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August 1995
DHHS (NIOSH) Publication Number 95-113
Washed Cotton

Washed Cotton in The 1978 OSHA Cotton Dust Standard

Current Intelligence Bulletin 56

Summary

The OSHA comprehensive cotton dust standard, originally promulgated in 1978 and revised in 1985, requires medical monitoring of workers and administrative controls as adjuncts to dust control for preventing occupational respiratory disease from cotton dust exposure. The standard also provides for alternative preventive strategies, including substitution of washed cotton for untreated cotton.

The 1978 standard completely exempted cotton that has been severely washed at 100°C for 30 min in a batch kier system (Table 1). However, the resulting fiber was characterized by severe processing difficulties in textile manufacturing. In 1980, a research program was initiated to evaluate the potential effectiveness of less severe washing of cotton. Conducted with funds from a special congressional appropriation to the U.S. Department of Agriculture, this research was conducted under the auspices of a tripartite (Industry/Government/Union) Task Force on Washed Cotton Evaluation (subsequently renamed the Task Force for Byssinosis Prevention).

Task Force studies demonstrated that mild washing (essentially water rinsing) of cotton in a continuous batt or rayon rinse system physically removes dust from the cotton and also markedly reduces adverse airway response to residual dust. In contrast, card-generated dust from cotton that was mildly washed in a now-outmoded batch kier washing system (though much less potent than dust from unwashed cotton) was found in some cases to retain measurable airway activity. The variable results observed in the early batch kier washing studies were attributed to channeling of wash and rinse solutions through the cotton, which prevented thorough washing of the cotton fiber. Channeling was caused by nonuniform hand loading directly from the bale without mechanical opening, cleaning, or prewetting.

In 1985 OSHA revised the washed cotton provisions in the cotton dust standard. In addition to specifying severe washing conditions necessary for complete exemption, the revised standard added partial exemptions for cotton that has been mildly washed in a continuous system (Table 1). No exemptions were provided for cotton that has been mildly washed in a batch kier system. Partly because of the extremely limited availability of continuous systems for washing cotton and the potential availability of production capacity on modern batch kier systems, OSHA solicited additional research to evaluate batch systems further.

Recent Task Force investigations have evaluated the effectiveness of mild washing on batch kier systems at two different companies using state-of-the-art automated systems for mechanically opening and thoroughly wetting cotton fiber during the kier-loading process. Results of several washing trials on different blends of cotton indicated that modern batch kier systems are capable of mildly washing cotton as effectively as the already partially exempted continuous batt process. This research has shown that mildly washing cotton in batch kier systems (using modern equipment that assures thorough wetting of the cotton fiber and no reuse of wash or rinse water) is, with respect to effectively removing potential respiratory toxicity, equivalent to mildly washing cotton on a continuous batt system. Assessment of washing effectiveness in these studies has been largely based on substantial removal of dust and on marked reduction of residual dust toxicity as measured by endotoxin content and by elimination of acute human ventilatory response. On the basis of results of experimental exposure studies and observational studies of workers exposed to cotton or other organic dusts, these beneficial effects can be expected to prevent chronic as well as acute respiratory effects in exposed workers.

In conclusion, the Task Force recommends that OSHA add mild washing in a modern batch kier system as an acceptable method to wash cotton under the 1985 cotton dust standard (Table 2). The Task Force also makes other recommendations intended to encourage voluntary substitution of washed cotton for unwashed cotton as a means for reducing potential risk of occupational respiratory disorders among workers exposed to cotton dust.

Acknowledgements

This document was prepared by the Task Force for Byssinosis Prevention, a tripartite coalition with government, industry, and union representatives. Current Task Force members and alternates (and the organizations they represent) include Jane F. Robens, D.V.M., and C. Kenneth Bragg, M.S. (Agricultural Research Service, U.S. Department of Agriculture); Eric Frumin (Amalgamated Clothing and Textile Workers Union); Lisa Ramber and John Markham (American Textile Manufacturers Institute); Preston E. Sasser, Ph.D., and Robert R. Jacobs, Ph.D. (Cotton Incorporated); Philip J. Wakelyn, Ph.D., and Andrew G. Jordan, Ph.D. (National Cotton Council of America); Robert M. Castellan, M.D., M.P.H., and Stephen A. Olenchock, Ph.D. (National Institute for Occupational Safety and Health). The contributions of Henry H. Perkins, Jr., M.S. (Agricultural Research Service) and the assistance of Laurence D. Reed (NIOSH) are also gratefully acknowledged.

 
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