Novartis Grimsby Ltd v Cookson

This is an appeal from the judgment of Mr Recorder Black QC handed down on 25^th May 2006, in which he held the defendant/appellant liable to compensate the claimant/respondent for the development of carcinoma of the bladder. The Recorder held that this condition was caused by exposure to carcinogens, in breach of duty, during the course of the respondent’s employment with the appellant.

It has been known since the late 19^th century that contact with some aromatic amines, used in the manufacture of azo dyes, is capable of causing bladder cancer. From 1876 until about two years ago, the appellant and its predecessors in title manufactured dyestuffs, including azo dyes, at premises at Ashton Road, Clayton, Manchester. Until the plant was modernised during the period 1957-63, the working conditions resulted in exposure of many employees to carcinogenic aromatic amines and a significant number of them developed bladder cancer. When sued by employees or former employees who had worked at the old premises, the appellant’s predecessors did not deny liability. However, the appellant’s belief was that, after the plant had been modernised, it had followed best practice and that the technology used was ‘state of the art’. Exposure to dangerous substances had been reduced to a level where there was no significant risk to their employees.

The respondent was employed at the plant from 1964. He worked in the new plant on the production of dyestuffs, including azo dyes. When, in 2001, he developed bladder cancer, he sued the appellant for damages. For the first time in such a case, the appellant denied liability. It wished to draw a line under the past. It contended that, throughout the respondent’s employment, his working conditions had been good. Any exposure the respondent had had to carcinogenic substances was minimal and had not caused his bladder cancer. It was far more likely that his cancer had been caused by his smoking habit.

The Recorder found that the working conditions had not been as good as the appellant contended, particularly in the early days of the respondent’s employment. He found that the appellant had exposed the respondent to significant amounts of carcinogenic amines and that such exposure was in breach of its duty to the respondent. Finally, the Recorder held that exposure to amines had probably made a material contribution to the development of the respondent’s bladder cancer. It followed that the appellant was liable to compensate the respondent for the development of his illness.

The appellant now appeals against the Recorder’s findings of negligence and breach of statutory duty and also his findings on causation. In a nutshell, the appellant’s contentions are, first, that the Recorder failed to analyse the implications of his findings of fact in the way necessary for a proper conclusion on the issue of breach of duty; instead he had equated the fact of exposure to carcinogens with breach of duty. Second, when considering causation, the Recorder had equated the fact of exposure with causation of the cancer. Third, he had applied the wrong legal test for causation. The respondent contends that the Recorder’s exposition on the issues of breach of duty and causation was brief but correct and that, in any event, the evidence which he had accepted made his conclusions inevitable. His approach to the issue of causation had been correct in law.

The judge identified at least four substances used at the appellant’s premises during the respondent’s employment which were either known to be carcinogenic or were thought to be so, so that the appellant was obliged to treat them as carcinogenic.

As I have said, the Recorder held that, on the balance of probabilities, dianisidine and o-tolidine are carcinogenic, although it is clear that he accepted that they were less carcinogenic than beta-napthylamine. In his written grounds of appeal, Mr Charles Feeny for the appellant sought to argue that the Recorder’s finding that these substances were probably carcinogenic was unjustified and was based on selective quotations from the published materials. He did not develop this submission at the hearing of the appeal. I do not propose to say anything more about it. The Recorder recognised that he was taking a bold step in making this finding but made it following what appears to me to have been a careful examination of the published work. In any event, for reasons which will become apparent, it seems to me that the point is not of any great importance in the context of the appeal.

The process of making dyestuffs consisted essentially of mixing and heating various chemicals together in liquid form in a large reaction vessel. When the reaction was complete, the liquid product was discharged into presses where it was filtered so that the dyestuff which had been in suspension was retained (in the form of filter cake) and the liquid discarded. The dyestuff was later transferred to a drier or oven for drying ready for sale.

The respondent commenced employment with the appellant in 1964. For the first year, he worked on filter presses in Building 48, where the large reaction vessels were housed on the upper level. The vessels were loaded by ‘pot men’, also known as ‘special operators’. Much dust was released into the atmosphere when the vessels were charged. The vessels had a negative pressure system which should have prevented the escape of dust and fumes into the atmosphere. However, this was not effective because the men used to leave the lids off the vessels during the heating process. As the negative pressure system served a row of vessels, leaving the lid off one or two vessels in the row reduced its effectiveness.

After the reaction was complete, the liquid product was pumped into filter presses situated alongside the reaction vessels, only a few feet away. The respondent noticed that there was always a layer of dust on surfaces in this building, for example on the plastic sheets used to cover the containers (known as coracles) in which the filter cake was stored. The liquid which drained from the presses gave off fumes as it ran into an open trough.

Many chemical substances were used. Of particular importance at this period was the use of alpha-napthylamine in dry form containing 4% -5% of beta-napthylamine as an impurity. Benzidine tetrazo was also used as a raw material during this period.

The respondent’s main job at this time was to remove the filter cake from a filter press and to scrape out the press using a wooden paddle. He worked mainly with the dyestuffs rather than the raw materials. However, at times, he worked close to the pot men and was exposed to dust from the charging operations and the fumes which escaped from the vessel and from the drainage trough. Special operators were provided with protective clothing because it was recognised that they were exposed to carcinogenic dust and fumes but the respondent was not.

During this period and until about 1970, the appellant provided underpants, socks and overalls for the respondent and he was able always to shower before putting on his own clothes to go home. However, he had to wear his working clothes for three days before being provided with clean ones. He also found that showering his body was not sufficient to remove the dyestuffs from his skin. His skin would exude colour, which would be found on his bed linen and the collar of his shirt.

One day a week, the respondent worked on the Venuleth driers, which I will describe below.

