Technology’s Impact on Asbestos Air Monitoring

However, it was later discovered that asbestos is extremely hazardous to human health and can cause serious respiratory illnesses, such as lung cancer,  , mesothelioma and asbestosis. Asbestos is classified as a known human carcinogen. As a result, the use of asbestos has been heavily regulated and banned in many countries, but the material remains a significant threat today due to legacy use in building materials, which remain in buildings across the country.

In the UK there are limits on asbestos airborne fibre concentrations, it is acknowledged that there is no known safe level of asbestos fibre in the air. The existing limits were set many years ago when technology dictated the maximum sensitivity that could be routinely monitored and reported on. These permissible levels are many orders of magnitude greater than what is now known to be the background or ambient airborne fibre concentrations across the UK.

Whilst the asbestos regulatory landscape in the UK remains largely unchanged in recent years, the European Parliament is in discussions around the lowering of their comparable airborne fibre limits, which are expected to be 10 or 100 times lower than those in the UK currently. Additionally, new technologies now allow for more accurate and sensitive monitoring of asbestos airborne fibre concentrations and many duty holders are seeking to utilise these methods to help reduce asbestos exposure even further than the regulatory limits require.

Case Study

At a High Court hearing on 24th July 2009 in a case against Knowsley Metropolitan Borough Council a medical expert witness statement stated: “Mesothelioma can occur after low level asbestos exposure and there is no threshold dose of asbestos below which there is no risk.” “Significant” is defined in accordance with the definition adopted in relation to mesothelioma causation by the Industrial Injuries Advisory Council in their 1996 report (CM3467) “A level above that commonly found in the air in buildings and the general outdoor environment.” It would be appropriate for the Court to conclude that each such exposure materially increased the risk that she would develop mesothelioma.”

The individual affected had been exposed to asbestos at school as a child and consequently developed mesothelioma. Sadly she died on 15th October 2009, the day after at the Appeal Court hearing,  the expert medical evidence was accepted by the Judges and was not disputed at the High Court or the Appeal Court.

The same benchmark is also advocated in the HSE Statisticians paper by Hodgson and Darnton. The paper is generally acknowledged as being the most definitive work on the risks from asbestos exposure, with the risk model being used as a basis for the Regulatory Impact Assessments for the 2002 Control Asbestos at Work Regulations and the subsequent Control of Asbestos Regulations. They state: “Taking this evidence together we do not believe there is a good case for assuming any threshold for mesothelioma risk”.

The above examples illustrate that whilst UK law does not permit exposures above defined levels, any exposure above the background/ambient levels can be deemed to have increased an individual’s risk of developing an asbestos-related disease. All employers have a duty to reduce the potential of ill health to the lowest practicable level.

Asbestos Airborne Limits

The Clearance Indicator Level of 0.01f/ml is the level below which a room can be legally occupied following licensed asbestos removal work in the UK. This is a level designed for asbestos contractors and not for the occupants of buildings, but by default has generally been adopted as the level which is used for air monitoring during asbestos works, however it is not a safe level. The HSE make this clear by stating: “The threshold of less than 0.01 f/ml should be taken only as a transient indication of site cleanliness and is not an acceptable permanent environmental level”. At the Clearance Indicator of 0.01f/ml a person inhales 6,000-10,000 fibres an hour.

The airborne asbestos fibre levels commonly found in the air in buildings and the general outdoor environment are given in the 1999 DETR document on asbestos materials in buildings. This document advises that the outdoor background level is between 0.000001f/ml and 0.0001f/ml, with the former generally being accepted as the outdoor rural level and the latter as the outdoor urban level. The same document gives an approximate level of 0.0005f/ml for buildings where asbestos is in good condition. The document states only where asbestos is regularly disturbed are the levels likely to be higher than 0.0005f/ml. The level therefore referred to as background (within a building containing asbestos) is 0.0005f/ml and expert opinion is that exposures to levels above that benchmark pose a “significant” risk of mesothelioma developing.

Given the above, there exists a significant difference between the clearance indicator, which was also traditionally the lowest level of technology that could be routinely relied on to report upon, and the background/ambient fibre levels in the UK. Advancements in technology now allow asbestos consultants to monitor airborne levels down to those deemed to be the background level, thus allowing clients to understand the potential exposure of their staff, within this otherwise unknown band.

High Volume Sampling

Traditional air monitoring regimes have focussed on the low-volume sampling of 480 litres which only allows fibre levels of 0.01 f/ml of air to be assessed. High-volume sampling allows those much lower background levels to be assessed by equipment, which analysts currently use. The main difference is that in order to achieve the required level of sensitivity, the air monitoring will use a combination of:

• Increased Flow Rates
• Increased Monitoring Times
• Increased Fields Counted

By implementing a regime of air sampling, which includes high-volume sampling, additional information will be gathered regarding the true background levels of airborne fibres in the premises, which could provide an early warning of potential problem areas and reduce exposure to building occupants.

Electron Microscopy

Electron microscopy is the approved analytical technique used in Europe and the United States for asbestos analysis. The use of Scanning Electron Microscopy (SEM) or Transmission Electron Microscopy (TEM) can observe fibres of all sizes, particularly thin asbestos fibrils which cannot be detected using the standard UK Phase Contrast Microscopy (PCM) methods. The use of SEM / TEM distinguishes asbestos fibres from other non-asbestos fibres and has improved limits of detection compared to PCM. 

Although SEM / TEM analysis is a more expensive and time-consuming test compared to standard PCM there is clearly a benefit in targeted use to provide definitive analysis at the lower limits of detection. The technology is available within the UK market but is not currently widely adopted.

Asbestos remains a threat

Asbestos remains a significant threat within the UK, but advances in technology, such as those outlined above have made it easier to detect and monitor asbestos in the workplace. By using these systems, employers can protect their workers from the serious health risks associated with asbestos exposure. It is essential that employers prioritise the safety and well-being of their workers and implement measures to reduce exposure to asbestos to the lowest levels reasonably practicable.