Why do we need to do surface Sampling for Asbestos Clearance?
Introduction
As far as I am aware New Zealand is the only country that requires surface sampling as part of the asbestos Clearance procedure.
The Regulations and Code of Practice while requiring surface sampling be undertaken, does not require the Asbestos Assessor to be bound by the results, this situation has created a level of confusion in the industry as to:
(1) Why do we need to undertake surface sampling?
(2) How can the results be meaningfully interpreted?
This blog will endeavour to provide some (but not all) answers to these two questions.
Regulatory framework
Regulation 41 of the Health and Safety at Work (Asbestos) Regulations 2016 (Asbestos Regulations) states:
41 Clearance inspection
(1) This regulation applies if a person commissions licensed asbestos removal work at a workplace.
(2) The person or, if the workplace is a home, the licensed asbestos removalist commissioned by the person must ensure that, when the licensed asbestos removal work is completed, a clearance inspection of the asbestos removal area at the workplace is carried out by,—
(a) in the case of Class A asbestos removal work, an independent licensed asbestos assessor; or
(b) in any other case, an independent competent person.
(3) In this regulation,—
clearance inspection means an inspection (including a visual inspection) of an asbestos removal area after asbestos removal work has been completed to verify that the area is safe for normal use, and—
(a) in the case of Class A asbestos removal work, includes surface testing and air monitoring in a dry condition before the enclosure is dismantled or removed from the asbestos removal area:
(b) in the case of Class B asbestos removal work, may include surface testing and air monitoring
competent person means a person who has acquired, through training and experience, the knowledge and skills of relevant asbestos removal industry practice and who holds—
(a) a certificate in relation to a training course specified by WorkSafe for asbestos assessor work; or
(b) a tertiary qualification in occupational health and safety, occupational hygiene, science, or environmental health. (Ministry of Business, Innovation, and Employment, 2016).
The Approved Code of Practice for the Management and Removal of Asbestos states:
“28.5 Surface Testing
Surface testing is mandatory for Class A asbestos removal work and optional for Class B asbestos removal work.
Current surface testing methods are insufficient for determining whether an asbestos removal area is safe for normal use. The licensed asbestos assessor or competent person should give greater weight to the visual inspection and clearance air monitoring results to determine if the asbestos removal area poses a risk to health and safety from asbestos exposure.
Surface testing results may be useful for clarifying the identity of materials detected during a visual inspection, or to track down sources of contamination that may cause trace level to be exceeded during clearance air monitoring…
28.5.3 Decision – Making
When the licensed asbestos assessor or competent person decides whether to issue a clearance certificate, they should take the following into account:
- asbestos fibres are only hazardous when airborne
- regardless of air monitoring results, asbestos fibres on surfaces may be disturbed later and lead to a rise in airborne asbestos fibres
- the Asbestos Regulations permit personal exposure to airborne asbestos fibres at concentrations that do not exceed 0.01 fibres/ml.
If the results of surface testing do not reveal any significant potential for this level to be exceeded, the assessor may be satisfied that the asbestos removal area does not pose a risk to health and safety, and may issue a clearance certificate. This assumes the other matters the assessor also needs to be satisfied of have also been met.
If asbestos is detected by surface testing but there is no information about its concentration, it is not possible to draw reliable conclusions about the risk that the respirable asbestos fibre level does not exceed 0.01 fibres/ml.
Note: The assessor is not required to refuse to issue a clearance certificate merely because asbestos has been detected.” (WorkSafe New Zealand, 2016)
So, in summary the Regulatory position is:
(1) For Class A work surface sampling is compulsory.
(2) For Class B work surface sampling is optional.
(3) The Asbestos Assessor has to interpret the results, and that a result showing asbestos does not mean that the enclosure fails the test.
Why the requirement to undertake surface sampling?
Listed below are some different situations where dust sampling as part of the Clearance process is important.
Demolition vs reoccupation
The Asbestos Regulations’ Clearance requirements are based around the determination as to whether or not the area is safe to reoccupy. Reoccupation is different to a building being ‘free of’ asbestos. In reoccupation any residual asbestos may either be:
- safely encapsulated (for example a painted and labelled asbestos cement pipe), or;
- the level of contamination is so low that in the Asbestos Assessor’s professional opinion the airborne contamination levels will never breach Trace Levels (0.01 respirable asbestos fibres per millilitre of air) if this residual asbestos material is disturbed during normal occupancy of the building.
The Asbestos Assessor must determine if “as far as can be determined from the clearance inspection, the asbestos removal area does not pose a risk to health and safety from exposure to asbestos.” (WorkSafe New Zealand, 2016, p. Appendix I) In normal situations the issuing of a Clearance Certificate is the end of project, as the client once more has free use of the space again.
When a building is to be demolished this might not be the situation. While the building may be safe to reoccupy, the act of demolition may release encapsulated asbestos fibres and also, the question remains as to the potential disposal location for the debris arising from the site. Cleanfill disposal sites have Resource Consents that explicitly exclude the ability to accept asbestos for disposal, and the material has to be ‘free of’ asbestos.
