IOSH 2016: The continuing challenge of occupational disease13 Jun 2016
Professor Sir Anthony Newman Taylor from Imperial College London is a keynote speaker at IOSH 2016 and gave a presentation on day one to delegates on ‘The continuing challenges of occupational health’. Here, Sir Anthony talks about occupational diseases, notably ‘dust diseases’ such as silicosis…
The marked reduction in the frequency of occupational diseases, notably of the ‘dust diseases’ such as silicosis, silico-tuberculosis and coal workers pneumoconiosis in the UK by the early 21st century, led to a belief that occupational disease is now a legacy problem.
Internationally, this is certainly not the case. Silicosis continues. An epidemic was reported quite recently in young men sandblasting jeans in Turkey to provide the currently fashionable ‘faded’ look. Silicosis cases also continue to occur in the UK with an estimated 250 cases in each of the past two decades.
More recently, consistent evidence has emerged that inhalation of respirable crystalline silica also causes lung cancer, probably with an increased risk at levels of exposure currently experienced in some sectors in the UK working population.
In their study of the current burden of occupational cancer in the UK, Dr Lesley Rushton and her colleagues estimated that 5.3 per cent of cases of cancer (8.2 per cent in men and 2.3 per cent in women), 8,010 deaths and 13,958 new cases, were attributable to occupation. Of these 8,010 deaths, 4,500 were attributed to past exposure to asbestos and 600 to past exposure to silica; without change they estimated that in 2060 more than 10,000 cases of cancer in the UK would be attributable to occupation. For long-latency diseases of 20 to 30 years or more, current improvements in exposure to carcinogens in the workplace would primarily benefit the next generation.
The incidence of long-latency diseases such as lung cancers and mesothelioma attributable to occupation reflect exposures 30 or more years ago. However, current levels of exposure in the workplace aren’t yet reliably and sufficiently low to have eliminated these risks. The current epidemic of mesothelioma in the UK is the consequence primarily of overlooking, during the 1960s and 1970s, the risks of exposure to amosite in asbestos insulation board to those in the construction industry, particularly carpenters, plumbers, painters and electricians.
At present, 23 million days each year – at an estimated loss of £9.3bn to the UK economy – are lost from work-related ill health, primarily from mental health and musculo-skeletal disorders.
The incidence of occupational asthma due to the majority of its causes, including isocyanates, has been falling in the past decade, with the exception of bakery workers allergic to flour dust and enzymes, added as improvers, whose rates remain essentially unchanged.
In coming to her estimates of occupational attribution of cancer, Rushton and her colleagues were limited by the quality of the evidence. In general, the strength of the evidence is a function of the potency of the agent as estimated by the size of the risk ratio (the ratio of the risk of disease in exposed/not exposed) and the validity and consistency, or repeatability, of the evidence.
Risk ratios of ten or more (e.g. mesothelioma in carpenters) are very unlikely to be due to confounding by other factors, whose prevalence difference would have to be of the same order. On the other hand, risk ratios of less than two (e.g. silica and lung cancer) need to be repeatable in several well-designed studies, taking account of potential confounders (e.g. cigarette smoking, ionising radiation and asbestos exposure) to be credible. The risk ratios of several relationships of current concern (e.g. silica and lung cancer, shift work and breast cancer) are less than 2; sufficient confidence in risk estimates of this magnitude require consistent evidence from several well-designed studies in different working populations.