The OSHA Cotton Dust Standard issued in 1985 exempted cottons washed either on a rayon rinse system or on a continuous batt system except for medical surveillance every two years. Human challenge studies with these cottons demonstrated that the acute pulmonary response, as measured by over-work shift changes in forced expiratory volume in one second (FEV(1)) to card generated dusts, was substantially reduced. Batch washed cottons were not exempted, because washing trials on antiquated equipment gave inconsistent results. Cottons have now been washed by batch processes on modern equipment. Lint and card generated dusts were assayed for endotoxin contents. The levels in lint were within the acceptable range established for continuous batt washed cottons, and the levels in dust were below reported levels associated with a zero percentage change in FEV(1).