CFD-based simulation and experimental verification of 222Rn distribution in a walk-in type calibration chamber

Assessment of health risks due to the inhalation of respiratory particulate matter generated in the community kitchens

Exposure to indoor air pollution (IAP) is a potential health hazard leading to premature deaths around the globe. Cooking activity is one of the primary sources of IAP in households. Many studies have focussed on IAP due to cooking practices worldwide, but studies in community kitchens, which serve food for many populations of different age groups, particularly in highly populated developing countries such as India, are non-existent. In this study, the concentrations of particulate matter (PM) of size fractions PM1, PM2.5, and PM10 in indoor air were measured simultaneously and continuously for a duration of up to 20 days in 15 community kitchens using real-time PM monitoring systems (Applied Particle Technology Inc, USA) to assess the associated health risks related to the cooking profession. Three categories of kitchens were studied based on the type of fuel used, viz., LPG, LPG + SBF, and SBF. The concentrations of PM1, PM2.5, and PM10 ranged from 40 to 286 µg m-3, 58 to 418 µg m-3, and 62 to 434 µg m-3, respectively, with corresponding geometric mean (GM) values of 74 µg m-3, 111 µg m-3, and 119 µg m-3. PM ratios were in the order PM2.5/PM10 > PM1/PM2.5 > PM1/PM10. A higher ratio of PM2.5/PM10 was due to the resuspension of particles generated from the cooking process. ELCR values (1.7 × 10-5-1.3 × 10-4) were higher when compared to the recommended limit for humans (1 × 10-6-1 × 10-5) by WHO and US EPA. The HQ values for PM2.5 and PM10 ranged from 1.8 to 13.7 and 0.9 to 4.5, respectively, with corresponding geometric mean (GM) values of 4.7 and 2.2. The ER and AF for all-cause mortality varied between 0.05-0.52 (GM = 0.13) and 0.05-0.34 (GM = 0.11), respectively. The HQ values for all community kitchens > 1, suggesting a high non-carcinogenic risk to the workers. This study revealed that the workers in the community kitchens are exposed to enhanced air pollution. This study has underlined the importance of health issues to the workers attributable to the inhalation of respiratory PM in the community kitchens.

Application of CFD modeling for indoor radon and thoron dispersion study: A review

This paper provides an in-depth discussion of the CFD implications to the design/study of interior environments and an overview of the most widely used CFD model for indoor radon and thoron dispersion study. For the design and analysis of indoor environments, CFD is a powerful tool that enables simulation and measurement-based validation. Simulating an indoor environment involves deliberate thought and skilful management of complicated boundary conditions. User and CFD programs can develop results through gradual effort that can be relied upon and applied to the design and study of indoor environments. Radon and thoron are natural radioactive gases and play a crucial role in accurately assessing the radioactive hazard within an indoor environment. This review comprise the work related to measurement and CFD modeling on these radioactive pollutant for indoors.Highlighting the current state of environmental radioactive pollutants and potentially identified areas that require further attention or research regarding investigating factors affecting indoor radioactive pollutants.

PM1, PM2.5 and PM10 size fraction distribution under steady-state conditions in a walk-in type 222Rn calibration chamber facility

Attachment of 222Rn progenies, upon their formation, to the atmospheric aerosols and inhalation of these radioactive aerosols causes inhalation dose to the human being. Aerosols have the characteristics of small particle size, long-time suspension and long-distance transmission and easy access to the deep respiratory tract. Aerosols are responsible for viral infection risk such as the recent worldwide pandemic caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2, or COVID-19). Understanding the formation and behaviour of aerosols in a confined environment in various human habitations is essential to combat such detrimental exposures. Experiments have been performed to study the distribution of aerosol size fractions in the walk-in type 222Rn calibration chamber. The real-time applied particle technology monitors (APT-Maxima stationary monitors) were used for the simultaneous measurements of PM1, PM2.5, and PM10 size fractions. The variation of the mass densities (μg m-3) of different size fractions at different positions inside the chamber was monitored by placing APTs. The PM1, PM2.5, and PM10 sizes fractions were distributed homogeneously within the chamber volume and the concentration ratios of these fractions were 1:1.5:1.6 for concentration values of < 1500 μg m-3, and 1:7:9 for the concentration values of > 1500 μg m-3.

