2015-12-17 09:07:16
In European regulations, the term asbestos refers to 6 minerals naturally present in several types of rock: on the one hand a serpentine, chrysotile, and on the other hand, five amphiboles, actinolite-asbestos, anthophyllite- asbestos, tremolite-asbestos, amosite and crocidolite.
Update on asbestos fibers and cleavage fragments
In the natural environment, actinolite, but also other amphiboles, can occur in different morphologies, called asbestiform or non-asbestiform. Non-asbestiform minerals and their asbestiform counterparts (ie actinolite and actinolite-asbestos) have the same chemical composition but differ in their mode of growth in rocks. Currently, only the asbestiform morphologies of the 5 aforementioned amphiboles and chrysotile are subject to regulation.
When a mechanical stress is applied to non-asbestiform minerals, such as during the grinding of rocks extracted from quarries for the manufacture of aggregates for example, these can split and release more or less elongated particles called “cleavage fragments”. . These particles can sometimes be counted as asbestos fibres, in particular because of their dimensional characteristics.
The Agency’s work
Following the identification of actinolite-asbestos fibers and actinolite cleavage fragments in road asphalt aggregates (rocks), ANSES was notified by the ministries responsible for health, labor and the environment to carry out an expert report on occupational exposure to cleavage fragments, their potential health effects and analysis methods in the air and materials. The cleavage fragments of interest are those likely to be counted as asbestos fibers during air analyses, i.e. cleavage fragments of minerals homologous to regulated asbestos, namely actinolite, anthophyllite, tremolite, grunerite and riebeckite having the dimensions of a fiber defined by the World Health Organization (length greater than 5 µm, diameter less than 3 µm, aspect ratio greater than 3) and therefore likely to be inhaled. In addition, data relating to amphiboles for which data of concern on health exist and having a chemical composition very close to that of some of the 5 amphiboles mentioned above were also studied.
In general, ANSES emphasizes the difficulty in identifying health data specific to cleavage fragments, due to co-exposure to asbestiform fibers or other respiratory risk factors, but also to the lack of data providing information on the dimensions or morphology of the mineral particles studied. In addition, the available studies do not discuss parameters other than dimensional criteria that may have an influence on the toxicity of these particles, such as biopersistence, contaminants, surface reactivity, etc.
In view of the data analysed, ANSES concludes that it is not possible to exclude a health risk linked to exposure to cleavage fragments of actinolite, anthophyllite, tremolite, grunerite and riebeckite. Furthermore, some data indicate health risks similar to those induced by asbestos for chemical species not currently subject to regulation: winchite, richterite, fluoro-edenite and erionite.
Finally, it was not possible to identify exposure data specific to cleavage fragments, due in particular to co-exposure with asbestos fibers, and analytical difficulties in formally distinguishing them from asbestos fibers. .
The Agency’s recommendations
In view of its conclusions, ANSES recommends changes to the current regulatory framework in order to take into account the health effects associated with actinolite, anthophyllite, tremolite, grunerite and riebeckite cleavage fragments, when they have the dimensions of a fiber as defined by the WHO.
Furthermore, given the health effects similar to those of asbestos demonstrated for winchite, richeterite, fluoro-edenite and erionite, ANSES also recommends that the regulations in force be extended to these four species mineral.
Beyond that, ANSES lists recommendations for the conduct of work likely to cause exposure to these mineral particles in the quarry and road construction sector. Other areas, such as the construction and public works sector in a natural environment or using materials manufactured from natural materials, may also be affected by this problem. Before starting this type of work, it appears necessary to carry out site maps to identify the presence of particles.
Finally, in terms of metrology, ANSES offers recommendations aimed at improving the sampling and analysis of mineral particles in natural materials, and at standardizing laboratory results.
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