilot study in a rural county of Taiwan

We conducted a pilot study to examine pesticides in dust of homes in a rural county of Taiwan. A total of 56 homes of pregnant women were included in the study. Indoor and outdoor dust was collected by a vacuum sampler and a dustpan/brush set, respectively. Nine pesticides were selected for analysis on gas chromatography-mass spectrometry with the detection limits being 0.088ng/g or lower. The most detected pesticides were cypermethrin and chlorpyrifos, which appeared in 82.7 and 78.8% of indoor samples and 48.2 and 39.3% of outdoor samples, respectively. The detection of pesticides from indoor and outdoor dust, however, was not consistent, indicating different sources of pesticides. In addition to those two most detected, permethrin, prallethrin, and tetramethrin, which were common ingredients of insecticide products for indoor use, were also frequently found in indoor dust, suggesting that indoor use of such pesticide products may have been a major source. Fewer pesticides were found in outdoor dust, but the outdoor detection of chlorpyrifos was significantly associated with farms present inside the circles with radii of 50 and 100m surrounding the homes (P = 0.021, 0.016). It is suggested that pesticide drift from agricultural areas to residential environments may have occurred. No seasonal effect on distribution of pesticides in dust was found, indicating that pesticides could be routinely used in Taiwan regardless of season. Compared with other international studies, this study shows relatively high levels of chlorpyrifos but low levels of pyrethroids (i.e., cypermethrin), reflecting a different pattern of pesticide use in Taiwan. Further studies need to be warranted for a better understanding of exposure to pesticides and the associated health effects.

Seasonal Variation and Exposure Risks of Perchlorate in Soil, Indoor Dust, and Outdoor Dust in China.

A total of 97 paired soil, outdoor dust, and indoor dust samples were collected in the national scale of China in summer, and the perchlorate levels were compared with those in soil and outdoor dust samples collected in winter in our previous study. The median perchlorate concentrations in the outdoor dust, indoor dust, and soil samples were 8.10, 11.4, and 0.05mg/kg, respectively, which were significantly lower than those in the winter samples due to the natural factors and human activities. No significant differences in perchlorate concentrations were found between Northern and Southern China in the dust samples, whereas the difference was obtained in the soil samples. In the terms of possible source, the perchlorate levels in the outdoor dust exhibited strong correlation with SO42- (r2 = 0.458**) and NO3- (r2 = 0.389**), indicating part of perchlorate in outdoor environment was likely from atmospheric oxidative process in summer. The perchlorate, SO42-, and Cl- levels in the indoor dust were significantly related to those in the outdoor dust, suggesting that outdoor contaminants might be an important source for indoor environment. Furthermore, the human exposure to perchlorate was under relatively safe state in China except for special sites or periods with high perchlorate levels. Dust made an unexpected contribution of 41.3% to the total daily perchlorate intake for children, whereas 2.46% for adults in China based on biomonitoring, which deserves more attention.

Selected organohalogenated flame retardants in Egyptian indoor and outdoor environments: Levels, sources and implications for human exposure

There is scant information on the presence of the polybrominated diphenyl ethers (PBDEs) and other alternative flame-retardants (NFRs) in Africa. Hence, to investigate their levels, sources, and human exposure scenarios, elevated fine dust (EFD) samples from apartments (n = 12), working places (n = 9) and cars (n = 12), floor dust (FD) samples (n = 5) and outdoor dust samples (n = 21) were collected from Alexandria, Egypt, during 2014. Gaseous concentrations were estimated using low density polyethylene sheets (n = 33 and 21 for indoor and outdoor sites, respectively). Indoor gaseous and dust PBDE (7.0–300 pg/m3; 4.0–770 ng/g), and NFR (0.40–48 pg/m3; 0.50–8.5 ng/g) concentrations were significantly higher (p = 0.004–0.02) than outdoor concentrations (PBDEs: 3.0–41 pg/m3, 1.5–195 ng/g; NFRs: 0.20–13 pg/m3, 0.50–4.0 ng/g). Median PBDE concentration in cars (210 ng/g) was higher than in apartments and working places (130 ng/g respectively). PBDE concentrations in FD were 7.0–14-folds lower than EFD concentrations. Outdoor PBDE concentrations were significantly higher (p < 0.01) at residential–industrial places with older buildings. All samples were dominated by BDE-47 and 99. HBB, BTBPE and DDC-CO were the most abundant NFRs in EFD samples. Profiles of PBDE and NFR in FD closely matched those of outdoor dust, indicating a possible carryover from the outdoor environment. Although factors such as number of electronics, construction year and floor type significantly correlated with the majority of PBDE congeners and some NFRs in apartments and working places, sources were not clearly identified for NFRs. Significant log-linear relationships were obtained between theoretical and calculated dust-air partitioning coefficients for all samples indicating an equilibrium state between dust and vapor. Low possibility of occurrence of adverse health effects was concluded, with the inhalation pathway (for adults) and dust ingestion (for children) acting as the most important exposure routes.

