The Claimant employee was exposed to asbestos dust during the course of his employment over 50 years ago. This judgement sheds light on the importance of selecting the correct expert and the need for sound methodology to analyse the possible extent of asbestos exposure when proving causation in industrial disease cases.
The Claimant was diagnosed with interstitial lung fibrosis, a disease which in 70% of cases is idiopathic (i.e. there is no identifiable cause). It can also be caused by exposure to asbestos, in which case the condition is known as “asbestosis”.
The single issue to determine was “how much asbestos had the Claimant been exposed to?” The judge accepted 25 f/ml years cumulative exposure as the benchmark for proving asbestos exposure caused the Claimant’s disease. The judge recognised, obiter, that this threshold might be decreased in some cases, but the fact both experts treated 25 f/ml years as a bright line meant there was no need to go behind that figure.
Exposure took place at the Defendant’s factory for 3 years, as a result of using dustbins full of asbestos to douse fires that were ignited during the production of magnesium. Further exposure to asbestos dust would occur in the 30 minutes during which the resultant mess was cleared. Around 9 fires would occur per year per machine. The Claimant operated one machine, and his colleagues the others.
The Claimant’s expert had no practical experience of measuring asbestos exposure outside the context of asbestos litigation. The judge accepted this would affect the weight of his evidence. Relying on an obscure TUC pamphlet aimed at informing workers of their rights, the expert concluded that the act of tipping out the dustbin, would result in a peak asbestos concentration 10,000 f/ml (the top-end of a concentration range of 10-1000 f/ml set out in abstract in the pamphlet) and so a mean of 1000 f/ml.
This figure of 10,000 f/ml far exceeded the figures provided in a seminal study (“Dr Harries’ study”), which provided that similar activities would result in concentrations of asbestos in the hundreds, not thousands f/ml. The Defendant’s expert stated that he had witnessed visually some of the activities in Dr Harries’ study, and believed the high levels of asbestos dust exhibited were similar to the release of dust in the present case.
The Defendant’s expert had been a member of the Committee for Fibre Measurement and so was strongly placed to assist with quantifying the asbestos exposure. He carefully analysed the degree of asbestos dust that would drift away from the Claimant along the rising thermal currents caused by the fire.
Further, he took issue with the Claimant’s assumption that the exposure to asbestos would be the same regardless of whether the fire was at the Claimant’s own machine or that of a co-workers. The figure the expert reached was a peak concentration of 2000 f/ml.
The judge concluded that he preferred the Defendant’s expert evidence. There was no provenance behind the 10,000 f/ml peak figure (a fortiori nor the 1000 f/ml mean figure), nor any clear reason why the highest possible figure in the pamphlet had been selected by the Claimant. Nor was the unexplained departure from the figures in Dr Harries’ study justified, where that study had been published in a reputable journal and had used clear methodology.
In contrast, the Defendant based his figures on Dr Harries’ study, but made appropriate allowances in the Claimant’s favour, such as account for any remaining dust lingering throughout the day. He properly considered the impact of the Claimant’s distance from the dust, and the fact that on the evidence, the workers would clean up as quickly as possible, reducing the exposure time.
The result of these findings was that the threshold of 25 f/ml years was not met. The figure was more likely to be below 10 f/ml years. This judgement is a welcome shift away from reactive, policy-driven decision-making and a nod toward logical, scientific analysis.
For a full copy of the judgement text, click here
Warne is an interesting decision for a number of reasons.
First, it represents a finding of causation by Idiopathic Pulmonary Fibrosis (“IPF”) in the face of known asbestos exposure. In this context, none of the clinical features are necessarily decisive. The late onset of disease and the significant progression did favour IPF, but they would have been trumped had there been a finding of sufficient asbestos exposure to cause asbestosis. Historically, such cases have been determined against Defendants because of the known asbestos exposure history. However, with the passage of time, cases involving genuine heavy exposure will become less common and it is likely that Defendants will be able to defend more cases by reference to the alternative diagnosis of IPF.
