In a rope works handling manila, sisal, and St. Helena hemps, the prevalence of respiratory symptoms and the change in forced expiratory volume (F.E.V.1·0) during the work shift were studied in a group of 41 women and 41 men who represented 93% of the population at risk.
Dust concentrations, measured with a modified Hexhlet, ranged from 0·11 to 4·51 mg./m.3 for total dust and 0·02 to 1·46 mg./m.3 for fine dust. The highest concentrations were found in the preparing rooms, in which the workers, all of whom were women, showed on the average a fall in ventilatory capacity during the shift. The workers in the rope walk, all of whom were men, showed a rise in ventilatory capacity during the shift. The difference between the men and women was statistically significant (p < 0·05). No worker gave a characteristic history of byssinosis, although nine women complained of chest tightness associated with their work.
Undue breathlessness on exertion and persistent cough and phlegm were also more common among the women, but they were on the average 18 years older than the men. When the ventilatory capacities and the prevalence of respiratory symptoms of women rope workers were compared with those of a group of women employed elsewhere in the dockyard, the only significant difference was that the rope workers had more chest tightness associated with their work (p < 0·02).
Exposure of volunteers to St. Helena hemp, which is apparently the most likely of the hard hemps to give rise to respiratory symptoms, caused only a slight fall in ventilatory capacity and a small rise in airways resistance.
A sample of St. Helena hemp assayed on guinea-pig ileum had only a relatively small degree of contractor activity. The evidence suggests that the dusts of hard hemps do not cause byssinosis under the conditions in this factory. However, the irritant nature of the dust indicates the need to prevent total dust levels exceeding about 2 mg./m.3.