Airborne concentrations of SARS-CoV-2 in indoor community environments in Italy

Environmental Science and Pollution Research - COVID-19 pandemic raised a debate regarding the role of airborne transmission. Information regarding virus-laden aerosol concentrations is still...     

Inter-comparison of air pollutant concentrations in different indoor environments in Hong Kong

Indoor air quality in selected indoor environments in Hong Kong such as homes, offices, schools, shopping malls and restaurants were investigated. Average CO₂ levels and total bacteria counts in air-conditioned classrooms, shopping malls and restaurants were comparatively higher than those measured in occupied offices and homes. Elevated CO₂ levels exceeding 1000 ppm and total bacteria counts resulted from high occupancy combined with inadequate ventilation. Average PM₁₀ levels were usually higher indoors than outdoors in homes, shopping malls and restaurants. The highest indoor PM₁₀ levels were observed at investigated restaurants due to the presence of cigarette smoking and extensive use of gas stoves for cooking. The restaurants and shopping malls investigated had higher formaldehyde levels than other indoor environments when building material, smoking and internal renovation work were present. Volatile organic compounds (VOCs) in both indoor and outdoor environments mainly resulted from vehicle exhaust emissions. It was observed that interior decoration work and the use of industrial solvents in an indoor environment could significantly increase the indoor levels of VOCs.     

Size-segregated measurements of particulate elemental carbon and aerosol light absorption at remote arctic locations

Size-segregated aerosol samples were taken during 2 winter pollution periods and in clean summer air at different remote locations in the European Arctic > 74°N. By means of a newly developed integrating sphere photometer these filter samples have been analysed for aerosol light absorption coefficients and particulate elemental carbon (PEC). The relatively high PEC concentrations in winter confirm other findings about the Arctic winter atmosphere having an aged continental aerosol burden. In summer very low light absorption coefficients of 4.5 × 10⁻⁸ m⁻¹ were measured, similar to upper tropospheric background values. For the climatically important months of March-May the key optical aerosol properties (extinction coefficient, single scattering albedo and absorption to backscatter ratio) were determined. Based on the approach of J.M. Mitchell (1971, in Man's Impact on Climate. MIT Press, Cambridge, MA) the Arctic haze aerosol is found to contribute to atmospheric heating, even in the summer. A first PEC size distribution was determined in a clean polar summer air. The results show systematic variations in the PEC size distribution from urban to remote locations and seasonal variations in the sink region which may be exploited to quantify aerosol removal process in long distance transport studies.     

Carbonaceous aerosol characteristics in outdoor and indoor environments of Nanchang, China, during summer 2009

A study of carbonaceous aerosol was initiated in Nanchang, a city in eastern China, for the first time. Daily and diurnal (daytime and nighttime) PM2.5 (particulate matter with aerodynamic diameter < or =2.5 microm) samples were collected at an outdoor site and in three different indoor environments (common office, special printing and copying office, and student dormitory) in a campus of Nanchang University during summer 2009 (5-20 June). Daily PM10 (particulate matter with aerodynamic diameter < or =10 microm) samples were collected only at the outdoor site, whereas PM2.5 samples were collected at both indoor and outdoor sites. Loaded PM2.5 and PM10 samples were analyzed for organic and elemental carbon (OC, EC) by thermal/optical reflectance following the Interagency Monitoring of Protected Visual Environments-Advanced (IMPROVE-A) protocol. Ambient mass concentrations of PM10 and PM2.5 in Nanchang were compared with the air quality standards in China and the United States, and revealed high air pollution levels in Nanchang. PM2.5 accounted for about 70% of PM10, but the ratio of OC and EC in PM2.5 to that in PM10 was higher than 80%, which indicated that OC and EC were mainly distributed in the fine particles. The variations of carbonaceous aerosol between daytime and nighttime indicated that OC was released and formed more rapidly in daytime than in nighttime. OC/EC ratios were used to quantify secondary organic carbon (SOC). The differences in SOC and SOC/OC between daytime and nighttime were useful in interpreting the secondary formation mechanism. The results of (1) OC and EC contributions to PM2.5 at indoor sites and the outdoor site; (2) indoor-outdoor correlation of OC and EC; (3) OC-EC correlation; and (4) relative contributions of indoor and outdoor sources to indoor carbonaceous aerosol indicated that OC indoor sources existed in indoor sites, with the highest OC emissions in I2 (the special printing and copying office), and that indoor EC originated from outdoor sources. The distributions of eight carbon fractions in emissions from the printer and copier showed obviously high OC1 (>20%) and OC2 (approximately 30%), and obviously low EC1-OP (a pyrolyzed carbon fraction) (<10%), when compared with other sources.     

