Total Internal Dose Research Articles

Characterizing the Contribution of Indoor Residential Phthalate and Phthalate Alternative Dust Concentrations to Internal Dose in the US General Population: An Updated Systematic Review and Meta-Analysis.

Diet is the primary exposure pathway for phthalates, but relative contributions of other exposure sources are not well characterized. This study quantifies the relative contribution of indoor residential dust phthalate and phthalate alternative concentrations to total internal dose estimated from the National Health and Nutrition Examination Survey (NHANES) urinary metabolite concentrations. Specifically, median phthalate and phthalate alternative concentrations measured in residential dust were determined by updating a pre-existing systematic review and meta-analysis published in 2015 and the attributable internal dose was estimated using intake and reverse dosimetry models. Employing a predetermined search strategy, 12 studies published between January 2000 and April 2022 from Web of Science and PubMed measuring phthalates and phthalate alternatives in residential dust were identified. From the data extracted, it was estimated that dust contributed more significantly to the internal dose of low-molecular weight chemicals such as DEP and BBP when compared to high-molecular weight chemicals such as DEHTP. Additionally, findings showed that the chemical profile of residential dust is changing temporally with more phthalate alternatives being detected in the indoor environment. Future studies should seek to characterize the contribution of dust to an overall phthalate and phthalate alternative intake for individuals who have higher than normal exposures.

Exposure to PAHs during Firefighting Activities: A Review on Skin Levels, In Vitro/In Vivo Bioavailability, and Health Risks.

Occupational exposure as a firefighter is a complex activity that continuously exposes subjects to several health hazards including fire emissions during firefighting. Firefighters are exposed to polycyclic aromatic hydrocarbons (PAHs), known as toxic, mutagenic, and carcinogenic compounds, by inhalation, dermal contact, and ingestion. In this work, a literature overview of firefighters’ dermal exposure to PAHs after firefighting and data retrieved from skin in vitro/in vivo studies related to their dermal absorption, bioavailability, and associated toxicological and carcinogenic effects are reviewed. The evidence demonstrates the contamination of firefighters’ skin with PAHs, mainly on the neck (2.23–62.50 ng/cm2), wrists (0.37–8.30 ng/cm2), face (2.50–4.82 ng/cm2), and hands (1.59–4.69 ng/cm2). Concentrations of possible/probable carcinogens (0.82–33.69 ng/cm2), including benzopyrene isomers, were found on firefighters’ skin. PAHs penetrate the skin tissues, even at low concentrations, by absorption and/or diffusion, and are locally metabolized and distributed by the blood route to other tissues/organs. Lighter PAHs presented increased dermal permeabilities and absorption rates than heavier compounds. Topical PAHs activate the aryl hydrocarbon receptor and promote the enzymatic generation of reactive intermediates that may cause protein and/or DNA adducts. Future research should include in vitro/in vivo assays to perform a more realistic health risk assessment and to explore the contribution of dermal exposure to PAHs total internal dose.

Association of arsenic and uranium concentrations in private wells and community water systems with urinary biomarkers in American Indian adults: The Strong Heart Family Study

