Inhalation Dose Rates Research Articles

Assessment of Be-7, Pb-210 and Po-210 Activities in Airborne Particulate Matter Over Istanbul, Türkiye.

Airborne particulate matter is one of the air pollutants which can have detrimental health effects in the human body. Radionuclides adsorb onto air particles and make their way to humans primarily through inhalation. Naturally-occurring radionuclides, 210Pb and 210Po, are of notable health concern due to their relatively elevated ingestion and inhalation doses. In the current study, activity concentrations of 7Be, 210Pb and 210Po were determined in air particulate matter (PM). PM2.5 was collected on the European side, while PM10 was collected on the Anatolian side of Istanbul. Be-7, 210Pb and 210Po activities were found to be 5.17 ± 2.35, 0.96 ± 0.42; 0.25 ± 0.14 mBq m- 3 in Anatolian side, respectively. Be-7, 210Pb and 210Po activities were found to be 3.81 ± 2.27, 0.62 ± 0.29, 0.29 ± 0.26, mBq m- 3 in European side, respectively. The ratio of 210Po/210Pb was found to be higher (0.47 ± 0.31 for PM2.5 and 0.34 ± 0.27 for PM10) than the global average of 0.1. This result can be explained by the fact that Po is more volatile than Pb and enhanced in the air by the combustion process. Inhalation dose rates of 210Pb and 210Po due to PM10 exposure were calculated to be 7.70 ± 3.30 and 4.05 ± 2.31 µSv year- 1, respectively. Pb-210 bioaccessibility was assessed by the extraction of the particles in simulated lung fluids. Approximately 24.8% of inhaled 210Pb was estimated to be bioaccessible. This study suggests that 210Po and 210Pb activities are partially enhanced in the air particles in Istanbul and should be regularly monitored.

Radiological risk estimation from indoor radon, thoron, and their progeny concentrations using nuclear track detectors.

In this paper, we report the results of seasonal variations of indoor radon and thoron concentrations, equilibrium factors for gas progeny, and radiological risks to dwellers in the hilly area of Guwahati City, Assam, India. Twin-cup dosemeters with LR-115 (II) nuclear track detectors were used in this study. The findings show that values vary significantly, with winter having the highest values and summer having the lowest, with spring and autumn having moderate values. In winter, radon concentrations range from 61.6 ± 11.2Bqm-3 (Mud) to 115.3 ± 34.3Bqm-3 (AT), with geometric mean values of 69.2 ± 13.8Bqm-3 and 109.4 ± 27.9Bqm-3, and in summer, they range from 21.1 ± 5.9Bqm-3 (Mud) to 28.4 ± 8.3Bqm-3 (AT), with geometric mean values of 22.7 ± 6.3Bqm-3 and 26.1 ± 7.1Bqm-3, whereas thoron concentrations range from 13.1 ± 5.1Bqm-3 (Mud) to 58.8 ± 12.6Bqm-3 (AT), with geometric mean values of 27.6 ± 7.0Bqm-3 and 52.9 ± 10.1Bqm-3 in winter, respectively, and in summer, from 8.8 ± 2.3Bqm-3 (Mud) to 13.0 ± 5.5Bqm-3 (Mud), with a geometric mean value of 1.87 ± 1.29Bqm-3. Radon and thoron progeny levels are reported to vary from 4.1 ± 0.3 mWL (Mud) to 15.1 ± 4.3 mWL (AT) and 2.6 ± 0.9 mWL (Mud) to 14.3 ± 4.2 mWL (AT) in winter and from 1.5 ± 0.7 mWL (AT) to 3.0 ± 2.5 mWL (Mud) and 0.9 ± 0.3 mWL (AT) to 2.7 ± 0.5 mWL (Mud) in summer, respectively. The equilibrium factors for radon and its progeny have been reported to range from 0.23 ± 0.1 (Mud) to 0.51 ± 0.3 (AT) in winter, whereas from 0.23 ± 0.1 (AT) to 0.48 ± 0.4 (Mud) in summer, respectively. The equilibrium factors for thoron and its progeny have been estimated in the range of 0.02 ± 0.01 (Mud) to 0.09 ± 0.06 (AT) in winter, whereas 0.02 ± 0.02 (AT) to 0.07 ± 0.05 (Mud) in summer, respectively. The inhalation dose rates differed from house to house, having values in the range of 1.2 ± 0.2mSvyear-1 (Mud) to 4.6 ± 1.3mSvyear-1 (AT) in winter, whereas 0.5 ± 0.3mSvyear-1 (AT) to 0.9 ± 0.5mSvyear-1 (Mud) in summer, respectively. The effective doses (EDs) due to the exposure of radon and thoron in the study area have been found to range from 2.5 ± 0.3mSv (Mud) to 9.1 ± 2.7mSv (AT) in winter and 0.9 ± 0.4mSv (AT) to 1.8 ± 1.3mSv (Mud) in summer, respectively. The levels of radon and thoron in similar types of construction were found to be significantly different from one house to another. The estimated radon and thoron concentrations in the houses of that region during winter are found to be substantially higher than the global averages as reported by UNSCEAR.

