Originally Posted by: johnmurray

I fail to see what you are getting at

What I'm getting at is quite simple. If the air concentration in buildings even with damaged asbestos in them is lower than 0.0003f/ml and no-one has done any tests to show what the long term exposure is from domestic scale interation with asbestos then there remains no evidence whatsoever to support the presumption that removing damaged or friable asbestos from buildings is safer than leaving it where it is. I think that would be a pretty important thing to find out for the safety of the general public considering asbestos abatement is going to increasingly become the main source of asbestos release for them.

Given that asbestos manufacturing has long been banned, the only people nowadays who would theoretically be in a position to make money from misinformation are asbestos abatement firms (whose interests are best served by promotong removal) and lawyers (whose interests might be best served either way depending on who they represent). Not to mention the deplorable way in which air fibre measurements which could be being used to help inform researchers are treated as "commercially sensitive data" by some of these firms (yes, I have personal experience of this). To my mind that gives a fairly equal proportion of potential for industries "to get rich over the bodies of its workers.... " or the public, on both sides of the debate, not just those trying to play down the risk, but those trying to inflate them. That's why I believe the only way forward is proper evidence. The whole reason why asbestos got banned in the first place (eventually) is because the asbestos firms could no longer deny the sheer weight of evidence. Same with smoking in public places, lead in petrol, etc.. Evidence is everything with these issues and I'm appalled at the complete lack of it for modern exposures and abatement practices.

http://www.hse.gov.uk/research/rrpdf/rr696.pdf

Is one example of studies undertaken on the exposure risks from domestic and environmental mesothelioma

If asbestos materials are damaged, it can be assumed fibres are being released, during the removing process, with the exception of non-friable materials (non-freely fibre releasing), asbestos enclosures fitted with HEPA filters and correct removal techniques, would control the release of asbetsos fibres and prevent further disturbance and deterioration of the asbestos and future higher exposures from occuring.

Asbestos abatement should not increase exposure to the public to asbestos fibres.  If deteriorated asbestos is constantly releasing fibres (due to even the movement of air over the surface), removing of the material (again using propoer abatement techniques, enclosures, HEPA filters etc) should result in a decrease of asbestos fibres in the air and reduced exposure / risk to the occupants.

After such removal works are undertaken, strict clearance procedures are followed to demonstrate safe re-occupancy

1. The air inside a building, is not a closed system, windows, doors all open and close but in general the whole atmosphere inside a house (even by design = air bricks) is replaced quite frequently - based on several factors, design, temperature, age and user influences.  There are some exceptions and examples when it can be seen poor ventilation within a building requires mechanical assistance - for example basements in areas with high natural radon.

2.  Im not sure you are comparing like for like in your ratios of deaths and HSE increased risk.  200:700,000 is the ration of asbestos related deaths to total deaths.  Where as the HSE acceptable risk is based on 1 death per 10:000 persons exposed to such a risk: "risk of death to any individual of 1 in 1000 per annum for workers and of 1 in 10 000 per annum for the public who have a risk imposed" http://www.hse.gov.uk/risk/theory/r2p2.pdf

So you would have to make a comparison by using the 200 figure in a ratio against the total number of UK residents that year

3.  Taking the statement in bold - No buildings regardless of the condition of ACM have a internal concentration greater than 0.0005f/ml. Perhaps based upon answer in 1. are you assuming the clearance level of 0.01f/ml - often the detection limit level, usually within an enclosure - so after enclosure removal there would also be significant dilution) would be ubiquitous throughout the house after asbestos removal?

4.  One recent example study I have found, which in my opinion supports the removal (if left and disturbed risks of exposure remain): https://academic.oup.com/annweh/article/60/1/27/2196148/Airborne-Asbestos-Exposures-from-Warm-Air-Heating?searchresult=1 whereby "four of the five classrooms sampled gave measurable concentrations of amosite by TEM during simulated disturbance conditions. The highest concentration of amosite fibres countable by PCM was 0.0043 f ml −1 with a pooled average of 0.0019 f ml −1" whereby the background without disturbance (which didnt involve any damage) was "below the LOQ <0.00005 f ml".  Though you could counter argue, leaving it in place would also not result in exposure (but this assumes it will not be damaged or disturbed) and all buildings at some point in time will require the asbestos to be removed regardless (depending on the age and condiiton of the building as cities are regenerated and houses rebuilt)

Some really helpful ideas, thanks.

1. Are you suggesting that more fibres are removed by air changes than settling rates alone would suggest? For my model I'm using settling rates for amosite of 0.3mm/sec and air change rates of 1ACH (average of domestic properties), but for an activity at about a meter high this doesn't allow the fibres enough time in the air to experience any significant losses, basically (depending on how much turbulence you add) about half the fibres could be removed by air changes before settling. Whilst this might sound like a lot, it is insignificant if the remaining half stay in the building for the next 30 years only removed at K factors for disturbance of dust of 1e-5. To get rid of these remaining fibres by air movement within a reasonable time scale we'd have to postulate much higher settling times, but that, in turn would make each interaction much less risky as the air fibre concentration would be reduced to background within hours.

