40 CFR Appendix IV
Reference Air Concentrations*
June 9, 2020
Open Table
| Constituent | CAS No. | RAC (ug/m3) |
|---|---|---|
| Acetaldehyde | 75-07-0 | 10 |
| Acetonitrile | 75-05-8 | 10 |
| Acetophenone | 98-86-2 | 100 |
| Acrolein | 107-02-8 | 20 |
| Aldicarb | 116-06-3 | 1 |
| Aluminum Phosphide | 20859-73-8 | 0.3 |
| Allyl Alcohol | 107-18-6 | 5 |
| Antimony | 7440-36-0 | 0.3 |
| Barium | 7440-39-3 | 50 |
| Barium Cyanide | 542-62-1 | 50 |
| Bromomethane | 74-83-9 | 0.8 |
| Calcium Cyanide | 592-01-8 | 30 |
| Carbon Disulfide | 75-15-0 | 200 |
| Chloral | 75-87-6 | 2 |
| Chlorine (free) | 0.4 | |
| 2-Chloro-1,3-butadiene | 126-99-8 | 3 |
| Chromium III | 16065-83-1 | 1000 |
| Copper Cyanide | 544-92-3 | 5 |
| Cresols | 1319-77-3 | 50 |
| Cumene | 98-82-8 | 1 |
| Cyanide (free) | 57-12-15 | 20 |
| Cyanogen | 460-19-5 | 30 |
| Cyanogen Bromide | 506-68-3 | 80 |
| Di-n-butyl Phthalate | 84-74-2 | 100 |
| o-Dichlorobenzene | 95-50-1 | 10 |
| p-Dichlorobenzene | 106-46-7 | 10 |
| Dichlorodifluoromethane | 75-71-8 | 200 |
| 2,4-Dichlorophenol | 120-83-2 | 3 |
| Diethyl Phthalate | 84-66-2 | 800 |
| Dimethoate | 60-51-5 | 0.8 |
| 2,4-Dinitrophenol | 51-28-5 | 2 |
| Dinoseb | 88-85-7 | 0.9 |
| Diphenylamine | 122-39-4 | 20 |
| Endosulfan | 115-29-1 | 0.05 |
| Endrin | 72-20-8 | 0.3 |
| Fluorine | 7782-41-4 | 50 |
| Formic Acid | 64-18-6 | 2000 |
| Glycidyaldehyde | 765-34-4 | 0.3 |
| Hexachlorocyclopentadiene | 77-47-4 | 5 |
| Hexachlorophene | 70-30-4 | 0.3 |
| Hydrocyanic Acid | 74-90-8 | 20 |
| Hydrogen Chloride | 7647-01-1 | 7 |
| Hydrogen Sulfide | 7783-06-4 | 3 |
| Isobutyl Alcohol | 78-83-1 | 300 |
| Lead | 7439-92-1 | 0.09 |
| Maleic Anhydride | 108-31-6 | 100 |
| Mercury | 7439-97-6 | 0.3 |
| Methacrylonitrile | 126-98-7 | 0.1 |
| Methomyl | 16752-77-5 | 20 |
| Methoxychlor | 72-43-5 | 50 |
| Methyl Chlorocarbonate | 79-22-1 | 1000 |
| Methyl Ethyl Ketone | 78-93-3 | 80 |
| Methyl Parathion | 298-00-0 | 0.3 |
| Nickel Cyanide | 557-19-7 | 20 |
| Nitric Oxide | 10102-43-9 | 100 |
| Nitrobenzene | 98-95-3 | 0.8 |
| Pentachlorobenzene | 608-93-5 | 0.8 |
| Pentachlorophenol | 87-86-5 | 30 |
| Phenol | 108-95-2 | 30 |
| M-Phenylenediamine | 108-45-2 | 5 |
| Phenylmercuric Acetate | 62-38-4 | 0.075 |
| Phosphine | 7803-51-2 | 0.3 |
| Phthalic Anhydride | 85-44-9 | 2000 |
| Potassium Cyanide | 151-50-8 | 50 |
| Potassium Silver Cyanide | 506-61-6 | 200 |
| Pyridine | 110-86-1 | 1 |
| Selenious Acid | 7783-60-8 | 3 |
| Selenourea | 630-10-4 | 5 |
| Silver | 7440-22-4 | 3 |
| Silver Cyanide | 506-64-9 | 100 |
| Sodium Cyanide | 143-33-9 | 30 |
| Strychnine | 57-24-9 | 0.3 |
| 1,2,4,5-Tetrachlorobenzene | 95-94-3 | 0.3 |
| 2,3,4,6-Tetrachlorophenol | 58-90-2 | 30 |
| Tetraethyl Lead | 78-00-2 | 0.0001 |
| Tetrahydrofuran | 109-99-9 | 10 |
| Thallic Oxide | 1314-32-5 | 0.3 |
| Thallium | 7440-28-0 | 0.5 |
| Thallium (I) Acetate | 563-68-8 | 0.5 |
| Thallium (I) Carbonate | 6533-73-9 | 0.3 |
| Thallium (I) Chloride | 7791-12-0 | 0.3 |
| Thallium (I) Nitrate | 10102-45-1 | 0.5 |
| Thallium Selenite | 12039-52-0 | 0.5 |
| Thallium (I) Sulfate | 7446-18-6 | 0.075 |
| Thiram | 137-26-8 | 5 |
| Toluene | 108-88-3 | 300 |
| 1,2,4-Trichlorobenzene | 120-82-1 | 20 |
| Trichloromonofluoromethane | 75-69-4 | 300 |
| 2,4,5-Trichlorophenol | 95-95-4 | 100 |
| Vanadium Pentoxide | 1314-62-1 | 20 |
| Warfarin | 81-81-2 | 0.3 |
| Xylenes | 1330-20-7 | 80 |
| Zinc Cyanide | 557-21-1 | 50 |
| Zinc Phosphide | 1314-84-7 | 0.3 |
*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
[56 FR 7232, Feb. 21, 1991; 56 FR 32691, July 17, 1991, as amended at 71 FR 40277, July 14, 2006]
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