From 1965 until 1970, the respondent worked mainly on Venuleth driers in building 48. Again, his work was with the product dyestuff rather than the raw materials. The raw materials used included all the carcinogenic substances mentioned in paragraph 6 above. The respondent had to shovel filter cake into the drier, where it would remain for 24 hours, and then open the base of the drier to allow the dried product to drop into a container. He then had to clean inside the drier ready for the next charge. When the lid at the top of the drier was opened, a great deal of dust would escape. The filter basket had to be removed for cleaning and this was also dusty. The respondent had to scrape the residues out of the drier; this was a very dusty job. If there was to be a colour change, he had to clean the drier thoroughly, which took several hours. Another aspect of the respondent’s work at this time was to load filter cake onto trays and slide them into ovens for drying. When the product was dry, the respondent would tip it into an open-topped drum.

During this period, the respondent was provided with a gauze mask and later a paper mask but the appellant now accepts that these were quite inadequate. There was so much dust that the men used to wear two masks at a time. The product was also in contact with the respondent’s skin. During this period, the respondent’s body exuded colour onto his shirts and bed linen.

From 1970 until 1989, the respondent worked on spray driers in Building 46. By this time the use of benzidine tetrazo had been discontinued and the alpha-napthylamine contained a lower level of impurity. Dianisidine and O-tolidine were used as raw materials. The respondent handled finished dyestuffs rather than the raw materials. The filter cake was loaded into the drier, together with dispersing agents and the mixture was atomised at high temperature so as to produce a fine powdery product. When ready, the product was dropped into a large container. The respondent would assist in this task. A great deal of dust was liberated during this process. Initially, the respondent was given a paper mask, which was ineffective, but later, in about 1987, he was given a Racal respirator, which was suitable and effective. From about 1970, the appellant provided clean underpants and working clothes each day.

From 1989 until 1992, the respondent was a supervisor in the spray drier department. He spent much of his time on the factory floor. He became unwell in 1992 and retired in 1993 on medical grounds unrelated to bladder cancer which did not manifest itself until 2001.

The respondent alleged that the appellant was in breach of its common law and statutory duties throughout his employment. Date of knowledge was not in issue (save in respect of the risk from metabolisation within the body which was not understood until about 1980).

The respondent alleged a breach of section 63(1) of the Factories Act 1961 which provides:

“In every factory in which, in connection with any process carried on, there is given off any dust or fume or other impurity of such a character and to such extent as to be likely to be injurious or offensive to the persons employed, or any substantial quantity of dust of any kind, all practicable measures shall be taken to protect the persons employed against inhalation of the dust or fume or other impurity and to prevent its accumulating in any workroom and in particular where the nature of the process makes it practicable, exhaust appliance shall be provided and maintained as near as possible to the point of origin of the dust or fume or other impurity so as to prevent its entering the air of any workroom. ”

In that connection, the respondent alleged that he was exposed to dust which was likely to be injurious, in that it contained carcinogens. In so far as exhaust appliances were provided, they were not effective in preventing the dust and fumes from entering the air of the workroom.

The respondent also alleged that, from December 1967, when the 1967 Regulations came into force, it had been in breach of its duties under those regulations. Regulation 4 prohibited the use of some substances (including beta-napthylamine and benzidine) save that it was permissible to use a substance which contained, as an impurity, less than 1% of a prohibited substance. Thus, from 1967, it was prohibited to use alpha-napthylamine containing 4% – 5% of the beta-isomer.

Regulation 6(1) designated various substances as ‘controlled substances’. Alpha-napthylamine, dianisidine and O-tolidine were included in the list. Regulation 6(2) provided that where any person was employed in the manufacture, formation or use of any controlled substance, the duties set out in Regulations 7 and 8 applied. The respondent alleged a breach of Regulation 7 which provided:

“All practicable steps shall be taken to prevent persons employed in any manufacture or process to which regulation 6(2) of these regulations applies, or in the storage or movement within a factory of any controlled substances in connection with any such manufacture or process, or in the maintenance or cleaning of plant or the cleaning of containers stores or workrooms in connection with any such manufacture or process, being exposed to the risk of inhaling ingesting or otherwise absorbing any of the said substances.”

The respondent contended that, even before the 1967 Regulations came into force in December 1967, the appellant was aware of all the risks that the forthcoming regulations were designed to overcome. Consequently, the appellant was under a common law duty even before 1967 to take all practicable steps to prevent him from being exposed to the risk of inhaling, ingesting or absorbing any alpha-napthylamine, dianisidine or O-tolidine. In addition, the respondent alleged that the appellant did not warn the respondent of the risks of exposure to aromatic amines and did not provide him with appropriate protective clothing.

In its defence, the appellant did not allege that it had taken all practicable steps to comply with Section 63(1) or with Regulation 7. It admitted that it had not taken sufficient care to protect the respondent from inhalation of dust and contact with finished dyestuffs. Its case was that exposure to carcinogens as had occurred was minimal and had not caused his cancer.

The appellant did not admit that the respondent had been exposed to any carcinogenic raw materials. However, it admitted that, if the respondent were to prove that he had been exposed to the raw material alpha-napthylamine during the charging process, such exposure would have been a breach of the appellant’s common law duty of care. The respondent was put to proof of the frequency and degree of such exposure. In its amended defence, the appellant ‘clarified’ this admission. It contended that there would only have been a breach of duty if the respondent could prove that he had been working immediately next to the special operator. That would be, it was pleaded, ‘unacceptable practice’. It would not have been a breach of duty if the respondent had merely been ‘in the area’ where the charging operation was being carried out. But, in any event, even if the respondent could show exposure in breach of duty, the appellant denied that the exposure was hazardous. It seems to me that this stance was somewhat inconsistent because it would only be a breach of common law duty to permit a workman to stand next to the special operator if doing so gave rise to a foreseeable risk of injury. However, that was the appellant’s position and it stated that, in support of its contention that the exposure was not hazardous, it would rely on documentary evidence of the results of air monitoring.