Contamination Characteristics and Human Exposure to Organophosphate Flame Retardants in Road Dust from Suzhou City

The contamination levels and distribution characteristics of four organophosphate flame retardants (OPFRs) in 25 outdoor dust samples collected in Suzhou were quantitatively analyzed by gas chromatography-mass spectrometry (GC-MS). The exposure to OPFRs via ingestion and inhalation of dust were also estimated for adults, children, and professional street sweepers. Four types of OPFRs were detected in all dust samples at different levels; the total OPFRs concentrations ranged from non-detected (ND) to 8901.66 ng·g-1, with a median of 1039.21 ng·g-1. The concentrations of TCPP, TBEP, TDCPP, and TCEP were in the range of 0-6931.46, 0-2021.15, 0-788.44, and 0-62.16 ng·g-1, respectively. The daily intake of ∑OPEs under a high dust ingestion scenario was 125.68, 915.78, and 6314.16 pg·kg-1 for adults, children, and professional street sweepers, respectively. The estimated exposure of children to ∑OPEs was six times higher than that of adults. However, the daily intake of OPFRs via dust inhalation was 3.07E-02, 1.89E-02, and 1.54E-01 pg·kg-1 for adults, children, and professional street sweepers, respectively. These findings indicated that the occurrence of OPFRs in the dust poses a significant risk to children and professional street sweepers.

Soiling-induced transmittance losses in solar PV modules installed in Kathmandu Valley

Renewable energy sources are fast emerging as more reliable supplement of conventional energy sources. Among the various renewable sources, solar energy is most sought after in today’s world. Solar PV modules when installed in outdoor environments suffer from various factors which are generally unaccounted in laboratory testing. Energy generation from solar collectors is primarily dependent on the amount of incident radiation on their surfaces. Soiling on modules is known to reduce the transmittance of incident rays to solar cell and cause significant output power degradation. Soiling is closely associated with the various factors such as module tilt angle, site-specific climate, outdoor exposure period, humidity, wind speed, dust characteristics and material properties. This experimental work is aimed to study the transmittance losses encountered by solar PV modules and the corresponding power degradation. The experimental results show an alarming reduction in transmittance as high as 69.06% over the dry study period experiencing no rain. The power of dusty solar module decreases by 29.76% compared to the module cleaned on daily basis. Dust deposition density on the PV module accounted to 9.6711 g/m2 over the study period.

Impact of dust exposure on mixed bacterial cultures and during eukaryotic cell co-culture infections.

On a daily basis, humans, and their colonizing microbiome, are exposed to both indoor and outdoor dust, containing both deleterious organic and inorganic contaminants, through dermal contact, inhalation, and ingestion. Recent studies evaluating the dust exposure responses of opportunistic pathogens, such as Escherichia coli and Pseudomonas aeruginosa, revealed significant increases in biofilm formation following dust exposure. In this study, the effects of dust exposure on mixed bacterial cultures as well as HT-29 co-cultures were evaluated. As it was observed in pure, single bacterial cultures earlier, neither indoor nor outdoor dust exposure (at concentrations of 100μg/mL) influenced the growth of mixed bacterial liquid cultures. However, when in paired mixed cultures, dust exposure increased sensitivity to oxidative stress and significantly enhanced biofilm formation (outdoor dust). More specifically, mixed cultures (E. coli-Klebsiella pneumoniae, K. pneumoniae-P. aeruginosa, and E. coli-P. aeruginosa) exhibited increased sensitivity to 20 and 50mM of H2O2 in comparison to their pure, single bacterial culture counterparts and significantly enhanced biofilm production for each mixed culture. Finally, bacterial proliferation during a eukaryotic gut cell (HT29) co-culture was significantly more robust for both K. pneumoniae and P. aeruginosa when exposed to both house and road dust; however, E. coli only experienced significantly enhanced proliferation, in HT29 co-culture, when exposed to road dust. Taken together, our findings demonstrate that bacteria respond to dust exposure differently when in the presence of multiple bacterial species or when in the presence of human gut epithelial cells, than when grown in isolation.

Air- and Dust-Borne Fungi in Indoor and Outdoor Home of Allergic Patients in a Dust-Storm-Affected Area

ABSTRACTDespite the recent increases in fungi-induced allergic diseases, there is no report yet in the region of the Persian Gulf on concentration levels of fungi in relationship with health state. Therefore, our aim was to measure fungi prevalence as well as to evaluate the relationships between air- and dust-borne fungal genera and allergic diseases. A matched case-control study was carried out including 45 allergic cases and 45 age- and gender-matched controls for each individual. Indoor and outdoor dust and indoor air samples were collected from participant homes during May to October 2015. A Quick Take 30 Pump and sterile wet swab were used to determine fungal types and their amounts in the air (CFU/m3) and dust (CFU/100 cm2) samples, respectively. A significant reverse association was found between indoor dust-borne Alternaria and asthma (Odds ratio (OR) = 0.14, 95% CI = 0.02–0.86). Contrarily, increased levels of indoor air-borne Aspegillus fumigatus (OR = 2.00, 95% CI = 0.37–10.55) and Alternaria (OR = 3.00, 95% CI = 0.34–25.83) were correlated with asthma development. Also, correlation analysis showed a significant relation between indoor air-borne Penicillium levels and reactivity to skin prick test in asthmatic patients (p = 0.04). Our findings support the notion that fungal exposures can either cause or prevent the development of allergic diseases. Accordingly, appropriate measures should be taken for a better management of fungi-induced allergic diseases.