As we move away from the traditional ‘heavy’ exposure asbestos claims of the 1960s and 70s, we may see more low exposure/marginal cases involving de minimis arguments – a belief that the law should not get involved in circumstances involving trivial matters.

The High Court decision in Bannister v Freemans Plc is an example of a low exposure success for those organisations or businesses that defend against such claims. Let's examine the key points:

Background of case

Mr Bannister (‘the deceased') died of mesothelioma in 2019 following an alleged single-episode exposure to asbestos following refurbishment works in his office, sometime in 1983/84. The works were carried out by contractors over a single weekend and involved the removal of infill panels from office partitions, which allegedly contained asbestos. There was evidence of a memo that had been circulated in the 1980s, notifying office staff that asbestos material was to be removed over the course of the following weekend.

The claimant (Mr Bannister's widow and executrix of his estate) alleged that there was asbestos residue and dust over his desk and the floor when he came into work on the Monday, which was not cleaned up until that evening by office cleaners. Her case was essentially a one-day exposure to asbestos with a reduced level of exposure for the rest of the week following the initial cleaning.

The deceased had worked in an office environment throughout his adult life and this asbestos exposure was the only one within his knowledge.

Expert evidence on alleged exposure to asbestos

The bespoke test for causation in mesothelioma claims was set out by the then House of Lords (now the Supreme Court) in Fairchild v Glenhaven Funeral Services (2002). In terms of that test, a claimant must prove that exposure to asbestos was of a sufficient level to create a “material increase in risk” of contracting mesothelioma. In order to guide the assessment of risk, forensic/hygiene experts will often provide a ‘dose’ estimate of a claimant’s exposure to asbestos fibres.

Assuming the dust was asbestos, the claimant’s forensic expert, Mr Raper, had initially estimated a slightly higher dose. Under cross examination, he conceded there were some inconsistencies in his figures. He accepted estimates more in line with the defendant’s expert, Mr Stear, who estimated a diminutive dose of 0.0004 fibre/ml years.

The next issue was whether such an exposure would materially increase the deceased's risk of contracting mesothelioma and medical evidence from two respiratory physicians was submitted on that issue. The claimant relied upon Dr Rudd who described the exposure as creating ‘a small but more than negligible risk’.

The defendant’s expert, Dr Moore-Gillon, sought to evaluate the significance of the dose by reference to the statistical risks provided by epidemiology (such as the 2000 Hodgson & Darnton study on the risks associated with low levels of asbestos exposure). Dr Moore-Gillon concluded the risk was insignificant and “vanishingly low.”

Outcome in favour of defendant

On the facts presented, the judge accepted that the panels in question probably contained asbestos in light of the memo circulated to forewarn staff and the use of contractors to remove it. However, the claimant failed to prove that the dust found in the deceased's office was in fact asbestos dust; it was plausible that it could have been other construction dust such as that from installation of the replacement panels.

The fact that the defendant had engaged contractors to carry out the removal works led the judge to find it very unlikely that asbestos dust would remain following the removal, because the defendant would have taken precautions. The judge did not accept that the resulting dust was asbestos and the case therefore failed on the facts.

Further, the claimant’s submissions that (i) she did not have to prove a particular level of exposure and (ii) any exposure was likely to be material when considering the question of breach of duty, were rejected.

The de minimis argument

The judge went on to consider the alternative scenario: if the claimant had proven the dust was asbestos, would this exposure have materially increased the risk of contracting mesothelioma? The judge held that such exposure should be treated as de minimis and the claim would also have failed on this basis.

In reaching this conclusion, the judge preferred Dr Moore-Gillon’s opinions, which were more firmly supported by epidemiology. The judge was critical of Dr Rudd for not offering a principled basis for assessing whether there was a material increase in risk and said he made no attempt to assess whether such risk in this case, was more than de minimis. In essence, the judge found that Dr Rudd’s opinions were not adequately justified to convince him.

Mesothelioma claims can be defended

Mesothelioma claims are notoriously difficult to defend but this case offers some reassurance for defendants:

  • Mesothelioma claims can be defended even when it appears there has been no other asbestos exposure.
  • Expert evidence will be even more crucial in low exposure cases. It is clear that these cases will require a dose estimate, an understanding of epidemiological literature and a medical expert to give a view on how any statistical risks can be interpreted.
  • The defence of de minimis may exist in mesothelioma claims even where the alleged exposure is the only exposure known. De minimis will continue to be decided on a case by case basis; the judge in this case did not give an indication of the level of dose that may be considered de minimis.
  • Of course, if a claimant has been exposed to asbestos elsewhere, a de minimis defence may have even greater prospects of success.
  • As we know, mesothelioma is almost always caused by exposure to asbestos, but the onus is on the claimant to prove that they have in fact been negligently exposed. It is not enough for them to cite a possible exposure to asbestos and expect the court to make the link.

For a separate discussion on the burden of proof in personal injury, see my article on the High Court clinical negligence decision of Collyer -v- Mid Essex Hospitals Services NHS Trust.


Laura McMillan

Partner & Director of Advocacy