The respondent’s evidence as to his working conditions, as I have set it out above, was barely challenged and was accepted by the Recorder. The evidence of a witness, Mr Healey, who worked as a special operator/pot man from 1976, was challenged by the appellant but the appellant did not call any evidence to contradict his account and the Recorder accepted it. Mr Healey said that it was normal practice for the special operator to leave the vessel open after charging while it was heated. He also described how, when loading a drum of alpha-napthylamine flake into the vessel, he would bang on the drum with a spanner or shake it up and down so as to loosen the flake and to ensure that the drum was completely empty at the end. This released a lot of dust into the air. He described loading dianisidine into the vessels. This was in powder form and came in bags. He would shake the bags to ensure that they were empty. Each load would take about 28 to 30 bags. Although the respondent did not work close to Mr Healey, his case was that the practices and conditions that Mr Healey described were the same as those followed in the 1960s.

The appellant called a witness, Mr Thorpe, who had been employed by the respondent since 1990, latterly as environmental health and safety manager. In response to a request for information lodged by the respondent’s solicitor, he produced several types of records maintained by the appellant. These included records (far from complete) of the chemicals used at the plant.

Mr Thorpe also produced the results of bio-monitoring of the respondent which was carried out from about 1988. These tests were designed to detect metabolites of carcinogens in the urine. All the respondent’s results were negative. However, the results of such tests on some men were positive and these were not limited to the special operators. The respondent also said that he had undergone a different form of urine test approximately every six months from the start of his employment but had never seen or known of the results.

Of greater importance as evidence in the case were the results of air monitoring which had begun in the 1980s. These results showed that the amounts of dust and fume in the atmosphere were usually (although not always) below the ‘recommended levels’. During the respondent’s employment, there were no internationally recognised threshold limit values for the various carcinogenic substances which were under scrutiny in the present case. The appellant itself had produced some figures which it regarded as ‘safe’ atmospheric concentrations for the various substances. These figures had been submitted to the Health and Safety Executive and had been accepted as recommended ‘safe’ levels. The Recorder was not shown any evidence of the research which underlay these in-house figures. However, for the purposes of the case, the respondent was content to accept that the atmospheric concentrations which the appellant advanced were indicative of a safe level of exposure.

The appellant’s case in respect of the air monitoring results was that, although the results related to working conditions in the 1980s, it could properly be inferred that the results would have been similar if tests had been carried out in the 1960s and 1970s. The respondent disputed that, pointing out that working practices had been improved in the 1980s. For example, in the 1980s, alpha-naphylamine was purchased and used in liquid form so that there was no dust generated during the charging process. In the 1960s, that raw material had been purchased in dry flake form. Also, the respondent’s evidence, accepted by the Recorder, was that much more care was taken in respect of working practices during the 1980s than before. The respondent also pointed out that some of the readings taken in the 1980s were very close to the allegedly safe limit and some of those for dianisidine actually exceeded the in-house limit. It could not be inferred that the concentrations in the air in the early days would have been below the ‘safe’ level. The Recorder accepted that the working conditions had indeed been significantly different in the 1960s and 1970s and that the readings for the later period could not be relied on as indicative of the respondent’s exposure during the earlier years.

Dr Keith Mullen, the consultant chemist called on behalf of the respondent, was of the view that the respondent had been exposed to carcinogens. He thought that the exposure to impure alpha-napthylamine and benzidine tetrazo during the 1960s (and in particular during the first year of his employment) was of particular concern. He was also of the view that, during the later periods, when the respondent had been exposed to dust while working on the Venuleth and spray driers, he had been exposed to carcinogenic amines still present in the finished product as unreacted material. He pointed out that the appellant’s own documents suggested that there were particular risks of finding unreacted amines in some specific dyestuffs. The respondent worked with those dyes. The appellant’s documents also showed that it had been recognised that men working on the charging of Venuleth driers should wear a Racal powered respirator but the respondent had never had one while doing that job. Dr Mullen also pointed to the air monitoring results which were sometimes very close to the in-house limit in the 1980s, even after there had been significant improvement in production methods. He concluded that the respondent’s exposure to carcinogens had created a significantly increased risk of him developing bladder cancer.

Mr G D Smith, an occupational hygienist called on behalf of the appellant, disagreed with Dr Mullen’s views. His opinion was that, when account was taken of the frequency and duration of the respondent’s exposure to the carcinogenic amines, the respondent’s daily and cumulative doses would not have exceeded the in-house exposure limits. However, he admitted in cross-examination that he had based this assessment on his understanding of the evidence before the trial had begun and that, in the light of the evidence as he now understood it (including the high level of beta-napthylamine impurity during the mid-1960s) it might be necessary to revise his assessment. That was never done and the Recorder preferred the evidence of Dr Mullen for reasons which he set out in full at paragraph 69 of his judgment. There is no need to burden this judgment with the detailed reasons but it is apparent that Mr Smith had been driven to make a number of concessions in the course of cross-examination.

The Recorder’s findings of fact in respect of exposure were set out at paragraph 72 of the judgment. He found that, during the first year of his employment, the respondent had been exposed to dust from the charging process. He found that the dust from the charging would be suspended in the atmosphere for some time and would settle on the surfaces, such as plastic sheets covering the coracles. The respondent would have inhaled it when it was first released and also when he removed the covers from the coracles. This dust would have contained 4% to 5% beta-napthylamine as an impurity in the alpha-napthylamine. He found that during the years 1965 to 1970, the respondent was exposed to substantial quantities of dust from dyestuffs. This would have entered his body by inhalation, ingestion and skin absorption. Between 1970 and 1992, while working on or near the spray driers, he was again exposed to substantial quantities of fine dust from dyestuffs. The Recorder did not expressly say so, but it is implicit that he accepted that this dust contained very small quantities of carcinogens. That was agreed by both experts.

