Toxic Air Contaminant (TAC) Identification List

This page last reviewed on August 16, 2010


Substance By Category

Click on the ++ to view its chemical summary from the Office of Environmental Health Hazard and Assessment website.

Category I Category IIa Category IIb Category IIIa / b Category IVa Category IVb Category V Category VI

Category I
Substances identified as Toxic Air Contaminants, known to be emitted in California, with a full set of
health values reviewed by the Scientific Review Panel.
Click on a substance name to view its fact sheet from the 1997 Toxic Air Contaminant Identification List Summaries.
Please note some of the health values have changed since 1997.
Click on the ++ to view its chemical summary from the Office of Environmental Health Hazard
and Assessment website.
Substance CAS
Number
Cancer
Potency
Value
Chronic
Reference
Exposure
Level
Acute Reference
Exposure Level
* Perchloroethylene (Tetrachloroethylene) 127-18-4 ++ ++ ++
  (There is a potential for 12 substances to move into this category after the SRP has reviewed the noncancer chronic Reference Exposure Levels being developed under the Air Toxics "Hot Spots" Program.)        

Category IIa
Substances identified as Toxic Air Contaminants, known to be emitted in California, with one or more health values under development by the Office of Environmental Health Hazard Assessment for review by the Scientific Review Panel.
Click on a substance name to view its fact sheet from the 1997 Toxic Air Contaminant Identification List Summaries.
Please note some of the health values have changed since 1997. Click on the ++ to view its chemical summary from the Office of Environmental Health Hazard and Assessment website.
Substance CAS
Number
Cancer
Potency
Value

