This rule was remanded by the U.S. Circuit Court of Appeals and the limits are not currently in force.
Ammonia is a primary eye and upper respiratory tract irritant.
In addition, a study of pigs conducted by Stombaugh et al. OSHA also finds that the fact that some workers may become acclimatized to ammonia exposures at concentrations as high as 50 ppm may account for the belief expressed by Mr. Seeman and others that 50 ppm is an acceptable exposure level. However, OSHA does not agree with this view of acclimatization because the long-term consequences of a continual assault on the sensory nerves are not known. However, OSHA interprets this study differently, believing instead that it shows a secondary effect of the irritation traditionally associated with ammonia exposure. Thus, OSHA does not find it necessary in the final rule to establish an 8-hour TWA limit for ammonia to protect against chronic effects.