Man-made mineral fibres (MMMF)

Man-made vitreous (silicate) fibres, also called man-made mineral fibres (MMMF) are a group of materials that include refractory ceramic fibres (RCF), special-purpose glass fibres, glass wool, rock wool, slag wool and continuous glass filaments. MMMFs are chemical fibres defined by various applications mainly in sound or heat insulation. Therefore, they are mainly used to control heat loss, absorb acoustic energy, filter impurities in gases and liquids, reinforce other materials and control condensation.

Their insulating properties mean that some of these fibres may replace asbestos in certain applications. Accordingly, questions have arisen as to their potential impact on the health of people exposed to them.

In this context, in July 2004, the Agency received a solicited request within the framework of the French National Environment & Health Action Plan (PNSE), to specify MMMF applications and assess the resulting exposure of both the general population and that of workers. It specifically focused on: 

• specifying past and present applications of these fibres, particularly how they had been used, how accessible they are, what becomes of them after use, technical characteristics and how fibrous materials alter due to aging over time. The study was also to identify the additives in these fibres, technical developments and the availability of substitute products or processes that are non-hazardous or less hazardous, indicating the frequency of use of these alternatives; 
• assessing exposure of the general and occupational populations. 

Moreover, when work on this request was carried out, it shed light on applications and uses of man-made mineral fibres, thereby avoiding confusion with other fibres, particularly asbestos.

The Agency asked the Expert Committee (CES) on Assessment of the risks associated with air environments to conduct this assessment in response to the solicited request. A working group reporting to the CES was formed for this purpose. This work resulted in two reports, the first on RCFs and special-purpose glass fibre types E and 475, the second concerning other members of the MMMF group, i.e., mineral wools and continuous glass filaments.

Results and recommendations

The first report, published in April 2007, on RCFs and special-purpose glass fibre types E and 475, contained an overview of data published in the literature and collected from the main MMMF producers, processors and users. Both of these types of fibres were deemed a priority given their international classification as possibly carcinogenic to humans (IARC  Group 2B for RCFs and special-purpose glass fibre types E and 475). 

This report sought to answer the questions raised by the request, particularly on the technical aspects associated with the characteristics and uses of these fibres, as well as to assess the exposure of the general and occupational populations, and the possibility of replacing them with less hazardous materials. It was adopted by the CES on Assessment of the risks associated with air environments during its meeting on 2 February 2007. 

The Agency, in this report’s conclusion, issued an opinion giving a series of recommendations to improve traceability and knowledge, and to reinforce prevention.

The second report, published in November 2008, was a continuation of the previous one and deals with other MMMF categories, i.e. mineral wools and continuous glass filaments. 

Mineral wools and continuous glass filaments were classified in IARC Group 3 “Not classifiable as to its carcinogenicity to humans”. They are exempted from classification as a carcinogen by the European Union if they fulfil the criteria of the European Directive 97/69/EC. Mineral wools are still classified as skin irritants. 

The Agency’s report identified issues related to the characteristics and traceability of the products and found that the data are limited for exposure of the general population to mineral wools and continuous glass fibres. The exposure of workers handling these materials was slightly better documented. 

The Agency, in this report’s conclusion, issued an opinion giving a series of recommendations specifically aimed at improving traceability and knowledge of the products in order to better characterise exposure of the general and occupational populations, and to establish preventive measures.