2013-01-17 08:44:36
In 2003, a publication challenged the scientific community on the possible pathogenicity linked to short asbestos fibers. These new data justify various questions regarding the relevance of taking into account the risks linked to asbestos in the regulations. In this context, the Agency was contacted in February 2005 by its supervisory ministries in order to carry out an assessment of the risks associated with short asbestos fibers (FCA: length L <5 microns, diameter d <3 microns and ratio L /d = 3). A complementary mission letter, requesting to extend the scope of investigations to fine asbestos fibers (FFA: L = 5 microns, d < 0.2 microns and L/d = 3), was sent to the Agency on May 16, 2007.
After preliminary analysis of the publication (expertise of the content and the potential impact of the publication at the origin of the referral), the work mainly focused on the following points:
- assess the toxicity of short asbestos fibers and fine asbestos fibers;
- characterize the particle size distribution of the fibers according to the circumstances of exposure (general or professional population) and the nature of the asbestos (chrysotile or amphiboles);
- assess the risks to human health linked to exposure to short asbestos fibers and fine asbestos fibres.
The evaluation should also make it possible to assess the relevance of the regulatory provisions in force, in particular the current thresholds and the absence of dust measurements for short asbestos fibers and fine asbestos fibers.
Description of the method
In this context, the National Institute of Health and Medical Research (Inserm) was mandated by the Agency to carry out a bibliographic review of current data concerning the influence of the dimensional parameter on the toxicity of asbestos fibers.
The Agency also contacted the laboratory for the study of inhaled particles (LEPI – city of Paris) and the Robert-Sauvé Research Institute in Occupational Health and Safety (IRSST – Quebec) in order to acquire knowledge on the particle size distribution of asbestos in the different types of environments (indoor or outdoor environment, nature of the materials present, professional population), in addition to a review of the literature carried out by the working group.
Furthermore, in order to compare expertise and discuss the work, then the proposals of the working group, the Agency organized, at the request of the experts, two days of exchanges (September 17 and 18, 2008) in Paris with representatives from the Agency for Toxic Substances and Disease Registry (ATSDR), the National Institute for Occupational Safety and Health (NIOSH), the Environmental Protection Agency (US-EPA), the Health & Safety Laboratory (HSL-UK) and from the Finnish Institute of Occupational Health (FIOH).
Principle results
The analysis of various studies has not made it possible to rule out with certainty the existence of carcinogenic properties of short asbestos fibers. In the hypothesis of toxicity of short asbestos fibers, it would certainly be lower than that of long fibers. The data acquired during this expertise concerning the particle size distribution of asbestos fibers, whether for the general or professional environment or near natural outcrops, underline the preponderance of short asbestos fibers associated with high concentrations.
For the general environment, samples containing only short asbestos fibers were associated with the release of materials or products containing asbestos located nearby, thus reflecting the degradation of the material. Ultimately, it is not possible, in the current state of knowledge, to construct a quantitative assessment of health risks linked to the entire particle size distribution of asbestos fibers or to short asbestos fibers alone.
For fine asbestos fibers, toxicological and epidemiological data confirm the existence of a carcinogenic effect associated with the inhalation of this particle size class. Analysis of the particle size distribution data for all environments indicates that fine asbestos fibers represent a small part of the distribution.
Conclusion of the expertise
Concerning fine asbestos fibers, the results of the expertise confirm the interest in measuring them within the framework of general environmental regulations and the experts agree on the need to recommend taking this particle size class into account in regulations in the professional environment.
In view of the expertise carried out concerning short asbestos fibers, and despite the numerous unknowns requiring the acquisition of additional data, it must be emphasized that the dangerousness of short asbestos fibers is not excluded and that this particle size class is systematically present, and in significant proportions, during metrological measurements. Moreover, the quantification and identification of short asbestos fibers can contribute to the diagnosis of environmental pollution from a potential source.
For the general environmentshort asbestos fibers might be used in regulations as indicator to demonstrate the degradation of materials or products containing asbestos.
For the professional environmenttaking short asbestos fibers into account in epidemiological studies might make it possible toimprove knowledge on dose-effect relationships and possibly reduce the inaccuracies of existing models for quantitative health risk assessment.
Recommendations from collective expertise
In view of the results of the collective expertise published in 2009, the Agency considers that a review of the regulations, both for the general and professional environment, is justified and proposes to rely on the following considerations in terms of management of health risks linked to asbestos:
- revision of standardized metrology methods, retaining analytical transmission electron microscopy for all environments;
- revision of regulatory thresholdsboth for the general and professional environment, for fibers of length greater than or equal to 5 µm.
A proposal for a VLEP for asbestos and an associated metrological method is the subject of a detailed and argued sheet by the Agency’s CES VLEP.
- extension for the general environment, when the regulatory visual examination has diagnosed degradation of the material, dust measurements for all materials or products containing asbestos, in particular asbestos-containing floor tiles, asbestos cement, etc. ., including a specific measurement of short asbestos fibers to assess the degradation of the material.
The extent of the recommendations and the inclusion of new standards such as short asbestos fibers reinforce the need for careful information and communication with stakeholders.
Furthermore, the Agency recommends supplementing knowledge on the influence of the dimensional criterion of fibers for the assessment of health risks linked to asbestos, particularly in the area of:
- toxicology, with the acquisition of new experimental data on short asbestos fibers;
- exposure assessment, with the acquisition of data on the particle size distribution of asbestos fibers, for:
- the professional environment;
- the general external environment with a view to having samples more representative of the national situation and more recent (particularly following the ban on asbestos);
- the release of fibers from materials or products containing asbestos into the general indoor environment.
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