OILSEED RAPE AND SEASONAL SYMPTOMS - EPIDEMIOLOGIC AND ENVIRONMENTAL-STUDIES

Background - There is widespread concern that the cultivation of oilse ed rape leads to seasonal epidemics of respiratory symptoms in populat ions living in the neighbourhood, and it has been suggested that the p lant is a potent allergen. A study was therefore undertaken to determi ne the prevalence of seasonal symptoms in rural populations close to a nd far from areas of oilseed rape cultivation, and to measure the leve ls of allergen and other potentially harmful substances released by th e crop. Methods - Random samples of 1000 adults from the general pract ice populations of two villages surrounded by oilseed rape fields, and 1000 adults from one village far from such cultivation, were taken. T he subjects completed a previously validated questionnaire on respirat ory and other symptoms, including questions on symptom seasonality, oc cupation, and smoking habits. Pollen and fungal spore counts were made around fields of oilseed rape and in the villages. The chemicals rele ased by oilseed rape were measured in the field. Results - Overall, 86 .8% of the subjects completed the questionnaires and the populations o f the two samples were generally comparable. Spring and summer exacerb ations of symptoms occurred equally in the two areas in approximately 25% of the population. There were small but significant excesses of co ugh, wheeze, and headaches in spring in the oilseed rape area (2.3% v 1.1%, 6.8% v 4.6%, and 4.8% v 2.8%, respectively), and cough, wheeze, and itchy skin were more prevalent in smokers. Counts of oilseed rape pollen were generally low except adjacent to fields, and counts of fun gal spores were mostly higher in the rape than the non-rape areas. Oil seed rape was shown to give off terpenes and these were detected close to fields. Conclusions - While it is likely that a proportion of the spring symptoms occurring in people living in close proximity to oilse ed rape is caused by the plant, the excess of such symptoms is small. This, together with the low levels of pollen in the area, suggests tha t allergy to oilseed rape pollen is uncommon. The general prevalence o f seasonal symptoms in rural areas is of interest, and a proportion of these cases is likely to be caused by factors other than allergy. Rel ease of chemicals by plants and natural rises in summer ozone levels m ay be contributors.