BACKGROUND AND AIM: Chronic exposure to inorganic arsenic (iAs) and uranium (U) has been associated with adverse health risks. High As and U levels occur in unregulated private wells and regulated community water systems (CWSs) serving tribal communities in the Southwest, Central Midwest, and Northern Plains. Our objective was to examine the contribution of CWS and private well As and U concentrations to urinary biomarkers of total internal dose in American Indian adults in the Strong Heart Family Study (SHFS). METHODS: 2,688 SHFS participants had dietary recall information and spot urine concentrations of U and iAs, estimated as the sum of inorganic and methylated species, collected between 2001-2003. We assigned participants zip code level area- and population- weighted CWS and private well As and U estimates based on previously developed nationwide estimates derived from US Environmental Protection Agency and US Geological Survey datasets, respectively. We used generalized linear mixed models to evaluate the geometric mean ratio (GMR) of urinary iAs or U concentrations per log unit increase in water As or U, respectively. Models were adjusted for sex, age, reported intake of As- and U- containing foods, and smoking status. Random effects were applied for zip code and family group. RESULTS: In fully adjusted models, the GMR of estimated iAs and U per log µg/L increase in CWS As and U was 1.11 (1.08-1.14) and 1.26 (1.15-1.39), respectively. The fully adjusted GMR of estimated iAs per unit (100%) increase in the probability of private well As >10 µg/L was 1.81 (1.35-2.41). Per log µg/L increase in mean private well U, the GMR of urinary U was 1.04 (0.91-1.19). CONCLUSIONS: Both regulated CWSs and unregulated private wells are important sources of iAs and U exposure for tribal communities in the SHFS, as reflected in urinary biomarkers. KEYWORDS: arsenic, uranium, environmental epidemiology

Assessment of the current levels of 241Am and 137Сs in soils and foodstuff, as well as of public internal exposure to ionizing radiation in populated areas adjacent to the Chernobyl NPP exclusion zone (case study: the Bragin district of the Gomel region, Belarus)

This paper is part of a research cycle focusing on studying the current levels of 241Am and 137Cs in soils and local foodstuffs of populated areas neighboring the Chernobyl exclusion zone. Our objective was to estimate the maximum annual committed internal doses to individuals of the Bragin-area settlements from inhalation and consumption of locally produced foods. We updated the data on the levels of 241Am and 137Сs in soils of 28 settlements of the district. Specific activity of 241Am in soils in two of the settlements were the highest of all; we took and analyzed samples of local-grown foodstuff. 241Am in food samples was measured via a radiochemical method with the use of selective chromatographic resins and alpha-spectrometry measurement. A gammaspectrometry technique was used to measure 241Am in soil and 137Сs in soil and food samples. The most contaminated by 241Am and 137Cs appeared the soils in the town of Bragin, the administrative center of the district where the respective levels were as high as 2.8 and 560 kBq/m2. Among the analyzed samples, the specific activities of 241Am in root and tuber crops were one-digit values, while the samples of leafy vegetables contained a few tens of mBq/kg of the same radionuclide. That said, however, 241Am concentrations in food samples were lower than those of 137Сs by three orders of magnitude. The results showed an apparent difference between estimated annual committed internal doses to the Bragin residents due to 241Am intake and that resulting from 137Сs with the respective 0.03 and 1.7 mSv/year. The maximum doses to population of the Bragin-district villages from inhalation of 241Am varied from 0.006 to 0.033 mSv/year exceeding the doses from inhaled 137Сs – 0.0002-0.002 mSv/year – by one order of magnitude. The major contribution to the public internal exposure today is 137Сs intake through consumption of contaminated food that produced locally; its contribution is about 93-99% of the total internal dose received by the Bragin-district residents.

Polycyclic aromatic hydrocarbons at fire stations: firefighters’ exposure monitoring and biomonitoring, and assessment of the contribution to total internal dose

This work characterizes levels of eighteen polycyclic aromatic hydrocarbons (PAHs) in the breathing air zone of firefighters during their regular work shift at eight Portuguese fire stations, and the firefighters’ total internal dose by six urinary monohydroxyl metabolites (OH-PAHs). Total PAHs (ΣPAHs) concentrations varied widely (46.4–428ng/m3), mainly due to site specificity (urban/rural) and characteristics (age and layout) of buildings. Airborne PAHs with 2–3 rings were the most abundant (63.9–95.7% ΣPAHs). Similarly, urinary 1-hydroxynaphthalene and 1-hydroxyacenaphthene were the predominant metabolites (66–96% ΣOH-PAHs). Naphthalene contributed the most to carcinogenic ΣPAHs (39.4–78.1%) in majority of firehouses; benzo[a]pyrene, the marker of carcinogenic PAHs, accounted with 1.5–10%. Statistically positive significant correlations (r≥0.733, p≤0.025) were observed between ΣPAHs and urinary ΣOH-PAHs for firefighters of four fire stations suggesting that, at these sites, indoor air was their major exposure source of PAHs. Firefighter’s personal exposure to PAHs at Portuguese fire stations were well below the existent occupational exposure limits. Also, the quantified concentrations of post-shift urinary 1-hydroxypyrene in all firefighters were clearly lower than the benchmark level (0.5μmol/mol) recommended by the American Conference of Governmental Industrial Hygienists.

