Summary

Although asbestos use was banned in Britain during the last century, its widespread use and long lag-time in causing disease means it still accounts for around 5,000 deaths annually. Current exposures are mainly in buildings with asbestos-containing materials (ACMs), affecting teachers, office workers, maintenance staff and others. HSEs studies show modern removal practices result in very low exposures for workers, particularly when using full-face respirators. However, despite low individual risk for building occupants, the large number of people who may potentially be exposed from ACMs in buildings (perhaps 15 million) suggests this group will contribute most to future disease burden. A risk-weighting analysis indicates proactive asbestos removal over the next 40-years could reduce future disease cases more effectively than waiting until building end-of-life. However, the likely number of deaths prevented remains uncertain, and may be relatively few. Prioritising asbestos removal in schools, where young people are at greater risk than adults, and conducting more comprehensive disease burden studies are key recommendations for policymakers.

Background

During the 1990s the Institute of Occupational Medicine (IOM) carried out an extensive exposure monitoring programme during asbestos removal activities[1]. They found levels up to 400 fibres/ml during work involving poor practice, but good manual wet removal produced median levels of 0.2 fibres/ml; no result was above 1 fibre/ml for this type of work.

High asbestos exposures during  much of the 20^th Century have left us with the legacy of around 5,000 deaths each year from mesothelioma and other asbestos-related diseases. Fortunately, we seem to have passed the peak of the asbestos epidemic, but it is still unclear how the future will pan out. There are suggestions of increasing numbers of deaths amongst younger people, women and teachers[2], and we still have a substantial amount of ACMs in our buildings.

The main question for policy makers is what, if anything, should be done to improve the management of future risks to minimise total asbestos-related deaths?

Where are the current exposures?

New uses of asbestos were banned in Britain during the last Century (1985 for amphiboles and 1999 for chrysotile) and since then the pattern of exposure has shifted to different population groups and the levels of exposure has decreased. The list below shows the scenarios where exposures currently occurs:

• Workers removing ACMs from buildings;
• Being in the vicinity of removal works or after works complete;
• Inadvertently disturbing ACMs in buildings, e.g. maintenance workers, firefighters etc.;
• Working or being in buildings containing ACMs, e.g. teachers, office workers;
• Working or being on contaminated land;
• Community exposure from industrial fires or storm damaged buildings with ACM.

There are increasing data on the likely exposure concentrations in these situations. HSE have recently investigated eight removal sites covering a variety of work with ACMs, measuring personal exposure for workers inside enclosures during removal using phase contrast optical microscopy (PCOM) analysis[3]. These data are not consistently averaged over four or eight-hour periods so comparison with other data are not straightforward, but most measurements were obtained from around 1 to 4-hour durations. The highest results were for removing sprayed coatings or insulation, where the average was just above 0.2 fibres/ml; other sites were less than 0.1 fibres/ml on average. It is notable that the median exposure from site 6, where there was removal of insulation, was like that from the good wet strip investigated by IOM in 1996. Of course, the workers in the HSE study all wore full-face respirators and so their actual exposure was much lower than these figures, perhaps on average around 0.0001 fibres/ml.

There are also data from a study carried out at fourteen worksites in Denmark, mostly involving removal of ACM tiles or panels, where they measured worker breathing zone concentrations using SEM analysis[4]. The highest measurements were from removal of asbestos containing pipes (one sample 0.04 fibres/ml, 8-hour average), removal of ceiling panels (0.013 fibres/ml) and removal of wall tiles (also 0.013 fibres/ml). Most data were on average below 0.003 fibres/ml, averaged over 8-hours, which is the Danish Occupational Exposure Limit.

In the HSE study described above airborne asbestos fibre concentrations during enclosure construction and dismantling were measured using TEM analysis. The highest results were from a single site (up to 0.017 fibres/ml, mostly amosite fibres), but most samples were below the limit of quantification; the average is <0.0025 fibres/ml. In the absence of better data it seems prudent to assume that people in the vicinity of asbestos removal could be exposed to 0.002 fibres/ml, and that these exposures might persist for up to about a month, although exposure of occupants after removal is finished will depends on the debris and dust left behind and the amount and frequency of disturbance after the removal.  This is still mostly unknown and we need more data on this type of exposure.

The quantity of information about the background airborne asbestos concentration in buildings containing ACM in Britain is limited. The HSE has estimated that between 210,000 and 400,000 buildings contain asbestos. There are around 25,000 schools in Britain and maybe 80% have ACMs within their estate. There are exposure data from surveys carried out by HSE of several schools in occupied classrooms after remediation that were analysed by TEM[5]; the average air concentration was <0.00005 fibres/ml. There are also data from an occupied office (a repurposed CLASP[6] school building); 0.00002 fibres/ml. Additionally, a very large study from the USA showed that in 317 occupied schools the average air concentration was 0.0001 fibres/ml and data from 752 other buildings had an average airborne asbestos fibre concentration of 0.00008 fibres/ml. Based on these data we might assume that the average asbestos air concentration in British buildings containing ACMs is around 0.00005 fibres/ml.

There are no data from contaminated land sites, but there might be around 10,000 sites in Britain and 100,000 people could be exposed to asbestos. Using data from experimental studies[7], it can be estimated that average background exposure on these sites could be around 0.001 fibres/ml, based on an airborne particle concentration of 1mg/m³ above the urban background concentration and 0.01% asbestos contamination in the soil. Similarly, there is very limited data on exposure from fires and from other damaged buildings, but what is available suggests exposure of the population surrounding a fire site is low. Community airborne asbestos exposures from fires involving ACMs will depend on many factors e.g. distance from source, wind direction, the amount of remaining debris and the clean-up procedures. However, an order of magnitude estimate could be around 0.001 fibres/ml for up to a month.