In paragraph 72, the Recorder did not go on to make any holding of law as to breach of duty. After dealing with exposure, he turned to deal with carcinogenicity and causation. After doing so, he returned to the issue of breach of duty at the very end of his judgment. At paragraph 109, he said:

“The Defendant has accepted, subject to causation, that it was in breach of its common law and statutory duties to the extent that the Claimant was not provided with or required to wear an adequate dust mask in dusty conditions. I do not read the admission to extend to ingestion of carcinogenic substances otherwise than through inhalation. On my findings on the basis of the medical evidence, the carcinogenic substances may also be ingested or absorbed though contact and accordingly I also find breach of the Defendant’s common law and statutory duties for failing to take all practicable steps to prevent such exposure as well.”

The notice of appeal sets out five grounds, on all of which permission was granted. I will deal at this stage with the ground relating to the Recorder’s holding on breach of duty.

Mr Feeny for the appellant submitted that the Recorder had failed to analyse the nature, degree and circumstances of the exposure to carcinogens. He had simply concluded that all the proven exposure to carcinogens amounted to a breach of common law and statutory duty. In short, he had equated the fact of exposure to a breach of duty. In ground 5 of his notice of appeal, Mr Feeny also complained that the Recorder had erred in some of his findings of fact. However, Mr Feeny did not seek to develop those points at the hearing and I think he accepted that they were properly subsumed into the ground relating to the Recorder’s holding on breach of duty.

At first sight, there seems to be considerable force in Mr Feeny’s submission that the Recorder’s judgment was very light on analysis. I have summarised the findings of fact and quoted the only passage in which he dealt with breach of duty. Although the findings of fact are clearly set out, the allegations of breach of duty are not separately dealt with and one does not see any reasoning by which the Recorder linked his findings of fact with his conclusions of law.

Mr Peter Cowan, who appeared for the respondent, pointed out, however, that the appellant had made quite significant admissions on the pleadings in relation to breach of duty. Also, the main thrust of its argument was not that the working conditions had been satisfactory; rather it was that the amounts of carcinogen to which the respondent had been exposed (albeit in breach of duty) had not caused or contributed to the development of his disease. The appellant had accepted that the respondent had been exposed to dust and that the protective masks had been inadequate. That, in itself, was sufficient for a finding of common law liability, provided that there was some risk of harm arising from the dust. That had never been seriously disputed. The fact that the appellant provided masks and eventually supplied Racal respirators was surely recognition that masks were needed. In any event, there was undisputed evidence that the dust from the finished dyestuffs contained some (albeit small) amounts of unreacted amine. Further, the appellant had admitted that, if the respondent had worked in close proximity (next to) to the pot men, that would have been unacceptable practice. The Recorder’s findings were that the respondent worked in the area of the pot men and that he inhaled the dust from the raw materials being loaded, both during the charging and also later when he disturbed the dust by lifting the covers off the coracles. Plainly, submitted Mr Cowan, if the dust from the charging of raw materials contained carcinogens, even if only present as impurity, there was a breach of section 63 of the Factories Act. It had not even been pleaded, let alone proved, that all practicable measures had been taken to avoid inhalation of that dust. Further, the Recorder’s findings of fact and his acceptance of Dr Mullen’s expert opinion as to the dangers of the substances to which the respondent had been exposed, taken together with the absence of any evidence of steps taken to avoid contact with carcinogenic substances (with consequential inhalation, ingestion and absorption) made a finding of breach of regulation 7 of the 1967 Regulations inevitable. Yet further, given that there was clear evidence (not referred to by the Recorder but apparent from the appellant’s own documents) that the appellant had been aware of the dangers of contact with aromatic amines since at least 1952, it was clear that the failure to minimize exposure to such substances was, of itself, a breach of the common law duty, even before 1967. The evidence showed a failure to take such steps, for example in the failure to provide adequate protective clothing and masks and the use of dry flaky alpha-napthylamine when a liquid product was available. In short, said Mr Cowan, the judgment might not have been as explicit as one would have wished, but the Recorder’s holding was unassailable.

I, for my part, accept Mr Cowan’s submissions. He made them good by taking the court through the pleadings and evidence in considerable detail. He also demonstrated the appellant’s state of knowledge by reference to the publications which the Recorder had seen. For example, Dr Scott, the appellant’s medical officer in the 1950s, had published a paper in 1957 which showed that the appellant’s predecessors were aware that there was a hazard to men working on driers because the dyestuff product contained unreacted carcinogenic amines. This was particularly so in respect of benzidine-based dyestuffs which could contain unreacted benzidine. Also, Dr Scott had recommended the use of alpha-napthylamine in liquid form but this recommendation had not been adopted until about 1980.

Mr Cowan also took us to the respondent’s evidence and that of Mr Healey to ensure that we understood the nature of the exposure which the Recorder had accepted. He took us through Dr Mullen’s evidence and drew attention to the shortcomings of Mr Smith’s opinion, which justified the Recorder’s rejection of it.

I am quite satisfied that the only criticism that can be made of the Recorder’s holdings on breach of duty is that they might have been more fully explained. I am satisfied that they were well-founded in the findings of fact that he was entitled, on the evidence, to make. As will become apparent later in this judgment, the crucial finding of liability related to the early years and in particular to the first year of the respondent’s employment when he was exposed to dust from the charging of flaky dry alpha-napthylamine containing 4% to 5% of the beta isomer. It is clear on the evidence that the Recorder was entitled to hold that this exposure was both a breach of section 63 of the Factories Act and amounted to common law negligence.

