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THIS IS A PUBLIC LECTURE
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This is a lecture I give to interested groups in the building/legal/property industries.
It explains what asbestos is, what it does to you and where it is commonly found. It is based on experience in New Zealand.
For questions/ideas/surveys, contact me via e-mail at [email protected] or phone Auckland, NZ, 025 965 177
Keith Patterson
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What is it
The term asbestos covers fibrous minerals of six types, so the name covers different rocks. Both amphiboles and serpentines are represented, the common property being that they are silicates that have crystallised as fibres. It is this property that makes them an inhalation hazard, as they can be split along their length to give an extremely fine fibre of sub-cellular diameter. This contrasts to fibreglass and other man-made mineral fibres that break across their length when stressed, so they do not get thinner.
The term respirable fibre or asbestos fibre refers to a diameter of less than 3 micron, and is tied into a length to width ratio of at least 3 to 1. The temperature and pressure required to produce fibrous crystals can be read from a phase diagram, and if crocidolite is melted at normal pressure it will lose its fibrous properties and revert to a riebeckite. A common intermediate form is "tigers eye", an attractive striped mineral used in jewellery.
This fibre diameter can be compared to fibreglass insulation, where the diameter range of 5-9 microns is controlled to keep it above the respirable size; and the thickness of a human hair at 100 micron.
What does it do to you
Although much information has been gathered about the medical effect of asbestos, I have yet to see any data on the doses experienced by the people affected.
Exposure to any type of asbestos leads to the development of scar tissue in the alveoli of the lung, as the body encapsulates the foreign material. The fibres appear to be permanent inside their spot of scar tissue, and large doses will cause thickening of the lung tissue, retarding the gas exchange rate and hence lowering the efficiency of the lungs. This is a permanent condition like emphysema, and people with asbestosis run out of breath easily.
Other fibres with their larger size are trapped before they penetrate deeply into the alveoli and mainly carried up and coughed out. Fibreglass fibres cause the same scarring reaction in the lung as they are attacked by the white cells of the immune system, but they are slowly dissolved and eliminated over time.
Completely different is the mesothelioma that can develop from crocidolite exposure. As well as asbestosis, blue asbestos can lead to a unique form of cancer of the chest wall lining that swiftly and irreversibly kills. People who worked in asbestos generally have more cancers than the norm, as the fibres travel around in the body.
I am hoping to find figures relating to the number of people who suffered asbestosis and mesothelioma as a fraction of the total who worked beside them, and hopefully get some idea of the fibre concentrations they breathed. The Dept of Labour have a database listing people exposed to asbestos and collect some sort of idea of the exposure. If you have been exposed in New Zealand you can get the form from your nearest OSH office.
Overall, considering we all have asbestos fibres in our lungs, the number of people dying from it is extremely small. You will get run over or struck by lightning before you die of non-occupational asbestos exposure. The US Environmental Protection Agency recently rated non-occupational asbestos deaths at 1 in 100 000 people, compared to 3 being struck by lightning, 7 dying by consuming Miami or New Orleans drinking water, and 22 000 dying from smoking. (The Australians rate working in asbestos removal with good protection as being twice as safe as in the general construction industry)
Smoking interacts with asbestos (and other cancers such as breast and cervical cancers) to increase the rate. If the standard cancer rate is 1, then the rate for asbestos workers is 5X, cancer from smoking is 10X, and people who smoke and work with asbestos suffer 70X times as many deaths. I imagine this synergy with smoking explains the asbestos related deaths among the generation of people who smoked heavily.
Where is it found
Being completely non-combustible and having excellent thermal/acoustic properties has meant a wide range of uses for asbestos. Starting from the last century, the fibres have been used anywhere a heat source is found and in a variety of forms.
Houses- In NZ most of the spray-on ceiling textures had asbestos in up to the mid-1980's. There are a couple of main types, both using a low percentage of chrysotile (white asbestos) as a binder, and the sparkle can be added to either. They do not present much of a hazard from an asbestos point of view, unless disturbed by builders, cleaning them, or the kids scraping at them, but I have heard that people with lung problems feel much better after they are removed. This could be from the lower mould spore concentration, as the damp textures encourage mould growth.