(Note 1)
Chronic
Reference
Exposure Level
(Note 2)
Acute Reference
Exposure Level
(Note 3)
  Acetaldehyde 75-07-0 ++ ++ Limited Data Available
  Acetamide 60-35-5 ++ Limited Data Available Limited Data Available
+ Acrolein 107-02-8 i (Note 1) X ++
  Acrylamide 79-06-1 ++ X Limited Data Available
  Acrylic Acid 79-10-7 ii (Note 1) X ++
  Acrylonitrile 107-13-1 ++ X Limited Data Available
  Allyl Chloride 107-05-1 ++ X Limited Data Available
  Aniline 62-53-3 ++ X Limited Data Available
  Antimony and Compounds (Note 4) 7440-36-0 ii (Note 1) Limited Data Available Limited Data Available
       Antimony Trioxide 1309-64-4 i (Note 1) X Limited Data Available
*+ Inorganic Arsenic and Arsenic Compounds
(Inoganic Including Arsine) (Note 4)
7440-38-2 ++ X ++
       Arsine 7784-42-1 ii (Note 1) X ++
* Asbestos [Asbestiform Varieties of Serpentine (Chrysotile), Riebeckite (Crocidolite), Cummingtonite-Grunerite (Amosite), Tremolite, Actinolite, and Anthophyllite] 1332-21-4 ++ Limited Data Available Limited Data Available
* Benzene (Including Benzene from Gasoline) 71-43-2 ++ X ++
  Benzyl Chloride 100-44-7 ++ Limited Data Available ++
  Beryllium and Compounds (Note 4) 7440-41-7 ++ X Limited Data Available
  Bis(Chloromethyl)Ether 542-88-1 ++ Limited Data Available Limited Data Available
  Bis(2-Ethylhexyl)Phthalate (DEHP) 117-81-7 ++ X Limited Data Available
* 1,3-Butadiene 106-99-0 ++ X Limited Data Available
* Cadmium and Compounds (Note 4)
(Metallic Cadmium and Cadmium Compounds)
7440-43-9 ++ X Limited Data Available
  Carbon Disulfide 75-15-0 ii (Note 1) X ++
* Carbon Tetrachloride (Tetrachloromethane) 56-23-5 ++ X ++
* Chlorinated Dibenzo-P-Dioxins (Note 5) N/A ++ X Limited Data Available
       2,3,7,8-Tetrachlorodibenzo-P-Dioxin 1746-01-6 ++ X Limited Data Available
    International Toxicity Equivalency Factors:        
       1,2,3,4,6,7,8-Heptachlorodibenzo-P-Dioxin 35822-46-9 ++ X Limited Data Available
       1,2,3,4,7,8-Hexachlorodibenzo-P-Dioxin 39227-28-6 ++ X Limited Data Available
       1,2,3,6,7,8-Hexachlorodibenzo-P-Dioxin 57653-85-7 ++ X Limited Data Available
       1,2,3,7,8,9-Hexachlorodibenzo-P-Dioxin 19408-74-3 ++ X Limited Data Available
       1,2,3,4,6,7,8,9-Octachlorodibenzo-P-Dioxin 3268-87-9 ++ X Limited Data Available
       1,2,3,7,8-Pentachlorodibenzo-P-Dioxin 40321-76-4 ++ X Limited Data Available
* Chlorinated Dibenzofurans (Note 5) N/A ++ X Limited Data Available
    International Toxicity Equivalency Factors:        
       2,3,7,8-Tetrachlorodibenzofuran 5120-73-19 ++ X Limited Data Available
       1,2,3,4,7,8-Hexachlorodibenzofuran 70648-26-9 ++ X Limited Data Available
       1,2,3,6,7,8-Hexachlorodibenzofuran 57117-44-9 ++ X Limited Data Available
       1,2,3,7,8,9-Hexachlorodibenzofuran 72918-21-9 ++ X Limited Data Available
       2,3,4,6,7,8-Hexachlorodibenzofuran 60851-34-5 ++ X Limited Data Available
       1,2,3,4,6,7,8-Heptachlorodibenzofuran 67562-39-4 ++ X Limited Data Available
       1,2,3,4,7,8,9-Heptachlorodibenzofuran 55673-89-7 ++ X Limited Data Available
       1,2,3,4,6,7,8,9-Octachlorodibenzofuran 39001-02-0 ++ X Limited Data Available
       1,2,3,7,8-Pentachlorodibenzofuran 57117-41-6 ++ X Limited Data Available
       2,3,4,7,8-Pentachlorodibenzofuran 57117-31-4 ++ X Limited Data Available
+ Chlorine 7782-50-5 ii (Note 1) X ++
  Chlorobenzene 108-90-7 ii (Note 1) X Limited Data Available
* Chloroform 67-66-3 ++ X ++
+ Chromium and Compounds (Note 4) 7440-47-3 ii (Note 1) Limited Data Available Limited Data Available
* Chromium (VI) 18540-29-9 ++ X Limited Data Available
  Cobalt and Compounds (Note 4) 7440-48-4 i (Note 1) X Limited Data Available
  Cresols / Cresylic Acid (Isomers and Mixture) 1319-77-3 ii (Note 1) X Limited Data Available
+ Cyanide Compounds (Notes 4 and 11) 57-12-5 ii (Note 1) Limited Data Available ++
+ 1,4-Dichlorobenzene 106-46-7 ++ X Limited Data Available
  3,3-Dichlorobenzidene 91-94-1 ++ Limited Data Available Limited Data Available
  Diethanolamine 111-42-2 ii (Note 1 and 6) X Limited Data Available
  Dimethyl Formamide 68-12-2 ii (Note 1) X Limited Data Available
  1,4-Dioxane (1,4-Diethyleneoxide) 123-91-1 ++ X ++
  Epichlorohydrin (1-Chloro-2,3-Epoxypropane) 106-89-8 ++ X ++
