Radiation Dosimetry of Inhaled Radioactive Aerosols: CFPD and MCNP Transport Simulations of Radionuclides in the Lung.

Despite extensive efforts in studying radioactive aerosols, including the transmission of radionuclides in different chemical matrices throughout the body, the internal organ-specific radiation dose due to inhaled radioactive aerosols has largely relied on experimental deposition data and simplified human phantoms. Computational fluid-particle dynamics (CFPD) has proven to be a reliable tool in characterizing aerosol transport in the upper airways, while Monte Carlo based radiation codes allow accurate simulation of radiation transport. The objective of this study is to numerically assess the radiation dosimetry due to particles decaying in the respiratory tract from environmental radioactive exposures by coupling CFPD with Monte Carlo N-Particle code, version 6 (MCNP6). A physiologically realistic mouth-lung model extending to the bifurcation generation G9 was used to simulate airflow and particle transport within the respiratory tract. Polydisperse aerosols with different distributions were considered, and deposition distribution of the inhaled aerosols on the internal airway walls was quantified. The deposition mapping of radioactive aerosols was then registered to the respiratory tract of an image-based whole-body adult male model (VIP-Man) to simulate radiation transport and energy deposition. Computer codes were developed for geometry visualization, spatial normalization, and source card definition in MCNP6. Spatial distributions of internal radiation dosimetry were compared for different radionuclides (131I, 134,137Cs, 90Sr-90Y, 103Ru and 239,240Pu) in terms of the radiation fluence, energy deposition density, and dose per decay.

Assessment of exposure to pesticides in rural workers in southern of Minas Gerais, Brazil.

The aim of the study was to assess of occupational exposure to pesticides in rural workers using genotoxicity test, bioindicators and clinical evaluation. Blood, urine and buccal samples from persons, rural workers exposed to a complex mixture of pesticides with organophosphates (n=94) and without organophosphates (n=94) were collected to compare the activities of cholinesterases, the levels of urinary dialkyl phosphates, genotoxicity data, from a cytome assay. Biomarkers were analysed by traditional/published methods Control group consisted of 50 other persons, non- occupationally exposed to pesticides from the city of Alfenas, Minas Gerais, Brazil. All subjects underwent a clinical evaluation. In the group exposed to organophosphates, the activity of acetylcholinesterase, butyrylcholinesterase and total cholinesterase was lower by 63.8%, 12.8%, and 14.8%, respectively, and 92.6% of the group had dialkyl phosphates present in their urine. The cytome assay was used to measure biomarkers of DNA damage (micronuclei and/or elimination of nuclear material by budding), cytokinetic defects (binucleated cells), and proliferative potential (basal cell) and/or cell death (condensed chromatin, karyorrhectic, pyknotic, and karyolytic cells). The group exposed to organophosphates showed significant changes in all these parameters compared to the control group and showed significant changes in budding, condensed chromatin and karyolytic cells compared with the group non-exposed to organophosphates. Data from the clinical evaluation showed significant changes in the central nervous, respiratory and auditory systems. The studied biomarkers are able to distinguish occupational and environmental exposure to pesticides and the data showed hazardous exposure to organophosphates and afforded valuable data to estimate the risk to cancer development.

Characterisation of secondary metal-bearing phases in used dental amalgam and assessment of gastric solubility.

Detailed SEM/EDS investigation of used dental amalgams was carried out in order to characterise morphology and chemical composition of secondary metal-bearing phases resulting from long-term exposure of dental amalgam to oral environment, and assess their solubility in gastric environment. The investigation revealed numerous secondary phases, represented by compositionally and morphologically complex Hg-, Cu-, Sn-, Ag-, Zn-bearing sulphides and oxides/hydroxides, while sulphates and phosphates are scarce. Secondary metal-bearing phases mostly occur at the amalgam/tooth interface; however, some phases were found only on the occlusal surfaces of amalgam. Secondary phases mostly form porous aggregates of minute crystallites and micro- or nanocrystalline crusts. In oral environment, these phases are mostly stable and represent trapping media for dissolved potentially toxic metals released during amalgam corrosion. Simplified PHREEQC calculations of solubility of secondary metal-bearing phases in aqueous environment under conditions similar to those in gastric environment showed that secondary phases are more soluble in gastric environment than in oral solutions, which is mostly due to their forms of occurrence. Secondary phases in gastric environment thus act as secondary sources of potentially toxic metals, particularly Sn, Zn and also Cu, which are released both under reducing and oxidising conditions especially in acidic environment. Only very small amounts of Hg are potentially released and should not represent serious threat. Secondary phases that contribute the most to bioaccessibility of these metals are Sn hydroxychlorides, Sn oxides/hydroxides, Sn sulphates/hydroxysulphates, Sn oxides, Zn sulphides and Cu sulphides (Cu2S).

The assessment of the robustness of microRNAs from oral cytological scrapings.

