An Isotopic Study of Bio-accessible Lead in Wheat, Miswak Toothbrush and Miswak Fruit Using the Continuous On-line Leaching Method with Inductively Coupled Plasma Mass Spectrometry
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Bibliographic record
Abstract
In this study, sources of Pb are investigated using the 206Pb/207Pb isotopic ratio measured by inductively coupled plasma quadrupole mass spectrometry in the bio-accessible fractions from wheat, Miswak toothbrush (also used as chewing stick) and Miswak fruit. These samples were obtained for the in vitro batch and on-line leaching methods that mimic the human gastrointestinal tract by sequentially using artificial saliva, gastric juice and intestinal fluid for extraction. The two methods provided similar results according to a Student’s t-test at the 95% confidence level. Significant (p < 0.05) differences in 206Pb/207Pb were noted at the 95% confidence level in different artificial body fluids. Except for unpolluted Miswak toothbrush and Miswak fruit, which only contained geogenic Pb, the samples contained a mixture of geogenic and anthropogenic Pb, with bio-accessible Pb in saliva being mainly from a geogenic source, whereas bio-accessible Pb in the stomach and intestinal fluids was mainly from anthropogenic sources. Despite the fact that leaded petrol was phased out in Saudi Arabia in 2001, a Miswak toothbrush collected on the side of a busy road after exposure for only a few days and Safeer wheat were still being contaminated with Pb and had an isotopic composition matching that of Pb added to petrol. The 208Pb/206Pb isotopic ratio for gastric bio-accessible Pb also matched that reported in tetraethyllead. The 206Pb/207Pb isotopic ratios of intestinal bio-accessible Pb from Qassim wheat and Safeer wheat point to coal combustion as the source. Overall, these results highlight the need for continued Pb monitoring and the value of examining bio-accessible fractions periodically to identify Pb sources.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it