Study of certain congenital malformations due to low-level radiation exposures from high background radiation areas

The coastal regions of some states (Kerala, Tamil Nadu, Andhra Pradesh and Orissa) in India are known to have plenty of thorium-rich minerals, therefore possess high external gamma radiation fields, and are identified as Natural High Background Radiation Areas. There are concerns about congenital malformations due to the high background radiation prevailing in the region.Therefore, scientists find interest to study the possible biological effects of low-level exposures on the local populace who are living with generations under these extraordinary radiation fields. The present study is an attempt to find the correlation between the incidences of certain congenital malformations through a 1:3 matched case-control study. A total of 75 subjects (58 mental retardation cases and 17 Cleft lip/palate cases) along with 225 controls were selected for the investigations. Indoor and outdoor gamma dose rates were measured using a halogen-quenched GM tube-based survey meter, while the indoor inhalation dose rates were measured based on the radon and progeny measurements using the twin cup dosimeters equipped with LR-115 Type II solid-state nuclear track detectors. Conditional logistic regression analysis was used to find out the correlation between the radiation dose with congenital malformation. This study found an insignificant risk of cleft lip/palate (but not for mental retardation) from the exposures to natural high external gamma radiation fields in the study area. Therefore, the results of the investigation indicate no explicit risk of congenital malformations by the high background natural radiation prevailing in the region.

Impact of microbial air quality in preschools on paediatric respiratory health

Microbial air quality (MAQ) is unambiguously linked with one’s health particularly in pulmonology. Children remain more vulnerable in acquiring airborne infections than adults. MAQ studies and management are being implemented in developed countries, yet such information and actions are scarce in developing countries. Herein, we aimed to determine the indoor and outdoor airborne microbial concentrations in a rural versus urban perspective and their association with paediatric respiratory health. Preschools, one representing an urbanized and the other, a rural area, from Kandy, Sri Lanka, were considered. Respiratory health of 146 children (age; 3–6 years) was examined, and questionnaire-based information was obtained from their parents. Air samples were taken using natural sedimentation, single-stage viable sampler and fine particulate sampler to calculate the total microbial and culturable counts. Inhalation dose rates were calculated as per standard reference values. Micro-organisms were identified using 16SrRNA sequencing. Accordingly, 57.97% (n = 40) urban and 31.17% (n = 24) rural subjects suffered from at least one respiratory disease, upper respiratory tract infections, rhinitis, wheeze, etc. High total microbial counts (cells/m3) were seen in urban preschool (indoor: 4.66 × 105 vs. 2.45 × 105, outdoor: 4.29 × 104 vs. 2.74 × 104). Inhalation dose rates were high in urban preschool, both indoor and outdoor (2.00 × 104 and 1.05 × 104 cells/kg day). Irrespective of the site, indoor microbial counts were high and majority were opportunistic pathogens: Pseudomonas stutzeri, P. fluorescens, P. putida, Brevundimonas diminuta, Enterobacter cloacae, Bacillus pumilus, Acinetobacter calcoaceticus, B. cereus, Pseudoescherichia vulneris and Morganella morganii. Accordingly, observed dynamics can be a risk factor for the higher respiratory disease prevalence seen among urban preschoolers.

