Population study in cotton ginnery workers in the Sudan

workers in the Sudan. An epidemiological study in cotton ginneries in the Sudan covered 323 permanently employed ginnery workers, a random sample of 35 seasonal farfara workers, and a control group of 24 members of a fire brigade. All the workers studied were men. The study showed a prevalence of byssinosis (defined as chest tightness starting on return from the annual holiday and continuing for at least three consecutive days) in 20 % of the ginnery workers and in 48-6 % of the farfara workers. Workers exposed to dust showed a mean fall in F.E.V.1.o of-0 10 litre during the shift, while workers not so exposed showed a mean rise of +0-23 litre; this difference was statistically significant. The FEV.1.0 was adjusted for age and standing height. The adjusted means of F.E.V.1.0 were significantly lower for workers exposed to dust compared with those in the control group. The workers with byssinosis showed a statistically significant fall in F.E.V.L.0 when com-pared with all ginnery workers; and a highly significant fall when compared with cotton workers without chest symptoms. An attempt was made to grade the byssinotics according to the extent of fall in F.E.V.L.0 during the shift. The concentration of fine dust (< 7 p,) was measured in each work place. There was