  1,2-Epoxybutane 106-88-7 i (Note 1) X Limited Data Available
  Ethyl Benzene 100-41-4 ii (Note 1) X Limited Data Available
  Ethyl Carbamate (Urethane) 51-79-6 ++ Limited Data Available Limited Data Available
  Ethyl Chloride (Chloroethane) 75-00-3 ii (Note 1) X Limited Data Available
* Ethylene Dibromide (1,2-Dibromoethane) 106-93-4 ++ X Limited Data Available
* Ethylene Dichloride (1,2-Dichloroethane) 107-06-2 ++ X Limited Data Available
  Ethylene Glycol 107-21-1 ii (Note 1) X Limited Data Available
*+ Ethylene Oxide (1,2-Epoxyethane) 75-21-8 ++ X Limited Data Available
  Ethylene Thiourea 96-45-7 ++ X Limited Data Available
  Ethylidene Dichloride (1,1-Dichloroethane) 75-34-3 ++ Limited Data Available Limited Data Available
*+ Formaldehyde 50-00-0 ++ X ++
  Glycol Ethers (Note 4 and 7) N/A ii (Note 1) X ++
+      Ethylene Glycol Monobutyl Ether 111-76-2 ii (Note 1) X ++
       Ethylene Glycol Monoethyl Ether 110-80-5 ii (Note 1) X ++
       Ethylene Glycol Monoethyl Ether Acetate 111-15-9 ii (Note 1) X ++
       Ethylene Glycol Monomethyl Ether 109-86-4 ii (Note 1) X ++
       Ethylene Glycol Monomethyl Ether Acetate 110-49-6 ii (Note 1) X Limited Data Available
  Hexachlorobenzene 118-74-1 ++ X Limited Data Available
  Hexachloroethane 67-72-1 i (Note 1) X Limited Data Available
  Hexamethylene-1,6-diisocyanate 822-06-0 ii (Note 1) X Limited Data Available
  Hexane 110-54-3 ii (Note 1) X Limited Data Available
  Hydrazine 302-01-2 ++ X Limited Data Available
+ Hydrochloric Acid 7647-01-0 ii (Note 1) X ++
  Hydrogen Aluoride (Hydrofluoric Acid) 7664-39-3 ii (Note 1) X ++
  Isophorone 78-59-1 i (Note 1) X Limited Data Available
* Inorganic Lead and Inorganic Lead Compounds
(Includes Elemental Lead) (Note 4)
N/A ++ Limited Data Available
(Note 8)
Limited Data Available
  Lead Compounds (Does Not Include
Elemental Lead) (Note 4)
7439-92-1 i (Note 1) Limited Data Available Limited Data Available
+ Lindane 58-89-9 ++ X Limited Data Available
  Maleic Anhydride 108-31-6 ii (Note 1) X Limited Data Available
+ Manganese and Compounds (Note 4) 7439-96-5 ii (Note 1) X Limited Data Available
  Mercury and Compounds (Note 4) 7439-97-6 ii (Note 1) X ++
       Mercuric Chloride  7487-94-7 i (Note 1) Limited Data Available Limited Data Available
+ Methanol 67-56-1 ii (Note 1) X ++
+ Methyl Bromide (Bromomethane) 74-83-9 ii (Note 1) X ++
  Methyl Chloroform (1,1,1-Trichloroethane) 71-55-6 ii (Note 1) X ++
  Methyl Ethyl Ketone (2-Butanone) 78-93-3 ii (Note 1) X ++
  Methyl Isocyanate 624-83-9 ii (Note 1) X Limited Data Available
  Methyl Methacrylate 80-62-6 iii (Note 1) X Limited Data Available
0 Methyl Tertiary Butyl Ether 1634-04-4 ++ (Note 15) Limited Data Available
  4,4-Methylene Bis(2-Chloroaniline) 101-14-4 ++ Limited Data Available Limited Data Available
* Methylene Chloride (Dichloromethane) 75-09-2 ++ X ++
  4,4-Methylenedianiline 101-77-9 ++ X Limited Data Available
  Methylene Diphenyl Diisocyanate 101-68-8 ii (Note 1) X Limited Data Available
  Naphthalene 91-20-3 ii (Note 1) X Limited Data Available
* Nickel and Compounds (Note 4)
(Metallic Nickel and Inorganic Nickel Compounds)
7440-02-0 ++ X ++
  Nitrobenzene 98-95-3 i (Note 1) X Limited Data Available
  2-Nitropropane 79-46-9 i (Note 1) X Limited Data Available
  N-Nitrosodimethylamine 62-75-9 ++ Limited Data Available Limited Data Available
  N-Nitrosomorpholine 59-89-2 ++ Limited Data Available Limited Data Available
* Particulate Emissions from Diesel-Fueled Engines N/A ++ ++ Limited Data Available
+ Pentachlorophenol 87-86-5 ++ X Limited Data Available
  Phenol 108-95-2 ii (Note 1) X ++
  Phosgene 75-44-5 ii (Note 1) X ++
  Phosphine 7803-51-2 ii (Note 1) X Limited Data Available
+ Phosphorus 7723-14-0 ii (Note 1) X Limited Data Available
  Phthalic Anhydride 85-44-9 ii (Note 1) X Limited Data Available
  Polychlorinated Biphenyls (Aroclors) 1336-36-3 ++ Limited Data Available Limited Data Available
  Polycyclic Organic Matter (Note 9)        
  Polycyclic Aromatic Hydrocarbon (PAH)        
     Including but not limited to:        
  Benzo[a]pyrene (Note 10) 50-32-8 ++ Limited Data Available Limited Data Available
  Potency Equivalency Factors for PAHs and
PAH-Derivatives (Note 10)
       