Modelling the dispersion of radionuclides in dust from a landform covered by low uranium grade waste rock

The dispersion of radionuclides in dust and inhalation dose rates to the public from the planned remediation of the Ranger uranium mine in the wet-dry tropics of Australia was modelled using RESRAD-OFFSITE. Dust inhalation dose rates were predicted to be highest on the remediated site and decrease with an approximate inverse square to inverse cubic dependence with distance from the site. The annual dose above natural background to a hypothetical individual permanently occupying the remediated site (representing the worst case scenario for radionuclide in dust exposure) was estimated to be 5.3 × 10−3 mSv. The estimated doses from exposure to radionuclides in dust were two to three orders of magnitude lower than those from exposure to 222Rn. A sensitivity analysis showed that source-related and receptor-related model parameters had direct proportional influences on dust inhalation dose rates. Four transport-related model parameters (atmospheric stability class, deposition velocity of particulates, precipitation and wind speed) were also influential and generally had an increasing influence with distance from the source. The results of this study may provide general guidance to similar sites elsewhere on the relative importance of dust versus gaseous 222Rn transport pathways and the relative influence of dispersion modelling parameters on predicted exposures and doses.

Measurement of Indoor Radon Concentration in Some Selected Offices of Adigrat University, Tigray Region, Ethiopia

Radon is an inert radioactive gas. A long term exposure to high concentration of radon causes lung cancer. Taking this into account, an investigation in some offices of Adigrat Universityhas been made to estimate the radon concentrations and to determine the health risk of the workers in the community. In the present study, Solid State Nuclear Track Detectors (LR-115 type II) has been used to measure the emission of radon from 12 offices for a period of 3 months. After an exposure time of 3 months, films were removed from each office andtaken for etching. After the etching, films were washed with distilled water and allowed to dry for 1day. Finally, alpha tracks were counted using an optical microscope at magnification power of 400X. Results obtained in the present study show that the value of concentration of radon ranges from 171.31 Bq.m−3 to 394.05 Bq.m−3 with mean concentration273.79 Bq.m−3 and standard deviation of 79.7Bq.m−3 and the inhalation dose rate varies from a minimum of 1.54 mSv.y−1 to a maximum of 3.55 mSv.y−1 with an average of 2.46 mSv.y−1 and standard deviation of 0.72 mSv.y−1. Even though, radon concentration levels were found to be higher the inhalation dose rate is safe within recommended limits

Indoor exposure to bioaerosol particles: levels and implications for inhalation dose rates in schoolchildren

Children spend most of their time inside schools and bioaerosol particles are part of their everyday environment. Although bioaerosol particles are considered to be a potential risk factor for various health concerns, information concerning the indoor exposures and inhalation doses is still limited. This study aimed (i) to quantify bacterial and fungal particles levels in indoor and outdoor air of public primary schools, (ii) to assess the influence of ambient air on bacteria and fungi presence indoors, and (iii) to estimate the inhalation dose rates for respective children (8–10 years old) in comparison with adult staff. Air samples were collected in 20 primary schools in a total of 71 classrooms during heating season with a microbiological air sampler. The results showed that indoor bacterial and fungal concentrations were higher than outdoor levels (p < 0.05), which could be explained by differences in density of occupation, occupant’s activities, and inadequate ventilation. CO2 levels were significantly correlated with indoor bacteria concentrations. Moreover, mean indoor bacteria concentrations were above national limit values in all the evaluated Porto primary schools, from two to nine times higher. Regarding fungi concentrations, indoor levels were above the reference value in 75% of the schools and overall indoor levels registered a 3-fold increase compared with outdoor values. Children had two times higher inhalation dose rates to bioaerosol particles when compared to adult individuals. Thus, due to their susceptibility, special attention should be given to educational settings in order to guarantee the children healthy development.

