Computational analysis of radon progeny deposition patterns in the human respiratory system

In the last year, the use of computational fluid dynamics (CFD) techniques has gained prominence as a powerful tool for modeling biological phenomena and influencing the design of biomedical devices. In this study, we utilized a computational fluid dynamics (CFD) model to simulate airflow and the deposition of aerosol particles within the human respiratory tract. To achieve this, we meticulously constructed a 3D model of the human tracheobronchial airways using SolidWorks software. Our computational analyses encompassed a range of breathing conditions, ranging from 15 to 60 (L/min). Through the application of discrete phase modeling (DPM), we investigate the behavior of two-phase flow dynamics. Our focus lies in the examination of aerosol particles, with diameters ranging from 1 to 10 (μm), in order to evaluate the influence of aerosol particle size on deposition rates. Our findings encompass velocity contour maps, deposition rates of aerosol particles, and insights into the process of aerosol particle entrapment at various locations within the respiratory tract. Our study reveals a direct correlation between higher inhalation rates and larger aerosol particle sizes, resulting in increased deposition rates. Additionally, we observe a heightened deposition of aerosol-particles at bronchi region. These computational results hold significant value in estimating the distribution of doses resulting from radon progeny exposure in distinct anatomical regions of the respiratory tract.

Updated general exposure factors for risk assessment in the Korean population

BACKGROUND

There has been an increasing need to update the recommended values of Korean exposure factors for adults aged 19 and older, as using exposure factors developed over a decade ago could reduce risk assessment reliability.

OBJECTIVE

Exposure factor data have been compiled and standardized using the latest national statistical reports and academic literature, as well as studies conducted from 2016 to 2018.

METHODS

The updated data contained anthropometric parameters, inhalation rates, food and drinking water ingestion rates, and time-activity patterns and provided technical information on Koreans' exposure factors classified by sex, age group, per capita and general population, and doer-only for various exposure assessments.

RESULTS

Although the average life expectancy, body weight, body surface area, and inhalation rate increased slightly compared to the 2007 Korean Exposure Factor Handbook, differences various in food consumption were remarkable. Because of Asians' similar food preferences, the intake rate of grain products and vegetables in Koreans, Chinese, and Japanese contributed much toward total intake. Koreans spent half their times outdoors compared to Americans and Chinese.

SIGNIFICANCE

This study provided the currently updated exposure factor information for Koreans and could be compared with recommendations provided by exposure factor resources in various countries.

IMPACT STATEMENT

Exposure to environmental pollutants may significantly vary depending on the exposure factors related to human behaviors and characteristics. Therefore the exposure factors need to be continuously updated along with more extensive survey areas and improved measurement methods. We utilized the existing data with the aim to develop general exposure factors for risk assessment in Korean aged ≥19 years. Measurements and questionnaire surveys were also performed if there were no existing data. This study provided the currently updated exposure factor information for Koreans and could be compared to those of other countries.

Influence of methodology on the estimation of the particle surface area dose received by a population in all-day activities

In everyday life, people are exposed to different concentrations of airborne particles depending on the microenvironment where they perform their different activities. Such exposure can lead to high sub-micron particle doses. The received dose depends on particle concentration to which people are exposed (typically expressed in terms of number or surface area), time spent in each activity or microenvironment (time activity pattern) and amount of air inhaled (inhalation rate). To estimate an actual value of the received dose, all these parameters should be measured under real-life conditions; in fact, the concentrations should be measured on a personal scale (i.e. through a direct exposure assessment), whereas time activity patterns and inhalation rates specific to the activity performed should be considered. The difficulties in obtaining direct measurements of these parameters usually lead to adopt time activity patterns and inhalation rates already available in scientific literature for typical populations, and local outdoor particle concentrations measured with fixed monitoring stations and extrapolated for all the other microenvironments. To overcome these limitations, we propose a full-field method for estimating the received dose of a population sample, in which all the parameters (concentration levels, time activity patterns and inhalation rates) are measured under real-life conditions (also including the inhalation rates, that were evaluated on the basis of the measured heart rates). Specifically, 34 volunteers were continuously monitored for seven days and the data of sub-micron particle concentrations, activities performed, and inhalation rates were recorded. The received dose was calculated with the proposed method and compared with those obtained from different simplified methodologies that consider typical data of particle concentrations, time activity patterns and inhalation rates obtained from literature. The results show that, depending on the methodology used, the differences in the received daily dose can be significant, with a general underestimation of the most simplified method.