Evidence that oilseed rape (Brassica napus ssp. oleifera) causes respiratory illness in rural dwellers.

A study of 25 residents in a small Scottish village over a two-year period investigated respiratory symptom reporting in the presence or absence of oilseed rape. Symptom reporting in the year when oilseed rape virtually surrounded the village, varied during the growing season of the crop and was at its highest coincident with peak flowering. At the same period of the following year when the crop was absent, symptom reporting was significantly lower. The symptoms which correlated most strongly with peak oilseed rape flowering were sneezing, cough, headache, eye irritation and the total of these and other symptoms. Increased symptoms were reported by 12 of the participants though only seven of these were judged to be atopic. The symptoms did not correlate with levels of oilseed rape pollen but there is no clear evidence as to which of the other factors associated with the crop might be the cause.