Asbestos Hazards Handbook - Chapter 7

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Asbestos Removal

The modern myth: asbestos removal is risky and a waste of money

As recently as 1993 the Financial Times ran an article with that very headline. Julian Peto is quoted as saying that asbestos exposure is a minor risk to the general public. He said, "The last 20 years have witnessed an extraordinary shift, from neglect of a major industrial hazard to irrational exaggeration of a negligible environmental pollutant. Ripping asbestos out of schools and other public buildings is usually a waste of money and can increase the risk to the public."

The HSE's Dr Trevor Ogden welcomed Peto's remarks. The best answer to this was provided by Dick Jackson, whose letter in reply was never printed, "As for removal of asbestos, it is of paramount importance that every fibre of this deadly material is removed and disposed of so that it cannot be the means of killing other generations. Most asbestos has been in place for 20-50 years, has deteriorated, and because of its make-up is a constant danger through fibre release, through draughts, vibration, and damage, and the practise of sealing in is only second best as once the asbestos is again damaged you are back to square one with the ever present potential health risk."

At the British Occupational Hygiene Society Conference in 1994 Peto went further. He did point out that exposure to asbestos dust goes on in the building trade all the time, but went on to rubbish the anti-asbestos lobby of the 1980s as "hysterical". He says industrial exposure is of the order of 10-20 fibres/ml, whereas the average levels in buildings rarely get higher than 1/1,000 fibre/ml. "The mean levels are much less than 1-2/1,000 fibre/ml and at these levels, however inaccurate our dose-response calculations are, we can be pretty certain that the risk is absolutely trivial."

Again, in the Lancet in March 1995, he says that the campaign to remove asbestos from schools and public buildings was founded on "fear rather than evidence" and that asbestos removal might actually increase airborne levels of fibres.

The counter arguments are straightforward:

a) Asbestos can be removed safely even in the most dangerous circumstances. Proper monitoring of fibre levels while work is in progress ensures that people outside the removal enclosure will not be put at risk.

b) Rip-it-out any old how merchants do put lives at risk. The campaign to remove asbestos fights as vigorously against using cowboy contractors as it does for the removal of dangerous, damaged, friable asbestos.

c) Having failed to ban asbestos, the failure to remove asbestos from buildings is the very reason plumbers, electricians, joiners, renovation, demolition and other maintenance workers are at risk of unsuspected exposure. Peto and the HSE now admit that these workers are at great risk. Although this is to be welcomed because construction workers are a high risk group, we believe that other groups of workers are also at risk and need to be warned. Recent mesothelioma deaths have included two teachers, a post office worker and a nurse.

d) Peak exposures: air tests often miss peak exposures which occur when asbestos is disturbed. Peak exposures can be 1000 times the background asbestos levels. The US Environmental Protection Agency (EPA) estimated that in for a peak exposure of one hour you would breathe in the same amount of asbestos would be breathed in as you would in one year by breathing in the general atmosphere in schools containing friable asbestos.

e) The 1980s strategy advocated by the people Peto dismisses as "hysterical" was to survey asbestos in buildings and prioritise the order in which it was to be removed. Nobody called for overnight removal of every fibre. Surveys uncovered tonnes of friable asbestos which could not be made safe by encapsulation. Much asbestos was left in place to be inspected annually. Now organisations such as TICA are arguing for progressive removal as the only long-term answer.

f) A key point is that asbestos is being removed all the time as buildings are refurbished. As long as general awareness about the hazards of removal is low, people will be at risk.

Sealing asbestos

Asbestos can be removed safely from buildings and indeed is the only long-term solution to making buildings safe. Official sources generally favour sealing asbestos because it is quicker and in the short term considerably cheaper. In calculating the true costs the following points need to be taken into account:

Any disturbance or deterioration of the seal allows the release of fibres. Often this occurs "deliberately". Asbestos monitoring companies see many examples of unmarked, sometimes previously sealed asbestos, damaged because it has been drilled through when central heating, telephones, computer wiring, shelving units, notice boards and so on are installed. Fire and flood damage sealed asbestos.

Ordinary paint or wallpaper is not a seal. The original Asbestos Factpack recommended Decadex Firecheck.

If a decision is taken to seal asbestos then it must be marked clearly and the sealing be checked on a regular basis as part of every routine safety inspection. The cost of a programme of managing asbestos safely, repairing it again if damaged, ensuring a "permit to work system" is in place for maintenance staff adds considerably over the years to the initially lower cost of sealing.

Eventually, asbestos has to be removed safely before a building is demolished.

Sealing can prove to be a false economy in other ways. Once sealed asbestos is marked "DANGER ASBESTOS - CANCER CAUSING DUST", powerful emotions are unleashed in those living and working in the vicinity. In one celebrated case, the management of the then North London Polytechnic spent thousands of pounds sealing asbestos panels in a common room only see the students refuse to enter the building. Thousands more had to be spent removing the panels completely.