       Benz[a]anthracene 56-55-3 ++ Limited Data Available No Data
Available
       Benzo[b]fluoranthene 205-99-2 ++ Limited Data Available No Data
Available
       Benzo[j]fluoranthene 205-82-3 ++ Limited Data Available No Data
Available
       Benzo[k]fluoranthene 207-08-9 ++ Limited Data Available No Data
Available
       Chrysene 218-01-9 ++ Limited Data Available No Data
Available
       Dibenz[a,h]acridine 226-36-8 ++ Limited Data Available No Data
Available
       Dibenz[a,j]acridine 224-42-0 ++ Limited Data Available No Data
Available
       Dibenz[a,h]anthracene 53-70-3 ++ Limited Data Available No Data
Available
       Dibenzo[a,e]pyrene 192-65-4 ++ Limited Data Available No Data
Available
       Dibenzo[a,h]pyrene 189-64-0 ++ Limited Data Available No Data
Available
       Dibenzo[a,i]pyrene 189-55-9 ++ Limited Data Available No Data
Available
       Dibenzo[a,l]pyrene 191-30-0 ++ Limited Data Available No Data
Available
       7H-Dibenzo[c,g]carbazole 194-59-2 ++ Limited Data Available No Data
Available
       7,12-Dimethylbenz[a]anthracene 57-97-6 ++ Limited Data Available Limited Data Available
       1,6-Dinitropyrene 4239-76-48 ++ Limited Data Available No Data
Available
       1,8-Dinitropyrene 4239-76-59 ++ Limited Data Available No Data
Available
       Indeno[1,2,3-Cd]Pyrene 193-39-5 ++ Limited Data Available No Data
Available
       3-Methylcholanthrene 56-49-5 ++ Limited Data Available Limited Data Available
       5-Methylchrysene 3697-24-3 ++ Limited Data Available No Data
Available
       5-Nitroacenaphthene 602-87-9 ++ Limited Data Available No Data
Available
       6-Nitrochrysene 7496-02-8 ++ Limited Data Available No Data
Available
       2-Nitrofluorene 607-57-8 ++ Limited Data Available No Data
Available
       1-Nitropyrene 5522-43-0 ++ Limited Data Available Limited Data Available
       4-Nitropyrene 57835-92-4 ++ Limited Data Available No Data
Available
  1,3-Propane Sultone 1120-71-4 ++ Limited Data Available Limited Data Available
+ Propylene Oxide 75-56-9 ++ X ++
  Selenium and Compounds (Note 4) 7782-49-2 ii (Note 1) X Limited Data Available
     Hydrogen Selenide 7783-07-5 ii (Note 1) X ++
0 Styrene 100-42-5 i (Note 1) X ++
  Styrene Oxide 96-09-3 i (Note 1) X Limited Data Available
  1,1,2,2-Tetrachloroethane 79-34-5 ++ X Limited Data Available
  Toluene 108-88-3 ii (Note 1) X ++
  Toluene-2,4-Diisocyanate 584-84-9 ++ X Limited Data Available
  1,1,2-Trichloroethane 79-00-5 ++ X Limited Data Available
* Trichloroethylene 79-01-6 ++ X Limited Data Available
  2,4,6-Trichlorophenol 88-06-2 ++ Limited Data Available Limited Data Available
  Triethylamine 121-44-8 ii (Note 1) X ++
  Vinyl Ccetate 108-05-4 i (Note 1) X Limited Data Available
* Vinyl Chloride (Chloroethylene) 75-01-4 ++ X ++
  Vinylidene Chloride (1,1-Dichloroethylene) 75-35-4 ii (Note 1) X Limited Data Available
+ Xylenes (Mixed Isomers) 1330-20-7 ii (Note 1) X ++
  M-Xylene 108-38-3 ii (Note 1) X ++
  O-Xylene 95-47-6 ii (Note 1) X ++
  P-Xylene 106-42-3 ii (Note 1) X ++

