IIAC Paper Considers Effect on IIDB Claims When Other Causes of Disease Arise

The Industrial Injuries Advisory Council (IIAC) has published a command paper on diseases with multiple known causes, occupational injuries and medical assessment[i]. This is the third in a series of Command Papers intended to clarify and simplify the decisions made in diagnosis and assessment of disability that results from occupational disease and injury.

This paper considers the assessment of disability in claimants where both occupational and non-occupational risk factors are present and are considered to have contributed to disability.

When a claimant has disability caused by work that meets certain criteria, they are entitled to compensation through the Industrial Injuries Disablement Benefits scheme (IIDB). In some cases, compensation may be deducted if the disability has several possible causes. This paper therefore provides evidence-based guidance of scientifically justifiable deductions.

Under the IIDB scheme, compensation is valued on a disability scale. Awards are sometimes subject to deductions, if it is the assessor’s opinion that a part of the disability is non-occupational. The legal basis for this is set out, inter alia, in Regulation 11 of the Social Security (General Benefit) Regulations 1982; the Regulations allow for disability, due to ‘other effective causes’, to be subtracted before the amount of awards are decided. ‘Other effective causes’ refers to impairments that are not caused by the scheduled employment but which contribute to the total loss of function and disablement.

In secondary legislation, ‘other effective cause’ refers to a birth defect, pre-existing injury or disease, whereas under primary legislation, assessment must be restricted to a claimant’s ‘physical and mental condition’.

There are differing views on whether non-occupational risk factors constitute ‘other effective causes’. Deductions for ‘other effective causes’ are relatively infrequent and typically small. However, they may have significant effects on individual claims. Deductions can only be made in respect of occupational injury claims, encompassing a restricted list of prescribed diseases.

The prescribed disease that is likely to be the most affected by deductions is osteoarthritis of the knee. Other diseases likely to be affected, include

  • focal dystonia of the hand or forearm;
  • tenosynovitis; carpal tunnel syndrome;
  • osteoarthritis of the hip;
  • anaphylaxis in healthcare workers due to rubber gloves;
  • dermatitis;
  • allergic rhinitis; and
  • asthma.

Risk factors are attributes that make one person more or less susceptible to a particular disease or injury than others. For example, some people may have a genetic predisposition that makes them susceptible to respiratory irritation from inhalation of dust. Indeed, there have been cases where risk factors have been considered to be ‘other effective causes’, despite there being no evidence of disability, caused by the risk factor, when the worker began their employment.

In one cited case, the report discusses that a coal miner, who had had surgery to the cartilage of his knee before becoming a miner, and who developed symptoms of knee osteoarthritis almost fourty years later, was deemed to have another effective cause. As such, one-third of the award deducted, despite his complete recovery from the earlier surgery and regained ability to work as a miner for many years.

Moreover, according to The Industrial Injuries Benefit Handbook 1 for Healthcare Professionals: The Principles of Assessment, deductions may be made for ‘degenerative changes’ on spinal X-rays, in respect of awards for back pain injury, on the basis that the degenerative change ‘would have caused problems eventually’, i.e. hypothetical ‘other effective causes’.

In the decision of the Social Security Commissioner[ii] (here), on appeal from the decision of the Medical Appeal Tribunal, the Commissioner cited Rowland. Medical and Disability Appeal Tribunals: the Legislation (1993 edition), which states that:

‘It cannot be emphasized too firmly that an offset cannot be justified merely by a finding that a claimant had some predisposition or liability to develop some disabling condition. There must be a finding that the claimant would have suffered a disability due to the other effective cause even if the industrial accident had never happened’.

In other words, mere predisposition to future disability is not enough; it needs to be established, as a medical fact, that the predisposition will cause disablement. This decision is more than 20 years old, and later judgements have not added to, challenged, or substantially amended this opinion.

The IIAC found that, in deciding the appropriate deduction from the claims where there is a known risk factor in the claimant’s medical history, the decision maker has to decide:

  1. how likely it is that a factor has contributed to their current disablement to any degree; and if so
  2. to what extent; and
  3. how likely it is that it will contribute to their future disablement to any degree; and if so
  4. to what extent,
  5. on the balance of probabilities.

Whilst it is conceivable that a condition causing no symptoms at the date of injury may cause disablement later, the issue is how the deduction can be justified scientifically. In making that judgement, the claimant should be compared to a ‘normal’ person of their age and sex. For example, an older person could be expected to have some symptomless degeneration of the spine. In this scenario, should a characteristic of the comparison group be considered as a risk factor?

The Council considered deductions in two categories of occupational disease.

In the first category, the claimant either has the disease or they do not. An example of this would be cancer. The disability would not have occurred had the injury not been inflicted.

In the second category, there is gradual development of functional impairment. An example of this would be deterioration in respiratory function or hearing ability. The damage that leads to disability in these cases can arise from multiple occupational and non-occupational risk factors.

It was concluded, in the first category of cases, that if the cause of the disability was accepted under the scheme, the disability would not have occurred had the injury not been inflicted. As a result, there are clear scientific grounds for avoiding deductions for non-occupational risk factors. If the disease can be attributed to work, on the balance of probabilities, the Council advises that the disease should be deemed to be caused by work, ‘irrespective of whether other identifiable causes may have played a role’. It follows that any disablement resulting from the disease would also have not occurred in the absence of occupational exposure.

The second category of cases is more complicated. The ‘causation’ question can be answered if it can be shown that, but for the relevant occupational exposure, the disease would not have reached the level of severity specified by the list of prescribed diseases. However, this does not preclude the existence of other contributing causes. Disability may also arise from simultaneous ill health that is wholly unrelated to the occupational disease or injury, but still results in the same type of disablement.

For example, a pre-existing genetic condition may impair lower limb function, and occur in conjunction with knee osteoarthritis, which is considered to have an occupational cause. Alternatively, a potential claimant may have previously had tuberculosis and may also have experienced hazardous occupational exposure. In that situation, both factors could contribute towards a decline in lung function.

In both of these cases, the claimant would have experienced some disability, even if they had never been occupationally exposed. Thus, a deduction in damages would be reasonable.

So, the aim investigations should be to determine how much additional disablement has occurred by way of the claimant’s employment, relative to disablement outside of employment.

The Council found that deductions would only be scientifically justifiable if the extent of disablement from a non-occupational cause could be ascertained reliably, at the commencement of the employment, as being responsible for the disability. In other words, the award can only be reduced if the amount of disability, due to a pre-existing cause, is known prior to any occupational exposure. Objective evidence, such as medical records, in support of disablement from a non-occupational cause, would be needed to warrant deductions. In practice, evidence of symptoms, or abnormal function, are rarely available.

The paper concluded by recommending that:

‘… deductions are not made under Regulation 11(3) for non-occupational risk factors for prescribed diseases or injuries, when these factors have not manifested as ascertainable disablement prior to the start of the responsible employment. We recommend that this should apply across the Scheme as a whole’.


[i] Diseases with multiple known causes, occupational injuries, and medical assessment. Industrial Injuries Advisory Committee. Command Paper Cm 9632. June 2018 https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/717108/diseases-with-multiple-known-causes-occupational-injuries-and-medical-assessment-iiac-report.pdf (Accessed 20 June 2018)

[ii] CI/34/93.