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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


A Review and Recommendations Regarding Batch Kier Washed Cotton

The Task Force for Byssinosis Prevention
(formerly the Industry/Government/Union Task Force for Washed Cotton Evaluation)

Member organizations:
Agricultural Research Service,
U.S. Department of Agriculture
Amalgamated Clothing and Textile Workers Union
American Textile Manufacturers Institute
Cotton Incorporated
National Cotton Council of America
National Institute for Occupational Safety and Health
U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES
Public Health Service
Centers for Disease Control and Prevention
National Institute for Occupational Safety and Health
Division of Respiratory Disease Studies

DISCLAIMER: Mention of any company or product does not constitute endorsement by the National Institute for Occupational Safety and Health. This document is in the public domain and may be freely copied or reprinted.

Table 1. Summary of occupational health regulatory history of washed cotton in the United States

Year Rule Exemptions for various washing conditions Comments
1978 OSHA Cotton Dust Standard [43 Fed. Reg. 27351 (1978)] Severe wash: Complete exemption for cotton "thoroughly washed in hot water" and "known in the cotton textile industry as purified or dyed." It was "not clear what cleansing processes ... qualify cotton for exemption" [50 Fed. Reg. 51120, (1985)]. Severely washed cotton is extremely difficult to process into textiles.
    Mild wash: None. Mildly washed cotton was not addressed in standard.
1985 Revised OSHA Cotton Dust Standard [50 Fed. Reg. 51120 (1985)] Severe wash: Complete exemption for "medical grade (USP) cotton, cotton that has been scoured, bleached, and dyed, and mercerized yarn." These processes are more severe than the mild wash. Severely washed cotton is extremely difficult
   

Mild wash: Partial exemptions* for cotton washed: (i) on a continuous batt system or rayon rinse system; (ii) with water; (iii) at a temperature of no less than 600°C; (iv) with a water-to-fiber ratio of no less than 40:1; and (v) with bacterial levels in the wash water controlled to limit bacterial contamination of the cotton.

*Exemption from all requirements except medical surveillance and medical recordkeeping for higher grade cotton (low middling light spotted or better) washed per above conditions.

*Exemption from all requirements except for medical surveillance, medical recordkeeping, and a 500-µg/m3 permissible exposure level (PEL) for airborne dust measured by the vertical elutriator sampler for lower grade cotton (below low middling light spotted) washed per above conditions.

Facilities for mildly washing cotton are limited. The continuous batt system used in the Task Force evaluations had a production capacity of only 500 lb/hr for washing cotton, and the rayon rinse system has very limited availability.

Table 2. Summary of Task Force recommendations for near-term future regulation of mildly washed cotton

  Recommended exemptions for various washing conditions Comments
Recommended amendment of OSHA Cotton Dust Standard Severe Wash: No change from 1985 Revised OSHA Standard Severe washing was not a focus of Task Force consideration. These processes were not further considered.
 

Mild wash: Partial exemptions* for cotton washed, either: (A) on a continuous batt system or rayon rinse system, (i) with water; (ii) at a temperature of no less than 60°C, (iii) with a water-to-fiber ratio of no less than 40:1, and (iv) with bacterial levels in the wash water controlled to limit bacterial contamination of the cotton; or (B) on a batch washing system, (i) with water, (ii) with cotton fiber mechanically opened and thoroughly prewet prior to forming the cake, (iii) for low temperature process, at a temperature of no less than 60°C with a water-to-fiber ratio of no less than 40:1, or for high temperature process, at a temperature of no less than 93°C with a water-to-fiber ratio of no less than 15:1, and (iv) with a minimum of one wash cycle followed by two rinse cycles for each batch, using fresh water in each cycle.

*Exemption from all requirements except medical surveillance and medical recordkeeping for higher grade cotton (low middling light spotted—grade code52—or better) washed per above conditions.

*Exemption from all requirements except for medical surveillance, medical recordkeeping, and a 500-µg/m3 permissible exposure limit (PEL) for airborne dustmeasured by the vertical elutriator sampler for lower grade cotton (below low middling light spotted—grade code 52) washed per above conditions.

The purpose of this recommendation is to encourage voluntary substitution of washed cotton for unwashed cotton as a strategy to prevent respiratory disorders induced by cotton dust.

Compared to unwashed cotton mildly washed cotton can be more difficult and more costly to process into fine textiles, so potential uses will probably involve smaller novelty or niche markets.

Mild washing may enhance textile processing characteristics of some cotton (e.g., "sticky" cotton), and may also enable value-added special effects (e.g., special dyeing characteristics for novelty yarns; improved quality of rotor-spun yarns).

Under the new USDA classification system begun in 1993, low middling light spotted cotton corresponds to color grade code 52, leaf grade code 5.

 

 
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