{"data":{"id":"us/40-cfr-appendix-iv-to-part-266","jurisdiction":"us","citation":"40 CFR Appendix IV to Part 266","heading":"Appendix IV to Part 266—Reference Air Concentrations*","body":"Constituent CAS No. RAC (ug/m3)\nAcetaldehyde 75-07-0 10\nAcetonitrile 75-05-8 10\nAcetophenone 98-86-2 100\nAcrolein 107-02-8 20\nAldicarb 116-06-3 1\nAluminum Phosphide 20859-73-8 0.3\nAllyl Alcohol 107-18-6 5\nAntimony 7440-36-0 0.3\nBarium 7440-39-3 50\nBarium Cyanide 542-62-1 50\nBromomethane 74-83-9 0.8\nCalcium Cyanide 592-01-8 30\nCarbon Disulfide 75-15-0 200\nChloral 75-87-6 2\nChlorine (free) 0.4\n2-Chloro-1,3-butadiene 126-99-8 3\nChromium III 16065-83-1 1000\nCopper Cyanide 544-92-3 5\nCresols 1319-77-3 50\nCumene 98-82-8 1\nCyanide (free) 57-12-15 20\nCyanogen 460-19-5 30\nCyanogen Bromide 506-68-3 80\nDi-n-butyl Phthalate 84-74-2 100\no-Dichlorobenzene 95-50-1 10\np-Dichlorobenzene 106-46-7 10\nDichlorodifluoromethane 75-71-8 200\n2,4-Dichlorophenol 120-83-2 3\nDiethyl Phthalate 84-66-2 800\nDimethoate 60-51-5 0.8\n2,4-Dinitrophenol 51-28-5 2\nDinoseb 88-85-7 0.9\nDiphenylamine 122-39-4 20\nEndosulfan 115-29-1 0.05\nEndrin 72-20-8 0.3\nFluorine 7782-41-4 50\nFormic Acid 64-18-6 2000\nGlycidyaldehyde 765-34-4 0.3\nHexachlorocyclopentadiene 77-47-4 5\nHexachlorophene 70-30-4 0.3\nHydrocyanic Acid 74-90-8 20\nHydrogen Chloride 7647-01-1 7\nHydrogen Sulfide 7783-06-4 3\nIsobutyl Alcohol 78-83-1 300\nLead 7439-92-1 0.09\nMaleic Anhydride 108-31-6 100\nMercury 7439-97-6 0.3\nMethacrylonitrile 126-98-7 0.1\nMethomyl 16752-77-5 20\nMethoxychlor 72-43-5 50\nMethyl Chlorocarbonate 79-22-1 1000\nMethyl Ethyl Ketone 78-93-3 80\nMethyl Parathion 298-00-0 0.3\nNickel Cyanide 557-19-7 20\nNitric Oxide 10102-43-9 100\nNitrobenzene 98-95-3 0.8\nPentachlorobenzene 608-93-5 0.8\nPentachlorophenol 87-86-5 30\nPhenol 108-95-2 30\nM-Phenylenediamine 108-45-2 5\nPhenylmercuric Acetate 62-38-4 0.075\nPhosphine 7803-51-2 0.3\nPhthalic Anhydride 85-44-9 2000\nPotassium Cyanide 151-50-8 50\nPotassium Silver Cyanide 506-61-6 200\nPyridine 110-86-1 1\nSelenious Acid 7783-60-8 3\nSelenourea 630-10-4 5\nSilver 7440-22-4 3\nSilver Cyanide 506-64-9 100\nSodium Cyanide 143-33-9 30\nStrychnine 57-24-9 0.3\n1,2,4,5-Tetrachlorobenzene 95-94-3 0.3\n2,3,4,6-Tetrachlorophenol 58-90-2 30\nTetraethyl Lead 78-00-2 0.0001\nTetrahydrofuran 109-99-9 10\nThallic Oxide 1314-32-5 0.3\nThallium 7440-28-0 0.5\nThallium (I) Acetate 563-68-8 0.5\nThallium (I) Carbonate 6533-73-9 0.3\nThallium (I) Chloride 7791-12-0 0.3\nThallium (I) Nitrate 10102-45-1 0.5\nThallium Selenite 12039-52-0 0.5\nThallium (I) Sulfate 7446-18-6 0.075\nThiram 137-26-8 5\nToluene 108-88-3 300\n1,2,4-Trichlorobenzene 120-82-1 20\nTrichloromonofluoromethane 75-69-4 300\n2,4,5-Trichlorophenol 95-95-4 100\nVanadium Pentoxide 1314-62-1 20\nWarfarin 81-81-2 0.3\nXylenes 1330-20-7 80\nZinc Cyanide 557-21-1 50\nZinc Phosphide 1314-84-7 0.3\n*The RAC for other appendix VIII part 261 constituents not listed herein or in appendix V of this part is 0.1 ug/m. 3","path":["Title 40—Protection of Environment","CHAPTER I—ENVIRONMENTAL PROTECTION AGENCY","SUBCHAPTER I—SOLID WASTES","PART 266—STANDARDS FOR THE MANAGEMENT OF SPECIFIC HAZARDOUS WASTES AND SPECIFIC TYPES OF HAZARDOUS WASTE MANAGEMENT FACILITIES"],"source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-25/title-40.xml","current_through":"2026-08-25","vintage":"","retrieved_at":"2026-08-27T02:26:04Z","sha256":"1ec67a226ccd0e8685dcae569e3fb5d021ff759ce63837d05d3f51c17644d928","source_id":"us-cfr","stale":true,"prev":"us/40-cfr-appendix-iii-to-part-266","next":"us/40-cfr-appendix-v-to-part-266"},"notice":"GroundRules: Original legal text. Not legal advice."}