Safe removal of asbestos

The methods available for safe removal or stripping of asbestos insulation, coatings and insulation board are given in detail in HSE Guidance Notes. The basic types are 1) dry stripping; 2) controlled wet stripping; 3) high pressure water jetting; and 4) air management for hot stripping.

The HSE favours controlled wet stripping. Dry stripping is the most common method but removing asbestos in a dry state without using any water will produce higher dust levels than other methods. Other methods should be preferred but if electrical equipment is near the asbestos there is pressure to use dry techniques.

High pressure water jetting is a specialised and potentially highly dangerous process usually used in large scale operations where access is difficult. It must not be used with electrical equipment. Workers must be specially trained in this technique. It should only be used for removing stubborn patches of asbestos where other methods have failed. There must be large warning signs: DANGER: HIGH PRESSURE WATER SPRAYING.

Wet removal by injection

This technique involves the use of wetting fluids which are injected under pressure through needles into the lagging material. This softens the insulation matrix, breaking down the binding agents and controlling the fibre release. The insulation is cut away in clean sections and transferred to the disposal system.

Tests have proved that, when properly saturated, the fibre release is very low so that this system offers the potential of dispensing with expensive enclosures although this is a possibility which should not be considered seriously.

The injection method is more suited to cold stripping as the choice of wetting fluid which does not vaporise at high temperatures is limited and those which are suitable give off toxic gases when heated.

Cost comparison for a job comprising cold stripping of two 200 mm diameter insulated pipes in an enclosure 36 metres long at high level in a factory environment

Dry strip 3,050 Injection strip 3,390

 For a similar job but with hot stripping

Dry strip 3,300 Air management 4,700

Air management

This method can be used for hot stripping and comprises a high velocity air flow, which directs the fibres released during cutting to a filtered exhaust at the end of a specially designed enclosure. The air flow is delivered via a flexible duct terminating with an air straightener to induce laminar flow. It is positioned along the work face.

While the insulation is cut and removed, it is sprayed to dampen the fibre release. Any residue remaining is cleaned using shadow vacuum techniques. Heat stress is greatly reduced due to the air movement and is further curbed by positioning reusable loose insulation quilts over exposed hot pipework.

Monitoring and sampling

Monitoring methods

There are three methods of assessing whether asbestos is present:

Bulk sampling:

involves taking a small sample of the material and it examining under a microscope. This is combined with a visual inspection to assess the condition of the material. This method is used in surveying buildings and sites to determine if a material contains asbestos. With this information a prioritisation system for removal and control can be developed.

Wipe testing:

involves taking a sample of dust from the area and inspecting it under a microscope. Used when asbestos has been disrupted or removed as an essential back up to air monitoring. It shows if asbestos fibres have settled out of the air onto surfaces.

Air monitoring:

involves drawing a sample of air through a filter by means of a pump, then counting the number of fibres trapped on the filter under the microscope. Used to check fibre levels in the air after removal or during disruption of asbestos materials.

Why air monitor?

The vast majority of asbestos fibres that damage the lungs are invisible to the naked eye so air monitoring is an important method for detecting asbestos contamination. It must be carried out in a very precise way to be accurate. It is necessary in checking to see whether asbestos has been safely removed. It can also be dangerously misleading, if not done properly by reputable firms working to the highest standards.

Air monitoring can be used to "blind you with science". Many tenants groups and workers have stories of employers and councils using air tests to "prove" that the asbestos in buildings is "safe," meaning that it is well below the control limits and action levels. But air tests can only measure the fibres floating in the air at the time the sample was taken; results could be thousands of times higher seconds later if the material is disturbed.

Air monitoring is no substitute for visual inspection and bulk sampling when diagnosing and assessing risk from asbestos.

Problems of collecting samples

1 Check how many tests are being carried out, the position of sampling units and their flow rates. If sampling heads are located far from the possible source of asbestos fibres they are unlikely to pick up any useful results, particularly when out of doors. Each sample is specific to a particular location at a particular time and is therefore not representative of all conditions at all times.

2 The size of the room or area is important in determining how many pumps to run. It is best to have two pumps per enclosure and three pumps for a space of 25 cubic metres, five for 50 cubic metres room and one additional sampler for every extra 25 cubic metres.

3. Any air sampling should be accompanied by wipe tests and dust and debris sampling as the air may be within the acceptable limits but the settled dust and debris may still contain asbestos.

The Scientific Service Branch at the London Residuary Body found in the monitoring of stripping, that of 60 jobs inspected, 97% met the air test standard. However, when testing the debris only 28% of the jobs showed a complete absence of asbestos. At Malmesbury School, London, teachers noted dust in classrooms cleared by air tests and demanded it be sampled. The dust was asbestos and was described as "gross contamination". This should never happen.

4. In order to collect a representative amount of dust, controlled disturbance tests should be carried out. A good policy on this is to sweep walls and floors during the monitoring period.

How to read a results sheet

The following factors should be checked when deciding whether the results of monitoring are reliable.

Filter Reference: all samples should be labelled and have a description of their location.

Pump Rate: anything between 1 and 8 litres of air drawn through the machine per minute is acceptable.

