This testimony presented before an OSHA Informal Public Hearing concerned the efforts of NIOSH to support OSHA's efforts to promulgate a new standard on air contaminants. Proposed exposure limits were questioned for some substances and the reasons for these questions were discussed for ethylene-glycol (107211), ethyl-ether (60297), and cresol (1319773) as examples of NIOSH's concern. NIOSH urged that additional chemicals be placed into the proposed rule and that Permissible Exposure Limits immediately be sought for several presently excluded. Additional chemicals which should be designated as potential occupational carcinogens were listed. Several workplaces established guidelines which were actually below the limits set in this proposed rule change. The need for OSHA to consider additional sources of information was discussed. Specific questions were addressed concerning the toxicity of C-5 to C-8 alkanes, the identification of special situations, alternative procedures for dealing with substances requiring special attention, what constitutes material impairment of health, and possible cost savings in the purchase of newer engineering controls.