Most currently available MMMF products do not readily release airborne fibres and those fibres that are released are relatively thick and do not persist in the lung. MMMF can cause irritation of the skin and eyes and excessively dusty conditions may cause irritation to the upper respiratory tract. While most peoples' skin becomes resistant after a period of adaptation, some need to take precautions to protect their skin and a small number may have to move to other work. Extensive research into the possible carcinogenicity of MMMF has produced inconclusive results. However, it has been concluded that in view of some uncertainties, it would be prudent to assume high exposures might pose a risk of lung cancer in workers. All mineral wool fibres are classified for irritancy, but classification for carcinogenicity applies only to fibres of <6mm diameter - coarser fibres are not respirable. If evidence is available from specified tests indicating certain types of effect, then classification as a category 3 carcinogen will not be necessary. However, on a precautionary basis, if satisfactory data are not available for a specific mineral wool product it must be classified as carcinogen of category 3.
LEGAL REQUIREMENTS
The COSHH Regulations apply to all forms of MMMF. An exposure level has been set; inhalation exposure to MMMF should always be reduced to a level as low as is reasonably practicable and, in any event, the exposure level should not be exceeded. The COSHH assessment will include breaking down the work into its constituent tasks and identifying the workers involved in each, assessing the duration and level of exposure and planning the control measures to be used and identifying the level of control that is deemed to be reasonably practicable. Factors to be considered should include:-
- location - e.g. higher exposure in enclosed areas or working with mineral wool above head height.
- materials - type will affect likely level of fibre release
- duration of work.
In all but the simplest cases the assessment should be written down. Insulation, construction and removal activities can create relatively high levels which may exceed the limits if suitable precautions are not taken. Some examples of typical workplace exposures are given below as a guide only as to what can be achieved under good conditions. The average concentrations are for the time during which the process/activity is actually taking place and are not 8 hour TWA concentrations.
PROCESS/ACTIVITY Airborne fibre limit(MEL 8hrTWA) of 2fibres/ml) Total inhalable dust(MEL (8hrTWA) of5mg/m3)
Hand laying of mineral wool Less than 1 30
Blowing of mineralfibre into lofts Less than 2 30
Loose fill cavity wall insulation Less than 0.1 Less than 1
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