epidemiological and environmental studies . Oilseed rape and seasonal symptoms :

Background There is widespread concern that the cultivation of oilseed rape leads to seasonal epidemics of respiratory symptoms in populations living in the neighbourhood, and it has been suggested that the plant is a potent allergen. A study was therefore undertaken to determine the prevalence of seasonal symptoms in rural populations close to and far from areas of oilseed rape cultivation, and to measure the levels of allergen and other potentially harmful substances released by the crop. Methods Random samples of 1000 adults from the general practice populations of two villages surrounded by oilseed rape fields, and 1000 adults from one village far from such cultivation, were taken. The subjects completed a previously validated questionnaire on respiratory and other symptoms, including questions on symptom seasonality, occupation, and smoking habits. Pollen and fungal spore counts were made around fields of oilseed rape and in the villages. The chemicals released by oilseed rape were measured in the field. Results Overall, 86-8% of the subjects completed the questionnaires and the populations of the two samples were generally comparable. Spring and summer exacerbations of symptoms occurred equally in the two areas in approximately 25% of the population. There were small but significant excesses of cough, wheeze, and headaches in spring in the oilseed rape area (2-3% v 1-1%, 6-8% v4-6%, 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 offungal spores were mostly higher in the rape than the nonrape areas. Oilseed 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 oilseed rape is caused by the plant, the excess of such symptoms is small. This, together with the low levels ofpollen in the area, suggests that allergy to oilseed rape pollen is uncommon. The general prevalence ofseasonal symptoms in rural areas is ofinterest, and a proportion ofthese cases is likely to be caused by factors other than allergy. Release of chemicals by plants and natural rises in summer ozone levels may be contributors. (Thorax 1994;49:352-356) The area of oilseed rape cultivation increased in the United Kingdom from 6500 hectares in 1968 to 421100 hectares in 1992. Over 85% is the species Brassica napus which is sown in winter and starts to flower, in north east Scotland, during late April for a period of six weeks. Brassica campestris, sown in spring, flowers in mid June. The crop is normally harvested in August and September and the oil produced from crushing the seed is used as a source of vegetable oil. Many doctors have been consulted by patients who attribute seasonal eye and respiratory symptoms to local cultivation of oilseed rape. While true allergy and IgE mediated reactions to extracts of the pollen have occasionally been found,'-3 most such patients do not have evidence of this. As oilseed rape is largely insect pollinated and gives off a number of chemicals, at least partly acting as insect attractants,45 it is possible that these, rather than pollen, are the cause of the symptoms. We have carried out a study of seasonal symptoms and airborne allergens and chemicals in relation to oilseed rape cultivation in north east Scotland.