Effects of temperature, surfactants and skin location on the dermal penetration of haloacetonitriles and chloral hydrate

Dermal exposure has been recognized as an important contributor to the total internal dose to disinfection-by-products (DBPs) in water. However, the effect of the use of surfactants, water temperature and area of the body exposed to DBPs on their dermal flux has not been characterized and was the focus of the present study using an in-vitro system. The dermal flux of mg/l concentrations of haloacetonitriles and chloral hydrate (CH), important cytotoxic DBPs, increased by approximately 50% to 170% with increasing temperature from 25 °C to 40 °C. The fluxes for the torso and dorsum of the hand were much higher than that of palm and scalp skin. An increase in flux was observed for chloroacetonitrite and dichloroacetonitrile, two less lipophilic HANs, but not for trichloroacetonitrile or CH, with the addition of 2% sodium lauryl sulfate or 2% sodium laureth sulfate, two surfactants commonly used in soaps and shampoos used in showering and bathing. Thus, factors such as temperature, surfactants and skin location affect dermal penetration and should be considered when evaluating dermal absorption.

238PU

The alpha spectrometry measurements of specific activity of 238Pu and 239Pu in urine from bioassay examinations of 1,013 workers employed at the radiochemical and plutonium production facilities of the Mayak Production Association and in autopsy specimens of lung, liver, and skeleton from 85 former nuclear workers who died between 1974-2009, are summarized.The accumulation fraction of 238Pu in the body and excreta has not changed with time in workers involved in production of weapons-grade plutonium production (e.g., the plutonium production facility and the former radiochemical facility). The accumulation fraction of 238Pu in individuals exposed to plutonium isotopes at the newer Spent Nuclear Fuel Reprocessing Plant ranged from 0.13% up to 27.5% based on the autopsy data. No statistically significant differences between 238Pu and 239Pu in distribution by the main organs of plutonium deposition were found in the Mayak workers. Based on the bioassay data,the fraction of 238Pu activity in urine is on average 38-69% of the total activity of 238Pu and 239Pu, which correlates with the isotopic composition in workplace air sampled at the Spent Nuclear Fuel Reprocessing Plant. In view of the higher specific activity of 238Pu, the contribution of 238Pu to the total internal dose, particularly in the skeleton and liver, might be expected to continue to increase, and continued surveillance is recommended.

간접흡연의 정량적 노출측정 방법의 고찰

Secondhand smoke (SHS) is one of major public health threats. Since secondhand smoke is complex mixture of toxic chemicals, there has been no standardized method to measure SHS quantitatively. The purpose of this manuscript was to review various quantitative methods to measure SHS. There are two different methods: air monitoring and biological monitoring. Air monitoring methods include exhaled carbon monoxide level, ambient fine particulates, nicotine and 3-ethenylpyridine. Measurement of fine particulates has been utilized due to presence of real-time monitor, while fine particulates can have multiple indoor sources other than SHS. Ambient nicotine and 3-EP are more specific to SHS, although there is no real-time monitor for these chemicals. Biological monitoring methods include nicotine in hair, cotinine in urine, NNK in urine and DNA adducts. Nicotine in hair can provide chronic internal dose, while cotinine in urine can provide acute dose. Since biological monitoring can provide total internal dose, identification of specific exposure source may be difficult. NNK in urine can indicate carcinogenicity of the SHS exposure. DNA adducts can provide overall cancer causing exposure, but not specific to SHS. While there are many quantitative methods to measure SHS, selection of appropriate method should be based on purposes of assessment. Application of accurate and appropriate exposure assessment method is important for understanding health effects and establishing appropriate control measures.

