Évaluation de la toxicité du béryllium en fonction de la forme chimique et de la taille des particules
Bibliographic record
Abstract
Click here for the English version of this report_x000D_ Au cours des dernières années, plusieurs auteurs ont remis en cause le niveau de protection accordé aux travailleurs par la valeur seuil reconnue pour le béryllium (Be) et ses sels (VEMP Québec, TLV (TWA) ACGIH). La prévalence des effets associés au Be suggère que les risques sont en fonction de sa spéciation. Par ailleurs, il semble que les particules fines constituent la fraction d’intérêt pour l’occurrence de tels effets. L’objectif de cette recherche est d’évaluer la toxicité du Be en fonction de la forme chimique et de la taille particulaire._x000D_ Pour chacune des formes chimiques visées par la présente étude (Be, BeO, BeAl), la toxicité a été évaluée à la suite d’une exposition subchronique par inhalation oro nasale à des particules fines et totales. À cette fin, un modèle animal (souris) a été utilisé. Au total, 245 souris ont été utilisées. Elles ont été subdivisées en sept groupes de 35 individus. Un groupe a servi de contrôle, alors que chacun des six autres a été exposé soit à des particules fines soit à des particules totales, pour chacune des trois formes chimiques de Be. La durée d’exposition pour chacun des groupes s’est étendue sur 3 semaines comprenant 15 jours d’exposition (5j/sem, 6h/j). Au moment du sacrifice, plusieurs tissus (poumon, rate, foie et reins) ainsi que des échantillons de sang ont été prélevés puis immédiatement congelés jusqu’à leur analyse pour la détermination de leur teneur en Be. De plus, certains poumons et rates ont été analysés pour l’évaluation de la sensibilité immunologique et de l'inflammation pulmonaire._x000D_ De nombreuses corrélations ont été établies entre les concentrations tissulaires en Be et les effets normalement observés chez le travailleur à la suite d’une exposition. Les coupes histologiques montrent que les souris exposées au Be présentent des niveaux d’inflammation pulmonaire similaires à ceux observés chez des patients atteints de bérylliose chronique (BC). Les résultats témoignent également d’une association entre la taille des particules, les concentrations pulmonaires, l’inflammation pulmonaire, la production de certaines cytokines et l’expression de certains lymphocytes._x000D_ Les effets dépendent aussi de la forme chimique de Be. Ainsi, ce sont le Be métallique et le BeO qui seraient les formes les plus toxiques. Manifestement, le diamètre aérodynamique et le caractère soluble ou insoluble ont joué un rôle significatif sur la déposition et la rétention pulmonaire. Les résultats de cette recherche contribueront d’une part à la compréhension du rôle de la taille des particules et de la forme chimique dans la toxicité du Be. Combinés à d’autres résultats, ils contribueront aussi à guider les actions de prévention relativement à l’exposition au Be, incluant éventuellement la révision de la valeur limite de l’exposition et possiblement l’établissement de valeurs limites en fonction de la forme chimique et de la taille des particules._x000D_ Abstract_x000D_ In recent years, many authors have questioned the level of protection that the accepted threshold value for beryllium (Be) and its salts provides to workers. This value is the TWAEV (Time-Weighted Average Exposure Value, sometimes simply called the TWA), and referred to in Québec as the VEMP; the TWA (Time-Weighted Average) is equivalent to the TLV (Threshold Limit Value) developed by the ACGIH (American Conference of Governmental Industrial Hygienists). The predominant effects associated with beryllium suggest that the risks are based on its speciation. Moreover, it appears that its fine particles constitute the part that is of interest in the occurrence of such effects. The objective of this research is to evaluate the toxicity of Be according to its chemical form and particle size._x000D_ For each chemical form covered by this study (Be, BeO, BeAl), toxicity was assessed following sub-chronic exposure, through oro-nasal inhalation, to either fine or total particles. For this purpose, an animal model (mouse) was used. A total of 245 mice were used. They were divided into seven groups, each of which had 35 mice. One group served as a control group, while each of the other six were exposed to either fine particles or total particles for each of the three chemical forms of Be. The duration of exposure for each group extended over a three-week period consisting of 15 days of exposure (5d/w, 6h/d). At the moment of sacrifice, multiple tissues (lung, spleen, liver and kidney) and blood samples were collected and immediately frozen until they were analyzed to determine their Be content. In addition, certain lungs and spleens were analyzed to evaluate immunological sensitivity and lung inflammation._x000D_ Many correlations were established between the tissue concentrations of Be and effects normally observed in workers following exposure. The histological sections showed that mice exposed to Be had levels of lung inflammation similar to those observed in patients with chronic beryllium disease (CBD). The findings also show an association between particle size, lung concentrations, lung inflammation, production of certain cytokines and the expression of certain lymphocytes._x000D_ The effects also depended on the chemical form of Be. Thus, Be metal and BeO were thought to be the most toxic forms. It became clear that aerodynamic diameter and solubility or insolubility played a significant role in deposition and lung retention._x000D_ The research findings will contribute to an understanding of the role of particle size and chemical form in Be toxicity. Combined with other findings, they will also guide preventive action relating to Be exposure, and may include a revision of the threshold limit value and the establishment of limit values based on the chemical form and particle size.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".