Health and Safety
Executive / Commission
Statistics
Chronic Obstructive Pulmonary Disease (COPD) is a term used to describe a progressive and irreversible decline in lung function which results in reduced airflow in the lungs. It includes two main diseases: bronchitis – in which inflammation of the bronchi (tubes carrying air to and from the lungs) both narrows them and causes chronic bronchial secretions – and emphysema – a permanent destructive enlargement of the airspaces within the lung without any accompanying fibrosis of the lung tissue. Asthma may also be included within the term COPD if there is some degree of chronic airway obstruction.
COPD accounts for a substantial number of deaths in Great Britain: it has consistently given rise to between 25,000 and 30,000 deaths each year over the last 25 years. The number of people suffering from the disease at any given time is likely to be in excess of 1 million1. COPD is a long-latency disease – meaning that cases tend to develop a number of years after first exposure to the particular causative agents – and in many cases symptoms become manifest during mid-life or later. The most important causative factor is smoking – but others include occupational exposures to fumes, chemicals and dusts, as well as genetic susceptibility and environmental pollution2.
The multi-factorial nature of COPD and the fact that cases resulting from different causes are clinically indistinguishable means that it is difficult to determine how many cases may be due to occupational exposures. Indeed, no detailed assessment is available for Great Britain. However, the estimated proportion of COPD which is work-related based on a recent review of epidemiological studies in various countries was 15%, which confirms estimates of the proportion based on an earlier review3, 4. None of the studies in these reviews were based in Great Britain, however, if this figure is broadly applicable to the British population, this would suggest that there could be around 4000 annual deaths due to COPD resulting from workplace exposures in the past.
Various agents and occupational groups have been implicated as being associated with an increased risk of COPD. Coal dust exposure through mining activities is an established cause of the disease, and cases of chronic bronchitis and emphysema (CBE) in coal workers with a specified level of lung function impairment and at least 20 years underground exposure have been eligible for compensation under the Department for Work and Pensions Industrial Injuries and Disablement Benefit (IIDB) scheme since 1993. This scheme also compensates those with emphysema arising from exposure to cadmium. Epidemiological studies have identified associations between a number of other occupational exposures, including cotton dust, grain dusts and endotoxin, flour dust, welding fumes, other minerals – such as silica and man-made vitreous fibres, other chemicals – such as isocyanates, cadmium, vanadium, and polycyclic aromatic hydrocarbons (PAHs) – and wood dust2. The strength of the evidence about the extent of these risks is variable and of these other agents currently only emphysema in relation to cadmium poisoning is compensatable under the IIDB scheme.
There was a large number of compensation claims for chronic bronchitis and emphysema among coal miners following its specification as a prescribed disease in September 1993. This resulted in a total of over 4000 assessed cases up to the end of 1994. Numbers fell back in 1995 and 1996 to around 270 per year, which is probably closer to the annual incidence of new cases meeting the DWP criteria. However, the number then rose dramatically in 1997 and 1998 to over 3000 per year, as a result of a relaxation in the criteria for benefit effective from April 1997, and in association with heightened publicity, particularly following successfully civil litigation in 1998 against the former British Coal Board. The number of cases fell to 600 in 2000, and since then has declined steadily to around 130 cases in 2006 suggesting that the backlog of claimants satisfying the current criteria and/or the incidence of disability giving rise to new eligible claims is reducing. So far over 460,000 respiratory disease claims have been settled as a consequence of failure on the part of the British Coal Board to properly protect coal miners from chronic bronchitis and emphysema during the relevant period starting in 19545. There have been fewer than 5 assessed cases of emphysema due to cadmium poisoning in each of the last 10 years within the Industrial Injuries Disablement Benefit scheme.
Cases of chronic bronchitis and emphysema in relation to any occupational exposure may also be recorded by occupational and chest physicians under the SWORD and OPRA surveillance schemes which form part of The Health and Occupation Reporting (THOR) network. However, the number of new cases reported each year has been consistently lower – typically less than 200 cases per year – than the number of disablement benefit cases in coal miners – as shown in Figure 1. This suggests that, even for more serious cases of chronic bronchitis and emphysema – that is, those more likely to be seen by specialist chest physicians – few are being attributed to occupational causes. Furthermore, the long latency of COPD means that cases arising in those who have had access to occupational health services while at work may occur after retirement, meaning that they will go un-reported by occupational physicians reporting to THOR.