The 1970's lino, with the dark browns and bold orange patterns had pure white asbestos as a backing. This greyish/cream layer is left stuck on the floor when the coloured part is stripped up, and is very difficult to remove. Most flooring sanders are awake to the problem now, as they form the biggest danger if they grind the fibre up into the air with sanding machines. Older lino tiles sometimes had asbestos actually in the matrix of the tile.
Very rarely we find other products made with asbestos in older (1930-40s) homes, perhaps in hot water systems.
Finally, James Hardy spread asbestos through-out Australasia with his ubiquitous asbestos cement sheet. This excellent building sheet has any of the three asbestos types or all together mixed in with a range of cement binders to give a long lasting interior/exterior cover. Super-six roofing abounds in Auckland, as does the wall sheeting both inside and out. The release of fibre is extremely slow normally, and not a problem. The Labour Dept. has declared its removal restricted work, to be undertaken by a person qualified to work with asbestos, and have banned waterblasting or wirebrushing it. Unfortunately most of it is getting very brittle, and walking on a roof can crack it. The repairing leads to more cracked sheets and soon disaster! However if left untouched a super-six roof will last 50 years, certainly longer than its replacement.
The reject product from the Auckland factory was used as roading material for farm tracks in the 1960's, the broken up chips used in muddy areas for vehicle access. Some of it was used as fill in gullies, and very occasionally limpet material was mixed in. Air monitoring tests have shown no airbourne fibre resulting from this usage currently, but further testing is underway to monitor the release of fibre from soil. There is a constant background fibre release from asbestos cement roofs is most of the Western world, and nearly everyone in the country has asbestos bodies in their lungs.
Water pipes were commonly made of asbestos cement through the 1960/70s, and many miles of these are still in use. These slowly release fibre into the water, and we drink it.
Being a natural rock, certain areas have a background concentration from outcrops naturally occurring. Certain products such as talc and fertilisers are found with asbestos rocks and become contaminated.
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Industrial and commercial areas of use follow-
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Boiler insulation commonly takes the form of a calcium silicate block with an asbestos fibre matrix holding it together. The blocks are stacked against the steel and held in place by chicken wire mesh, which is then covered by calico and paint or galvanised sheet steel. Corners and angles are formed by a wet plaster/asbestos mix and left to dry, often reinforced as well as covered with wire mesh. Hard set plaster is layered over the top to completely seal in the fibres. This can be very dusty and releases a lot of asbestos fibre when disturbed.
Steam and hot water pipes have a type of soft preformed plaster section held on by calico and clips. This also collapses very easily once the calico is disturbed and leads to high fibre concentrations. We have found this around the school buildings in Auckland. With its long fibres amosite can be applied directly onto steel pipes and flues with a mesh reinforcing. We found this style on the boilers and flues in an Auckland hotel, about 5cm thick with a calico exterior.
Fireproofing steel and wooden beams was a major application for limpet (sprayed on) asbestos, where amosite or crocidolite was mixed with a cement binder and sprayed onto a surface. With 5cm of amosite scraped off the beam, I have seen steel looking like brand new after a fire has completely destroyed the building it was holding up. A two hour fire rating was easily obtainable and meant the roof didn't fall in during a blaze. The stainless walls of the Silver Fern carriages were untouched in the two burntout ones we stripped.
Noise insulation led to crocidolite being limpet sprayed onto the ceiling of the Mayoral Chamber in the Town Hall. This was fairly common on the underside of the early steel roofs such as Brownbuilt/Longrun, as it cut out the noise of the rain and gave good thermal properties in summer and winter.
Air conditioning systems use the insulating properties also, with multi-storey buildings around town having asbestos lined walls in their air ducts. These removals need eight levels of scaffold or more, or a travelling crane. Shutting down the HVAC system leads to major disruptions and possible evacuation of the whole building for some weeks. The smaller sheet-steel ducts on each floor are often asbestos insulated on their exterior with a painted calico covering.