Radiocontamination of hydrobionts within the Chernobyl accident Exclusion Zone

The territory of the Chernobyl accident Exclusion Zone is characterised by significant heterogeneity of radionuclide contamination, which is significantly reflected by the radioactive substance contents in aquatic ecosystem components. Primarily this is due to the composition and the dynamics of radionuclide emissions into the environment as a result of accident in 1986 as well as to the subsequent processes of radioactive substances transformation and their biogeochemical migration in aquatic ecosystems. Our studies were conducted to identify dynamics of Sr-90, Cs-137, Pu-238, 239, 240 and Am-241 in components of freshwater biocenose and to assess the major factors, which determine radionuclide accumulation and internal absorbed dose rate in hydrobionts. The construction of flood protection dams on the most contaminated areas of the Exclusion Zone to prevent washing away of radioactive substances from soils was by the reason of strengthening of over-moistening and swamping processes within embankment territories. As a result - on a background of the common tendencies of increase of the mobile forms of radionuclides in soils of catchment territories and bottom sediments of the Exclusion Zone, there is an increase of the water-soluble forms of Sr-90 in waterlogged soils of flood-lands. Thus the increase of concentrations of the mobile radionuclide forms and their inclusion into biotic circulation of aquatic ecosystems is observed. Our studies during 1993-2007 have shown that since the late 1990-s the higher aquatic plants and fish related to different ecological groups is indicating a frank tendency to Sr-90 content increase in tissues. The specific activity of Cs-137 either decreases or remains practically constant. Hence, in the middle 1990-s specific activity of Cs-137 in tissues of aquatic biota was much higher than specific activity of Sr-90 in them, whereas in the late 1990-s these values became comparable, and at present specific activity of Sr-90 greatly exceeded of Cs-137 content. Such dynamics of Sr-90 contents is significantly reflected on dose rate for hydrobionts due to incorporated radionuclides. At rather stable internal absorbed dose rate, caused by Cs-137 the dose, caused by the Sr-90 content, has grown more than in 20 times for some species of higher aquatic plants and fish in comparison with the beginning of 1990-s. As a result the total internal dose of plants and fish irradiation has increased more than in 6 times, that testifies to essential deterioration of radiating conditions for aquatic biota within the Chernobyl accident Exclusion Zone.

Reconstruction of doses from radionuclide inhalation for nuclear power plant workers using air concentration measurements and associated uncertainties.

This paper presents a case study to illustrate the influence of parameter uncertainties on calculating an internal radiation dose of one actual nuclear plant worker, alias Mr. X, as well as the utility of air sampling for internal dose reconstruction. Input probability distributions for air concentrations of radionuclides were derived from empirical air measurements taken by fixed area air samplers. The total internal dose was calculated by multiplying radionuclide intake by dose conversion factors in Monte-Carlo simulations. There is significant variability in dose conversion factors and uncertainty in the estimated concentrations of radionuclides in the air to which Mr. X was exposed. The high variability and uncertainty of the model parameters contributed to large ranges of predicted internal doses for Mr. X. Two-dimensional Monte-Carlo simulations were conducted to separate contributions of the uncertainty and variability. Sensitivity analysis was conducted to determine which of the input parameters contributed most to uncertainty in internal dose estimates. Our analysis suggests that the uncertainty resulting from use of general air surveys contributes more to the internal dose ranges than the variability from DCFs and other population-derived parameters. Reduction of the uncertainty in reconstructed internal dose can be achieved by using personal air sampling and/or individual bioassays and regular whole-body counting.

