DHHS (NIOSH) Publication Number 95-113
Washed Cotton in The 1978 OSHA Cotton Dust Standard
Current Intelligence Bulletin 56
More than 30 years ago, a study of workers processing medical grade cotton (severely washed with alkali scour and bleach) found that despite very high dust levels (median concentration of 12 mg/m3 by electrostatic precipitation), exposed workers had no symptoms of byssinosis, whereas the prevalence rate for such symptoms was 25% in a comparison group working with unwashed cotton (median concentration less than 7 mg/m3) [El-Batawi and El-Din Shash 1962]. This same study also found no decrease in ventilatory capacity over the workshift among medical cotton workers; this finding was in contrast to an overall significant acute reduction in ventilatory capacity among workers processing unwashed cotton.
In the early 1960s, leading authorities on byssinosis, intrigued by the implications for prevention of these and related findings, commented in a summary report of a conference:
- As there is evidence that there are very few cases of byssinosis among workers in mills processing cotton which is treated with sodium hydroxide and bleached with hypochlorite, and that the pharmacologically-active substances are water soluble, the possibility should be considered of washing the cotton to remove the harmful substances before it is processed [Schilling et al. 1963].
- Experimental studies by McDermott and colleagues included exposures of human subjects to dust from washed cotton. This dust had only half the histamine-releasing activity of dust from unwashed cotton and caused only minimal changes in airways resistance and forced expiratory volume in one second (FEV1) despite "no change in the physical properties of the dust clouds compared with the unwashed cotton" [McDermott et al. 1968]. The investigators concluded that compared with a "large increase in airways resistance induced by exposure to dust from unwashed cotton, washed cotton dust in similar concentration and particle size does not produce any response" [McDermott 1969].
- In an experimental study employing card-generated cotton dust and selected mill employees, Merchant and colleagues demonstrated that acute ventilatory responses were substantially reduced or eliminated by severely washing cotton before processing [Merchant et al. 1973]. Overall, processing strict low middling (grade code 41) cotton that had been washed not only reduced respirable dust concentrations by more than 80% but also reduced frequency of byssinosis symptoms by nearly 90% compared with processing unwashed cotton of the same grade. Furthermore, mean FEV1 increased slightly during the washed cotton exposures in contrast to substantial mean FEV1 reduction in response to dust from the unwashed cotton. The investigators summarized by stating that "of the dust that remained after washing, no biological activity could be detected by our indicators, although the respirable dust level with one trial was as high as 0.26 mg/m3" [Merchant et al. 1973]. However, the resulting fiber did not process well in yarn manufacturing, and the authors recommended that "because washing cotton appears to eliminate completely biological activity, further efforts should be made to wash cotton...in a manner compatible with subsequent processing" [Merchant et al. 1973].
1978 Complete Exemption for Severely Washed Cotton
Based on "the effectiveness of the washing process in significantly reducing or eliminating the biological effects of cotton dust," a provision of the 1978 standard exempted cotton "thoroughly washed in hot water" and "known in the cotton textile trade as purified or dyed" [43 Fed. Reg. 27351 (1978)].
Limitations of the 1978 Complete Exemption for Severely Washed Cotton
In retrospect, the 1978 OSHA standard was admittedly ambiguous as to the exact washing processes which would produce non-reactive cotton. The only cotton which was clearly covered by it was the severely washed cotton tested by Dr. Merchant. ...Although "purified or dyed" cotton was exempted, it was not clear what cleansing processes must be included to qualify cotton for exemption [50 Fed. Reg. 51120 (1985)].
In practice, the least severe wash approved for exemption was a batch system with water/wetting agent at 100°C for 30 min. The resulting fiber, characterized by severe technical processing difficulties, could not feasibly be used to manufacture quality yarn. Therefore, although the Department of Labor reported in 1979 that "washed cotton technology is ...on the verge of technological and economic feasibility" [USDOL 1979], there was a need for substantial research to evaluate the effectiveness of less severe washing as a means for eliminating or substantially reducing the cotton dust hazard. In response, in 1980 and following years, the United States Congress appropriated funds for "high-priority research to develop solutions to the byssinosis health hazard caused by prolonged exposure of textile mill workers to cotton dust" [Committee on Appropriations 1980].
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