## Facts

- Mr. McGhee was employed by the National Coal Board to work in brick kilns, resulting in regular exposure to brick dust.
- The employer did not provide showering facilities, requiring McGhee to cycle home while still covered in brick dust.
- Exposure to brick dust was not, on its own, considered negligence; the lack of washing facilities was the negligent act.
- McGhee subsequently developed dermatitis.
- Medical evidence indicated that dermatitis could result from either a single exposure or from prolonged exposure to brick dust.
- It was scientifically impossible to determine whether McGhee’s dermatitis was caused by the initial work exposure (not negligent) or the prolonged exposure during his journey home (linked to the employer's negligence).
- The central question was whether the National Coal Board’s negligence in failing to provide showers caused, or materially contributed to, McGhee’s dermatitis, given the uncertainty over the precise origin of the harm.

## Issues

1. Whether causation could be established against the National Coal Board given scientific uncertainty about the precise source of Mr. McGhee’s dermatitis.
2. Whether a "material increase in risk" due to the defendant’s negligence was sufficient to satisfy the causation requirement in negligence claims.
3. Whether the existing "but for" test for causation must be satisfied, or if an exception should apply in cases of scientific ambiguity.

## Decision

- The House of Lords found in favour of Mr. McGhee, holding the National Coal Board liable for his dermatitis.
- The court determined that it was not necessary to prove the prolonged exposure during travel home definitively caused the dermatitis.
- Instead, it was sufficient that the employer's negligence had materially increased the risk of the injury occurring.
- The judges held that there was no substantial difference, for practical purposes, between materially increasing the risk of injury and materially contributing to that injury in situations of scientific uncertainty.
- The burden remained on the claimant to prove that the defendant’s conduct increased the risk, but the need for strict proof of direct causation was relaxed in such circumstances.

## Legal Principles

- A claimant may establish causation in negligence by showing that a defendant’s breach of duty materially increased the risk of the type of harm suffered, especially where scientific uncertainty prevents pinpointing a single cause.
- The strict "but for" test for causation admits exceptions in instances where it is scientifically impossible to identify the precise mechanism of harm.
- The principle of "material increase in risk" serves as an exception but does not replace the general requirement that causation must still be established on the balance of probabilities.
- Later cases, such as Wilsher v Essex Area Health Authority [1988] AC 1074 and Heneghan v Manchester Dry Docks [2016] EWCA Civ 86, have clarified that the burden remains with the claimant and limited the scope of the exception to specific scenarios involving scientific uncertainty and multiple potential causes.

## Conclusion

McGhee v National Coal Board significantly broadened the approach to causation in negligence, allowing recovery where a defendant’s breach materially increased the risk of harm in situations of scientific uncertainty, subject to later refinements restricting its application and confirming that the claimant bears the burden of proof.


McGhee v National Coal Board [1973] 1 WLR 1