Overall, the available data on current asbestos exposure in Britain paints a picture of very low exposure levels.

What does this mean for health risks?

Ideally, we would like to use whatever data we have to assess the future health burden from current asbestos exposure. This has previously been done for all occupational carcinogens in Britain, including asbestos, although in a fairly simplistic way[8]. To do these types of calculations you need to have information about the number of people exposed, the duration of their exposure, the level of exposure and other data. It is a complex and time-consuming process to make these calculations, but it is possible to produce relative estimates of risks for different exposed groups as a simple weighting, i.e. by multiplying the estimated number of people exposed by the average asbestos air concentration and the estimated duration of exposure in years.  The table below shows my estimates for the key parameters and the calculated weighting.

Table 1: Weighting analysis of relative risks from current asbestos exposure

Based on this analysis the main source of future mesothelioma cases and asbestos-related lung cancers is likely to arise from background exposure for people like teachers and office workers in buildings containing ACMs. Their estimated average level of exposure is the lowest of all the groups but there are so many people at risk that this dominates the weighting. In contrast those removing ACM have a low risk weighting, partly because there are few people in this group and partly because when wearing respirators their exposure is likely to be very low. However, there are, as discussed earlier, several stages to removal and clean-up, and different levels of user experience and respirator types in use between licenced removal, other unlicensed removal and maintenance work. Nevertheless, it seems appropriate to assume that in general, exposures in this sector are very low.

The main problem with this analysis is that it doesn’t tell us how many cases of disease might occur. These weightings may represent thousands of cases or a handful. It is important for the research community to undertake the more extensive disease burden analysis to clarify the situation.

What should be done about the asbestos legacy?

It is possible to use the weighting analysis approach and the more comprehensive burden assessment to evaluate the relative merits of different approaches to managing the removal of ACMs from buildings in the future. Table 2 shows estimates for the exposure parameters and the weighting scores for two alternative approaches to deal with our asbestos legacy. First, we look at the situation where we remove the ACMs at the end of building life. Here we have low-level background exposure for the building occupants for the remaining lifetime of the building (assumed to be 60 years) and exposure from inadvertently disturbing the ACM or repairing it during this period. The overall weighting score for this scenario is 48,000. The second scenario assumes a progressive approach to removal of the ACMs from all buildings over the next 40 years, where the overall weighting value is 23,625. There is therefore a benefit, in terms of lives saved, in proactively removing the ACM, but as with the earlier analysis we don’t know how many people will be saved. Of course, there is considerable uncertainty in the estimated exposure of those removing the asbestos and bystanders and the amount of residual asbestos  remaining. However, given the likely very low levels of exposure it is plausible that it could be that relatively few additional lives would be saved.

Table 2: Weighting analysis of two alternative strategies for managing the removal of ACMs from buildings

Conclusions

The above analysis shows that most asbestos-related deaths from current and future exposure in Britain are likely to be amongst people working in buildings containing ACMs, but not actively disturbing the materials. It is not clear how many cases might arise from these exposures but given that the levels they are experiencing are most likely extremely low it is probable that the numbers affected will be in the 100s rather than the thousands or tens of thousands.

There is merit in terms of reduced health impact in proactively removing ACMs from buildings rather than waiting until the end of building life to remove the materials. In planning this work priority should be given to schools because asbestos exposure during childhood carries a greater risk than the same exposure as an adult.

A rigorous estimate of the cancer disease burden from current and future asbestos exposure would help clarify the best policy options for government.

[1] Howie, R. et al (1996). Workplace effectiveness of respiratory protective equipment for asbestos removal work (No. HSE CRR 112:90). HSE.

[2] Based on a talk by Prof Newman-Taylor at a recent HSE Asbestos Research Summit. He stressed that his remarks were based on very small numbers of deaths, but there is a suggestion that the rate of mesothelioma at ages 25-39 for those born 1980-84 is about double that for those born 1970-74. He also highlighted the slightly higher mesothelioma death rates amongst teachers and administrative occupations born between the 1930s to 50s compared to other workers.

[3] Barrowcliffe D, Saunders M. (2024) The use of control measures during licensed asbestos removal. HSE Research Report RR1217.

[4] Brostrøm A, Harboe H, Fonseca AS, Frederiksen M, Kines P, Bührmann W, Bønløkke JH, Jensen KA. (2025) Asbestos fiber levels from remediation work. Journal of Hazardous Materials Advances; 17.

[5] Burdett G, Cottrell S, Taylor C. (2009) Airborne fibre and asbestos concentrations in system built schools. Journal of Physics: Conference Series; 151.

[6] The Consortium of Local Authorities Special (CLASP) programme ran from the 1950s to the 1980s. It provided fast and efficiently constructed permanent buildings, that were constructed without using traditional building skills.

[7] Jones et al. (2010) Laboratory Tests to Compare Airborne Respirable Mass and Fibre Concentrations from Soil Samples from Libby, Montana. Indoor and Built Environment; 19: 286-97

[8] Rushton L, Hutchings SJ, Fortunato L, Young C, Evans GS, Brown T, Bevan R, Slack R, Holmes P, Bagga S, et al. (2012) Occupational cancer burden in Great Britain. British Journal of Cancer; 107: S3-S7.