Characteristics of 222Rn and 220Rn equilibrium factors in the indoor environments

Humans receive a significant portion (˃50%) of the total dose attributed to all the natural radiation sources from indoor radon (222Rn), thoron (220Rn), and their progeny. While progeny contributes an overwhelming part to the dose, in most surveys, only radon gas is measured because of the simplicity of measurement. Progeny concentration is usually estimated by multiplying gas concentration with an assumed factor, called the equilibrium factor, and taken from literature. Recently, results of the measurements of equilibrium factors for 222Rn and 220Rn were reported from various parts of the globe. In India, many such studies have been conducted in the current decade. The studies show a wide variation of equilibrium factors which suggests that they depend on environmental factors and measurement conditions. Therefore, they should be determined site specifically if accurate site-specific dose estimation is targeted. This paper summarizes concepts, definitions, and methods to determine equilibrium factors and reviews literature about reported equilibrium factors worldwide, focusing on data reported from India.

A CFD-based approach to study the deposition and distribution behaviour of 212Pb in a calibration chamber

Among the several aspects of decay products behavior, deposition is of special significance because of its prominent role in the activity removal from the environment, which eventually results in the occurrence of decay product disequilibrium with the parent gas. This point is particularly important in case of thoron dosimetry where thoron progeny ²¹²Pb accounts for the most of the radiological dose. The deposition depends on the size distribution of decay products and the structure of air turbulence at the air-surface interface. In the present work, the effect of varying air-flow (fan speed) and aerosol count median diameter (CMD) was studied on the deposition and distribution profile of ²¹²Pb using computational fluid dynamics (CFD). The simulations have been carried out in a cubical calibration chamber of volume 8 m³, facilitated at RP&AD, BARC. Simulated results showed that the increase of total depositional loss rate of attached fraction of ²¹²Pb due to increase of the fan speed was significant for CMD up to 400 nm, beyond which this effect started becoming less prominent with increasing diameter. Besides, a minimum of the total depositional loss rate curve was seen to be shifted to the higher CMD with increase of the fan speed. CFD results were found to be in good agreement with experimental observations obtained in the controlled conditions with thoron source.

A periodic pumping technique of soil gas for 222Rn stabilization in large calibration chambers: part 2-theoretical formulation and experimental validation

In an adjoining publication, we demonstrated the novel technique to harvest soil gas of natural origin as a highly efficient source of 222Rn for calibration applications in a large volume 222Rn calibration chamber. Its advantages over the use of conventional high strength 226Ra sources, such as the capability to serve as a non-depleting reservoir of 222Rn and achieve the desired concentration inside the calibration chamber within a very short time, devoid of radiation safety issues in source handling and licensing requirements from the regulatory authority, were discussed in detail. It was also demonstrated that stability in the 222Rn concentration in large calibration chambers could be achieved within ± 20% deviation from the desired value through a semi-dynamic mode of injection in which 222Rn laden air was periodically pumped to compensate for its loss due to leak and decay. The necessity of developing a theory for determining the appropriate periodicity of pumping was realized to get good temporal stability with a universally acceptable deviation of ≤ ± 10% in the 222Rn concentration. In this paper, we present a mathematical formulation to determine the injection periods (injection pump ON and OFF durations) for the semi-dynamic operation to achieve long term temporal stability in the 222Rn concentration in the chamber. These computed pumping parameters were then used to efficiently direct the injection of soil gas into the chamber. We present the mathematical formulation, and its experimental validations in a large volume calibration chamber (22 m3). With this, the temporal stability of 222Rn concentration in the chamber was achieved with a deviation of ~ 3% from the desired value.