Rapid measurements and mapping of tracer gas concentrations in a large indoor space

Rapid mapping of gas concentrations in air benefits studies of atmospheric phenomena ranging from pollutant dispersion to surface layer meteorology. Here we demonstrate a technique that combines multiple-open-path tunable-diode-laser spectroscopy and computed tomography to map tracer gas concentrations with approximately 0.5 m spatial and 7 s temporal resolution. Releasing CH₄ as a tracer gas in a large (7 m×9 m×11 m high) ventilated chamber, we measured path-integrated CH₄ concentrations over a planar array of 28 “long” (2–10 m) optical paths, recording a complete sequence of measurements every 7 s during the course of hour-long experiments. Maps of CH₄ concentration were reconstructed from the long path data using a computed tomography algorithm that employed simulated annealing to search for a best fit solution. The reconstructed maps were compared with simultaneous measurements from 28 “short” (0.5 m) optical paths located in the same measurement plane. On average, the reconstructed maps capture ∼74% of the variance in the short path measurements. The accuracy of the reconstructed maps is limited, in large part, by the number of optical paths and the time required for the measurement. Straightforward enhancements to the instrumentation will allow rapid mapping of three-dimensional gas concentrations in indoor and outdoor air, with sub-second temporal resolution.     

Environmental tobacco smoke particles in multizone indoor environments

Environmental tobacco smoke (ETS) is a major source of human exposure to airborne particles. To better understand the factors that affect exposure, and to investigate the potential effectiveness of technical control measures, a series of experiments was conducted in a two-room test facility. Particle concentrations, size distributions, and airflow rates were measured during and after combustion of a cigarette. Experiments were varied to obtain information about the effects on exposure of smoker segregation, ventilation modification, and air filtration. The experimental data were used to test the performance of an analytical model of the two-zone environment and a numerical multizone aerosol dynamics model. A respiratory tract particle deposition model was also applied to the results to estimate the mass of ETS particles that would be deposited in the lungs of a nonsmoker exposed in either the smoking or nonsmoking room. Comparisons between the experimental data and model predictions showed good agreement. For time-averaged particle mass concentration, the average bias between model and experiments was less than 10%. The average absolute error was typically 35%, probably because of variability in particle emission rates from cigarettes. For the conditions tested, the use of a portable air filtration unit yielded 65–90% reductions in predicted lung deposition relative to the baseline scenario. The use of exhaust ventilation in the smoking room reduced predicted lung deposition in the nonsmoking room by more than 80%, as did segregating the smoker from nonsmokers with a closed door.     

Determination of elemental carbon component of soot in ambient aerosol samples

A reflectance method for the determination of the elemental carbon component of soot in atmospheric fine particulate matter collected on a filter has been developed. Two instruments are described. One operates continuously as the aerosol sample is being collected, measuring the decrease in reflectance of light from the filter spot through which air is aspirated. The other instrument measures the reflectance of samples mounted after a collection on a filter. The instruments have been calibrated with soot standards of known total non-volatile carbon content determined by the GRALE technique after heating. Limited field data are presented on both the total carbon and soot carbon content of the St. Louis urban fine aerosol.     

SARS-CoV-2 surveillance in indoor and outdoor size-segregated aerosol samples

Environmental Science and Pollution Research - We aimed to determine the presence of SARS-CoV-2 RNA in indoor and outdoor size-segregated aerosol samples (PM10-2.5, PM2.5). Five outdoor daily...     

含碳气溶胶研究进展：有机碳和元素碳

含碳气溶胶是我国大气区域性复合型污染的重要物种,对全球气候变化、辐射强迫、能见度、环境质量、人类健康等会产生重要影响.主要从含碳气溶胶来源及成因、环境影响、样品采集及测试等方面对国内外相关研究进行了评述,讨论了有机碳和元素碳研究中存在的关键和难点问题,并对其发展前景进行了展望.     

室内生物气溶胶消杀措施及启示

关注室内空气中生物气溶胶的危害和传播规律,对于及时采取有效措施降低室内环境中病原体的传播以及交叉感染风险具有重要的意义。在充分认识生物气溶胶来源、危害及其传播规律,了解室内生物气溶胶的防控措施以及主要消杀手段的基础上,通过分析SARS冠状病毒的非光催化消杀技术案例,提出了室内非光催化消杀材料与高效滤除、紫外、臭氧等其他技术复合形成室内病原体消杀整体方案建议,为传染疾病的预防起到积极的作用。     

Satellite measurements of aerosol mass and transport

The aerosol optical thickness over land is derived from satellite measurements of the radiance of scattered sunlight. These data are used to estimate the columnar mass density of particulate sulfur on a day with a large amount of sulfur. The horizontal transport of the particulate sulfur is calculated using wind vectors measured with rawins.     

