The relationship between smoking, exposure to asbestos and the development of mesothelioma or asbestosis disease can affect a court’s decision on the degree of contributory negligence caused by smoking and the amount of asbestos compensation.

Smoking cannot cause or increase the risk of developing mesothelioma. However, smoking is known to increase the chances of causing asbestos-related conditions. Researchers have found that smoking and asbestos exposure, together, can increase the risk of asbestos-related diseases by up to 90 per cent in some cases. Exposure to asbestos is also a known contributing factor in developing lung cancer among smokers.

As exposure to asbestos can cause both conditions, the difference between lung cancer and mesothelioma can also be confused , even though the two occur in different tissues of the body. While lung cancer is a disease which affects just the lung tissue, mesothelioma attacks the lining of the lungs, heart, or abdomen, and is only caused by the breathing in of airborne, asbestos dust fibres.

So what would be the court’s view of a smoker who has developed lung cancer as a result of their occupational exposure to asbestos? Should any contributory negligence be based solely upon the injury-causing ability of smoking when compared to that of inhaled asbestos?

In 1974 around 45 per cent of the population smoked

The potential for developing asbestos related diseases can take up to 40 or 50 years or more before asbestosis symptoms appear. Most victims will only receive a confirmed diagnosis when they reach their 70s and 80s, many of whom would have smoked during most of their adult life. Smoking was a “way of life” for many from the generations who grew up and worked from the 1940s to the 1970s and 80s in asbestos-using industries, such as shipbuilding, railway and vehicle assembly, and construction.

In 1974 – at the peak period of UK asbestos use – around 45 per cent of the population smoked, which dropped to 30 per cent by the early-1990s (Public Health England). The numbers are very different today. In 2016, under 16 per cent of adults aged 18+ smoked (Office for National Statistics).

It is now known that the combination of cigarette smoking and asbestos exposure can have a significant effect upon the risk of developing lung cancer for those who were occupationally exposed. In 2011, the Health and Safety Executive (HSE) published a report, which revealed that of the 1,878 lung cancer deaths among 98,912 UK workers who were exposed to asbestos, just 2 per cent of lung cancer deaths occurred to those individuals who had never smoked.

The report also found that of those who worked with asbestos and also smoked, an estimated 3 per cent of lung cancer deaths were caused by asbestos exposure, 66 per cent to smoking only, and 28 per cent to both asbestos exposure and smoking.

Level of individual contributory negligence by smokers

The figures reflect the potential difficulties in determining the level of individual contributory negligence by smokers exposed to asbestos. Among a number of factors, there is the challenge in drawing a comparison between a former employer’s responsibility for a victim’s asbestos exposure as opposed to the responsibility of the smoker in continuing his habit at a time when they should have given up. Will this have a bearing on the court’s assessment in making a deduction in compensation for contributory negligence?

A former employer defendant can argue that there should be a deduction made for any damages representing the claimant’s smoking from the time they knew or ought to have known of the risks of continuing the habit. A level of contribution, which is usually around 85 per cent could be reduced to 30 per cent to reflect the relative contributory responsibility.

Whatever was the specific cause of the lung cancer in any particular case, it can be found in law to have materially contributed to the condition, and could be taken to have been the entire cause for the purpose of awarding compensation. It means that a court can find that several competing causes were, in fact, each the entire cause of a condition provided that each competing cause materially contributed to the outcome , even if cannot be precisely determined.

Despite mesothelioma cancer being responsible for less than 1 per cent of all cancers diagnosed in the UK, prevalence of the disease has increased almost four-fold since the mid 1980s.