Asbestos Risk Assessment
In the UK employers are obliged by law to perform a risk assessment whenever they identify potential safety hazards within the working environment. Thus whenever asbestos containing materials are identified a risk assessment needs to be carried out. The risk posed by asbestos is determined by the current and potential level of employee exposure to asbestos fibres.
Asbestos Type
There are six types of asbestos used in the UK. Studies have identified that they each pose different health risks. Crocidolite is the most dangerous and Chysotile the least. everything else falls somewhere in the middle.
Surface Treatment
Surface treatment is a term used to describe how the fibres in the material are protected from release. The safest materials are composites such as cement and plastic where the fibres are contained within a material within a strong matrix. At the other end of the scale are materials that damage easily and have no protective coating such as paint or wall paper. A good example of his would be sprayed asbestos and boiler lagging.
Friability
Products that damage easily such as sprayed asbestos are clearly more likely to release fibres than strong materials such as cement. This 'likelihood of fibre release' or crumbliness is commonly referred to as friability. Materials with high friability (such as insulation) are higher risk than thse with low friability (such as cement).
Condition
Clearly products which are damaged are more likely to release fibres than those in good condition.
Calculating a risk assessment
So, when calculating a risk assesment its important to take into account each of these four factors. There is no hard and fast way of calculating a meaningful risk assessment but there is an algorithm suggested in the Methods of Determing Hazardous Substances (MDHS) 100 publication which attributes values to each of the factors allowing you to calculate a material risk assessment.
Material Assessment Algorithm
The material assessment algorithm is commonly used in most by most asbestos software and by most surveying organisations to give an indication of how dangerous a material is. Each of the four risk factors (friability, condition, surface treatment and asbestos type) that we've already outlined are attributed a score of between 0 and 3 (see below). These scores are accumulated to give a risk score of between 0 and 12 (where 12 is the highest risk).
When using this algorithm it is commonly accepted that materials with a value of 0-4 are very low risk, 5-6 low, 7-9 medium and 10-12 high and these can be used in your risk assessment. Any material with a high risk assessment needs to be contained and removed or repaired before anyone accesses it without RPE.
Table 1. friability scores
| Friability |
Score |
Example |
| Low |
1 |
Strong products such as bitumen, floor tiles, artex and asbestos cement. |
| Medium |
2 |
Non-cement boards (like AIB), ropes, gaskets, millboard and paper. |
| High |
2 |
Insulation products (other than boards i.e pipe lagging), sprayed asbestos, packing. |
Table 2. condition scores
| Condition |
Score |
Example |
| No damage |
0 |
|
| Low damage |
1 |
Slight damage, scrapes, damaged edges. |
| Medium |
2 |
Broken with fibrous areas reveled. The majority still being in tact. |
| High |
3 |
Badly damaged wth debris. |
Table 3. surface treatment
| Surface Treatment |
Score |
Example |
| Composites |
0 |
Floor tiles and bitumastics. |
| Enclosed/sealed |
1 |
Enclosed highly friable materials (sprays, lagging), sealed (painted or papered) medium friable materials (insulation boards), unsealed low friable materials (cement boards, artex) |
| Bare (medium) |
2 |
Unsealed medium friability materials (insulation boards) |
| Bare (high) |
3 |
Unsealed high friability materials (sprays, laggings) |
Table 4. asbestos types
| Asbestos Type |
Score |
Example |
| Chrysotile |
1 |
Any product containing only Chrysotile fibres |
| Amosite |
2 |
Amosite, tremolite, anthothylite, actinolite. |
| Crocidolite |
3 |
Crocidolite |
Example
An asbestos insulation board is found in a garage roof. Its exposed surface is bare (unpainted) and there are a few visible scratches and a few damaged edges. A sample analysis has been undertaken and the material has been found to contain amosite.
Friability : medium (2)
Condition : low damage (1)
Surface : bare medium (2)
Asbestos Type : amosite (2)
Risk Assessment 7 (our of 12) : Medium