Neutral Citation Number: [2016] EWHC 1971 (QB)
Case No: HQ15A00754
IN THE HIGH COURT OF JUSTICE
QUEEN'S BENCH DIVISION

Royal Courts of Justice
Strand, London, WC2A 2LL

Date: 29 July 2016

Before :

MR MARTIN CHAMBERLAIN QC
(Sitting as a Deputy Judge of the High Court)
- - - - - - - - - - - - - - - - - - - - -
Between :

	PATRICK WARNE	Claimant	
	- and -		
	VINTERS-ARMSTRONGS LIMITED	Defendant	

- - - - - - - - - - - - - - - - - - - - -
- - - - - - - - - - - - - - - - - - - - -

Mr Simon Levene (instructed by Boyes Turner) for the Claimant
Mr Charles Feeny (instructed by Weightmans) for the Defendant

Hearing date: 19 July 2016
- - - - - - - - - - - - - - - - - - - - -
Judgment Approved
Mr Chamberlain QC : 
Introduction  
1.	The Claimant, Mr Patrick Warne, was employed between 1952 and 1966 by the Defendant, Vinters-Armstrongs Ltd, in their factory at Wyke Regis on the outskirts of Weymouth. On the agreed medical evidence, he suffers from interstitial lung fibrosis, which has significantly affected his lung function and is progressing. In 70% of cases, this condition has no identifiable cause and is termed “non-specific interstitial pneumonitis” or “usual interstitial pneumonitis”. But it can also be caused by exposure to organic fibres such as asbestos. When caused by exposure to asbestos, it is known as “asbestosis”.
2.	The Claimant contends that his condition was caused by his exposure to asbestos dust over a period of between two and three years in the late 1950s, when it was provided to those working in the machine shop for suppressing fires caused by machining magnesium. The Claimant says that, in consequence, the Defendant is liable in the tort of negligence and for breach of various statutory duties imposed by the Factories Act 1937.
3.	The Defendant has no reliable records of what was or was not done in the 1950s and, in its Defence, put the Claimant to strict proof of his case, in particular on the extent of his exposure to asbestos dust. The Defendant, however, conceded that it would admit breach of the relevant common law and statutory duties if the Claimant could prove that, while employed by the Defendant, he had been exposed to materials comprising or containing asbestos or asbestos dust in substantial concentration. A limitation defence was also pleaded. 
The issue in dispute
4.	By the trial, the issues between the parties had narrowed in effect to one. This single issue is encapsulated in paragraph 4 of the second joint statement prepared by the two medical expert witnesses, Prof. Charles Twort (for the Claimant) and Dr Charles Hind (for the Defendant):
“If the Court finds that Mr Warne was exposed to 25 fibres/ml-years of mixed asbestos fibres, or greater, we attribute his interstitial lung fibrosis to asbestosis.
If the Court finds that he was exposed to less than 25 fibres/ml-years of mixed asbestos fibres, we attribute his interstitial lung fibrosis to idiopathic pulmonary fibrosis.”
5.	Concentration of asbestos fibres in air is measured in fibres/ml (f/ml). The figure of 25 f/ml years is a cumulative exposure or dose and has long been accepted as the threshold at which exposure to asbestos causes asbestosis. The genesis of this figure is described in some detail by in Sabin v BRB (Residuary) Ltd [2010] EWHC 267 (QB), at [32]-[34]. In the course of her judgment in that case, Swift J noted that there was some evidence that a lesser cumulative exposure than 25 f/ml years can result in asbestosis, depending on the type of fibre. A similar suggestion was tentatively made in paragraph 6 of the Claimant’s skeleton argument and at the start of the trial. But it was not reflected in the reports of either of the two medical experts instructed in these proceedings, nor in either of their joint statements (as is apparent from the excerpt quoted above). As the key aspects of the medical evidence were agreed, neither expert gave oral evidence. In those circumstances, it is difficult to see how I could properly go behind the agreed position of the two medical experts, which is to treat a cumulative exposure of 25 f/ml years as a “bright line” for the purposes of causation.