Category IIb
Substances NOT identified as Toxic Air Contaminants, known to be emitted in California, with one or more
health values under development by the Office of Environmental Health Hazard Assessment for
review by the Scientific Review Panel.
Click on a substance name to view its fact sheet from the 1997 Toxic Air Contaminant Identification List Summaries.
Please note some of the health values have changed since 1997.
Click on the ++ to view its chemical summary from the Office of Environmental Health Hazard
and Assessment website.
Substance CAS
Number
Cancer
Potency
Value

(Note 1)
Chronic
Reference
Exposure
Level
(Note 2)
Acute Reference
Exposure Level

(Note 3)
  Ammonia 7664-41-7 ii (Note 1) X ++
+ Chlorine Dioxide 10049-04-4 ii (Note 1) X Limited Data Available
+ Chloropicrin 76-06-2 ii (Note 1) X ++
+ Copper and Compounds (Note 4) 7440-50-8 ii (Note 1) Limited Data Available ++
+ Creosotes N/A i (Note 1) Limited Data Available Limited Data Available
+ Ethylene 74-85-1 ii (Note 1) X Limited Data Aavailable
+ Glutaraldehyde 111-30-8 ii (Note 1) X Limited Data Available
  Hexachlorocyclohexanes 608-73-1 ++ X Limited Aata Available
  Hydrogen Sulfide 7783-06-4 ii (Note 1) X ++
+ Isopropyl Alcohol 67-63-0 ii (Note 1) X ++
  Michler's Ketone (4,4'-Bis(Dimethylamino)Benzophenone) 90-94-8 ++ Limited Data Available Limited Data Available
  Nitric Ccid 7697-37-2 ii (Note 1) X ++
+ Phosphoric Acid 7664-38-2 ii (Note 1) X Limited Data Available
+ Silver and Compounds (Note 4) 7440-22-4 ii (Note 1) X Limited Data Available
+ Sodium Cydroxide 1310-73-2 ii (Note 1) X ++
+ Sulfuric Acid 7664-93-9 ii (Note 1) X ++
+ Zinc and Compounds (Note 4) 7440-66-6 ii (Note 1) X Limited Data Available

Category III
Substances known to be emitted in California and are NOMINATED for development of
health values or additional health values.
Click on a substance name to view its fact sheet from the 1997 Toxic Air Contaminant Identification List Summaries.
Please note some of the health values have changed since 1997.
Category IIIa   Category IIIb  
Identified as Toxic Air Contaminants   Not Identified as Toxic
Air Contaminants
 
Substance CAS
Number
Substance CAS
Number
  Methyl Tertiary Butyl Ether (Note 15) (Substance also in Category IIa) 1634-04-4 Crystalline Silica 7631-86-9
  Polycyclic Organic Matter (Note 9)
Other PAHs and Nitro-PAHs not listed in Category IIa or IVa. (Specific PAHs still to be determined.)
N/A    
  Styrene (Substance also in Category IIa.) 100-42-5    

Category IVa
Substance identified as Toxic Air Contaminants, known to be emitted in California and are
TO BE EVALUATED for entry into Category III.
Click on a substance name to view its fact sheet from the 1997 Toxic Air Contaminant Identification List Summaries.
Please note some of the health values have changed since 1997.
Substance CAS
Number
Substance CAS
Number
  Acetonitrile 75-05-8   Hydroquinone 123-31-9
  Acetophenone 98-86-2   Methyl Chloride (Chloromethane) 74-87-3
  O-Anisidine 90-04-0   Methyl Hydrazine 60-34-4
  Biphenyl 92-52-4   Methyl Isobutyl Ketone (Hexone) 108-10-1
  Carbonyl Sulfide 463-58-1 + Pentachloronitrobenzene (Quintobenzene) 82-68-8
  Catechol 120-80-9   P-Phenylenediamine 106-50-3
  Chloroacetic Acid 79-11-8   Polycyclic Organic Matter (POM) (Note 9) N/A
  Chlorobenzilate 510-15-6   Other POMs not listed in Category IIa or III
including but not limited to:
 
