Respiratory physician causation reporting in asbestos and smoking claims

The role of the respiratory physician in causation reports

In industrial disease litigation, the respiratory physician’s report must assess the relative contributions of inhaled asbestos fibres and cigarette smoke to a claimant’s respiratory impairment. The expert must apply the evidential base to the legal tests for causation, distinguishing between pathology attributable to occupational exposure and that linked to lifestyle factors. This distinction defines the scope of the claim and the defendant’s liability.

Scope of the expert opinion

A respiratory physician’s report in this context is typically instructed to determine whether a clinical condition, such as asbestosis or asbestos-related pleural disease, results from a breach of duty. The expert must evaluate whether the alleged exposure was sufficient in intensity and duration to induce the condition. In England and Wales, the report must comply with CPR Part 35, providing an objective opinion that adheres to the expert’s duty to the court under CPR 35.3. The expert must specify the medical evidence relied upon, separate facts from opinion, and justify conclusions regarding the initiation or progression of the disease.

Causation analysis in overlapping exposures

The standard of causation in England and Wales requires the claimant to prove, on the balance of probabilities, that the defendant’s breach of duty caused or materially contributed to the injury. Where a claimant has a significant smoking history, the physician must determine whether the specific pathology—such as interstitial fibrosis—is consistent with asbestosis or more readily explained by smoking-related disease, such as emphysema or idiopathic pulmonary fibrosis.

The but-for test remains the primary analytical framework. However, where evidence suggests that multiple factors may have interacted, the expert should clarify whether a material contribution analysis is appropriate. This applies only where the medical evidence supports a finding that the defendant’s exposure, while not the sole cause, made a significant contribution to the development of the condition. The expert should avoid assigning causation based on simplistic mathematical or risk-ratio assumptions. Instead, the opinion should reflect an analysis of the individual’s cumulative asbestos exposure and the pathology evidenced by imaging and lung function testing.

The evidential base and its limitations

The reliability of the expert opinion depends on the quality of the underlying records. The physician should integrate:

• Employment and occupational history records to assess the intensity and duration of asbestos exposure.
• GP and hospital clinical notes to establish the chronology of respiratory symptoms.
• Radiological evidence, including high-resolution computed tomography (HRCT) and plain chest radiographs.
• Lung function testing results, interpreted in the context of the claimant’s age and smoking status.

Where key records are missing, the expert must state the limitation clearly. For example, if occupational records are absent, the expert should note the reliance placed on the claimant’s witness statement and clarify that the validity of the causation opinion depends on the accuracy of that history. If radiological interpretation is disputed, the expert may be required to engage in a discussion under CPR 35.12, if directed by the court, to determine whether the findings are characteristic of asbestos-related disease or smoking-related pathology.

Discipline boundaries and expert overlap

The respiratory physician’s opinion is distinct from other expert contributions. For instance, a pathologist may be required if biopsy evidence is available, or an occupational hygienist may be instructed to estimate fibre concentration in a workplace environment. The respiratory physician should not attempt to calculate exposure levels but should provide a clinical assessment of whether the condition is consistent with the level of exposure described by the hygienist or the factual evidence. In Scotland, the role of the skilled witness is to assist the court in evaluating the interactions between occupational and lifestyle factors, though the procedural rules differ from those in England and Wales.

Procedural management of medical evidence

Where questions arise regarding the interpretation of clinical data, legal teams may use CPR 35.6 to submit written questions to the expert. These questions should clarify the expert’s reasoning on causality rather than re-litigate the facts. If the court directs the instruction of a single joint expert under CPR 35.7, that expert must remain independent of either party, adhering to the duty to the court under CPR 35.3. The expert must not allow the instruction to influence the neutrality of the report. The final opinion on causation, whether provided by a single joint expert or separately instructed experts, informs the legal team’s approach to quantifying the claim.