Contribution of Visible Surface Mold to Airborne Fungal Concentration as Assessed by Digital Image Quantification

The rapid monitoring of total fungi, including air and surface fungal profiling, is an important issue. Here, we applied air and surface sampling, combined with digital image quantification of surface mold spots, to evaluate the contribution of surface fungi to airborne fungal concentrations. Cladosporium, Penicillium, Aspergillus, and yeast often appeared in the air or on wall surfaces during sampling. The indoor/outdoor concentration ratios (I/O ratios) demonstrated that the airborne concentrations of commonly found fungal genera outdoors were higher than those indoors (median I/O ratio = 0.65–0.91), excluding those of Penicillium and yeast. Additionally, the surface density (fungal concentration/area) of individual fungi showed no significant correlation with the airborne concentration, excluding that of Geotrichum. However, if a higher surface ratio (>0.00031) of mold spots appeared in the total area of an indoor environment, then the concentrations of Aspergillus and Geotrichum in the air increased significantly. Our results demonstrated that the airborne concentration of indoor fungi is significantly correlated with the outdoor concentration. A higher density of surface fungi does not necessarily contribute to a high fungal concentration in the air. In contrast to fungal density, quantification of the surface fungal area is recommended to assess the risk of surface fungi propelling into the air.

Intercomparison of Indoor and Outdoor Pollen Concentrations in Rural and Suburban Research Workplaces

Pollen exposure in occupational settings involves different categories of workers. In this paper the effects of diurnal pollen variations have been evaluated in two sites characterized by different vegetation and urbanization: the suburban site of Tor Vergata (TV) and the rural site of Monte Porzio Catone (MPC). Aerobiological and meteorological monitoring was performed in the two sites during the winter of 2017. The data analysis focuses on the comparison between pollen concentrations observed in relation to meteorological variables. In general, it can be stated that the indoor and outdoor dynamics for MPC and TV are different, with the outdoor concentration of pollen for MPC always higher than for TV, in accordance with significant presence of vegetation. The high nocturnal peaks detected in MPC and completely absent in TV could be caused by the presence of particular conditions of stagnation combined with greater emissions from the pollen sources. Furthermore the higher I/O ratio observed during the working hours in TV compared to MPC could be ascribed to the workers’ behavior. Exposure to pollen can be responsible for several health effects and the knowledge of its level can be useful to improve the evaluation and management of this biological risk.

Secondary Organic Aerosol Formation from the Oxidation of Decamethylcyclopentasiloxane at Atmospherically Relevant OH Concentrations

Decamethylcyclopentasiloxane (D5, C10H30O5Si5) is measured at ppt levels outdoors and ppb levels indoors. Primarily used in personal care products, its outdoor concentration is correlated to population density. Since understanding the aerosol formation potential of volatile chemical products is critical to understanding particulate matter in urban areas, the secondary organic aerosol yield of D5 was studied under a range of OH concentrations, OH exposures, NOx concentrations, and temperatures. The secondary organic aerosol (SOA) yield from the oxidation of D5 is extremely dependent on the OH concentration, and differing measurements of the SOA yield from the literature are resolved in this study. Here, we compare experimental results from environmental chambers and flow tube reactors. Generally, there are high SOA yields (> 68 %) at OH mixing ratios of 5 × 109 molec cm−3. At atmospherically relevant OH concentrations, the SOA yield is largely < 5 % and usually ~1 %. This is significantly lower than SOA yields used in emission and particulate matter inventories and demonstrates the necessity of OH concentrations similar to the ambient environment when extrapolating SOA yield data to the outdoor atmosphere.

Distribution Characteristics of Indoor PM2.5 Concentration Based on the Water Type and Humidification Method

With the industrialization and rapid development of technology that can measure the concentration of pollutants, studies on indoor atmosphere assessment focusing on occupants have been recently conducted. Pollutants that worsen indoor atmosphere include gaseous and particulate matter (PM), and the effects and diffusion characteristics that influence indoor atmosphere vary depending on the indoor and outdoor concentration. White dust is a PM generated from minerals in water used for humidifiers during winter. Therefore, studies on the impact of white dust on human health and its size distribution are being actively conducted. However, since the indoor PM concentration varies depending on the humidification method and water type used, relevant studies are needed. Accordingly, this study examined the change in the PM2.5 concentration and relative humidity on the basis of water types and humidification method. It was found that the indoor PM2.5 concentration varied from 16 to 350 ug/m3, depending on the water types used for an ultrasonic humidifier. Conversely, when using a natural evaporative humidifier, white dust did not increase the indoor PM2.5 concentration, regardless of the mineral content of the water used. Considering both humidification ability and continuous humidifier use indoors, water purifier with nano-trap filters must be utilized for ultrasonic humidifiers.

Indoor and outdoor 222Rn and 220Rn and their progeny levels surrounding Bayan Obo mine, China

More than half of the total natural ionizing radiation dose received by the human population is caused by radon and thoron (Rn and Tn) and their progeny. To estimate the level of radiation due to radon and thoron and their progeny, an investigation was conducted in a residential area near the world’s largest open-pit mine of Bayan Obo in Inner Mongolia, China. The concentration of Rn, Tn, and their decay products in air and soil were studied by using AlphaGUARD, RAD7, and ERS-RDM-2S for a discrete period of time in three different locations. The average indoor concentration of radon and thoron was 62.6 ± 44.6 Bq/m3 and 108.3 ± 94.5 Bq/m3 respectively, and the outdoor concentration was 12.9 ± 6.3 Bq/m3 and 55.8 ± 18.5 Bq/m3, respectively. Relatively high concentrations were recorded in the area near to the mine, with a significant increasing trend observed in indoor thoron concentration. A prominent hotspot in thoron concentration was found in a single-story house with values 747 ± 150 Bq/m3. The equilibrium equivalent thoron concentration (EECTn) varies from 0.48 Bq/m3 to 2.36 Bq/m3 with an arithmetic mean of 1.37 ± 0.64 Bq/m3, and comparatively higher than EECRn. Concluding that the mining activity at Bayan Obo mine is significantly increasing the level of indoor thoron and its progeny in surroundings. It is suggested to further systematically investigate the indoor Rn and Tn progeny concentrations in the residential dwellings of the Bayan Obo mining area, and 232Th content of the building materials, to provide a basis for calculating the radiation dose.

Feature analysis of indoor particulate matter concentration using fiber filtration for mechanical ventilation

Experiments and theoretical analyses are conducted in an office in Xi’an to study indoor particle concentration through establishing a mass balance equation and real-time monitoring. Meanwhile, the filtration efficiencies for different grades of filter media have been tested and verified by experiments. Studies are conducted on indoor particulate emission source and concentration change in combination with equation of linear regression, linear fitting curve of indoor–outdoor concentration, as well as indoor concentration decay profile. The results indicate that coarse filters G1 to G4 are used in mechanical ventilation to filter larger particles. However, it can only achieve 1.6%–15.2% for PM2.5 filtration efficiency. On the other hand, F7 to H10 filters could reach the high efficiency of 55.6%–69.7%. Furthermore, indoor PM2.5 concentration with a coarse filter using G4 filter can obviously reduce the indoor particulate concentration to 69–75 μg/m3. It ranges from 87 to 90 μg/m3 using a G3 filter, while the outdoor PM2.5 concentration is 135–150 μg/m3.