> Appendix D - Substances with No Established RELs

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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.

Adapted from: NIOSH Publication Number 2005-149

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