The inportance of organic and elemental carbon in the fine atmospheric aerosol particles

During a field campaign the chemical character of fine (d<2.5 μm) aerosol particles was studied at K-puszta, Hungary within the framework of a project of the European Union. The organic and elemental carbon fraction, as well as the concentration of major inorganic constituents with respect to the total fine aerosol mass are presented in this paper. It was found that organic compounds constituted a significant fraction of the total fine aerosol mass, their contribution is comparable to or larger than that of the major water soluble ions. The diurnal variation of aerosol composition was also studied. It can be concluded that the relative abundance of the major constituents is practically the same during the day and at night. The samples were also classified and studied according to the air mass history. It is stated that the aerosol can be separated into two populations with different regression lines between organic and elemental carbon.     

Screening of organophosphorus compounds and their distribution in various indoor environments

Twelve organophosphorus compounds (OPs), which are used for diverse purposes (e.g. as plasticizers and flame retardants), were analysed in settled house dust from 15 indoor environments and in wipe test samples from computer screens and covers. Seven of the substances analysed dominated Swedish imports of OPs in 1999, six of these are also listed as EU High Production Volume Chemicals. Eight of the substances were found in all samples. Tris(2-butoxyethyl)phosphate was the most abundant in most of the samples, with levels ranging from 0.014 to 5.3 g/kg followed by tris(2-chloroethyl)phosphate, tris(chloropropyl)phosphate and tris(1,3-dichloropropyl)phosphate. In wipe test samples from computers, triphenyl phosphate proved to be the main component of the OPs analysed (4.0 microg/m2). Potential sources of these compounds include, inter alia, floor polish, polyvinylchloride floor coverings, upholstery and plastic products. The distribution patterns of the OPs differed between the sites and generally reflected the building materials and consumer products used in their vicinity.     

Use of atmospheric elemental size distributions in estimating aerosol sources in the Helsinki area

In June 1996–June 1997 Berner impactors were used in the Helsinki area to measure size distributions of atmospheric aerosols simultaneously at an urban and at a rural site. Ten sample pairs were collected in the size range of 0.03–15.7 μm of equivalent aerodynamic diameter (EAD). Average size distributions at the two sites were calculated for 29 elements, particulate mass, and sulphate. At both sites especially sulphate, As, B, Bi, Cd, Ni, Tl, and V were enriched in fine particles (EAD<2.3 μm). In order to estimate local fine-particle sources of the various chemical components, the similarities and dissimilarities in the accumulation-mode parameters were studied separately for both sites. It was observed that often in different samples, different components had similar accumulation modes. At both sites, particulate mass, As, and Pb had similar accumulation modes to sulphate which suggests that long-range transport (LRT) is important for these components. V, Ni, Mo, and Co formed another group of similar accumulation modes at both sites suggesting that these elements largely originated from local and regional oil combustion. In addition, other groups of similar accumulation modes were observed but these groups were different between the sites. The meteorological parameters indicated that seven sample pairs formed a subset of the data in which the local emissions of the Helsinki area were transported to the urban site but not to the rural site. For this subset the rural fine-particle concentrations were considered to represent an upper limit estimate for the LRT. These upper limit LRT estimations were further improved by utilising the quantitative relative size distributions (QRSD) method at the rural site. The QRSD method supposes that in the fine-particle size range the LRT fractions of all chemical components have a similar shape in their size distributions. Fine-particle sulphate is typically long-range transported, and was therefore selected as the model component that represents the shape of LRT material. Sulphate size distribution was then scaled to give an estimation of the LRT contribution of each component at the rural site. These rural “sulphate scaled” LRT estimates were subtracted from the corresponding urban concentrations to give the local contributions (ng/m³) downwind of the Helsinki area. In particles with EAD below 2.3 μm, the highest absolute and relative downwind local contributions were observed for several common sea-salt and road-dust components. Also the combustion-related elements Ni and V showed fairly high downwind local contributions. Because of the limited number of samples, the local and LRT contributions were not estimated for different wind directions.     

Predicting residential indoor concentrations of nitrogen dioxide,fine particulate matter,and elemental carbon using questionnaire and geographic information system based data