2. Yes, there is a presumption in my comparison that in 1968, the whole population would be exposed to some sort of asbestos incident of a similar scale to that which we might envisage nowadays in a domestic setting. I'm not sure that this is an unwarranted presumption though, especially when you consider how much of the population would have been exposed to much higher levels than that. I think, if anything the comparison is likely to over estimate exposure risk nowadays. Not only that, but it would be an exactly like for like comparison if you were to include having an asbestos survey or test done in the first place. In that scenario we would be comparing the combined risk of both encountering a piece of asbestos and being exposed to sufficient fibres to cause you harm. For this scenario the figures are indisputable because the outcome of both of those factors together is recorded in the mortality statistics and they show that in 1968(ish) that combined risk was 3:10,000. So presuming even a moderate drop in asbestos use the risk now must be less than 1:10,000 (the risk in this case being both encountering some asbestos and being exposed to enough fibres to do you harm) the HSE standards would suggest that one need take no action to counter that risk (i.e. one need not find out if a thing is asbestos at all because it is either very unlikely to be, or it is very unlikely to harm you if it is, it must be one of those two otherwise more non-occupational deaths would turn up in the mortality statistics).

3. Partly, yes. I was also considering reassurance testing which would consider the whole building but also depending on the size of the enclosure a dispersal to the whole building could involve as little as a quarter reduction (say a whole room in a four room house was enclosed), maybe a tenth at most so 0.01 becomes 0.001 presuming the clearance testers even did their job correctly, which is still double the exposure the building was in all likelihood at before the removal.

4. Thanks for the link, I'm not sure if I'm reading this right but it does seem to be saying that for AIB in the ceiling plenum, in two out of three cases there was no measurable increase from background (which in these schools was even lower at 0.00005f/ml) and in one case levels rose to 0.002f/ml average. Doesn't that mean that in neither case could removal demonstrate a lower air concentration than just leaving it and for any given l contemplating such action there is a two out of three chance of removal making matters worse? If that's the case for an entire ceiling made out of AIB with forced air being blown over it then where does that leave my model risk assessment for finding a small piece of damaged AIB in a domestic property, the chances of harm from just leaving it must be astronomically small, such that the chances of increasing exposure by some accident or poor workmanship during removal must surely be much higher. Am I reading this wrong?

Well, I'm not sure where the rest went but a few found their way into my left lung.  I'm not to happy about the situation but considering that the problem was noted before 1900 I feel a little P***** off that the problem was left to run riot by various people in positions of power.  To them it's 'Thanks folks' from one 16 year old apprentice electrician back in '69!!!

Originally Posted by: Bob Hansler

Well, I'm not sure where the rest went but a few found their way into my left lung.  I'm not to happy about the situation but considering that the problem was noted before 1900 I feel a little P***** off that the problem was left to run riot by various people in positions of power.  To them it's 'Thanks folks' from one 16 year old apprentice electrician back in '69!!!

I'm sorry to hear of your condition. The result no doubt of a lot of private firms putting profit before their duty of care and government unwilling to look at exactly what's happening. I'd like to think we've learnt our lesson, but with the only remaining threat being the disturbance or removal of asbestos in buildings, I can't help thinking we have exactly the same situation (albeit less severe), the whole event is being handled by a collection of private firms who (I see no reason to believe) will not just put profit before their duty of care again, unless the quality of humanity has changed since the 1960s and the bosses of these firms are just "better" people. At least the government seem a bit more willing this time round, but personally, I fear not sufficiently so.

Originally Posted by: johnmurray

http://www.hse.gov.uk/ab...010206/paper2annex2b.pdf http://www.hse.gov.uk/ab.../010206/paper1annex2.pdf May be of small interest

Thank you so much, the paper on drawing pins contains some data which is almost exactly what I'm looking for in my models. I'd read the summary published results of the drawing pin tests, but they were not nearly as exhaustive as this document. I will have to digest the data and put it into my models, I'm particularly intested in the experiment with the drill and cowl which they seem to imply will have picked up all the airborne fibres. Given the size of the hole (at least 100 billion potential fibres in volume) and only a few thousand airborne fibres picked up, this initially supports the theory that the discrepancy is indeed caused by a very low (0.000000001%) proportion of all possible fibres involved in any disturbance actually ending up of respirable size.

Still doesn't answer what happens to the rest though. They can't get broken up into respirable sized fibres as that would bring the building air concentration higher than the measurements taken. I can only presume they get swept/vacuumed and the tests showing that normal vacuuming doesn't work are flawed because they use artificially inoculated carpets etc, not ones resulting from real damage where most fibres are in agglomerated bundles and so more easily picked up.

The consequence of this theory though would be that the advice to remove damaged AIB that can't be encapsualted should depend heavily of the success rate of the industry. Even if we were to generously give it a 99% success rate (i.e only 1 in 100 jobs go wrong in any way, which is much better than the HSE report seems to show) you'd want to know that leaving the AIB in place was going to cause a risk 100 times greater than a botched removal job, otherwise your total risk from getting it removed exceeds your total risk from leaving it in place. I'm not sure these results support that theory as they seem to show that even drilling damage to AIB (which is quite substantial) releases a few thousand fibres of a dangerous size, which once distributed through a 10x10 office room would give air concentrations below the clearance level (which is the best even a perfect removal operation can promise, let alone a botched one), but without accurate data on the safety of the abatement industry I can't be sure.

Still, thanks again for digging those papers out for me, sometimes doing research one cannot see the wood for the trees.

Originally Posted by: johnmurray

I suspect the employee problem is less due to them not trusting the advice, as to them being lazy...in any case, it is an employers requirement to ensure they follow procedures.

Yes, that's basically what concerns me in my risk assessments. Conventional risk assessment procedures for asbestos in buildings seem to take into account pretty much the worst case scenario for leaving the material in place, but presumes the removal operation will be carried out perfectly with no other consequenses. If building workers can be sufficiently lazy/unaware/incompetant as to damage ACMs even if they are labelled as such, the so can the workers of asbestos abatement firms. As for the duty of care being with the employers, if the bosses of private companies cared about the safety of their workers we wouldn't be in this mess in the first place.