6.	In any event, it is academic to consider what consequence would flow from a cumulative exposure marginally under 25 f/ml years: Mr Levene conceded that causation would not be made out if the cumulative exposure was significantly less than 25 f/ml years; and the Defendant’s expert Mr Martin Stear contends that it was below (and possibly well below) 10 f/ml years: on any view significantly less than 25 f/ml years. If, as the Claimant contends, it was higher than 25 f/ml years, Mr Feeny accepted that both breach of duty and causation would be established. If, as the Defendant contends, the cumulative exposure was significantly less than 25 f/ml years, Mr Levene accepted that causation would not be made out and the issue of breach of duty would not arise.
7.	At the start of the trial, it became clear that the extent of the Claimant’s exposure was now the only issue in dispute. Mr Feeny indicated that he no longer relied on any limitation defence. Quantum was agreed.
The Claimant’s evidence of fact
8.	The Claimant’s evidence in chief was contained in two witness statements. He gave oral evidence by video-link. He accepted that there were certain details of the factory’s working practices that he could not remember with precision. That was inevitable given that the exposure occurred more than 50 years ago. On the important points, however, his recollection was clear and his answers quick and straightforward, even when they did not assist his case. He was an honest and impressive witness. Having heard his evidence, Mr Feeny accepted that it should form the basis of my assessment of the extent of his exposure to asbestos.
9.	This makes it unnecessary for me to say anything about the factual witness statements from others who had worked in the same factory around the same time. None of them, in any event, makes reference to the use of asbestos dust or powder to suppress fires.
10.	The factory at Wyke Regis was built in the 1890s by Robert Whitehead to manufacture torpedos. It produced torpedos throughout the First and Second Worlds Wars with some breaks in between. After 1945 demand for torpedos declined and the factory began producing parts for Vickers aircraft.
11.	The Claimant worked in the machine shop using, among other things, a turret lathe to machine metals including steel, cast iron, aluminium and – for a period – magnesium. There were three other such machines in his immediate vicinity, each with its own operator. The most distant of these was about 20 to 30 ft away. Magnesium is highly flammable and if pressed against the turning parts of the machine for even a second too long a spark could ignite the magnesium powder generated by the cutting action. Although the Claimant and his co-workers were careful, fires did start. They would often start in the swarf tray, which collected the residue of metal shards and powder from the part being machined.
12.	The Claimant estimates that there were between 8 and 10 fires per year when magnesium was being machined at his machine. The position is likely to have been the same for each of his three co-workers. In paragraph 9 of his second witness statement, the Claimant said that “[m]agnesium was machined between 1958 and 1960 for a period of 2 years”. In his oral evidence, he said the period was between two and three years.
13.	A dustbin around 4 feet tall and 3 feet in diameter, and full to the brim of grey powder, was placed next to each machine. The machine operators were told by their employer that the powder was asbestos, which had been selected for its fire-retardant properties. When a fire started, it could spread quickly, so the operator would immediately pick up the bin with both hands and tip or throw on to the fire as much of the asbestos powder as was needed to suppress it. This caused a large plume of asbestos dust, which was visible in the air and which gradually settled on the operator’s hands, face, hair and clothes as well as on the tools, benches and floor. 
14.	Once the fire was out, a labourer would use a broom, dustpan and brush to remove the dust from the floor and surrounding work surfaces. The powder was not dampened down. A compressed air line was used to clean the dust from the machine and tools. These cleaning activities caused further dispersal of asbestos dust into the air. The machine operators were paid on a piecework basis and were keen to get back to work, so the operator at whose machine the fire had started might help the labourer to clear up. The clearing up would take about 30 minutes. An operator would not generally help to extinguish a fire, or clear up, when the fire was started at a machine other than his own.
15.	There was reference in the expert reports to certain other features of the machinery and premises (brake and clutch linings, lagging to pipework and general environmental pollution) that may have involved exposure to asbestos, but it was agreed that none of them would have given rise to any significant exposure. So I need say no more about them.
