Quantification of short and long asbestos fibers to assess asbestos exposure: a review of fiber size toxicity.

International audienceThe fibrogenicity and carcinogenicity of asbestos fibers are dependent on several fiber parameters including fiber dimensions. Based on the WHO (World Health Organization) definition, the current regulations focalise on long asbestos fibers (LAF) (Length: L ≥ 5 μm, Diameter: D  3). However air samples contain short asbestos fibers (SAF) (L < 5 μm). In a recent study we found that several air samples collected in buildings with asbestos containing materials (ACM) were composed only of SAF, sometimes in a concentration of ≥10 fibers.L-1. This exhaustive review focuses on available information from peer-review publications on the size-dependent pathogenetic effects of asbestos fibers reported in experimental in vivo and in vitro studies. In the literature, the findings that SAF are less pathogenic than LAF are based on experiments where a cut-off of 5 μm was generally made to differentiate short from long asbestos fibers. Nevertheless, the value of 5 μm as the limit for length is not based on scientific evidence, but is a limit for comparative analyses. From this review, it is clear that the pathogenicity of SAF cannot be completely ruled out, especially in high exposure situations. Therefore, the presence of SAF in air samples appears as an indicator of the degradation of ACM and inclusion of their systematic search should be considered in the regulation. Measurement of these fibers in air samples will then make it possible to identify pollution and anticipate health risk

Corps asbestosiques et fibres d'asbeste dans les échantillons pulmonaires: utilisation comme marqueurs d'expositions professionnelles ou environnementales ;[Thèse annexe :Importance de la migration des fibres d'asbeste vers la plèvre pariétale dans la pathogenèse]

Doctorat en sciences médicalesinfo:eu-repo/semantics/nonPublishe

Analyses minéralogiques et cancers thoraciques: intérêt et limites.

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Asbestos exposures, asbestos-related diseases and fiber analysis in lung samples

Use of asbestos is now banned in many industrialized countries, but health consequences are still expected for at least two decades. Moreover, exposure to asbestos currently continues in several emerging countries. Asbestos-related diseases are usually the consequence of occupational exposures, but cases occurring from para-occupational, bystander or intra-mural exposures were also reported. In rural areas of several countries, fibres naturally occurring in local soils are responsible for a high incidence of asbestos diseases. Health effects of asbestos include malignant and non-malignant lesions of the lung and pleura, and more rarely peritoneum. It is often necessary to assess past exposures to asbestos for clinical, epidemiological, occupational health or even legal purposes. The difficulties and uncertainties associated with the use of occupational histories, job exposure matrixes or calculations from specific exposure databases have led to investigate the capabilities of fiber analysis in lung samples. Key points related to this topic will be reviewed here. Guidelines about technical aspects of fiber analysis and rules to interpret results were published by a workgroup of the European Respiratory Society (1). Evidence of exposure can be obtained by demonstrating elevated levels of asbestos bodies or fibres by light or electron microscopy in samples of lung tissue, bronchoalveolar lavage fluid or sputum. Relevant data are sought about the fiber types present, their amounts, their sizes, composition and crystalline structure and about their importance as aetiological agent. The measured fiber burdens integrate both phenomena of lung deposition and clearance. Compared to amphibole asbestos, chrysotile has a much lower biopersistance and evaluation of past exposures to this variety of asbestos by analysing lung samples is difficult. Interestingly, chrysotile elementary fibrils are morphologically similar to sepiolite and attapulgite fibrils. There are different dose-response relationships between lung parenchyma and pleura in response to asbestos exposure. The highest cumulative exposures and hence pulmonary asbestos bodies and fibres levels are found in asbestosis. Lower levels, corresponding sometimes to very low cumulated exposure, are usually expected in mesothelioma and in pleural plaques. However, it must be stressed that bronchoalveolar lavage fluid and lung tissue analyses are markers of alveolar and parenchymal retention of fibres, but do not reflect directly the accumulation of fibres in the parietal pleura which is very heterogeneous. (1) De Vuyst P, Karjalainen A, Dumortier P, Pairon JC, Monso E, Brochard P, Teschler H, Tossavainen A, Gibbs A (1998). Guidelines for mineral fibre analyses in biological samples: report of the ERS Working Group. European Respiratory Society. Eur Respir J;11:1416-1126.info:eu-repo/semantics/nonPublishe

Translocation des fibres inhalées et pathogenèse des affections pleurales

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Inhaled non-fibrous particles in lung samples

