I think all of us in the asbestos industry are familiar with the above term, but nowhere in the published guidance is the phrase actually defined. We are indeed told that exposure to asbestos of more than 0.6 fibres per cubic centimetre over a 10-minute period CANNOT be regarded as sporadic, low-intensity and therefore work where such exposure was likely to occur would require a licence; however this does not define what the phrase means, only what it doesn’t!
What about work with asbestos cement panels on a regular, daily basis? Is this sporadic? Not in my book.
“Most work with asbestos cement will not require a licence”, or so we are told. Yet go and check out the table of expected exposure concentrations in HSG 189/2 and what do you find? Only that the majority of such expected exposures are above the Control Limit (if carried out for long enough of course)!
“Risk is dependent upon dose” we are also told – and yet we also know that the chances of developing mesothelioma are notoriously dose independent. Many people have contracted this horrid disease after only brief exposure to what may well have been comparatively low fibre concentrations.
So who do we believe? What do we really need to do to protect ourselves and others?
I read somewhere that the comparative risk (for equivalent exposure) of developing mesothelioma from the various common asbestos types was 1 to 100 to 1000 for chrysotile (white); amosite (brown); and crocidolite (blue) respectively. In other words, we would need 1000 times the exposure to white asbestos fibres to equal the risk from exposure to blue asbestos. But is this correct? Where are the actual figures to show it?
Not being an epidemiologist, the situation as I see it (and this is probably the case for a lot of other people too) is that the waters are so muddied on this issue that it is best to assume that no exposure to asbestos is acceptable, no matter how low. Yes, exposure to chrysotile asbestos isn’t likely to be as risky but we’re much more likely to be exposed to dust and fibres from white asbestos anyway (perhaps the likelihood ratio for encountering white: brown: blue asbestos is almost the same as the mesothelioma risk ratio, thus cancelling out any difference? Just a thought!
I am often asked by asbestos courses delegates, “What is the chance of someone developing an asbestos disease if exposed to fibres near to the Control Limit on a daily basis?” This is a good question and we should be able to answer it properly. Of course it depends on the type of asbestos (see above) but it’s extremely difficult to quantify. Yes, it’s easy enough to count the bodies so to speak but to try to relate the mortality rate to the exposure levels 30 or 40 years ago is a bit more difficult… just not enough reliable exposure data is available. Only the Central Electricity Generating Board produced any really meaningful statistics, but this is a very small pool of data from which to extrapolate risk. We do know that the exposure was high though and much, much higher than most exposures today. Yet we still here of teachers developing mesothelioma following exposure to dust emanating from holes in insulating board panels made by drawing pins!
In the absence of definitive answers to the many questions still being asked about asbestos, let us all remember: Asbestos (in all its forms) is a proven human carcinogen with the potential to kill. It must be treated with caution and respect, and we must take all steps we reasonably can to prevent exposure to fibres of any type.
Alex Nicoll CCP (Asb.), AFOH
Senior Consultant
