Bonnington Castings Ltd v Wardlaw

A breach of statutory duty does not itself reverse the burden of proving causation. Unless the legislation provides otherwise, the claimant must establish on the balance of probabilities that the breach caused or materially contributed to the injury.

Where disease results cumulatively from harmful material originating from several sources, the claimant need not prove that the culpable source was the sole or predominant cause. A causal contribution is material if it is more than de minimis. Material contribution may be inferred from prolonged exposure to an inseparable atmosphere which the defendant’s breach helped to pollute.

In Bonnington Castings Ltd v Wardlaw, the respondent contracted pneumoconiosis after eight years in the appellants’ foundry. He inhaled silica dust from pneumatic hammers, for which the appellants were not at fault, and from swing grinders whose extraction appliances were repeatedly obstructed in breach of Regulation 1 of the Grinding of Metals (Miscellaneous Industries) Regulations, 1925.

Lord Wheatley, sitting as Lord Ordinary, awarded £2,000 damages. The First Division adhered to that interlocutor by a majority, with the Lord President dissenting. The central issues before the House were whether breach of a safety regulation shifted the burden of disproving causation to the employer and whether the swing-grinder dust had materially contributed to the disease.

1. Disposition. The House unanimously dismissed the appeal with costs. Viscount Simonds agreed in all respects with Lord Reid’s leading speech. Lord Tucker and Lord Keith of Avonholm delivered concurring reasons, and Lord Somervell stated that he agreed.

2. Burden of proving causation. Per Lord Reid, a claimant must prove both breach of duty and that the breach caused or materially contributed to the injury. The ordinary civil standard applies equally to common-law negligence and breach of statutory duty. The passage in Vyner v Waldenberg Brothers Limited [1946] K.B. 50 suggesting that proof of a safety breach shifts the burden to the employer was erroneous.

   Lord Tucker likewise held that no special onus arises unless the statute or regulation expressly or impliedly provides for one. Lord Keith agreed that the principle attributed to Vyner could not be supported.

3. Material contribution. Per Lord Reid, pneumoconiosis was caused by the cumulative inhalation of the whole body of noxious silica dust. The relevant question was therefore not which source was the most probable cause, but whether dust released through the appellants’ breach materially contributed to the disease. A contribution was material if it was not so small as to fall within the de minimis principle.

   Lord Tucker similarly regarded non-negligible swing-grinder dust as a contributory cause. Lord Keith reasoned that even a proportionately small contribution could become substantial through continuous exposure over eight years.

4. Application to the evidence. Per Lord Reid, the respondent probably inhaled much more dust from the pneumatic hammers. Nevertheless, he continuously inhaled the workshop atmosphere, and a non-negligible quantity of its noxious dust came from the swing grinders. Evidence that visible dust remained suspended supported the inference that smaller, invisible silica particles remained suspended for at least as long.

   Lord Keith considered that the components of the atmosphere could not realistically be divided into independent causal factors. The appellants’ repeated failure to maintain the extraction system therefore materially contributed to the cumulative disease. The respondent had discharged the burden of proof, although the lower courts had partly reasoned from an erroneous reversal of that burden.

1. House of Lords: In Bonnington Castings Ltd v Wardlaw [1956] AC 613, also reported as [1956] UKHL 1, the House unanimously dismissed the employers’ appeal with costs.

2. Court of Session, First Division: Lord Carmont and Lord Russell formed the majority which adhered to the Lord Ordinary’s interlocutor. The Lord President dissented.

3. Lord Ordinary: Lord Wheatley held the employers liable and awarded the pursuer £2,000 damages.