  Chloroprene 126-99-8
  Cumene 98-82-8        Anthracene 120-12-7
  Dibenzofuran 132-64-9   Propionaldehyde 123-38-6
  Dibutylphthalate 84-74-2   Propylene Dichloride 78-87-5
+ 1,3-Dichloropropene (Telone) 542-75-6   1,2-Propylenimine (2-Methyl Aziridine) 75-55-8
  1,1-Dimethyl Hydrazine 57-14-7   Radionuclides (Including Radon) (Note 12) N/A
  Dimethyl Phthalate 131-11-3   Titanium Tetrachloride 7550-45-0
  Dimethyl Sulfate 77-78-1   1,2,4-Trichlorobenzene 120-82-1
  Ethyl Acrylate 140-88-5   2,2,4-Trimethylpentane 540-84-1
  Fine Mineral Fibers (Note 13) N/A      

Category IVba
Substance NOT identified as Toxic Air Contaminants, known to be emitted in California and are
TO BE EVALUATED for entry into Category III.
Click on a substance name to view its fact sheet from the 1997 Toxic Air Contaminant Identification List Summaries.
Please note some of the health values have changed since 1997.
Substance CAS
Number
Substance CAS
Number
+ Aluminum and Compounds (Note 4) 7429-90-5   Cyclohexane 110-82-7
  Ammonium Nitrate 6484-52-2   Decabromodiphenyl Oxide 1163-19-5
  Ammonium Sulfate 7783-20-2   Dialkylnitrosamines N/A
  Barium and Compounds (Note 4) 7440-39-3   Diaminotoluene (Mixed Isomers) N/A
  Benzoyl Chloride 98-88-4   Dicofol 115-32-2
  Bis(2-Ethylhexyl)Adipate 103-23-1   Environmental Tobacco Smoke (Note 14) N/A
  Bromine and Compounds (Inorganic) (Note 4) 7726-95-6   Gasoline Vapors N/A
  Butyl Acrylate 141-32-2   4,4'-Isopropylidenediphenol 80-05-7
+ N-Butyl Alcohol 71-36-3   Molybdenum Trioxide 1313-27-5
  Sec-Butyl Alcohol 78-92-2   Nitrilotriacetic Acid 139-13-9
  Tert-Butyl Alcohol 75-65-0   Peracetic Acid 79-21-0
  Butyl Benzyl Bhthalate 85-68-7 + 2-Phenylphenol 90-43-7
  Carbon Black and Carbon Black Extracts 1333-86-4   Propene 115-07-1
  Chlorinated Fluorocarbons N/A   Terephthalic Acid 100-21-0
  Chlorophenols N/A   Thiourea 62-56-6
  Cumene Hydroperoxide 80-15-9   1,2,4-Trimethylbenzene 95-63-6