The Claimant’s expert evidence on asbestos exposure
16.	The Claimant instructed Mr Kenneth Taylor, a consulting forensic engineer, to report on the extent of his asbestos exposure. Mr Taylor worked with asbestos from his apprenticeship as a plumber in 1956 onwards. He then trained as an engineer and later worked as Chief Building Services Engineer for a large local authority. He has been accepting instructions to act as an expert in asbestos-related litigation since 1975. 
17.	It is clear that Mr Taylor is qualified to give expert evidence on the handling of asbestos. But Mr Feeny put to him – and he accepted – that, outside the context of asbestos litigation, he does not have practical experience of the measurement or assessment of asbestos exposure. Mr Feeny did not submit that this made his evidence on the extent of exposure inadmissible. He did, however, submit that it affected the weight to be attached to it. In my judgment, that is the correct approach. As observed by Christopher Clarke LJ (with whom Arden and Treacy LJJ agreed) in Rogers v Hoyle [2014] EWCA Civ 257, [2015] QB 265, at [43]:
“The bar to be surmounted in order to count as an expert is not particularly high, the degree of expertise going largely to the weight to be given to the evidence rather than its admissibility.”
18.	It is convenient to consider: first, Mr Taylor’s analysis of the concentration of asbestos fibres to which the activities described by the Claimant would give rise; and secondly, his calculations of the Claimant’s cumulative exposure.
Concentration of asbestos fibres
19.	Mr Taylor gave at paragraph 13.03 of his report his estimate of the asbestos concentration in the air caused by the use of asbestos powder to suppress magnesium fires, and the clearing up afterwards. At his paragraph 13.03.1, he said this:
“(a) The most significant exposure is that mentioned by Mr Warne in extinguishing magnesium fires with asbestos dust. The initial concentration for several minutes will be extremely high and could peak at 10,000 f/ml.
…
(d) There are no test figures for throwing bins of asbestos dust into the air and using compressed air to blow it off surfaces. The best I can do is note the TUC data in Appendix A for over 10,000 f/ml in removing asbestos. This is not for pure asbestos dust but debris including dust generated during removal. My best estimate is an average 1,000 f/ml for one hour during an occasion when a fire occurs.
(e) Using compressed air on the machinery and brushing down clothing and also sweeping the floor dry would also generate high concentrations of asbestos dust into the air. Dr Harries in his tests (Clause 10 of Appendix A) note [sic] a concentration of 489 for blowing down and 564 f/ml for sweeping amosite. I will use 500 f/ml for 30 minutes on each occasion.”
20.	The figure of 10,000 f/ml mentioned in sub-paragraphs (a) and (d) was also set out in a table reproduced in Appendix A under the heading “TUC Data”. The first row of that table reads as follows:
Task	Fibres/ml	
Old lagging and sprayed asbestos insulation during removal	10s to 10,000s	
21.	The TUC document containing these data was not exhibited to Mr Taylor’s report. No copy of it could be located during the trial. Mr Taylor was asked whether he had had the document before him when he wrote his report in this case. He answered that it had been referred to in his reports for a number of years, that he had a copy and that he was trying (with the help of his wife) to find it. Since it was clear from the report that this document was the source of Mr Taylor’s figure of 10,000 f/ml, I invited Mr Levene to apply to adduce the document after the trial if, after considering it, he wished to do so. I made clear that I would consider any objection by Mr Feeny to its admission in evidence.
22.	The TUC document – or at any rate the part of it containing the table reproduced in Mr Taylor’s Appendix A – was in due course produced. Although there was no opportunity to ask either expert witness any questions about it, I have decided that it should be admitted. It appears to be part of a pamphlet (or possibly an online guidance document) entitled “TUC Hazards at Work”. As might be expected, it appears to be aimed at workers with no or very limited knowledge about asbestos. The document begins with a number of questions or headings: “Why is asbestos dangerous?”, “Is there a safe level of asbestos dust?”, “Are some asbestos products more dangerous than others?” “Does smoking increase the risk of lung cancer?”, “Is there a legal limit?”, “How do I know the control limit is exceeded?”, “The law”, “Avoiding asbestos danger”, “What should I do if I have already worked with asbestos?”, “How do I claim compensation?” and “Further information”.