This requirement is derived from the Ministry for the Environment’s Cleanfill Guidelines, see below:
“Cleanfill material
Material that when buried will have no adverse effect on people or the environment. Cleanfill material includes virgin natural materials such as clay, soil and rock, and other inert materials such as concrete or brick that are free of:
- combustible, putrescible, degradable or leachable components
- hazardous substances
- products or materials derived from hazardous waste treatment, hazardous waste stabilisation or hazardous waste disposal practices
- materials that may present a risk to human or animal health such as medical and veterinary waste, asbestos or radioactive substances
- liquid waste.
Cleanfill
A cleanfill is any landfill that accepts only cleanfill material as defined above.” (Beca Carter Hollings & Ferner Ltd, 2002)
I have personally been involved in several asbestos clearances prior to demolition where the requirement to be ‘free of’ asbestos is an issue. The use of clearance surface sampling, with clear results, has been accepted by the disposal location as sufficient evidence to satisfy their Resource Consent requirements.
In summary then, if a demolition contractor wishes to send the residual concrete waste to a Cleanfill, the clearance requirements can often be more rigorous than that required for reoccupation. In these situations, the Asbestos Assessor will need to be aware of this when interpreting the results. A Clearance Certificate based purely on the ‘reoccupation’ standard may be worthless and may have significant financial implications.
Dust contamination
A PCBU may have engaged an Asbestos Surveyor to undertake an asbestos survey (management/renovation/demolition), during this survey a dust sample may be taken. For the purposes of this blog let us assume that there was visually no indication of asbestos contamination, however based on the professional judgement of the surveyor a sample was taken nevertheless.
This sample comes back positive for asbestos, and a clean-up is instigated, most likely as a Class A activity, assuming the extent of the contaminated area breaches the definition of a ‘minor dust contamination’ (refer Appendix D of the Approved Code of Practice for the Management and Removal of Asbestos) (WorkSafe New Zealand, 2016, p. Appendix D)
In this situation the original decision to undertake the clean-up was based on the results of surface sampling, and therefore it is only reasonable that the Clearance assessment will also be based on the same method, and Clearance would not be given until all results came back clear.
How many samples should you take?
As the use of surface sampling for Clearance purposes is a new requirement there is not that much guidance available on where and how to take samples. In the absence of any dedicated guidance the closest useful document is the WorkSafe Good Practice Guidelines for Conducting Asbestos Surveys, specifically Appendix A.
The example I use as a reference on the number of samples to be taken is the example detailing how to sample sprayed coatings. I chose this product type as it is a homogeneous product, in a similar manner to any residual dust across an enclosure. The example states:
“If the material appears uniform and consistent, two samples should usually be enough, if taken at either end of the sprayed surface. If the installation is large (eg >100 m2), one sample should be taken approximately every 25–30 m2.” (WorkSafe New Zealand, 2016, p. Appendix A)
How should the sample be taken?
In taking a sample the Asbestos Assessor should be using the types of sampling techniques used as if an Asbestos Survey was being undertaken. As generally it is dust that is being sampled the following sampling techniques are common.
- Black or clear adhesive tape. In this test the tape is applied to the surface and then pulled off, any fibres should adhere to the tape itself. Some use people use standard PVC tape, while others use perforated tape.
- Swabs, normally using either ‘Ghost wipes’ or ‘wet wipes’. In this test the surface is wiped with the aim of entrapping fibres in the wipe itself.
- Micro-vacuuming (the least common method). With this method a slightly modified personal air monitor and sampling cassette is often used, and the surface is ‘vacuumed’. The filter membrane is analysed as a bulk sample.
Each method has its advantages and disadvantages, and the various asbestos analytical laboratories can have their own preference in what they prefer to analyse. It is often easiest to use the method that the laboratory prefers. It is not in the scope of this blog to discuss the comparative advantages of the methods.
References
Beca Carter Hollings & Ferner Ltd. (2002, January). A guide to the management of cleanfills. Retrieved 28 March 2018, from Ministry for the Environment: https://www.mfe.govt.nz/publications/waste/guide-management-cleanfills
Ministry of Business, Innovation, and Employment. (2016). Health and Safety at Work (Asbestos) Regulations (2016). Retrieved 12 March, 2018, from New Zealand Legislation: http://www.legislation.govt.nz/regulation/public/2016/0015/19.0/DLM6729706.html
WorkSafe New Zealand. (2016, October). Conducting asbestos surveys. Retrieved 12 March 2018, from WorkSafe: https://worksafe.govt.nz/topic-and-industry/asbestos/working-with-asbestos/conducting-asbestos-surveys/#lf-doc-25282
WorkSafe New Zealand. (2016, November). The Code of Practice for the Management and Removal of Asbestos. Retrieved 19 March 2018, from WorkSafe: https://worksafe.govt.nz/topic-and-industry/asbestos/management-and-removal-of-asbestos/#lf-doc-29878