Concrete buildings can have limpet spray on the underneath of each floor, above the suspended ceiling. This gets disturbed by tradesmen and technicians working in the ceiling space, and falls onto the tiles until the next person takes the tile out. Limpet asbestos on the steel beams also gets knocked off onto the top of the ceiling and spread by workmen crawling through it.
Friction plates have had up to 40% asbestos in until just recently. These include clutch and brake linings, many of which still contain asbestos as their replacements are abysmal. Our 1 million cars around Auckland have been pumping 25 tons into the air each year! Only in the last Bathurst race have they had asbestos free disc pads working successfully.
What to do about it
Asbestos regulations are enforced by the Labour Dept.- now the Dept. of Occupational Safety and Health. ( OSH ) They oversee all asbestos work, either by being called in by someone that finds it on site, or by the removal contractor filing a notification. (Being restricted work covered by the asbestos regulations of 1985, all work involving asbestos must be notified to the nearest office of the dept. at least two days before commencement.)
If the asbestos is not causing a hazard to the normal building occupants it may be noted and left in place. If it is likely to be disturbed in repairs or renovations its removal is programmed into the alterations.
Anyone finding fibrous insulation lying around a site or in a building is advised to have it checked. If you're working amongst it dont hesitate to have it sampled by OSH or a union delegate, as it is one time when it is better to be safe than sorry. Most asbestos we find is not a particularly high risk to the people in the building normally, but turns into a massive dose for someone crawling through it in a ceiling. Similarly, for years the asbestos in the ceiling has been sealed away from the office personnel, then the builders arrive and rip the ceiling down in a cloud of dust and 'stos!
If your working in the service areas of a lot of buildings a high quality mask of the new paper type is worth having around in your pocket for emergencies, but they are junk for working in asbestos dust. If you end up covered in it- Carefully move to the edge of the contaminated area, take off your outer clothes and leave them in there, and have a shower as soon as possible. There is absolutely nothing modern medicine can do, but certainly I'd suggest giving up smoking!
Monitoring
If the asbestos can be encapsulated and left undisturbed, the development of a register is very important. Most building owners just want to hide the whole thing away, to the detriment of themselves later on. The risk to building occupants is negligible and the laboratories can easily test the airborne fibre content.
However, personal worries aside, asbestos in a building can be a problem when trying to sell it. I've seen heart-broken owners who have just realised they have bought a big problem, not just a building, when they start their alterations. Certainly valuers and real estate agents should be a lot more aware of the problems than they are. Already I know of a 14 storey lease in town being made conditional on the asbestos being removed, and this can run to large numbers- over a quarter of a million dollars for that one.
Other Dusts
To get into a less fatal subject, asbestos is being replaced by fibreglass or mineral fibre. These man made mineral fibres (MMMF's) or synthetic mineral fibres (SMF's), or man made vitreous fibres (MMVF's) are completely different to asbestos. They are formed by melting minerals and forming them into fibres that are amorphous, in other words have no crystal structure. This means they break across their length and don't split to finer fibrils like asbestos. If the diameter is controlled at manufacture, they will never get small enough to be a respirable fibre. Their coarseness makes them liable to cause itching and sore throats, so never work with them without protection. The body will actually dissolve the fibres away, so occasional exposure is completely cleared over several years.
The most common dust fibres in the air come from plants and wool via textiles, our clothes and carpets. Add some cigarette and exhaust smoke, tyre dust, topsoil, oil and fat condensate and you have the mess found in most air conditioning grilles. I have a feeling that air pumped past a magnetic field, as in an electric motor, suffers a change in its electrostatic properties and this causes dust to precipitate. There seems to be a market for the devices that push negative ions into the air, with claims that the air is cleaner and fresher. Certainly there is scope for a lot more research into what happens to dust and bacteria when they get pumped through an airconditioning system fifty times, but that will have to wait until later.
Thank you
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