In the case of Dryden and others v Johnson Matthey PLC [2018] UKSC 18 The Supreme Court had to decide whether sensitisation caused by exposure to platinum salts was an actionable personal injury.

The defendant company made catalytic convertors and some of the work force were exposed to platinum salts used in the production process which caused sensitisation. Platinum salt sensitisation itself does not cause any symptoms but further exposure after sensitisation can cause an allergic reaction involving physical symptoms such as running eyes or nose, skin irritation and bronchial problems. The claimants’ sensitisation was detected through routine screening and after the sensitisation was detected they were no longer permitted by the company to work in areas where they might be further exposed to platinum salts to avoid developing allergic symptoms.

Both the High Court and the Court of Appeal had ruled that the claimants had not suffered actionable personal injury, the Court of Appeal noting that  the physiological change of platinum salt sensitisation was “not harmful in itself in any relevant sense”. The claimants’ appealed to the Supreme Court.

The Supreme Court considered that it was necessary to understand the medical evidence about the claimants’ condition for the purposes of the appeal. A person who is sensitised to platinum salts will have a particular type of antibody in their immune system and although they may not yet have developed any physical symptoms of the sensitisation if exposure to platinum salts continues the medical evidence is that most people will develop physical symptoms. At this point they will have developed an allergy, but physical symptoms will not develop if there is no further exposure.

The Supreme Court compared the development of platinum salt sensitisation to the development of pleural plaques as a result of exposure to asbestos fibres which on its own was not an actionable injury. The difference between platinum salt sensitisation and pleural plaques was that slight further exposure to asbestos would not materially worsen pleural plaques, but slight further exposure to platinum salts is likely to increase the degree of sensitisation and cause allergy symptoms. Pleural plaques do not, themselves, turn into any other injury attributable to asbestos unlike platinum salt sensitisation.

Pleural plaques is a marker of exposure to asbestos dust being symptomless in themselves but not leading to or contributing to any condition which would produce symptoms even if the sufferer was exposed to further asbestos dust. The sensitisation of the claimants to platinum salts in this case marks that they have been exposed to platinum salts but unlike the plaques it constitutes a change to their physiological make-up which means further exposure now carries with it the risk of an allergic reaction and the claimants must change their every day lives so as to avoid such exposure. The differences between the development of pleural plaques and the development of sensitisation to platinum salts was sufficient to enable the Supreme Court to consider that platinum salt sensitisation was an actionable injury for which damages could be claimed.