Byssinosis: some unanswered questions

Unexpected excessive chronic obstructive pulmonary disease mortality among female silk textile workers in Shanghai, China

OBJECTIVE

To investigate chronic obstructive pulmonary disease (COPD) mortality among textile workers.

METHODS

A total of 267,400 Chinese female textile employees were monitored for COPD mortality from 1989 to 2000. Textile factories in the cohort were classified into 10 industrial sectors. Age-adjusted mortality, standardized mortality ratios (SMRs) and 95% CIs were calculated by sector. In addition, RRs (HRs) adjusted for smoking and age were calculated for exposure to cotton and silk textile work compared with the other sectors in the cohort.

RESULTS

A majority of textile sectors had lower or similar COPD mortality (age-adjusted SMRs=0.58-1.15) compared with the general female population in the city of Nanjing, China. SMRs for cotton and silk workers were, respectively, 1.02 (95% CI: 0.81 to 1.28) and 2.03 (95% CI: 1.13 to 3.34). Compared with all other textile sectors in the cohort, there was greater COPD mortality among cotton workers (HR=1.40, 95% CI: 1.03 to 1.89) and silk workers (HR=2.54, 95% CI: 1.47 to 4.39).

CONCLUSION

Elevated COPD mortality among cotton workers is consistent with previous reports of adverse respiratory effects of cotton dust. The higher rate of COPD deaths among silk workers was unexpected.

Physiological evidence that emphysema is not a feature of byssinosis

A group of women with byssinosis of grades 2 and 3 were seen consecutively over three years in an occupational outpatient clinic. Detailed lung function tests were performed and the results for smokers and non-smokers compared. One hundred and fifty three patients were seen and 50 of these were life time non-smokers, 35 smoked one to nine cigarettes a day, and 68 smoked 10 or more cigarettes a day. After correction for age the mean FEV1 was found to be significantly lower (p less than 0.01) in heavy smokers than in non-smokers. In a subgroup of 89 subjects who were able to perform the carbon monoxide gas transfer test significantly lower values were obtained for the carbon monoxide transfer factor (TLCO), (p less than 0.001), TLCO % predicted (p less than 0.001), and the transfer coefficient (KCO) (p less than 0.001) in the heavy smokers than in the non-smokers, despite the fact that the non-smokers had worked longer in the cotton mills (p less than 0.02). The mean TLCO was significantly lower than predicted in the heavy smokers (p less than 0.001) but not in the non-smokers. A significant negative correlation was found between the number of cigarettes smoked per day and the TLCO (p less than 0.01), TLCO % predicted (p less than 0.001), and KCO (p = 0.005), but not with the number of years spent in the carding area. These results provide evidence supporting recent pathological observations that emphysema is probably due to concomitant cigarette smoking and is not itself a feature of byssinosis.

Byssinosis: a role for public health in the face of scientific uncertainty

Byssinosis, a lung disease caused by cotton dust, has been the subject of recent controversy. Debates over the nature of the disease, possible interactions with cigarette smoking, and the proposed reevaluation of the cotton dust standard by the Occupational Safety and Health Administration have tended to overlook the plight of affected workers and to obscure the most effective means for preventing the disease. The present lack of definitive information is no reason for inaction, nor for depriving disabled workers of adequate financial compensation. In this respect, byssinosis is no different from other public health hazards for which action must often be taken on the basis of incomplete evidence.