INSIGHT | H&S - COMPRESSED AIR WORK
Above Left: A humeral shaft lesion as seen on MRI (Ref:
https://www.eurorad.org/case/14398 , with permission) Above right: A Chinese air diver with significant advanced DON of both femurs reported in 2018 (Re:
https://doi.org/10.1136/bmj.k637, with permission)
In a manual labour workforce, DON is therefore a
potentially career-ending condition. Affected workers are eligible to claim compensation through the Industrial Injuries and Disablement Benefit scheme11
and are liable
to litigate against employers through the civil courts due to enforced unemployment or change of career.
THE EVOLUTION OF DON IN COMPRESSED AIR WORK DON, historically known as ‘caisson disease of the bone,’ was first described in 191312
1940s revealed a 75% prevalence among asymptomatic compressed air workers, prompting more systematic investigation13
. By 1980, UK radiological data from over
2,500 compressed air workers demonstrated a 17.6% DON prevalence—significantly higher than the 4.2% observed in North Sea divers9
. Despite improved decompression protocols and
hyperbaric working practices over time, DON remains a risk in CAW. To this day, fear of ‘bone rot’ persists in the UK
compressed air workforce, particularly those with family or community members who have worked in the tunnelling industry and developed functionally limiting disease in the second half of the 20th Century. Modern data regarding the condition is scarce. A 1996
Japanese study found an 11.1% prevalence among 3,554 compressed air workers14
reported a prevalence of 34.5%15
, while a 2018 Chinese study . The decompression
techniques used for the respective compressed air work were inaccessible or not documented. This appears to represent the most recent published evidence and highlights the ongoing risk of the condition in hyperbaric tunnelling work globally.
32 | July 2025
The last reported case of DON in the UK was in . Initial skeletal surveys in the
1999, in a worker exposed using the standard UK air decompression table (Blackpool Air Table) despite using relatively conservative work exposures and good site management of the decompression procedure. Since the introduction of statutory oxygen decompression in 2001, no further UK cases have been recorded. However, recognition of the condition has always been hindered by difficulties in following up a typically transient workforce. The apparent decrease in the incidence of DON in UK compressed air workers coincided with a significant reduction in the number of hyperbaric tunnelling exposures compared to historical averages. This limits the ability to draw any definitive conclusions. Comparison between historical and modern
compressed air projects illustrate this shift. The Second Dartford Tunnel, hand-excavated between 1974–1977, required 1,200 compressed air workers who incurred 122,000 pressure exposures. In contrast, each of the twin tunnels at Swanscombe on the High Speed 1 (HS1) line, excavated by TBM in 2002-2003 under similar geological conditions, required roughly 125 hyperbaric exposures by a workforce of 20-3016
. The continued incidence of decompression sickness
in modern compressed air work remains significantly higher than commercial diving practice. The strong association between decompression sickness and DON suggests that compressed air work still presents a risk for bone disease. While improvements in decompression safety have
likely contributed to a reduction in DON incidence, definitive surveillance data is lacking. There is no published evidence, either in the UK or from overseas, which confirms the incidence or absence of DON
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