Previous studies have identified associations between traffic-related air pollution and adverse health effects. Most have used measurements from a few central ambient monitors and/or some measure of traffic as indicators of exposure, disregarding spatial variability and factors influencing personal exposure-ambient concentration relationships. This study seeks to utilize publicly available data (i.e., central site monitors, geographic information system, and property assessment data) and questionnaire responses to predict residential indoor concentrations of traffic-related air pollutants for lower socioeconomic status (SES) urban households.As part of a prospective birth cohort study in urban Boston, we collected indoor and outdoor 3–4 day samples of nitrogen dioxide (NO₂) and fine particulate matter (PM_2.5) in 43 low SES residences across multiple seasons from 2003 to 2005. Elemental carbon (EC) concentrations were determined via reflectance analysis. Multiple traffic indicators were derived using Massachusetts Highway Department data and traffic counts collected outside sampling homes. Home characteristics and occupant behaviors were collected via a standardized questionnaire. Additional housing information was collected through property tax records, and ambient concentrations were collected from a centrally located ambient monitor.The contributions of ambient concentrations, local traffic and indoor sources to indoor concentrations were quantified with regression analyses. PM_2.5 was influenced less by local traffic but had significant indoor sources, while EC was associated with traffic and NO₂ with both traffic and indoor sources. Comparing models based on covariate selection using p-values or a Bayesian approach yielded similar results, with traffic density within a 50 m buffer of a home and distance from a truck route as important contributors to indoor levels of NO₂ and EC, respectively. The Bayesian approach also highlighted the uncertanity in the models. We conclude that by utilizing public databases and focused questionnaire data we can identify important predictors of indoor concentrations for multiple air pollutants in a high-risk population.     

Longitudinal variations in indoor VOC concentrations after moving into new apartments and indoor source characterization

This study examined the indoor concentrations of a wide range of volatile organic compounds (VOCs) in currently built new apartments every month over a 24-month period and the source characteristics of indoor VOCs. The indoor total VOC (TVOC) concentrations exhibited a decreasing tendency over the 24-month follow-up period. Similar to TVOCs, the median indoor concentrations of 33 of 40 individual VOCs (all except for naphthalene and six halogenated VOCs) revealed decreasing tendencies. In contrast, the indoor concentrations of the six halogenated VOCs did not reveal any definite trend with time. Moreover, the indoor concentrations of those halogenated VOCs were similar to the outdoor concentrations, suggesting the absence of any notable indoor sources of halogenated VOCs. For naphthalene (NT), the indoor concentrations were significantly higher than the outdoor concentrations, suggesting the presence of indoor NT source(s). The floor/wall coverings (39 %) were the most influential indoor source of indoor VOCs, followed by household cleaning products (32 %), wood paneling/furniture (17 %), paints (7 %), and moth repellents (5 %).     

Characterization of the Atlanta area aerosol,elemental composition and possible sources

This paper presents a study or the elemental characterization of the Atlanta area aerosol at one rural and several urban sites. It includes a determination of the concentrations of major elemental components of the aerosol and a statistical analysis of the relationships between these components as a means of investigating possible sources. This research has emphasized the study of the graphitic carbon, C_e, and elemental sulfur, S, components of the aerosol (these two components are important in visibility reduction studies). The measurements show that C_e and S represent, respectively 3.1–9.9% and 1.9–4.4% of the total suspended paniculate, TSP, mass. The concentrations of C_e, S and TSP exhibit strong seasonal variations with C_e decreasing from winter to summer and S and TSP increasing over this period. All elemental components exhibit less concentration at the rural site than at the urban sites. Analysis results show that C_e appears to be statistically separate from S, which is assumed to be present as sulfate, indicating that the sources for C_e and particulate sulfate are distinct. S and TSP, however, appear to be linked through common regional scale meteorological processes.     

The influence of aerosol dynamics on indoor exposure to airborne DEHP

A mass-balance model was extended to investigate the influence of aerosol particles on the accumulation of indoor airborne DEHP, which allows the consideration of a variable particle concentration. The calculated gas-phase di-2-ethylhexyl phthalate (DEHP) concentration is consistent with those measured within residences in both the United States and Europe. Model predictions suggest that there are differences of more than 10% of particle-phase DEHP concentrations between the variable-particle-concentration case and the constant one for over half (578 days) within the calculation time of 1000 days. Airborne DEHP consists primarily of a particle phase. The exposure data indicate that the influence of particle dynamics remains significant throughout the calculation period, and the size fraction of 0–0.5 μm contributes the most, at 39.1%, to the total exposure to particle-phase DEHP as a result of a strong “source” effect which brings particles into the indoor air and a weak “sink” effect which removes particles from the indoor air. The sensitivity analysis indicates that deposition exhibits the most apparent influence, and particle emission from cooking is a significant factor, as cooking is the main source of particles in the size fraction of 0–0.5 μm. The sensitivity analysis also shows that particle penetration has a less obvious influence on the exposure to airborne DEHP because air exchange rate caused penetration introduces and removes particles simultaneously, thus having a limited influence on the airborne DEHP; while resuspension exhibits the weakest influence because it contributes little to the small particles which are the main component of aerosol particles indoors. Strategies for enhancing deposition and reducing particle emissions from cooking and penetration may be helpful to reduce residents’ exposure to airborne SVOCs.