It is true that the judgment did not contain a quantitative analysis of the extent of the respondent’s exposure. In my view that was because the material was not available to permit such analysis. The appellant had sought to rely on air monitoring which did not begin until the 1980s. The Recorder held that these results were not representative of working conditions in the 1960s and 1970s. He could not say by how much the results of air monitoring, if done in the earlier decades, would have exceeded the recommended levels. The extent of the exposure had to be a matter of impression for the experts. Dr Mullen’s impression, accepted by the Recorder was that the exposure was harmful. That impression become important in the context of the next ground of appeal, to which I will shortly turn. However, I would reject the first ground of appeal.

Before turning to the appeal on this issue, it is necessary to set out some uncontroversial facts about the causes and aetiology of bladder cancer and also to introduce the experts who gave evidence on causation.

Besides the occupational exposure to aromatic amines in the dyestuffs industry, which has been recognised as a cause of bladder cancer for many years, it is also known that cigarette smoking can be a cause, as can the ingestion of certain drugs. More than one potential cause was present in this case. As well as working for the appellant for many years, Mr Cookson had been a moderate cigarette smoker (10 to 20 a day) for about 20 years. He had given up the habit in about 1980. He had also taken potentially harmful drugs for a time but it was not suggested by either side that those drugs had had any significant effect on the causation of his bladder cancer. Cigarette smoke contains amines and the amines from both sources act on the body in the same way. It was accepted by both sides that the two forms of exposure would have had at least an additive, if not multiplicative, effect. The argument between the parties was about the relative potency of the effects of smoking and occupational exposure. In essence, the argument was whether the occupational exposure was sufficient to have caused or materially contributed to the development of the cancer.

One of the issues much discussed during the evidence was the extent to which the risk of developing bladder cancer as the result of cigarette smoking declines with the passage of time after the patient has stopped smoking. Much research has been done on this topic and, although the extent of such reduction was not agreed between the experts, it was common ground that the risk was very substantially reduced after a period of 20 years had passed. Exactly how this theory fitted in with the agreed evidence as to the mechanism by which the cancer was triggered was never fully explained by either expert. The experts agreed that a certain level of exposure to carcinogen was required to overcome the body’s natural defence mechanisms so as to trigger an abnormal cell development. The latent period between exposure and manifestation of the cancer could be very long. The average appeared to be about 16 years but 40 years was not uncommon. The experts also agreed that the risk of developing bladder cancer was dose related; the risk increased with increased exposure. I myself have found it hard to understand how the passage of time after stopping smoking could result in a reduced risk of developing the disease if the aetiology of the disease is that the cancer begins at the time of exposure but does not manifest itself until later. However, as I have said, this issue was not fully explored in evidence and both experts agreed that the risk of developing bladder cancer from smoking decreased after smoking ceased.

The respondent’s expert was Mr Robin Barnard FRCS, a consultant urologist who had practised for many years in Manchester and had seen many cases of bladder cancer among the appellant’s employees and former employees. In February 2002, before proceedings were commenced, he provided a medical report which dealt mainly with the respondent’s condition and prognosis and only briefly with the issue of causation. He was of the view that the long exposure to carcinogenic chemicals at work was probably responsible.

In January 2004, the appellant instructed a consultant urologist, Mr Philip Smith FRCS. He too gave an opinion, mainly on condition and prognosis. He also noted the respondent’s smoking habit and observed that smoking was the most common cause of bladder cancer. He expressed the opinion that smoking must be considered to be the cause of the respondent’s cancer until evidence of other aetiological factors could be determined. He felt unable to express any opinion about the nature and extent the respondent’s occupational exposure or its causative potency.

When it became apparent that causation was a live issue, the two urologists agreed that it would be a good idea if Professor Ray Cartwright were to be jointly instructed. He is an epidemiologist who has published widely on the causes of bladder cancer. In October 2004, Professor Cartwright produced a report in which he discussed the respondent’s exposure to bladder carcinogens at work and through cigarette smoking. He opined that the respondent had been at only a low risk of developing cancer but that, of the two sources of risk, the risk from smoking was the greater. He acknowledged that, in assessing the nature and extent of the respondent’s occupational exposure, he had been dependent upon others. Professor Cartwright cited various publications in support of his opinion, some of which were his own work.

In January 2005, Professor Cartwright provided an additional report after being shown additional material, including the report of Mr G D Smith. This, observed Professor Cartwright, dealt in great detail with the quantitative aspects of the occupational exposure. As a result of reading this material, the Professor declared himself satisfied that the respondent’s exposure to alpha-napthylamine had been very low. In particular, he said that it was clear that any contamination with beta-napthylamine would have been of the order of 1% or less. He accepted that sight of Mr G D Smith’s report had made it apparent that the respondent’s potential exposure to amines had lasted for rather longer than he had previously thought. However, this exposure was of such a low level that he did not wish to revise his previous conclusion.

Mr Barnard did not agree with Professor Cartwright’s opinion. In particular, he considered that its conclusions did not properly reflect the results of the Professor’s own published work, specifically in respect of the reduction in risk due to smoking caused by the passage of time after cessation. Mr Barnard was of the view that Professor Cartwright’s published research suggested a much more significant reduction in risk than he had adopted in his report. The upshot was that Mr Barnard was asked to prepare a detailed opinion on causation. This was produced in February 2005. In this report, Mr Barnard reviewed the published work on the causes of bladder cancer and considered the relative risks arising from smoking, working in the dyestuffs industry and the combination of the two. His conclusion was that the respondent’s cancer had been caused by the additive effects of occupational exposure and smoking but that the occupational exposure had been ‘the major contributing factor’. When asked to expand on that in March 2005, he assessed the contribution of smoking at 25%-30% and that of occupational exposure at 70%-75%. Finally, in November 2005, Mr Barnard provided a consolidated report containing his updated opinion on condition and prognosis. He also reviewed the relevant publications on causation and dealt in detail with that issue. It was clear from this report that he had read the documents disclosed by the appellants and the reports of Dr Mullen and Mr G D Smith. His opinion remained as before, that both industrial exposure and cigarette smoking had been causative but that the industrial exposure had been ‘the major source’.