23.	Under the heading “Are some asbestos products more dangerous than others?” the following appears:
“Blue, brown and white asbestos can cause asbestosis, lung cancer and mesothelioma, but blue and brown seem to cause more mesothelioma than white asbestos. This has led to the dangerous myth that white asbestos is ‘safe’. All types of asbestos are dangerous.
Those that can give off dust easily are the most dangerous unless they are weathered, broken up, or cut up with tools.
The following panel is a rough guide to the dustiness of some of the different products if appropriate dust control measures are not applied.
Range of likely dust concentration without proper control measures (fibres per millilitre)”
24.	The table reproduced in Mr Taylor’s Appendix A is then set out. There are no footnotes, references or other indication of the provenance of the figures it contains. 
25.	Mr Taylor was cross-examined as to the process of reasoning by which he had selected 10,000 f/ml-years as the peak concentration figure. He answered that there was no reliable evidence of the concentration that would be expected from the use of asbestos powder to extinguish fires, but that the activities described by the Claimant would give rise to very high dust concentrations, greater than the concentration caused by other activities such as hacking off asbestos lagging or removing sprayed asbestos with a wire brush. That being so, Mr Taylor explained, it was appropriate to select the highest figure to which he could find reference.
26.	Mr Taylor was asked questions about the paper by Dr P.G. Harries to which he had referred at paragraph 13.03.1(e) of his report (quoted at paragraph 18 above): ‘Asbestos Dust Concentrations in Ship Repairing: A Practical Approach to Improving Asbestos Hygiene in Naval Dockyards’, Annals of Occupational Hygiene, vol. 14, pp. 241-254 (1971). He agreed that the paper was regarded as “seminal” and was widely cited in the scientific literature and by courts. Dr Harries was a Surgeon Commander in the Royal Navy. His paper formed part of a study of asbestos hazards undertaken by the Medical Research Unit at HM Dockyard, Devonport. The methodology is described in detail. It involved sampling the air in the breathing zones of workers employed in various tasks, as well as in the general environment around them. Multiple samples were taken to show the change in dust concentrations at varying distances and the rate of change after work had stopped. Dr Harries noted at p. 242 that “[t]hese methods now form the basis of dust monitoring to be used in naval dockyards”.
27.	Among the data presented are concentrations of asbestos found during removal of pipe and machinery lagging. The figures are presented for “general atmosphere” (where the samples were taken at convenient points in the compartment) and “breathing space” (where the samples were taken as near as possible to the faces of the men performing the task). The mean concentrations vary depending on the type of compartment in which the activity is undertaken. The mean figures for “general atmosphere” are 171 f/ml (with a range of 0.04-1062 f/ml) in boiler rooms, 88 f/ml (with a range of 0.16-3021 f/ml) in engine rooms and 257 f/ml (with a range of 0-592 f/ml) in a brick stowage space. Dr Harries explains these differences as follows:
“…there is more insulting material in a boiler room than in an engine room, and… work proceeds on at least two levels in boiler rooms so that a lot of debris falls 3-4 m to the deck and creates more dust in the general atmosphere. The very high dust levels in the brick stowage space (mean 259 [sic] fibres/ml) are the result of a lot of insulation being removed in a small space.”
The mean concentrations in the sample taken from the breathing space in the boiler rooms and engine rooms were 97 f/ml and 91 f/ml respectively. Other activities are considered later. Mr Taylor was asked about one in particular: mixing asbestos cement in buckets and removing the dry material from a bag. This gave rise to “high general concentrations (167/199 fibres/cm3) and even higher breathing zone levels (217-256 fibres/ cm3)”.
28.	It is immediately apparent that both Mr Taylor’s peak concentration (10,000 f/ml) and his mean concentration (1,000 f/ml) substantially exceed the figures reported by Dr Harries for activities that he identified as giving rise to very high dust levels. Mr Taylor’s explanation for this was that the activities described by the Claimant were “extreme” (a word he deployed on a number of occasions) in the sense that they would lead to a much greater dispersal of dust than any of the activities considered in Dr Harries’ study.
