BACKGROUND RADIATION LEVELS NEAR A MINERAL SAND MINING FACTORY IN SRI LANKA: CORRELATION OF RADIATION MEASUREMENTS WITH MICRONUCLEI FREQUENCY

Combined X-ray absorption and SEM-EDX spectroscopic analysis for the speciation of thorium in soil

Mobility and bioavailability of radionuclides in the environment strongly depend on their aqueous speciation, adsorption behavior and the solubility of relevant solid phases. In the present context, we focus on naturally occurring Th-232 at a location in central Sri Lanka presenting high background radiation levels. Four different soil samples were characterized using X-ray Absorption Spectroscopy (XAS) at the Th L₃-edge (16.3 keV), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) spectroscopy. X-ray Absorption Near Edge Structure (XANES) spectra are applied as a fingerprint indication for Th existing in different chemical environments. Linear combination fitting (LCF) of the Extended X-ray Absorption Fine Structure (EXAFS) data involving reference Th-monazite (phosphate) and thorianite (oxide) compounds suggested that Th is mostly present as Th-phosphate (76 ± 2%) and Th-oxide (24 ± 2%), even though minor amounts of thorite (silicate) were also detected by SEM-EDX. Further studies on selected individual particles using micro-focus X-ray Fluorescence (μ-XRF) and micro-X-ray Absorption Spectroscopy (μ-XAS) along with SEM-EDX elemental mapping provided information about the nature of Th-bearing mineral particles regarding mixed phases. This is the first study providing quantitative and XAS based speciation information on Th-mineral phases in soil samples from Sri Lanka.

Risk of genotoxic damage in schoolchildren exposed to organochloride pesticides

This study identified and determined organochloride pesticide (OCs) concentrations in hair samples from children at two elementary schools: one exposed to fumigations in agricultural fields, the other unexposed. Three concentrations of OCs levels in the hair were compared (high, medium, low), and total nuclear abnormalities in buccal cells were determined: micronuclei (MNi), condensed chromatin, karyorrhexis, pyknosis, binucleate cells, karyolysis, lobed nuclei, and apoptosis. No significant differences were found for the presence of MNi between the schoolchildren from the exposed and unexposed schools, but the prevalence of OCs in both schools was over 50%, as well as the frequencies of MNi in the children were over 58%. Findings show a significant difference between the frequency of MNi in the total sample of schoolchildren (exposed school + unexposed school) in relation to the concentration of OCs detected in their hair. The children from exposed school that showed the higher concentrations of OCs in hair had higher levels of genotoxic damage in the buccal cells; compared against children with lower concentrations of OCs. The most frequent nuclear abnormalities in the exposed children were lobed nuclei (79.4%), binucleate cells (66.66%), apoptosis (65.07), and MNi (58.7%). We determined the prevalence ratio (PR) and prevalence odds ratio (POR) for the presence of MNi in buccal cells in relation to the OCs concentrations in the hair samples. Both ratios were high for MNi [PR 3.93, 95% confidence interval (CI) 1.97–7.84, p = 0.0003; and POR 7.97, 95% CI 2.62–24.28, p = 0.0003], indicating a 7.97 times greater risk that the exposed children will present > 0.2% of MNi when OCs concentrations exceed 0.447 μg/g. These indicators may be useful biomarkers of genotoxic damage in children exposed to persistent, highly-toxic compounds. Results suggest the potential risk to which those schoolchildren are exposed on a daily basis due to fumigations in nearby agricultural fields.