John Cherrie - Li and colleagues [1] have estimated that in China about 3% of all cancer deaths in men and about 2% in women are due to workplace exposures. However, as the authors acknowledge these figures are likely to underestimate the true situation for a number of reasons. Most importantly, they only considered risks from eleven agents or work circumstances and missed a number of exposures that are likely to have importantly contributed to the true occupational cancer burden. Lesley Rushton and colleagues [2] estimated that in Britain about 8% of cancer deaths in men and 2% in women were due to occupational exposures. They considered forty one exposures causing 24 different types of cancer, so this was a much more comprehensive evaluation.
When we compare the attributable fraction of cancers of a specific type with the exposures considered by both studies we get higher attributable fractions in Britain for four of the five cancers. 
For leukaemia the attributable fraction of incident cases is more than ten times higher in China than in Britain (9.9% v 0.9%), which may reflect historically higher benzene exposure in China. However, for the others attributable fraction in Britain is generally more than twice the Chinese figure. The mesothelioma data is particularly odd because the attributable fraction in China is just 19% whereas in Britain it is assessed to be 97% What else is causing mesothelioma in China? Important causes of cancer omitted from the Chinese evaluation are diesel engine exhaust particulate (13% of the UK occupational lung cancer burden), mineral oils (9%), painters (4%) and environmental tobacco smoke (5%). In fact the lung cancer risk factors not considered by Li et al make up about a third of the estimated British occupational lung cancer burden.
Where there is comparable substance attributable fractions from both studies the picture is inconsistent. For example, for arsenic and chromate the the lung cancer attributable fraction is about ten times higher for China whereas for asbestos and crystalline silica the British estimate is higher. The only way that this could occur is if in the past exposure to crystalline silica and asbestos had been lower in China than in Britain.
Read on from John Cherrie
When we compare the attributable fraction of cancers of a specific type with the exposures considered by both studies we get higher attributable fractions in Britain for four of the five cancers.
 |
| Attributable fraction for five lung carcinogens |
Read on from John Cherrie