Cumulative exposure
29.	Mr Taylor’s calculations of the Claimant’s cumulative exposure were presented in a table at paragraph 13.04 of his report. That was updated during the course of the trial because the wrong figure had been used for hours per year at work. The updated table was as follows:

Exposure	Hrs/yr exposed	Yrs exposed	Conc f/ml	Lifetime exposure f/ml years	
Throwing asbestos over fire	36	2	1,000	37.5	
Blowing down and sweeping	18	2	500	9.38	
General environment	1,860	2	0.5	0.97	
			Total	47.85	
30.	As became clear when Mr Taylor was cross-examined, these calculations depend critically on three assumptions.
31.	The first assumption is that the activity of suppressing a fire using asbestos powder gives rise to a peak concentration of 10,000 f/ml when the powder is initially tipped or thrown on to the fire and a mean concentration of 1,000 f/ml for a period of one hour afterwards. I have already considered that under the heading “Concentration of asbestos fibres” above.
32.	Secondly, it is assumed that the Claimant’s exposure to asbestos from the dust used to suppress fires would be the same whether the fire occurred at his machine or at another machine some way away from him. The figure of 36 fires per year is derived by multiplying 9 (the mean of the Claimant’s estimate of 8-10 fires per year) by 4 (the number of machines at which fires could occur).
33.	Thirdly, it is assumed that the blowing down and sweeping up take place over a period of 30 minutes after the hour referred to at paragraph 30, giving rise to an additional period of exposure to air with a mean concentration of 500 f/ml.
The Defendant’s expert evidence on asbestos exposure
34.	The Defendant instructed Mr Martin Stear, a chartered Occupational Hygienist and Fellow and Registrar of the Faculty of Occupational Hygiene, part of the British Occupational Hygiene Society. Mr Stear began his work in this field in 1983 with National Occupational Hygiene Services Ltd, where he carried out asbestos surveys for clients, managed large asbestos removal projects and conducted clearance inspections. He then joined the Health and Safety Executive and worked as an inspector and later Principal Specialist Inspector heading the Organic Chemicals and Asbestos section. In the latter capacity, he was (among other things) a member of the Committee for Fibre Measurement and a member of the tri-partite liaison group, which promoted good practice in asbestos work. Since 2003 he has worked as a consultant in occupational hygiene. Mr Levene understandably did not challenge Mr Stear’s expertise in the measurement and assessment of asbestos exposure.
35.	Mr Stear noted at paragraph 4.8 of his report that he was not aware of data specific to the kinds of activities described by the Claimant. He went on at paragraph 4.10 to set out some of the ranges and means recorded by Dr Harries. He continued:
“4.11	This shows that vigorous activities on asbestos result in very high exposures. I believe that the Claimant, at the moment he threw the asbestos powder on the fire, would have received an exposure of over 1,000 fibre/ml. A lot of the fibre would have been caught on the rising thermal air currents, however, some would also have been thrown back at him. This is on the basis of the large amount of material that he suggests he threw onto the fire.
…
4.13	It is difficult to properly model this as the exposure would start to decay as he moved away from the quelled fire and as asbestos dispersed on air currents. The above data from Harries (1971) is largely with regard to ongoing disturbance…
4.14	The labourer also causes further exposure during cleaning, with his exposure possibly being a few hundred fibre/ml. If and when he used an airline, there would probably have been much higher peak exposures although this activity was probably fairly brief. The claimant does not state how long the cleaning took but I will assume half an hour and assume this to be at 500 fibre/ml. If the labourer received this level of exposure, then the Claimant would have received less unless he was standing beside him. A tenth is often used for proximity exposure which suggests 50 fibre/ml for the Claimant, although given his contamination and to err on the high side, I will assume an exposure of half the labourer’s at 250 fibre/ml. Will assume this level persisted for 30 minutes, although in reality it was probably higher at the start of the period than the end (i.e. this figure represents an average).”
36.	Mr Stear’s key conclusions were as follows:
“5.3  Whatever the amount thrown on, exposure at the moment the fire was extinguished would have been very high (substantial). I assume the Claimant would have done this quickly and then stood back, with much of the asbestos fibre caught on the thermal air currents above the fire. Nevertheless, his exposure would have been very high. Exposure would also have been high in the minutes after this due to his bodily contamination and the work of a labourer who would then clean up the mess. Further exposure from the general contamination would have persisted for the remainder of that day.