Dip coating of air purifier ceramic honeycombs with photocatalytic TiO2 nanoparticles: A case study for occupational exposure

Nanoscale TiO2 (nTiO2) is manufactured in high volumes and is of potential concern in occupational health. Here, we measured workers exposure levels while ceramic honeycombs were dip coated with liquid photoactive nanoparticle suspension and dried with an air blade. The measured nTiO2 concentration levels were used to assess process specific emission rates using a convolution theorem and to calculate inhalation dose rates of deposited nTiO2 particles. Dip coating did not result in detectable release of particles but air blade drying released fine-sized TiO2 and nTiO2 particles. nTiO2 was found in pure nTiO2 agglomerates and as individual particles deposited onto background particles. Total particle emission rates were 420×109min−1, 1.33×109μm2min−1, and 3.5mgmin−1 respirable mass. During a continued repeated process, the average exposure level was 2.5×104cm−3, 30.3μm2cm−3, <116μgm−3 for particulate matter. The TiO2 average exposure level was 4.2μgm−3, which is well below the maximum recommended exposure limit of 300μgm−3 for nTiO2 proposed by the US National Institute for Occupational Safety and Health. During an 8-hour exposure, the observed concentrations would result in a lung deposited surface area of 4.3×10−3cm2g−1 of lung tissue and 13μg of TiO2 to the trachea-bronchi, and alveolar regions. The dose levels were well below the one hundredth of the no observed effect level (NOEL1/100) of 0.11cm2g−1 for granular biodurable particles and a daily no significant risk dose level of 44μgday−1. These emission rates can be used in a mass flow model to predict the impact of process emissions on personal and environmental exposure levels.

Inhalation exposures due to radon and thoron (222Rn and 220Rn): Do they differ in high and normal background radiation areas in India?

In India, High Background Radiation Areas (HBRAs) due to enhanced levels of naturally occurring radionuclides in soil (thorium and, to a lesser extent, uranium), are located along some parts of the coastal tracts viz. the coastal belt of Kerala, Tamilnadu and Odisha. It is conjectured that these deposits will result in higher emissions of radon isotopes (222Rn and 220Rn) and their daughter products as compared to Normal Background Radiation Areas (NBRAs). While the annual external dose rates contributed by gamma radiations in these areas are about 5–10 times higher, the extent of increase in the inhalation dose rates attributable to 222Rn and 220Rn and their decay products is not well quantified. Towards this, systematic indoor surveys were conducted wherein simultaneous measurements of time integrated 222Rn and 220Rn gas and their decay product concentrations was carried out in around 800 houses in the HBRAs of Kerala and Odisha to estimate the inhalation doses. All gas measurements were carried out using pin-hole cup dosimeters while the progeny measurements were with samplers and systems based on the Direct radon/thoron Progeny sensors (DRPS/DTPS). To corroborate these passive measurements of decay products concentrations, active sampling was also carried out in a few houses. The results of the surveys provide a strong evidence to conclude that the inhalation doses due to 222Rn and 220Rn gas and their decay products in these HBRAs are in the same range as observed in the NBRAs in India.

Industrial worker exposure to airborne particles during the packing of pigment and nanoscale titanium dioxide

Context: Titanium dioxide (TiO2) factory workers’ source specific exposure and dose to airborne particles was studied extensively for particles between 5 nm and 10 μm in size.Objective: We defined TiO2 industry workers’ quantitative inhalation exposure levels during the packing of pigment TiO2 (pTiO2) and nanoscale TiO2 (nTiO2) material from concentrations measured at work area.Methods: Particle emissions from different work events were identified by linking work activity with the measured number size distributions and mass concentrations of particles. A lung deposit model was used to calculate regional inhalation dose rates in units of particles min−1 and μg min−1 without use of respirators.Results: Workers’ average exposure varied from 225 to 700 μg m−3 and from 1.15 × 104 to 20.1 × 104 cm−4. Over 90% of the particles were smaller than 100 nm. These were mainly soot and particles formed from process chemicals. Mass concentration originated primarily from the packing of pTiO2 and nTiO2 agglomerates. The nTiO2 exposure resulted in a calculated dose rate of 3.6 × 106 min−1 and 32 μg min−1 where 70% of the particles and 85% of the mass was deposited in head airways.Conclusions: The recommended TiO2 exposure limits in mass by NIOSH and in particle number by IFA were not exceeded. We recommend source-specific exposure assessment in order to evaluate the workers’ risks. In nTiO2 packing, mass concentration best describes the workers’ exposure to nTiO2 agglomerates. Minute dose rates enable the simulation of workers’ risks in different exposure scenarios.

