Talc is a mineral with the chemical formula Mg3Si4O10(OH)2. Talc particles generally occur in the form of platelets but can more rarely be found as long, thin fibres, which thus form fibrous talc. The chemical composition of talcs and the presence of associated minerals depend on the type of the original rock and the nature of the geological transformation that formed them. Therefore the chemical composition of talc deposits and the presence of other minerals and mineral fibres (at differing concentrations) can vary within single deposits as well as within relatively close geographical areas.
Following several reports concerning the use in the workplace of an epoxy coating manufactured from talc that was suspected of containing asbestos fibres, the Agency was asked in March 2009 to evaluate the mineral fibre and cleavage fragment composition of talcs, as well as the health risks related to their use. The study addressing these questions has now been published and focuses on three main areas:
Presence of asbestos fibres in talcs
The studies conducted by the Agency show that, depending on the different production deposits from which it originates, talc can contain other fibrous or non-fibrous minerals. In particular, it can contain mineral fibres with chemical structures that are comparable to those of the six mineral fibres that are classified as asbestos fibres according to the regulatory definition*.
Knowledge of the mineral structure and the composition of the different talc deposits in the world is incomplete, and only some European and North American talcs have been properly studied. The presence of asbestos fibres cannot be ruled out in talcs, whether they are asbestiform or non-asbestiform. In addition, the cleavage fragments, which come from breaks in the mineral blocks and which are found in crushed and ground talc, can therefore come either from talc fibres, or from asbestiform or non-asbestiform mineral fibres.
Analytical methods, as recommended by the regulations for the determination of asbestos fibres, are not always capable of differentiating asbestiform mineral fibres from their non-asbestiform counterparts. There is currently no reliable and reproducible method for differentiating cleavage fragments from asbestiform or non-asbestiform fibres in a simple manner and in all cases.
Occupational exposure to talc
Talc is used in many areas of industrial activity. Different grades of talc, which have physical characteristics that can be more or less specific to certain industrial applications, are available on the market.
Occupational exposure to talc dust occurs during mining operations, grinding, bagging and loading of talc. It also occurs when processing and using the talc. This is especially the case in the rubber industry and with the manufacture of ceramics, paints, enamels and various other products. Exposure usually involves a mixture of talc and mineral dust of variable composition. Quartz and mineral fibres (asbestiform or non-asbestiform) are common contaminants.
The gross occupational exposure levels in mines and mills are relatively well known. In most cases, however, exposure characterisation often remains inadequate and vague, and there is usually no mention of the mineralogical structure of the talcs studied. In particular, there is no information available on the potential presence of tremolite, asbestiform or non-asbestiform, in the talc deposits. The exposure values in other sectors (excluding mines and grinding mills) are very limited and cannot be used for assessing exposures or evaluating health risks.
Health effects of talc
The Agency’s assessment confirms the health data relative to the effects of talc exposure on health, particularly the non-carcinogenic (talcosis) effects, which occur after long-term exposure in particular.
With regard to the potential carcinogenic effects of talc containing non-asbestiform mineral fibres or cleavage fragments, the epidemiological and toxicological data are currently insufficient for issuing an opinion on this risk.
Considering these different factors, the Agency recommends:
- accurately mapping the various talc deposits in the world with identification of the other mineral fibres that they are likely to contain, and ensuring the traceability of the talcs, from their extraction to their marketing in France;
- that, given the absence of reliable and validated information on the origin of talcs, which would enable confirmation as to the absence of asbestiform fibre contamination, research should be conducted on the presence of actinolite, tremolite and anthophyllite (ATA) fibres in talcs or in products containing talc that are marketed in France, in accordance with the regulatory methods concerning asbestos research in materials;
- implementing asbestos regulatory procedures if ATA fibres are found in products containing talc, whether they are being marketed or have already been put to use;
- implementing asbestos regulatory procedures in the workplace if amphibole ATA fibres are found in the air inhaled by workers exposed to talc or to products containing it;
- lastly, developing analytical methods and studies on the health effects both to differentiate asbestiform fibres from non-asbestiform fibres, and to improve knowledge of the health effects of the different non-asbestiform fibres.
* What is asbestos?
The name “asbestos fibre” refers to six mineral fibres, which are distinguished by their so-called “asbestiform” shape, i.e., having the shape of asbestos. The term “asbestiform” refers to a morphology resulting from natural and one-dimensional crystallisation of a mineral producing fibres with a hair-like appearance. This morphology gives the mineral special characteristics, including a high aspect ratio (length/diameter ratio) and increased mechanical properties (e.g., strength, flexibility and durability). In addition, there are homologous fibres with the same chemical composition as asbestos fibres, but which do not develop one-dimensionally with long fibres, but rather two- or three-dimensionally, resulting in a more extensive morphology.
The six types of asbestos fibres are divided into two families: the serpentines, which only contain one type of fibre (chrysotile), and the amphiboles, which combine five types of asbestiform fibres: actinolite, anthophyllite, tremolite, amosite and crocidolite. To distinguish them from their “non-asbestiform” counterparts, these names are followed by the term “asbestos”.