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Appendix D - Substances with No Established RELs

After reviewing available published literature, NIOSH provided comments to OSHA on August 1, 1988, regarding the “Proposed Rule on Air Contaminants” (29 CFR 1910, Docket No. H-020).

In these comments, NIOSH questioned whether the PELs proposed (and listed below) for the following substances included in the Pocket Guide were adequate to protect workers from recognized health hazards:

  • Acetylene tetrabromide [TWA 1 ppm]
  • Chlorobenzene [TWA 75 ppm]
  • Ethyl bromide [TWA 200 ppm; STEL 250 ppm]
  • Ethylene glycol [Ceiling 50 ppm]
  • Ethyl ether [TWA 400 ppm; STEL 500 ppm]
  • Fenthion [TWA 0.2 mg/m3 (skin)]
  • Furfural [TWA 2 ppm (skin)]
  • 2-Isopropoxyethanol [TWA 25 ppm]
  • Isopropyl acetate [TWA 250 ppm; STEL 310 ppm]
  • Isopropylamine [TWA 5 ppm; STEL 10 ppm]
  • Manganese tetroxide (as Mn) [TWA 1 mg/m3]
  • Molybdenum (soluble compounds as Mo) [TWA 5 mg/m3]
  • Nitromethane [TWA 100 ppm]
  • m-Toluidine [TWA 2 ppm (skin)]
  • Triethylamine [TWA 10 ppm; STEL 15 ppm]

At that time, NIOSH also conducted a limited evaluation of the literature and concluded that the documentation cited by OSHA was inadequate to support the proposed PEL (as an 8-hour TWA) of 10 mg/m3 for alpha-alumina, benomyl, emery, glycerine (mist), graphite (synthetic), magnesium oxide fume, molybdenum (insoluble compounds as Mo), particulates not otherwise regulated, picloram, and rouge.

Page last reviewed: October 18, 2018