Concept To Estimate Regional Inhalation Dose of Industrially Synthesized Nanoparticles

The use of nanoparticles (NPs) in industry is increasing rapidly, but knowledge of the occupational health and safety aspects of NPs is still limited. This is because quantitative NP exposure levels are scarce, and the metrics to describe doses are unclear. This study presents one method for estimating workers' calculated regional inhalation dose of deposited particles from size-fractionated concentrations. It was applied to estimate workers' regional inhalation dose rates and doses separately for NPs and NPs with background particles during NP synthesis. Dose analysis was performed in units of particle number (particles and particles min(-1)), active surface area (μm(2) and μm(2) min(-1)), and mass (ng and ng min(-1)) for three respiratory regions: head airways, tracheobronchial, and alveolar. It was found that in NP synthesis NPs were deposited mainly in the alveolar region in all units. However, when the dose of all particles was examined, it was found that dose and the main deposition region were mainly defined by the synthesized NPs for particle number, as active surface area was described by both NPs and background particles, and mass by background particles. This study provides fundamental data for NP inhalation exposure risk assessment, regulations, dose metrics for NP synthesis, and a basis for defining metrics of dose-biological response and helps us understand the magnitude of doses in NP synthesis. It also illustrates the necessity to obtain size-fractionated measurements of NP concentrations to support accurate dose estimation.

Indoor radon concentration and its possible dependence on ventilation rate and flooring type

The results of radon concentration measurements carried out in dwellings with natural ventilation for 1 y in Bangalore are reported. Measurements, covering three sessions of the day (morning, afternoon, night) were performed two times in a month for 1 y at a fixed place of each dwelling at a height of 1 m above the ground surface in selected dwellings. The low-level radon detection system (LLRDS), an active method, was used for the estimation of radon concentration. The measurements were aimed to understand the diurnal variation and the effect of ventilation rate and flooring type on indoor radon concentration. The geometric mean (± geometric standard deviation) of indoor radon concentration from about 500 measurements carried out in 20 dwellings is found to be 25.4 ± 1.54 Bq m⁻³. The morning, afternoon and night averages were found to be 42.6 ± 2.05, 15.3 ± 2.18 and 28.5 ± 2.2 Bq m⁻³, respectively. The approximate natural ventilation rates of the dwellings were calculated using the PHPAIDA--the on-line natural ventilation, mixed mode and air infiltration rate calculation algorithm and their effects on indoor radon concentrations were studied. The inhalation dose and the lung cancer risk due to indoor radon exposure were found to be 0.66 mSv y⁻¹ and 11.9 per 10⁶ persons, respectively. The gamma exposure rate was also measured in all the dwellings and its correlation with the inhalation dose rate was studied.

Radioactive aerosols released from the Chernobyl Shelter into the immediate environment

The release of radioactive particles through large gaps in the containment of the destroyed Chernobyl reactor was assessed during two measurement periods. In 1996-1999, a total radionuclide flow rate of 274 Bq s(-1) or 8.64 x 10(9) Bq year(-1) was determined. These releases were predominantly due to (137)Cs (78.5%), (90)Sr (21.1%), and (239+240)Pu (0.4%). The mean activity concentration in the aerosol measured directly at the gaps was about 240 mBq m(-3) with an activity median aerodynamic diameter (AMAD) of 2.4 microm for (137)Cs, 120 mBq m(-3) with an AMAD in the range 3.1-13 microm for (90)Sr, 1.8 mBq m(-3) with an AMAD in the range 3.5-11 microm for (239+240)Pu, and 2.0 mBq m(-3) with an AMAD of 1.5 microm for (241)Am. The resulting total inhalation dose rate calculated close to the gaps was about 100 nSv h(-1). In the near environment, the mean (137)Cs activity in the aerosol was 2.2 mBq m(-3) with an AMAD of 2.2 microm, which gave rise to an inhalation dose rate of about two orders of magnitude lower than the corresponding dose rate at the gaps. Occasionally, however, dose levels were measured in the near environment that were similar to those at the gaps. In 2000-2003, lower activity concentrations were observed. The decrease was more pronounced at the gaps than in the near environment. The results indicate that effective dose due to inhalation must be considered for the dose assessment of construction workers who will be deployed at the Chernobyl site to reconstruct the old or to build the new Shelter, in the future.

