Respiratory ill-health pinned on coke works' emissions

A convincing association between air pollution levels and respiratory ill-health around a coke works in north-east England has been found in a study of unprecedented depth conducted by the Division of Epidemiology and Public Health at Newcastle University.1

The research was financed by South Tyneside Metropolitan Borough Council when a dispute about emissions from the Monkton coke works, near Hebburn, was at its height early in 1990.

The plant was operated by Coal Products Ltd, a British Coal subsidiary. It was the subject of a two-stage public inquiry and a High Court hearing between 1987 and 1990 - the issue at stake being sulphur dioxide emissions (ENDS Reports 163, p 3, and 195, pp 5-6). A local action group was formed in 1980, providing a focus for residents' complaints that dust, fume and gaseous emissions were being controlled inadequately by HM Inspectorate of Pollution and affecting their health. The works was closed abruptly in October 1990.

The health study was continued despite the shut-down. Its design lends considerable weight to the conclusions. The components of the research included an analysis of mortality and cancer data, a postal health questionnaire survey, an analysis of visits to doctors and their relationship to air quality, and a lung function survey.

Public health was assessed in three areas with a total population of some 56,000. These were an inner area, an outer area, and a control area some six kilometres from the works. The three groups were comparable on a wide range of socio-economic indicators, workplace exposures to chemicals and lifestyles. The prevalence of smokers was highest in the control area.

One of the hypotheses tested in the study was that any excess mortality andcancer would be most marked for respiratory conditions in people living close to the works. This was not upheld for adults. A clear excess of childhood deaths was found in the inner area, but a wide range of causes were involved, and any effect of emissions from the Monkton works could not be demonstrated.

One of the most striking findings concerned the pattern of consultations with doctors, which were analysed in relation to daily SO2 levels measured at three monitoring stations less than two kilometres from the works over a period of more than four years.

The records revealed that respiratory problems accounted for a greater proportion of consultations in the inner and outer areas than in the control area. In addition, a clear increase in consultation rates for respiratory disorders was evident on days when SO2 levels were elevated, with the difference between the inner and outer and the control areas being greatest at the highest SO2 levels.

The examination of doctors' records also showed that repeat prescriptions for respiratory conditions were twice as high in the inner and outer as in the control areas.

These findings provided powerful substantiation to the evidence from the questionnaire survey, carried out shortly after the works' closure. Almost 70% of a random sample of 4,350 people replied.

On virtually every aspect of respiratory health, as well as sinus problems, hay fever, allergies and headaches, the reported ill-health in the inner area exceeded that in the control area, usually by a large margin, with the outer area generally being intermediate.

The lung function study was inconclusive because of a low response rate. However, women in the inner area, but not men, performed poorly on two or three measures of lung function, and the study suggests tentatively that this may be attributable to women being present in the vicinity of the coke works for more of the time because of domestic responsibilities.

The overall conclusions of the study are that the health of people living closest to the coke works is comparable to that of the remoter populations, except for respiratory health. A clear gradient for many respiratory problems is evident with distance from the works, and is most apparent in children. "Much of the excess of respiratory ill-health," it says, "is likely to have arisen as a result of exposure to emissions" from the Monkton plant.

The study leaves open the question of what pollutants may be responsible, not least because data on pollutants other than SO2 were unavailable. The peak levels of SO2, in fact, hardly ever exceeded guide values recommended by the World Health Organization.

However, the authors say that their findings raise questions about the effects of SO2 in combination with other pollutants at low concentrations, and advance the view that "long term exposure to levels of air pollution which are usually low, but intermittently high, holds risk."

The study will have done nothing to disabuse local residents of the view that HMIP took an unduly relaxed approach to the need to install desulphurisation and coke-side arrestment equipment at the works.

The findings also have implications for research which the Government is sponsoring at the Small Area Health Statistics Unit (SAHSU). The programme is aimed at identifying possible clusters of disease around plants operated by five industries, including coke works (ENDS Report 190, pp 7-8).

When the programme was launched at the end of 1990, the Government hoped to have the studies completed by the end of 1991. But only one has been finished, and the research on coke works has not even begun.

More tellingly, the Monkton study has called into question whether the health statistics available to SAHSU will tell anything like the full story. As its authors point out, what their research highlighted is that "community-based surveys are of the greatest importance, but that these need to be supplemented by other forms of data, including environmental monitoring, to enable a full assessment of the health of a community."

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