Secondly, the Judge acknowledged the greater expertise of a trained Occupational Hygienist, Martin Stear, over that of a traditional experienced engineer, Ken Taylor. Whilst experts such as Ken Taylor can bring great value to these cases in terms of their contemporaneous knowledge of working conditions in the 1950s and 1960s, they were trained in an environment in which numerical assessment of asbestos exposure was unknown. Mr Stear, on the other hand, through his training as an Occupational Hygienist and experience as a Principal Specialist Inspector at the HSE, had much greater insight into the likely actual levels of exposure from the situation as described in the evidence. At one stage, there appeared to be a curious judicial hostility, in particular in the High Court in London in relation to the instruction of occupational hygienists in cases of this nature. This hostility does now appear to have ended and decisions such as this show the wisdom of so doing.
Thirdly, perhaps the most interesting point is one which did not require resolution on the facts of the case, that is whether the exposure would be considered substantial within the meaning of Section 47 of the Factories Act 1937. The point did not arise for consideration since if the Claimant’s case in relation to exposure and causation had succeeded, then the exposure would inevitably be regarded as substantial, that is at 25 fibre/ml years, creating a risk of asbestosis specifically. If the claim, however, had been a mesothelioma claim and Martin Stear’s evidence was accepted, then there would undoubtedly have been sufficient exposure to cause mesothelioma and the question would then arise as to whether the Defendants would have been in breach of their statutory duty to prevent dust exposure under Section 47 of the Factories Act 1937.
Sammy’s article, which appears below, discusses the relevant authorities. This issue is becoming increasingly important; in particular in the light of the Macdonald v National Grid  UKSC 53 decision (see below), which confirmed that exposure need only be substantial at emission, not necessarily inhalation, to amount to a breach under the Act. It is obvious that the exposure must be substantial at its occurrence, often synonymous with a large dust-cloud. The more difficult issue to determine is whether any degree of duration or repetition is necessary so as to constitute substantial exposure within the Act.
Against this background, it is instructive to consider how the term was regarded at the enactment of Section 47 of the Factories Act 1937. The Chief Inspecting Officer of Factories wrote in his annual report for 1938,
“While Section 47 of the Factories Act 1937 may be thought somewhat ambiguous in its reference to a “substantial quantity of dust of any kind”, it is I consider, an admirable one in that it requires precautions even before it is possible to say specifically that the dust in question is harmful to a recognisable pathological extent. There can be no doubt that dust if inhaled is physiologically undesirable. Moreover, dust that is thought today to be harmless may, following research, be viewed in another light tomorrow. It is not many years ago when the dust of asbestos was regarded as innocuous, while today it is recognised as highly dangerous”.
This would imply that during the course of the enforcement of the Factories Act 1937, the terms “substantial” and “likely to be injurious” would have been interpreted by the Inspectorate in a synonymous way in relation to asbestos, so that very brief irregular exposures would not have been thought to be substantial within the meaning of the Act.
Against this background, as we have argued in PI Update ( link ) ,it would be reasonable to assume that there must be some degree of duration or repetition so as to create a substantial exposure under the Act.
In the present case, the issue would likely have been determined against the Defendants, even on Mr Stear’s evidence, by reference to the concept of potential exposure, which was developed by the Court of Appeal in Jeromson v Shell Tankers (UK) Limited  EWCA Civ 101. The Claimant was only exposed for two to three years but if such exposure occurred at this level and at this frequency during a working lifetime, then a risk of asbestosis would have been apparent. On this basis, the exposure could be considered substantial at the time of occurrence, even if the Claimant himself would not be regarded as being foreseeably at risk given his short period of exposure.
The problem will become more acute if the exposures were much less frequent and of much shorter duration, even perhaps a one-off. In this context, it would appear difficult to argue that the exposure would ever have been considered substantial within the meaning of the 1937 Act. In this context, Smith v Portswood  EWHC 939 (QB) probably represents the better approach as a matter of law. Given the lack of precision in measurement, substantial must to an extent be impressionistic. It follows that there will be cases either side of the borderline as evidenced by the conflicting decisions discussed in the article below.