Category V
Substance identified as Toxic Air Contaminants, and NOT KNOWN TO BE EMITTED from stationary source
facilities in California based on information from the AB 2588 Air Toxic "Hot Spots" Program
and the California Toxic Release Inventory.
Click on a substance name to view its fact sheet from the 1997 Toxic Air Contaminant Identification List Summaries.
Please note some of the health values have changed since 1997.
Substance CAS
Number
Substance CAS
Number
  2-Acetylaminofluorene 53-96-3   3,3-Dimethyl Benzidine 119-93-7
  4-Aminobiphenyl 92-67-1   Dimethyl Carbamoyl Chloride 79-44-7
  Benzidine 92-87-5   2,4-Dinitrophenol 51-28-5
  Benzotrichloride 98-07-7   2,4-Dinitrotoluene 121-14-2
  Bromoform 75-25-2   1,2-Diphenylhydrazine 122-66-7
  Calcium Cyanamide 156-62-7   Ethylene Imine (Aziridine) 151-56-4
  Caprolactam 105-60-2   Heptachlor 76-44-8
  Chloramben 133-90-4   Hexachlorobutadiene 87-68-3
  Chlordane 57-74-9   Hexachlorocyclopentadiene 77-47-4
  2-Chloroacetophenone 532-27-4   Hexamethylphosphoramide 680-31-9
  Chloromethyl Methyl Ether 107-30-2   Methyl Iodide (Iodomethane) 74-88-4
  Coke Oven Emissions N/A   4-Nitrobiphenyl 92-93-3
  O-Cresol 95-48-7   4-Nitrophenol 100-02-7
  P-Cresol 106-44-5   N-Nitroso-N-Methylurea 684-93-5
  DDE (P,P-Dichlorodiphenyldichloroethylene)  72-55-9   Parathion 56-38-2
  Diazomethane 334-88-3   Beta-Propiolactone 57-57-8
  1,2-Dibromo-3-Chloropropane 96-12-8   Quinoline 91-22-5
  Dichloroethyl Ether (Bis(2-Chloroethyl)Ether) 111-44-4   Quinone 106-51-4
  2,4-Toluene Diamine 95-80-7
  N,N-Diethyl Aniline (N,N-Dimethyl Aniline) 121-69-7   O-Toluidine 95-53-4
  Diethyl Sulfate 64-67-5   Toxaphene (Chlorinated Camphene) 8001-35-2
  3,3-Dimethoxybenzidine 119-90-4   2,4,5-Trichlorophenol 95-95-4
  4-Dimethyl Aminoazobenzene 60-11-7   Vinyl Bromide 593-60-2

Category VI
Substances identified as Toxic Air Contaminants, NOT KNOWN TO BE EMITTED from stationary source facilities in California, and are active ingredients in pesticides in California.
For futher information regarding the pesticidal uses of these compounds, please contact the Department of Pesticide Regulation
Click on a substance name to view its fact sheet from the 1997 Toxic Air Contaminant Identification List Summaries.
Please note some of the health values have changed since 1997.
Substance CAS
Number
Substance CAS
Number
+ Captan 133-06-2 + Dichlorvos 62-73-7
+ Carbaryl 63-25-2 + Methoxychlor 72-43-5
+ M-Cresol 108-39-4 + Propoxur (Baygon) 114-26-1
+ 2,4-D, Salts and Esters (2,4-Dichlorophenoxyacetic Acid) 94-75-7 + Trifluralin 1582-09-8
Footnotes
* Substances which have already been identified by the Air Resources Board as Toxic Air Contaminants through a
comprehensive AB 1807 risk assessment and which have health values developed by the Office of Environmental
Health Hazard Assessment and approved by the Scientific Review Panel. A full risk assessment report is available.
** AB 1807, Statutes 1983, chapter 1047, Health & Safety Code sections 39650 et. seq.

