Novartis Grimsby Ltd v Cookson

An employer was liable for bladder cancer where its employee had been exposed, in breach of common law and statutory duties, to carcinogenic aromatic amines and that exposure was proved to be the major contributing cause of the disease. A precise quantitative analysis was unnecessary where historical exposure could not be measured and the trial judge was entitled to accept expert evidence assessing its significance.

Even if the conventional “but for” test alone governed an indivisible cancer, it was satisfied where occupational exposure accounted for 70–75% of the total causal contribution and more than doubled the risk attributable to smoking. Whether the material-contribution principle or the Fairchild exception could apply more widely to carcinogens operating through the same biological mechanism was left open.

The respondent developed bladder cancer after working from 1964 to 1992 at the appellant’s dyestuffs plant. He had been exposed to dust containing carcinogenic aromatic amines, particularly during the early years of his employment. He had also smoked moderately for about 20 years.

Mr Recorder Black QC held the appellant liable in negligence and for breach of statutory duty. He accepted expert evidence that occupational exposure had contributed 70–75% of the total causal risk and was the major contributing cause of the cancer.

The employer appealed from Manchester County Court. It challenged the findings on breach, the assessment of the medical evidence and the Recorder’s use of the material-contribution approach in Bonnington Castings Ltd v Wardlaw [1956] AC 613. The central questions were whether the findings supported breach of duty and whether occupational exposure had legally caused the cancer.

1. Appeal dismissed unanimously. The Recorder’s findings on breach of duty were inadequately explained but were supported by findings he was entitled to make. The employee had inhaled dust from dry alpha-naphthylamine containing 4–5% beta-naphthylamine during the early years of his employment. Permitting that exposure was both common law negligence and a breach of section 63(1) of the Factories Act 1961. The absence of evidence that all practicable precautions had been taken also supported breach of regulation 7 of the Carcinogenic Substances Regulations 1967.

2. A quantitative reconstruction of the employee’s historical exposure was unavailable. Air-monitoring data gathered in the 1980s did not represent conditions in the 1960s and 1970s. The experts therefore had to exercise judgment about the nature and extent of exposure. The Recorder was entitled to prefer the evidence that exposure had been harmful and that the occupational exposure was the major contributing cause of the cancer.

3. The Recorder had accepted without qualification that occupational exposure accounted for 70–75% of the total causal contribution and more than doubled the risk arising from smoking. Even if the strict “but for” test were the only applicable test, the natural inference was that the respondent would not have developed bladder cancer without the occupational exposure. The occupational cause was therefore proved on the balance of probabilities.

4. The court did not decide whether the material-contribution principle in Bonnington Castings Ltd v Wardlaw [1956] AC 613 applies only to divisible conditions, or whether it also applies where exposures contribute to the risk of an indivisible disease. Nor was it necessary to determine the full extent of the Fairchild exception. It was, however, highly arguable that the exception could apply where aromatic amines from smoking and occupational exposure operated upon the body through the same mechanism. Those issues were hypothetical because conventional causation had been proved.

1. Court of Appeal (Civil Division): Dismissed the employer’s appeal unanimously and upheld the finding of liability.
2. Manchester County Court: Mr Recorder Black QC held that the employer’s breaches of common law and statutory duty had caused or materially contributed to the employee’s bladder cancer and awarded compensation.