Sources of nitrate exposure in residents of rural areas in Quebec, Canada

Nitrate exposure was investigated in a group of 187 people using well water and living in four areas of rural Quebec (Canada) with intensive agricultural activities. Nitrate intake was evaluated using a 24-h dietary recall and a food frequency questionnaire, in conjunction with a validated food database and measurements of nitrate concentrations in private wells. The total internal dose was estimated by means of the 24-h urinary nitrate excretion, while taking into account risk factors for endogenous nitrate formation. Mean (geometric) 24-h urinary nitrate excretion was 16.9 mg N for the 100 people with low groundwater contamination (mean nitrate concentration=0.18 mg N/l) and 23.3 mg N in the 87 individuals with moderate groundwater contamination (mean nitrate concentration=7.1 mg N/l). A multivariate analysis revealed that dietary nitrate intake during the last 24 h was the principal source of exposure, followed by water intake during the last 24 h. The Quetelet index was also a significant predictor of urinary excretion. The total predictive model explained only 29% of the variability in urinary nitrate excretion (R2=0.286). Neither the inflammatory status as indicated by elevated C reactive protein, the presence of Helicobacter pylori antibodies nor the occurrence of diarrhea during the last 24 h prior to urine collection were associated with urinary nitrate excretion. In conclusion, food and to a lesser extent water contribute to nitrate exposure in this rural setting with moderate water contamination. Better predictors of endogenous nitrate production are needed to improve our ability to model nitrate body burden and estimate associated health risks.

ESR isochron dating for teeth: A brief demonstration in solving the external dose calculation problem

The radiation sensitive ESR signal at g = 2.0018 in fossil enamel can be used to date teeth absolutely, providing a suitable U uptake model can be selected, and the external dose rate, D ext can be accurately calculated. Apart from the uptake model, the most obvious uncertainty lies in D ext. With the isochron method, D ext can be derived easily during the ESR analysis. By plotting the AD vs. the total internal dose rate for teeth where multiple subsamples have been analyzed, a regression line, the isochron, can be determined for each model age calculation. Each isochron slope represents the sample age, while its y-intercept gives the total external dose, A ext. In the preliminary test, the isochron method was used to date two teeth from Bau de l'Aubesier, Provençe. Both isochron calculations produced a good estimate for the total external dose, A ext. Although the external dose rate, D ext, so derived is now uptake-model dependent, this method should revolutionize ESR dating.

Polonium-210 in cartilaginous fishes (Chondrichthyes) from south-eastern Australian waters

A study was made of the concentration of the naturally occurring radionuclide polonium-210 in the livers of cartilaginous fishes (chondrichthyans) caught in the waters of Port Phillip Bay, Victoria, Australia in 1991. Five elasmobranch species had 210Po concentrations in the range 1-31 Bq kg-1 (wet weight) and one holocephalian species, the elephant fish (Callorhynchus milii), was exceptional with a 210Po range of 60-270 Bq kg-1 (n=3, mean 180 Bq kg-1). Lead-210 was present at 0.1- 1.1 Bq kg-1 and activity concentration ratios of 210Po:210Pb were all greater than 1, indicating that the 210Po could not all have grown in from in situ decay of 210Pb within the chondrichthyan liver. The concentration of 210Po in the livers appeared to be species related. Concentrations of the trace metals Cu, Fe and Zn showed no correlation with the 210Po and were not species-related. The mean concentration of 210Po measured in Port Phillip Bay water was 0.32 mBq kg-1. This yields concentration factors of 3.2 × 103 to 8.4 × 105 for unsupported 210Po in the livers of the chondrichthyans. The total 210Po (using Q=20) exposes the livers to a weighted absorbed dose of up to 140 mGy year-1 (16�Gy h-1), which is >99% of the total internal dose and three orders of magnitude greater than the external dose based on estimated levels of 40K.