Meanwhile, Professor Cartwright had been asked to comment on the risks associated with finished products in dyestuff manufacturing. He observed that the sources of risk were from unreacted amines and from metabolisation within the body. He noted that the results of air-monitoring of alpha-naphylamine, dianisidine and o-tolidine showed levels which were low and within ‘local guidelines’. He could not address the question of whether the results of air monitoring in the 1980s were representative of working conditions in 1960s and 1970s. It appears that he assumed that they were. He commented that the results of bio-monitoring (urine tests) did not give sufficient information to be useful.

In November 2005, Professor Cartwright and Mr Barnard provided a joint statement outlining their areas of agreement and disagreement. The main area of disagreement was that Mr Barnard thought that the occupational exposure was significant and was the main contributor to the causation of the respondent’s cancer. Professor Cartwright considered that the occupational exposure was so low that the exposure to amines in cigarette smoke must be regarded as the major contributor. On that basis, battle was joined at the trial: Mr Barnard, the clinician opposed to Professor Cartwright, the epidemiologist.

The two experts heard the evidence in the case before giving their own evidence. Although cross-examined, it does not appear that either gave way on their opinions. Indeed, towards the end of his cross-examination, Mr Barnard reasserted his opinion as to the relative potency of the effect of occupational exposure and smoking. The question was put to him in the form of relative risk and he therefore expressed his view in a different way from that used in March 2005 when he had estimated that occupational exposure had made a contribution of 70% to 75% of the total risk. In oral evidence, he said that occupational exposure had more than doubled the risk due to smoking. These two ways of expressing his opinion were entirely consistent and no one has suggested otherwise. Mr Barnard also made it plain that he thought the main exposure had taken place in the early years (1964-1967) and was related to the use of alpha-napthylamine in flake form with a high level of beta-napthylamine impurity. The carcinogen in the later exposures was ‘just a smaller addition’. By the later exposures he meant exposure to dyestuffs containing unreacted amines and compounds which could metabolise to benzidine within the body.

In oral evidence, Professor Cartwright did not change his opinion but he admitted that, when he had formed his opinion, he had been handicapped by the inaccuracies of his understanding of the exposures. He had not initially known that, until 1967, the alpha-napthylamine in use would have contained as much as 4%-5% beta-napthylamine as an impurity. Nor had he appreciated that the results of the air monitoring carried out in the 1980s might not be representative of the conditions in the 1960s and 1970s. He had not appreciated the extent of the respondent’s exposure to raw dianisidine in the early years. However, he did not consider that these differences gave rise to the need for him to change his mind on the respective contributions of smoking and occupational exposure.

The Recorder stated that he preferred the evidence of Mr Barnard to that of Professor Cartwright and, at paragraph 105, set out his reasons in detail. These included the points I have just mentioned. The Recorder plainly thought that these were matters of some importance. Also, the Recorder was not impressed by the Professor’s unwillingness to reconsider his opinion on causation in the light of the new information brought to his attention.

Mr Feeny submitted that the Recorder ought not to have preferred the evidence of Mr Barnard. As an epidemiologist, Professor Cartwright was the real expert on these issues. Only he could have a full appreciation of the comparative risks from smoking and occupational exposure as revealed in the published literature. The literature did not support the proposition that occupational exposure of the level revealed by the evidence increased the risk of bladder cancer. Mr Barnard’s opinion was pure assertion and went beyond his expertise as a clinician. Moreover, because he had worked in Manchester for many years and had seen many former employees with bladder cancer who had worked in the old plant, he had been too ready to assume that working for the appellant gave rise to an increased risk.

I cannot accept Mr Feeny’s criticism of the Recorder’s reasons for accepting Mr Barnard. The proposition that a clinician is not capable of fully understanding the published epidemiological literature on the causation of a condition within his own specialty seems unsustainable and would, I think, surprise many clinicians and epidemiologists. In my view, it was clear from his detailed reports on causation that Mr Barnard was familiar with the published work and he was also able to discuss it intelligently when giving evidence. The Recorder was plainly of that view. As for the suggestion that Mr Barnard was too ready to assume that working for the appellant created an increased risk, this was a good ‘jury point’ but, if it did not appeal to the Recorder, that was an end to it.

Mr Feeny also submitted that the Recorder did not undertake any adequate analysis of the competing views. I am not sure how he could have done. As Mr Barnard repeatedly pointed out, this was not a case in which the extent of the occupational exposure could be quantified. The published work does not say how much exposure is needed to cause bladder cancer. The material for the kind of analysis advocated by Mr Feeny simply was not available. This is in marked contrast to the situation which pertains with a number of other conditions, such as noise-induced deafness and vibration white finger where, nowadays, the experts are able to measure a workman’s lifetime exposure to noise or vibration and the published epidemiology enables some prediction to be made of the extent of the risk of harm and the degree of harm that is likely to eventuate. That process was not possible in this case because the lifetime exposure could not be measured; nor does the epidemiology relating to bladder cancer descend into the kind of detail that would be required to enable the consequences of such exposure to be predicted.

