NIHL Diagnostic Guidelines - MLC Guidelines attract criticism at first instance hearing

Whilst the tsunami of noise induced hearing loss (NIHL) claims faced by compensators between 2012 and 2017 may now be consigned to a footnote in history, an academic debate has raged over the last three years as to how noise induced hearing loss should be diagnosed. The issue has significance for both claimants and compensators as this sets the evidential bar which claimants must clear to establish that their hearing loss as caused by occupational exposure to noise.

The guideline debate

The established Guidelines were first published in 2000 and are referred to as the Coles, Lutman Buffin Guidelines. An alternative set of Guidelines was published in 2022 and are referred to as the MLC Guidelines - they are generally regarded as more permissive in allowing a diagnosis of NIHL.

Whilst debate has ensued between the respective authors, the issue as to which set of Guidelines should be preferred in a medico-legal context has hitherto not been tested or resolved until now.

Cook V Ketson: first judicial consideration of the guidelines

In a first instance judgment - Cook v Ketson (December 2024), Recorder William Evans provided litigators with some guidance having heard competing arguments from both claimants and defendants as to which Guidelines should be adopted to reach a diagnosis of NIHL. In the present case, the claimant was exposed to noise in breach of duty between 1975 and 1980, with engineers calculating that his lifetime noise dose was 96.8db(A)NIL. The medical experts agreed that the most reliable of three audiograms showed that the claimant was not unusually sensitive to noise damage and, therefore, if the CLB Guidelines were followed, the claimant needed to show a lifetime noise dose of 100db(A)NIL - as this noise dose was likely to cause NIHL in more than 50% of people.

The claimant’s medical expert, Mr Zeitoun, relying on the MLC Guidelines argued that a lower dose exposure - >90db(A) NIL was all that was needed. He argued that, if a given noise immission level (NIL) is sufficient to produce NIHL in 50% of individuals then it follows that at least some individuals will experience NIHL for lower exposure. In short, the claimant advanced the proposition through the MLC Guidelines that ‘fairness to a claimant requires only noise exposure to be sufficient to produce NIHL in a reasonable proportion of individuals’ - a lower threshold than the conventional balance of probabilities.

In rejecting the MLC Guidelines in this case, Recorder Evans found:

“The criteria to determine the evidence required to find causation proved on a balance of probabilities should be determined first and not be determined to make good a theory which is not based on any pre-determined criteria. They also fail to explain why it is they consider that a proven noise level which causes NIHL in 10% of the exposed population can possibly amount to proof of causation on a balance of probabilities in all such persons exposed’’.  

Whilst the decision was at first instance and is therefore not binding, the judgment is likely to prove persuasive if similar arguments are ventilated at any future hearing.

Nick Grimshaw of Deans Court Chambers appeared for the defendant.