Cal/OSHA Cotton Dust Safety

Case Study: In 1962, researchers noticed that people working with medical-grade cotton (that is, cotton that had been washed with alkali scour and bleach) experienced no byssinosis symptoms despite being exposed to high levels of cotton dust. On the other hand, twenty-five percent of workers exposed to similar levels of unwashed cotton experienced symptoms. Furthermore, workers exposed to medical-grade cotton were found to have no decrease in their breathing capacity, compared to a significant decrease in breathing capacity in those exposed to unwashed cotton, even when the amount of dust and the particle size remained the same. Shortly afterward, another study determined that the harmful substances in cotton dust are water soluble, suggesting that milder washing was also a possible means of reducing byssinosis. More severe forms of washing make it harder to process cotton into yarn, so it is not always possible to reduce exposure this way.

Key Takeaways: This research is the foundation of the exemption levels in 8 CCR 5190. It helped establish a minimum level of washing that could safely remove contaminants. It also helped build an understanding of why cotton dust is harmful, although scientists have yet to agree on what substance within cotton dust causes byssinosis.