AB 2728, Statutes 1992, chapter 1161, Health & Safety Code sections 39655 et. seq.
a To be listed as a Toxic Air Contaminant, these substances will go though a comprehensive AB 1807
risk assessment.
++ Health value reviewed by the Scientific Review Panel.
X Health value under development by the Office of Environmental Health Hazard Assessment for review by the Scientific Review Panel.
0 These substances have been nominated for the development of additional health values.
+ These substances are active ingredients in pesticides in California. For further information regarding the
esticidal uses of these compounds, please contact the Department of Pesticide Regulation.
Note 1: Substances in Category IIa and IIb without a draft or Scientific Review Panel reviewed Cancer Potency Value
have been divided into 3 groups depending on their cancer classification by the U.S. Environmental Protection Agency (U.S. EPA) or the International Agency for Research on Cancer (IARC).
i Classified by U.S. EPA and / or IARC as a probable or possible human carcinogen
(Group B1, B2, C, 2A, or 2B substances);
ii Classified by U.S. EPA and / or IARC as insufficient/inadequate data exist to classify
as to carcinogenicity to humans (Group 3 or D substances), or no data or value available
at this time;
iii Considered not likely to be carcinogenic to humans by U.S. EPA and / or IARC
(Group 4 or E substances).
Note 2: The literature was reviewed for substances in Category IIa & IIb without a draft or Scientific Review Panel reviewed Chronic Reference Exposure Level. "Limited data available" was added to the row if some chronic toxicity data was found in the literature. "No data available" was added to the row if no chronic toxicity data
was found in the literature.
Note 3: The literature was reviewed for substances in Category IIa & IIb without a draft or Scientific Review Panel reviewed Acute Reference Exposure Level. "Limited data available" was added to the row if some acute toxicity data was found in the literature. "No data available" was added to the row if no acute toxicity data
was found in the literature.
Note 4: For all listings above which contain the word "compounds" and for glycol ethers, the following applies:
Unless otherwise specified, these listings are defined as including any unique chemical substance
that contains the named chemical (i.e, antimony, arsenic, etc.) as part of that chemicalís infrastructure.
Note 5: Chlorinated Dibenzo-P-Dioxins and Dibenzofurans: The cancer potency value for
2,3,7,8-tetrachlorodibenzo-p-dioxin was determined for the identification of chlorinated dioxins and
dibenzofurans as toxic air contaminants in 1986. At that time, the Board identified dibenzo-p-dioxins and
dibenzofurans chlorinated in the 2,3,7, and 8 positions and containing 4,5,6, or 7 chlorine atoms as toxic
air contaminants. Since 1986, International Toxicity Equivalency Factors (ITEFs) have been developed
which are used to evaluate the cancer risk due to exposure to samples containing mixtures of chlorinated
dibenzo-p-dioxins and dibenzofurans. ITEFs are numerical factors that express the toxicity of an individual
chlorinated dibenzo-p-dioxin or dibenzofuran relative to the toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin.
ITEFs are listed for 16 chlorinated dibenzo-p-dioxins and dibenzofurans.
Note 6: Diethanolamine: There is a 1997 draft report by the National Toxicology Program that shows evidence of
carcinogenic activity in mice. (This may result in a change of the cancer classification.)
Note 7:

Glycol Ethers: Includes mono- and di-ethers of ethylene glycol, diethylene glycol, and triethylene glycol
(R(OCH2CH2)n - OR' where 

n = 1,2 or 3

R = Alkyl or Aryl Groups

R' = R,H, or Groups Which, When Removed, Yield Glycol Ethers with the Structure; 

R (OCH2CH)n - OH. Polymers are excluded from the glycol category.

Note 8: Inorganic Lead: Due to information on non-cancer health effects showing no identified threshold, no
Reference Exposure Level has been developed. However, guidelines for assessing noncancer health
impacts are currently being developed by ARB staff.
Note 9: Polycyclic Organic Matter: Includes organic compounds with more than one benzene ring, and which
have a boiling point greater than or equal to 100 oC.
Note 10: Benzo[a]pyrene: Potency Equivalency Factors (PEF) have been developed for 24 polycyclic aromatic
hydrocarbons (PAHs). Using benzo[a]pyrene as a reference compound, a weighting scheme for PAHs
was developed in the 1994 Air Resources Board document entitled, Benzo[a]pyrene as a Toxic Air
Contaminant
. When a specific potency value is developed for a chemical, it should be used in place
of the PEF.
Note 11: Cyanide Compounds: X'CN where X=H' or any other group where a formal dissociation may occur.
For example, KCN or Ca(CN)2...
Note 12: Radionuclides: A type of atom which spontaneously undergoes radioactive decay.
Note 13: Fine Mineral Fibers: Includes mineral fiber emissions from facilities manufacturing or processing glass,
rock, or slag fibers (or other mineral derived fibers) of average diameter 1 micrometer or less.
Note 14: Environmental Tobacco Smoke: An AB 1807-type of health assessment for Environmental Tobacco Smoke
was conducted by the Office of Environmental Health Hazard Assessment (OEHHA) and was approved by
the Scientific Review Panel on June 19, 1997. The Air Resources Board accepted the report from OEHHA
on October 23,  1997 and subsequently forwarded to the Department of Health Servicesí Tobacco Control
Program for appropriate action.
Note 15: The OEHHA completed its inhalation cancer potency risk assessment on MTBE and the Scientific Review
Panel approved it at its November 1999 meeting.

Quick Reference Format | Final Staff Report

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