In this case, both experts on causation had to make judgments and their judgments on whether smoking or occupational exposure was the more potent cause were heavily dependent on the assessments of the nature and extent of the occupational exposure, derived to a large extent from Dr Mullen and Mr G D Smith. As to those assessments, Dr Mullen’s view had been preferred. Dr Mullen’s view of exposure had informed Mr Barnard’s opinion on the contribution of occupational exposure. To that extent, Mr Barnard’s opinion had a head start. However, the extent of the exposure was not the only factor in the formation of the experts’ opinions. The length of the exposures and the periods of time that had elapsed since cessation of the exposures were also taken into account by both experts. Professor Cartwright thought that the risk arising from occupational exposure would also decrease with the passage of time, as with smoking. Mr Barnard disagreed. However, the published work did not provide any answer to this issue and the Recorder had to make the best of the evidence he received.

In my view, the Recorder was entitled to prefer the opinion of Mr Barnard for the reasons that he gave. In short, he was entitled to accept that, of the two contributory causes, the occupational exposure had been the major contributing cause of the respondent’s cancer. For those reasons, I would reject the second ground of appeal.

Having accepted Mr Barnard’s opinion, the Recorder went on to consider legal causation. He noted that Mr Cowan had submitted that the conventional legal test was whether the breach of duty had caused or materially contributed to the development of the disease complained of. If it had, legal causation was established. Mr Cowan urged the Recorder not to overcomplicate the issue of causation which was, he submitted a question of fact to be decided by the judge performing the function of a jury.

It seems to me that that was a sound submission by Mr Cowan. I would have thought that, once the Recorder had accepted Mr Barnard’s opinion that occupational exposure was the major contributing cause (as clarified by him as contributing 70% of the total risk or as more than doubling the risk due to smoking), the case was virtually over. Had the Recorder merely said that he was satisfied that virtually all the occupational exposure was the result of the appellant’s breach of duty in the years 1964 to 1967 (which was Mr Barnard’s view) and that he was therefore satisfied that the exposure in breach of duty had caused the bladder cancer, he could not have been criticised. It seems to me that Mr Barnard’s assessment of risk, if accepted, made it inevitable that the Recorder would find causation proved. However, matters were not dealt with so simply.

The Recorder began by citing the well-known passage from Bonnington Castings Ltd v Wardlaw [1956] AC 613 at page 621, where Lord Reid said that it is not sufficient for a claimant to show that his injury might possibly have been caused by the breach of duty he has just proved but must show that it was so caused on the balance of probabilities. In that same passage, Lord Reid went on to say that where, as in that case, the disease has resulted from the cumulative effect of dust from two sources, one resulting from negligence, the other not, the claimant did not have to prove which source had been the more probable cause of his disease. It was sufficient if he proved that the negligent exposure had made a material contribution to the development of the disease. What was a material contribution was a question of degree but any contribution which was more than minimal would be material.

The Recorder also cited a passage from the speech of Lord Keith of Avonholm at pages 626-7, where his Lordship noted that pneumoconiosis was a disease of gradual incidence caused in that case by long term exposure to silica dust and that the pursuer’s condition had been caused by the cumulative effect of dust from two sources, one negligent and the other not. His Lordship considered that the natural inference to draw was that, had it not been for the cumulative effect, the pursuer would not have developed the disease when he did and might not have developed it at all. He concluded that the defendant’s negligence had made a material contribution to the plaintiff’s disease notwithstanding the fact that the non-negligent exposure had been greater than the negligent. The negligent exposure had not been insignificant and therefore he was persuaded that the pursuer had discharged the onus upon him of showing that the defendant’s negligence had been a material contributing cause of his illness.

The Recorder then said that he could not distinguish between the situation in Bonnington and that in the present case. The doctors had agreed that occupational exposure to aromatic amines and smoking were at least additive factors in the causation of bladder tumours. He was satisfied that the occupational exposure had materially contributed to the development of the respondent’s tumour.

Mr Feeny submitted that, by holding that the present case was analogous to Bonnington, the Recorder had applied the wrong legal test. Although Bonnington had not been overruled or disapproved, it was not nowadays appropriate to adopt the test of causation applied there. Bonnington had only ever applied where the disease was caused gradually by the cumulative effect of the exposure; in other words, where the disease was directly caused by and became gradually worse as the result of year on year exposure to dust (or fumes or noise or vibration or whatever). In such a case, it could properly be said that the negligent component of the exposure had made a contribution to the disease. He submitted that a case which would formerly have been determined in accordance with the principle in Bonninigton would nowadays be subject to apportionment of damages. Where only part of the exposure had been caused by the defendant’s breach of duty, the court would apportion the damages, so as more accurately to reflect the extent of the damage caused by that breach of duty. The claimant would no longer recover all the damages. That had first been done in Thompson and others v Smiths Shiprepairers (North Shields) Ltd [1984] 1 AER 881 (a noise deafness case) and had been followed in many other cases since then.

By contrast, in the present case, the respondent’s disease had been triggered by the cumulative effect of exposure to carcinogenic amines from smoking and his occupation. Each exposure gave rise to some risk that the respondent would develop bladder cancer and the combined effect of the two exposures increased the overall risk (either additively or possibly multiplicatively). However, the disease was not divisible in the way that pneumoconiosis is divisible. It could not be said that either of the exposures made the disease more severe. Therefore it could not be said that either exposure had contributed to the disease. Each had contributed only to the risk that the disease would develop. Once it had developed, the seriousness of the disease was wholly independent of the extent of the exposures. By approaching the issue as he had done, the Recorder had in fact permitted the respondent to prove causation by showing only that the occupational exposure had made a material contribution to the risk that he would develop the disease.