Total Volume: the minimum volume of air which should be drawn through is 240 litres; e.g. a 4.0 litre per minute pump should have on for one hour.

Fibre Concentration: this is the key figure. It is quantified in fibres/ml. Results using optical microscopy (membrane filter method) can only give results to an accuracy of 0.01. As this is the environmental limit, anything higher should be considered as "dirty", requiring a re-clean or further consideration. For figures below 0.01 fibres/ml transmission electron microscopy (TEM) gives an accurate evaluation of the fibre concentration. TEM has to be used if accurate results to below 0.0005 fibres/ml are needed.

Comments: types of asbestos identified, other materials identified, any problems with the sample i.e. dirty.

Other information that should be provided: name of agency, place of test, Purpose of test, sources of asbestos, known or suspected.

Protocol used: this means type of microscope, disturbance tests used, number of air pumps per room, any peculiar circumstances

Problems of monitoring accuracy

1 With the membrane filter method (the normal method using approximately 400 times magnification) some fibres are missed in counting. For example, long thin fibres may be missed, which although invisible, are particularly dangerous. Consequently air sampling using this method is likely to underestimate the size of the problem drastically.

2 Only transmission electron microscopy (TEM) is powerful enough to observe all asbestos fibres accurately. This expensive method is rarely available. Demand its use if there is uncertainty about the accuracy of other tests. Good practice would be to use electron microscopy to double check when initial results are low or there is conflict. It is the only accurate way of determining the low levels of environmental contamination found in buildings during normal activities, rather than in the process of removing asbestos.

3 The membrane filter method cannot accurately measure less than 0.01 fibres/ml. There is always an environmental level of asbestos in the air and it may be difficult to assess the difference between this and the level near a particular source of asbestos fibre. For instance the general level in city air may be of the order of 0.0005 fibres per/ml; a 15-fold increase in this level is still not detectable by optical microscopy (the membrane filter method) yet there is an enormous increase in the number of fibres breathed in.

Checklist for monitoring contractors

Removing or sealing asbestos in buildings is an expensive job, if done properly. Cowboy contractors will try and undercut the responsible operators. Use the checklist to make sure this does not happen.

THE CONTRACTOR

1. Is the company licensed under the Asbestos Removal Licensing Regulations which came into force in 1984?

2. Is the company a member of the Asbestos Removal Contractors Association?

3. Are the workers unionised with at least one qualified thermal insulation engineer?

4. Has the company supplied copies of its safety policy and work methods with the tender? Ask for these.

5. Can the company demonstrate its familiarity with the HSE's ACoP on Work with Asbestos Insulation and Sprayed Coatings?

6. Has the company good references from previous asbestos removal work? Check with the previous clients and with any safety representatives who may be there.

THE WORK METHOD

7. Can the company supply a detailed method statement with relevant all points covered?

8. Where does the company propose to locate its decontamination unit (i.e. "dirty" and "clean" changing rooms and shower unit)?

9. Who will do the environmental monitoring for asbestos contamination and who will do the analysis (ie fibre counting)? Are they financially independent from the removal company?

10. What limit will be used to protect people in the building?

11. If the company uses hired vacuum equipment, how do they make sure that the equipment is free of asbestos when hired and returned?

12. Are there penalty clauses in the contract for breaches of safety procedures or failure to clean up satisfactorily?

CHECKING THE WORK DONE

13. Is the work area cordoned off and, where necessary, signposted Asbestos - Cancer Hazard - Keep Out?

14. Is the work area sealed up with heavy duty polythene sheeting, sealed air-tight with tapes, etc? Has it been tested for leaks with a smoke bomb? Is there an air lock at the entrance/exit to the work area?

15. Are the polythene sheets billowing inwards, showing that the work area is under negative air pressure from the exhaust ventilation inside the plastic tent?

16. Do the workers wear transit overalls between the decontamination unit and the work area?

17. Are the workers wearing respirators or breathing apparatus approved for asbestos removal work by the HSE (see HSE Form F.2486 11984 updated each year)?

18. Are there monitoring instruments outside the work area checking on asbestos contamination, especially if normal work is continuing?

19. Are monitoring results given to the client's supervisors and safety representatives?

20. Is waste asbestos removed in double, heavy duty plastic sacks labelled Asbestos - Cancer Hazard, or better still by large-diameter vacuum pipes feeding directly into sealed waste hoppers outside the building?

21. How and where is the asbestos toxic waste to be disposed? Only licensed dumps should be used.

FINAL VISUAL INSPECTIONS

22.It is important to look for evidence of gross visible contamination following the final stage of cleaning the removal enclosure. It should be done by an experienced and independent person who has not been involved in the removal process. S/he should decide whether or not to conduct clearance air sampling. If any clearance air tests give adequate it is reasonable to assume everything is safe.

23. Are surfaces where asbestos was sealed, rather than removed, conspicuously labelled Asbestos - Cancer Hazard, so that future maintenance workers are warned?

24. Is there a system for checking the safety of all asbestos sealed or left in good condition?

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