BACKGROUND: Sampling of suspect oral lesions in the general dental clinic may increase early carcinoma detection thus oral cancer survival rates. One means of lesion sampling that is an alternative to incisional biopsy is cytological scraping. MicroRNA alterations are also being explored as a means of diagnosing carcinoma as an alternative to histopathology. METHODS: We obtained cytological scrapings using 10 strokes ('light') or 40 strokes ('heavy') from the buccal mucosa of one healthy subject using a dermatological curette. MicroRNA was isolated from oral cytological scrapings immediately, or the scrapings were stored in buffer or RNA later, at 4°C, room temperature or 36°C, from 1 to 7 days prior to RNA isolation. All scrape comparisons and test conditions were conducted in triplicate. MicroRNAs were measured using qRT-PCR. RESULTS: MicroRNAs can be obtained from cytological scrapings independent of the number of strokes and can be measured using qRT-PCR after storage under all conditions tested. CONCLUSION: MicroRNAs are robust to a wide range of storage conditions that bodes well for use of cytological scrapings to be of use in a clinical setting as a chair side sampling method for suspect oral lesions.

Assessment of oral bioaccessibility of arsenic in playground soil in Madrid (Spain): a three-method comparison and implications for risk assessment.

Three methodologies to assess As bioaccessibility were evaluated using playground soil collected from 16 playgrounds in Madrid, Spain: two (Simplified Bioaccessibility Extraction Test: SBET, and hydrochloric acid-extraction: HCl) assess gastric-only bioaccessibility and the third (Physiologically Based Extraction Test: PBET) evaluates mouth-gastric-intestinal bioaccessibility. Aqua regia-extractable (pseudo total) As contents, which are routinely employed in risk assessments, were used as the reference to establish the following percentages of bioaccessibility: SBET-63.1; HCl-51.8; PBET-41.6, the highest values associated with the gastric-only extractions. For Madrid playground soils--characterised by a very uniform, weakly alkaline pH, and low Fe oxide and organic matter contents--the statistical analysis of the results indicates that, in contrast with other studies, the highest percentage of As in the samples was bound to carbonates and/or present as calcium arsenate. As opposed to the As bound to Fe oxides, this As is readily released in the gastric environment as the carbonate matrix is decomposed and calcium arsenate is dissolved, but some of it is subsequently sequestered in unavailable forms as the pH is raised to 5.5 to mimic intestinal conditions. The HCl extraction can be used as a simple and reliable (i.e. low residual standard error) proxy for the more expensive, time consuming, and error-prone PBET methodology. The HCl method would essentially halve the estimate of carcinogenic risk for children playing in Madrid playground soils, providing a more representative value of associated risk than the pseudo-total concentrations used at present.

Prevalence of long-term use of medicines with prolonged oral clearance in the elderly: a survey in north east England.

AIM: To determine the prevalence of long-term use by the elderly of prescribed and over-the-counter (OTC) medicines with prolonged oral clearance (POC), with regard to sugars content, dose form and therapeutic groups of medicines used. DESIGN AND SETTING: Two cross-sectional observational surveys in ten general medical practices in north-east England during 1996. METHODS: Computerised patient records of all elderly patients (aged 60 years and over) were surveyed for prescribed medicines use. Within these practices, 50% of elderly patients registered with ten general medical practitioners were surveyed by postal questionnaire to assess over-the-counter (OTC) medicines use. RESULTS: Of 20,731 elderly patients registered, prevalence of use of prescribed prolonged oral clearance (POC) medicines was 9.8% (95% CI: 8.2%, 11.3%) and use in females aged 75 years and older was significantly more likely (P < 0.0001). Of 2,796 prescribing instances (PIs) for 143 POC medicines used long-term, 53% were gastrointestinal and 72% were sugars-free; however, 82% of 542 PIs for generic liquids were sugars-containing compared with 8% of 685 PIs for proprietary liquid oral medicines. Of 1,532 elderly respondents to a postal questionnaire, 17 were using 13 different OTC medicines with POC regularly and long-term (mean prevalence; 1.1%). Of the 17 instances of regular long-term use of OTC medicines, 59% were sugars-free. CONCLUSIONS: Prescribed medicines represent the bulk of regular, long-term medicines use in the elderly. Generic prescribing is more likely to result in sugars-containing medicines being dispensed. Generic medicines manufacturers must be encouraged to provide sugars-free alternatives to POC medicines used long-term, and health professionals should be vigilant when prescribing and dispensing these medicines to the increasingly dentate elderly.

Pictorial assessment of the delivery of oropharyngeal rinse versus oropharyngeal spray.

Oral rinses/gargles and oral sprays are frequently used in the management of oropharyngeal inflammation. This pictorial study, using methylene blue dye as a marker of the distribution of these topical preparations in the oropharynx, suggests that oral sprays are more effective in coating the oropharynx than oral rinses, whilst oral rinses are better at staining the oral cavity and base of tongue. The authors therefore suggest that oral rinses should be used to treat disease in the oral cavity and oral sprays should be used to treat ailments in the oropharynx.