5.4  I have suggested an exposure of 2,000 fibre/ml for 1 minute as the fire was suppressed, 250 fibre/ml from subsequent excessive contamination and being near to the labourer leaning and, for completeness, 20 fibre/ml for the remainder of the day. This gives a shift average of 39 fibre/ml.
5.5  I believes [sic] this errs on the high side as it assume each fire started at the beginning of a shift, cleaning took 30 minutes and that he was always close by, and that exposure was as high as 20 fibre/ml for the remainder of the day. This gives a dose of 2.6 to 3.3 fibre/ml years.
5.6  If the same exposure is assumed when others quelled fires, then his overall dose was, based on my assumptions, up to 13.2 fibre/ml years. However, his exposure was probably less when others quelled fires. I have provided illustrations based on his exposure being a tenth for those other fires and it being half that of those dealing with fires. This suggest [sic] dose of up to 4.3 and 8.2 fibre/ml respectively.”
37.	As can be seen, Mr Stear took issue with each of three key assumptions made by Mr Taylor and identified at paragraphs 31-33 above. 
38.	In cross-examination, it was put to him that the activities considered by Dr Harries were not analogous to those described by the Claimant. He accepted that they were not identical but gave evidence from his own experience about the level of dust generated by removing asbestos insulation using axes and power tools. He had been present (wearing appropriate protective clothing) when this was done and described it as producing “vast amounts” of visible fibre. His point was that the concentrations reported by Dr Harries for this kind of activity should themselves be regarded as close to the very high end of the scale in terms of the quantity of dust dispersed into the air. He accepted that the action of sweeping up the debris and of blowing down the machine and tools with a compressed air line would in increase the concentration of fibres in the air, but emphasised that the concentration would decay as the fibres were dispersed from the immediate locality to other parts of the machine shop.
Analysis and conclusions
39.	I have structured my analysis of the expert evidence by considering, in turn, each of three assumptions set out at paragraphs 31-33 upon which Mr Taylor’s conclusions depend.
(1) A peak concentration of 10,000 f/ml and a mean concentration of 1,000 f/ml for one hour
40.	Mr Taylor’s starting point is the figure of 10,000 f/ml for peak concentration at the point when the fire is extinguished and immediately afterwards. I consider that Mr Taylor’s use of this figure is open to criticism in three respects.
41.	First, Mr Taylor derived the figure of 10,000 f/ml from data presented in the TUC document without any consideration of the provenance of those data. The features of the TUC document described at paragraphs 22-24 above (and in particular the complete absence of any sources for the figures set out) provide no basis for relying on the accuracy of those data. The vagueness of the relevant figures (“10s to 10,000s”) gives further cause to doubt their reliability.
42.	Secondly, the concentrations recorded in the TUC document for the removal of asbestos lagging and insulation contrast markedly with those for the same activity set out in Dr Harries’ study. The former are, as I have said, of unknown provenance. The latter are actual observed data, gathered using a clearly explained methodology and published in a reputable, specialist journal. Mr Taylor had no cogent explanation for preferring the TUC data in these circumstances.
43.	Thirdly, Mr Taylor accepted that he had selected the figure of 10,000 f/ml because it was the highest figure available. His reason for doing so was that the activity described by the Claimant was likely in his view to generate a higher concentration of asbestos dust than any of the other activities for which data were available. But, even if that were true, there was no scientific or rational justification to jump straight to the figure of 10,000 f/ml. Even if suppressing fires was indeed at the extreme end of the spectrum of dust-generating activities, this represents a critical gap in Mr Taylor’s reasoning.
44.	The selection of 1,000 f/ml as the mean concentration over a period of one hour after the asbestos was first thrown was based on the peak concentration of 10,000 f/ml. Once the latter is shown to be unreliable, so must be the former.