Cost assessment of ventilation and averted dose due to radon in dwellings

The inhalation dose due to radon and its progenies could be averted by ventilation in dwellings; however, on the other hand the increased ventilation augments the heating cost. Therefore a cost–benefit analysis could contribute to optimise the ventilation rate. In our current work we applied our former defined parameters of the optimising procedure to assess the optimised ventilation and radon concentration in dwellings with average parameters. To assess the inhalation dose rates the time-dependent concentrations of all the progenies were calculated in case of periodic and continuous ventilation as well, at three different radon entry rates (5, 10, 20 kBq h −1). The optimal ventilation rates in case of continuous ventilation are 0.22, 0.40 and 0.66 h −1, respectively. By these conditions the optimal radon concentration takes 160–210 Bq m −3. According to the more detailed analysis the periodic ventilation gives, in general, a better solution than the continuous one. The Monte Carlo simulations provided a large uncertainty; therefore, before the practical application of the results the uncertainty should be decreased taken into account the local conditions.

A set-up, calibration, acquisition and analysis program (SCAAP) for gamma-ray spectroscopy

A computer program entitled SCAAP (Set-up, Calibration, Acquisition and Analysis Program) has been designed to make gamma-ray spectroscopy easily useable by staff in laboratories at the Slowpoke-2 Facility at RMC and in support of the Canadian Forces Nuclear Emergency Response Teams (NERTs). The former group utilises gamma-ray spectroscopy for neutron activation analysis (NAA), while the latter may need to have inhalation dose rates calculated. The intent of this program, written using Microsoft Visual Basic, is to provide a simplified interface between the operator and the spectroscopy equipment and to provide the calculations necessary to produce results quickly. There are five sections (Setup, Calibrate, Acquire, Analyse and NAA) of which the first four are linked. In these sections, a checklist of procedures is presented and automated for the user to set up and calibrate the equipment and then to analyse spectra to provide various dose rates. In the unlinked section, NAA, gamma-ray spectra are analysed to provide elemental concentrations in samples.

Methodology for Mixed Field Inhalation Dosimetry in Monazite Areas using a Twin-Cup Dosemeter with Three Track Detectors

A methodology is proposed for estimating the gas and potential alpha energy concentrations (PAECs), and inhalation dose rates due to a mixed field of radon, thoron and their progeny present in the indoor atmosphere, using a radon-thoron discriminating dosemeter having three solid state nuclear track detectors (SSNTDs). The gas concentrations present in the vicinity of the dosemeter are directly measured through SSNTDs exposed in the 'cup mode'. The bare track density rates are related to the gas and the progeny concentrations by incorporating ventilation rate dependent spatial profiles for thoron gas. The ventilation rate is extracted as a real positive root of the governing equation and from this, the PAECs as well as the inhalation dose rates are estimated through the use of standard formulae. Error estimates on the dose rates have been carried out. Analyses of the field data from a sample survey of 35 houses situated in monazite bearing high background radiation areas of Kerala indicate that the methodology works successfully in a majority of the cases. Results for 22 cases which showed less than 100% statistical error are presented. These show median values of about 4.8 Bq.m-3 and 462 Bq.m-3 for radon and room averaged thoron concentrations, 0.5 mWL and 129 mWL for radon progeny and thoron progeny PAECs, and 1.21 µSv.h-1 for inhalation dose rate. Although a complete picture would emerge only at the end of the ongoing large scale survey, the sample survey already indicates that indoor thoron levels in the Kerala monazite area are the highest reported so far in the literature.