Respiratory morbidity in Merseyside schoolchildren exposed to coal dust and air pollution

A cross sectional study was carried out to determine whether schoolchildren in a specific locality exposed to pollution from steam coal dust have an excess of respiratory symptoms compared with children in control areas. A total of 1872 primary schoolchildren (aged 5-11 years) from five primary schools in the Bootle dock area of Liverpool (exposed area), five primary schools in South Sefton (control area), and five primary schools in Wallasey (control area) were studied. A questionnaire was distributed through the schools and was completed by the parents of the children. The questionnaire inquired about respiratory symptoms (cough, wheezing, and shortness of breath), allergy, atopy, smoking, and socioeconomic factors. Height, weight, and peak expiratory flow were measured. Compliance was good (92%) and similar in the three study areas. The children in the three areas were of similar mean age (7.5 years), height (1.24 m), sex ratio, and had a similar prevalence of paternal (6.2%) and maternal (7%) asthma. The exposed zone contained more unemployed parents (41, 29, and 29% respectively), more rented housing (64, 45, 34%), and more smoking parents (71, 60, 59%) than the control areas. Respiratory symptoms were significantly more common in the exposed area, including wheeze (25.0, 20.6, and 17.5%), excess cough (40.0, 23.4, and 25.1%), and school absences for respiratory symptoms (47.5, 35.9, and 34.9%). These differences remained significant even if the groups were subdivided according to whether or not parents smoked or were employed. Multiple logistic regression analysis confirmed the exposed zone as a significant risk factor for absenteeism from school due to respiratory symptoms (odds ratio 1.55, 95% confidence interval 1.17 to 2.06) after adjusting for confounding factors. Standard dust deposit gauges on three schools confirmed a significantly higher dust burden in the exposed zone. An increased prevalence of respiratory symptoms in primary schoolchildren exposed to coal dust is confirmed. Although the association with known coal dust pollution is suggestive a cross sectional study cannot confirm a casual relation and further studies are needed.