Respirable particles from environmental or occupational air pollution are continuously inhaled and part of them is retained in the lungs over time. Accumulated particles may induce various respiratory diseases (pneumoconiosis, lung granulomatosis, alveolar proteinosis,). Most of these diseases are dose related. Since it is often difficult to obtain a thorough exposure history from the patients, mineralogical analysis of the particles recovered from their lungs can be used to get individual estimates of previous exposures. Compared to the numerous studies about asbestos burden in lungs, systematic data about the non-fibrous mineral particles (NFPs) contained in lung samples (bronchoalveolar lavage fluids (BAL) or lung tissue (LT)) are currently scarce. This is perhaps due to the complexity and diversity of the analytical methods (light and electron microscopy, x-ray diffraction) required to analyse particles in the submicron range and to the lack of specific markers for routine analysis. Other obstacles are the variety of particles to be analysed and the existence of a background burden of NFPs in the lungs of everyone which may interfere with the particles directly related to the exposure or disease under investigation. Our experience with NFPs analysis will be summarized and compared to the data available from the literature. From one to over 20 different particle types can be detected in lung samples by analytical transmission electron microscopy. The most frequent are silica, silicates (including clay minerals), iron compounds and titanium oxide. Particle sizes are log normally distributed. Geometric mean diameter range from 0.21 to 1.13 µm. Considering the influence of particle type on particle size, the following gradation can be established; Ø metallic compounds < Ø non lamellar silicates (silica, feldspar, siliceous flyash,) < Ø lamellar silicates (kaolinite, illite, mica, talc, chlorite). NFPs concentrations range from X*104 to 107 P/ml in BAL and from 109 to 1010 P/gm dry tissue in LT. Reference levels are obtained by analysing samples for individuals without particular dust exposures. An “abnormal” result can help to confirm the diagnosis of a suspected particle-induced lung disease. In the absence of detectable disease an abnormal mineralogical analysis result is in no way a proof of disease. Nevertheless, these individual situations need a follow up, since the probability of developing a pathological reaction to inhaled dusts increases with time. The absence of mineralogical abnormalities is an argument against particle-induced lung disease and further investigations are needed to obtain a diagnosis. By helping to the etiological diagnosis of a lung disease, these analyses may have clinical implications in case treatment is available and social benefit if disease can be compensatedinfo:eu-repo/semantics/nonPublishe

Object-marking, a bridge between light and analytical electron microscopy for particles characterization.

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Place des analyses biometrologiques dans l'evaluation retrospective des expositions a l'amiante

Despite intrinsic limitations due to differences in the biopersistence of the various asbestos types, in the definition of control populations and in analytical techniques used by the laboratories, mineralogical analysis of biological samples is useful in the assessment of past exposure to asbestos. It provides additional information to occupational and environmental questionnaires, particularly when exposure to asbestos is doubtful, unknown or forgotten by a subject. Results should be interpreted taking into account clinical information. A positive result does not mean existence of asbestos- related disease. A negative result does not exclude previous significant asbestos exposure, clearly identified by an occupational questionnaire (particularly for exposure to chrysotile). Threshold values indicative of a high probability of previous asbestos exposure have been established for bronchoalveolar lavage fluid (BALF) samples and lung tissue samples. Quantification of asbestos bodies by light microscopy is easy to perform. Sensitivity and specificity of this analysis towards the total pulmonary asbestos fiber burden is good. Therefore this analysis should be performed first. Mineralogical analysis in BALF or lung tissue should be considered only when sampling is supported by diagnostic or therapeutic implications.SCOPUS: cp.jinfo:eu-repo/semantics/publishe

Place des analyses biométrologiques dans l'évaluation rétrospective des expositions à l'amiante.

Despite intrinsic limitations due to differences in the bio-persistence of the various asbestos types, in the definition of control populations and in analytical techniques used by the laboratories, mineralogical analysis of biological samples is useful in the assessment of past exposure to asbestos. It provides additional information to occupational and environmental questionnaires, particularly when exposure to asbestos is doubtful, unknown or forgotten by a subject. Results should be interpreted taking into account clinical information. A positive result does not mean existence of asbestos-related disease. A negative result does not exclude previous significant asbestos exposure, clearly identified by an occupational questionnaire (particularly for exposure to chrysotile). Threshold values indicative of a high probability of previous asbestos exposure have been established for bronchoalveolar lavage fluid (BALF) samples and lung tissue samples. Quantification of asbestos bodies by light microscopy is easy to perform. Sensitivity and specificity of this analysis towards the total pulmonary asbestos fiber burden is good. Therefore this analysis should be performed first. Mineralogical analysis in BALF or lung tissue should be considered only when sampling is supported by diagnostic or therapeutic implications.Comparative StudyEnglish AbstractJournal ArticleReviewSCOPUS: cp.jinfo:eu-repo/semantics/publishe

Mineralogical Analysis of Lung Samples

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