Mr Feeny submitted that that approach was wrong, as had been made plain in Gregg v Scott [2005] 1 AC 176. A claimant whose case depended upon showing that the defendant’s negligence had given rise to a risk of harm had to show, on the balance of probabilities that, if it had not been for the defendant’s negligence, he would not have suffered the relevant harm. This was the ‘but for’ test of causation. That was the test which the Recorder should have applied but had not. The Recorder had failed to ask himself whether, if it were not for the occupational exposure (in breach of duty), the respondent would probably not have developed bladder cancer. Mr Feeny submitted that, if the Recorder had asked himself the right question, he could not possibly have answered it in the respondent’s favour.

Further, Mr Feeny submitted that the only circumstances in which it was possible for a claimant to prove causation merely by showing that the defendant’s breach of duty had increased the risk that he would develop the disease were those which arose in cases of mesothelioma, as explained in Fairchild v Glenhaven Funeral Services Limited [2002] UKHL 22. In such cases, it was impossible for a claimant who had been exposed to asbestos by more than one employer to demonstrate which exposure had probably caused his disease. In that special category of cases, an exception is made to the usual rule of causation and the claimant can succeed merely by showing that the defendant’s breach of duty has increased the risk that he will develop the disease.

As Mr Feeny pointed out, in argument before the Recorder, no one had suggested that bladder cancer was analogous to mesothelioma so that the respondent could take advantage of that exception. That appears to be so and, subject to reservations which I will explain briefly below, I for my part am content to work on the assumption that it is not.

Mr Cowan submitted that the Recorder had not erred and that Bonnington was still good law. However, he accepted that cases to which that principle would formerly have applied are nowadays usually subject to apportionment, provided that the necessary information is available to the court to carry out that exercise in a fair and sensible way. His main point was that Bonnington merely demonstrated another way of stating the general rule of causation, namely that the claimant must show that the negligent exposure has probably caused his condition. It was, to all intents and purposes, another way of putting the ‘but for’ rule. In the alternative, if the Recorder had erred by not applying the ‘but for’ rule, Mr Cowan submitted that, if he had applied it, he would have been bound to find in favour of the respondent.

It seems to me that Mr Feeny’s argument raises, in a theoretical way, a particularly difficult aspect of the law on causation. In my view, the law on causation is uncertain in a number of respects. For example, does the principle in Bonnington apply only to ‘divisible’ conditions, where the various exposures contribute to the severity of the disease or does it also apply to cases in which the various exposures contribute only to the risk that the disease will develop? Another uncertainty is the extent of the mesothelioma exception. It is not limited to mesothelioma; indeed has its origins in McGhee v NCB [1973] 1 WLR 1. In Gregg v Scott, the House of Lords held that it did not extend to a case in which the negligence of a doctor (in failing timeously to diagnose the claimant’s cancer) had increased the risk that the claimant would die prematurely but the increase was not such as to make it probable that that would be so. In Barker v Corus (UK)PLC [2006] UKHL 20, Lord Hoffman reviewed the opinions of each member of the Appellate Committee in Fairchild and concluded at paragraph 24:

“It is an essential condition for the operation of the exception that the impossibility of proving that the defendant caused the damage arises out of the existence of another potential causative agent which operated in the same way. It may have been different in some causally irrelevant respect …. but the mechanism must have been the same. So, for example, I do not think that the exception applies when the claimant suffers lung cancer which may have been caused by exposure to asbestos or some other carcinogenic matter but may also have been caused by smoking and it cannot be proved which is more likely to have been the causative agent”

Although Lord Hoffman was there saying that the exception would not apply where one causative agent was occupational and the other was smoking, he plainly had in mind that the two agents would act on the body in a different way. In the present case, the evidence was that the amines in cigarette smoke act on the body in the same way as the amines in the occupational exposure. It seems to me that it is highly arguable that the mesothelioma exception should apply to bladder cancer and that it would be sufficient if a claimant were to prove that the occupational exposure had made a material contribution to the risk of him developing the disease.

If the facts of this case were that the respondent’s occupational exposure to carcinogenic amines had contributed to the risk of his developing bladder cancer but to a lesser extent than the contribution made by smoking, these difficult issues would have to be resolved. But in my view, they do not. It would have been open to the Recorder to accept Mr Barnard’s evidence only in part and to have held that the occupational exposure, although significant, had made only a minor contribution to the overall exposure and risk. Indeed, by invoking Bonnington, and the concept of material contribution, the Recorder might be thought to have accepted Mr Barnard’s evidence only to that limited extent. However, that is not what the Recorder said. He said that he preferred the evidence of Mr Barnard to that of Professor Cartwright. He gave cogent reasons for that preference and he did not qualify his preference or acceptance in any way. Why the Recorder thought it necessary to go into Bonnington at all I do not know, but I am not prepared to infer that he had any reservations about Mr Barnard’s evidence.

The evidence of Mr Barnard which the Recorder accepted was that occupational exposure accounted for 70% to 75% of the total. Put in terms of risk, the occupational exposure had more than doubled the risk due to smoking. In my view, if Mr Feeny is right and the correct test for causation in a case such as this is the ‘but for’ test and nothing less will do, that test is plainly satisfied on the facts as found. The natural inference to draw from the finding of fact that the occupational exposure was 70% of the total is that, if it had not been for the occupational exposure, the respondent would not have developed bladder cancer. In terms of risk, if occupational exposure more than doubles the risk due to smoking, it must, as a matter of logic, be probable that the disease was caused by the former.

It follows that, on the facts of this case, the difficult issues of causation which Mr Feeny so persuasively advanced are hypothetical and I am not prepared to burden this judgment by any further discussion of them. Even if Mr Feeny is right, it cannot avail the appellant. The respondent’s case on causation is made out and for the reasons I have explained, I would dismiss this appeal.