45.	In my judgment, Mr Stear’s methodology and conclusions are to be preferred on this issue. He accepted that the initial peak exposure would have been very high. But rather than simply reaching for the highest figure available, irrespective of its provenance, his methodology was to base himself on the figures recorded by Dr Harries, whilst making what he considered were appropriate allowances in the Claimant’s favour. I accept Mr Stear’s view that, while the activities described by the Claimant would have generated a great deal of dust, so would the activities in Dr Harries’ study. That appears from Dr Harries’ paper (see the excerpt at paragraph 27 above) and from Mr Stear’s oral evidence of his own experience of being present when asbestos lagging was removed. My confidence in Mr Stear’s conclusions was enhanced by his answers under cross-examination. He made appropriate concessions, but they did not undermine his central conclusions.
46.	I accordingly accept Mr Stear’s evidence that the activity of suppressing a magnesium fire using powdered asbestos would result initially in dust with a concentration of 2,000 f/ml but that this would only persist for about 1 minute.
(2) Every fire would give rise to the same exposure irrespective of its distance from the Claimant
47.	Mr Taylor’s report gave no reason for his assumption that every fire would give rise to the same exposure irrespective of its distance from the Claimant. His answers in cross-examination disclosed no convincing explanation for the assumption, which seems inherently unlikely to be correct. It is true that a magnesium fire generates a great deal of heat and that, when powder is poured on to it, much of that dust will be dispersed on thermal currents and, being hot, will remain in the air for some time. As Mr Stear said, however, dispersal would be in all directions. Mr Stear must therefore be right to say that, in the case of a fire at a machine other than his own, the concentration affecting the Claimant would be significantly lower than that at the site where the powder had been thrown.
48.	It follows that I agree with Mr Stear when he said at paragraph 4.22 of his report that “the Claimant’s exposure would be less when others quelled fires as he was not throwing asbestos and would not have received the same bodily contamination”. In fact, Mr Stear’s illustrative figure of 13.2 f/ml years assumes in the Claimant’s favour the same concentration irrespective of proximity to the fire. As Mr Stear suggests at paragraph 4.26, this latter figure should accordingly be regarded as an overestimate.
(3) Over what period should exposure be calculated?
49.	The third assumption underlying Mr Taylor’s report was that there would be a mean exposure of 1,000 f/ml for an hour after the asbestos was thrown, followed by an exposure of 500 f/ml for an additional 30 minutes while the dust was cleared up. This was both implausible and inconsistent with the Claimant’s evidence.
50.	A mean exposure of 1,000 f/ml for one hour was implausible because, even though the action of throwing dust on to a fire would generate a high initial concentration, there would be no continuous activity giving rise to further dust dispersal after that (apart of course from the clearing up, which is addressed separately).
51.	The hypothesis that the clearing up would only start an hour after the fire had been suppressed is not consistent with the Claimant’s evidence, which was that he and his co-workers were keen to get back to work as quickly as possible, because they were paid on a piecework basis, and that work did not start until the dust had been cleared up. The Claimant’s evidence was that the clearing up took about 30 minutes. Once the clearing up was finished, there would have been no activity causing any further disturbance or dispersal of dust. Some dust would, of course, have remained in the air even after this time, but Mr Stear’s calculations allow for this (see paragraph 4.17(c)).
Summary of my conclusions
52.	For these reasons I reject the conclusions of Mr Taylor and, accepting the conclusions of Mr Stear at paragraph 4.26 of his report, find that the Claimant’s cumulative exposure to asbestos arising from his employment with the Defendant was “probably no more than 10 f/ml years and possibly well below this”. The Claimant’s oral evidence that he did not always use all the powder available, but only as much as was needed to suppress the fire (not known to Mr Stear when he produced his report), makes it likely that the figure is indeed well below 10 f/ml years. For completeness I note that the calculations of both experts were based on exposure for a period of 2 years (consistently with what the Claimant said in paragraph 9 of his second witness statement). The Claimant’s oral evidence was that he had worked with magnesium for 2 to 3 years. But even if the period were 3 years, the Claimant’s cumulative exposure would have been below (and likely well below) 15 f/ml years.
53.	This means that, on any view, the Claimant’s cumulative exposure was significantly below 25 f/ml years. Given the agreed medical evidence, and in the light of Mr Levene’s concession recorded at paragraph 6 above, the claim must therefore be dismissed.