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Border Air Quality Data - About AQS Hazardous Air Pollutants 
The Clean Air Act designates 188 substances, known to have harmful health effects, as hazardous air pollutants (HAPs). The table below lists hazardous air pollutants as they are defined in EPA's ambient air pollution monitoring database, the Air Quality System (AQS). The table gives each pollutant's name, alternative names, Chemical Abstracts Service number, and AQS parameter code.
The Clean Air Act designates the compounds of some metals as hazardous air pollutants - cadmium compounds, for example. AQS has multiple designations for some of those pollutants, to indicate the type of particulate matter that was collected and analyzed to determine a metal's ambient concentration. For example, AQS defines three HAPs - cadmium (PM2.5), cadmium (PM10), cadmium (TSP) - for cadmium concentration determined from a sample collected as fine particulate matter (PM2.5), coarse particulate matter (PM10), or total suspended particulate matter (TSP). Due to the difference in terminology, AQS has more than 188 hazardous air pollutants.
Ambient concentration monitoring data are available for less than half of the hazardous air pollutants. The availability of monitoring data is indicated in the Data? column of the table below, and by the background color of table rows.
| Hazardous Air Pollutant | Alternative Names and Notes |
CAS Number | AQS Code | Data? |
|---|---|---|---|---|
| Acetaldehyde | Ethanal; Acetic Aldehyde | 75-07-0 | 43503 | Yes |
| Acetamide | Acetic acid amide | 60-35-5 | 16717 | No |
| Acetonitrile | Methyl cyanide; Cyanomethane | 75-05-8 | 43702 | Yes |
| Acetophenone | 1-Phenylethanone | 98-86-2 | 16526 | No |
| 2-Acetylaminofluorene | 2-Acetamidofluorene | 53-96-3 | 17154 | No |
| Acrolein | 2-Propenal; Acrylic aldehyde; Acrylaldehyde | 107-02-8 | 43505 | Yes |
| Acrylamide | Propenamide; Vinyl amide | 79-06-1 | 16718 | No |
| Acrylic acid | 2-Propenoic acid; Propene acid | 79-10-7 | 16425 | No |
| Acrylonitrile | 2-Propenenitrile; Vinyl cyanide | 107-13-1 | 43704 | Yes |
| Allyl chloride | 3-Chloro-1-propene | 107-05-1 | 43335 | No |
| 4-Aminobiphenyl | p-Aminodiphenyl; p-Phenylaniline | 92-67-1 | 17719 | No |
| Aniline | Benzenamine | 62-53-3 | 45701 | No |
| o-Anisidine | 2-Anisidine; 2-Methoxy-1-Aminobenzene | 90-04-0 | 17343 | No |
| Antimony (TSP) | Antimony compounds in total particulate sample | (None) | 12102 | Yes |
| Arsenic (PM10) | Inorganic arsenic compounds (including arsine) in PM10 sample | (None) | 82103 | Yes |
| Arsenic (PM2.5) | Inorganic arsenic compounds (including arsine) in PM2.5 sample | (None) | 88103 | Yes |
| Arsenic (TSP) | Inorganic arsenic compounds (including arsine) in total particulate sample | (None) | 12103 | Yes |
| Asbestos | Asbestos amphibole | 1332-21-4 | 12803 | No |
| Benzene (including benzene from gasoline) | Benzol | 71-43-2 | 45201 | Yes |
| Benzidine | [1,1'-Biphenyl]-4,4'-diamine | 92-87-5 | 17715 | No |
| Benzotrichloride | Trichloromethylbenzene; Trichlorotoluene | 98-07-7 | 17834 | No |
| Benzyl chloride | Chloromethylbenzene; Chlorotoluene | 100-44-7 | 45809 | Yes |
| Beryllium (PM10) | Beryllium compounds in PM10 sample | (None) | 82105 | No |
| Beryllium (PM2.5) | Beryllium compounds in PM2.5 sample | (None) | 88105 | No |
| Beryllium (TSP) | Beryllium compounds in total particulate sample | (None) | 12105 | Yes |
| Biphenyl | Phenyl benzene | 92-52-4 | 45301 | No |
| Bis(2-ethylhexyl)phthalate (DEHP) | DEHP; Di(2-ethylhexyl) phthalate | 117-81-7 | 16455 | No |
| Bis(chloromethyl) ether | Oxybis(chloromethane); Bis-CME | 542-88-1 | 43357 | No |
| Bromoform | Tribromomethane | 75-25-2 | 43806 | Yes |
| 1,3-Butadiene | Butadiene | 106-99-0 | 43218 | Yes |
| Cadmium (PM10) | Cadmium compounds in PM10 sample | (None) | 82110 | Yes |
| Cadmium (PM2.5) | Cadmium compounds in PM2.5 sample | (None) | 88110 | Yes |
| Cadmium (TSP) | Cadmium compounds in total particulate sample | (None) | 12110 | Yes |
| Calcium cyanamide | Cyanogas | 156-62-7 | 53503 | No |
| Captan | N-(trichloromethylthio)-4-cyclohexene-1,2-dicarboximide; Orthocide | 133-06-2 | 53401 | No |
| Carbaryl | 1-Naphthalenol methylcarbamate | 63-25-2 | 51506 | No |
| Carbon disulfide | Carbon bisulfide | 75-15-0 | 42153 | Yes |
| Carbon tetrachloride | Tetrachloromethane | 56-23-5 | 43804 | Yes |
| Carbonyl sulfide | Carbon oxysulfide | 463-58-1 | 43933 | No |
| Catechol | 1,2-Benzenediol | 120-80-9 | 17317 | No |
| Chloramben | 3-Amino-2,5-dichlorobenzoic acid | 133-90-4 | 51119 | No |
| Chlordane | Dichlorodene; Dowchlor; Octachlor | 57-74-9 | 51104 | No |
| Chlorine | Chlorine | 7782-50-5 | 42215 | No |
| Chloroacetic acid | Chloroethanoic acid | 79-11-8 | 16411 | No |
| 2-Chloroacetophenone | 2-Chloro-1-phenylethanone | 532-27-4 | 16527 | No |
| Chlorobenzene | Monochlorobenzene; Benzene chloride | 108-90-7 | 45801 | Yes |
| Chlorobenzilate | 4-Chloro-a-(4-chlorophenyl)-a-hydroxybenzeneacetic acid | 510-15-6 | 52202 | No |
| Chloroform | Trichloromethane | 67-66-3 | 43803 | Yes |
| Chloromethyl methyl ether | Chloromethoxymethane | 107-30-2 | 16365 | No |
| Chloroprene | 2-Chloro-1,3-butadiene | 126-99-8 | 43835 | Yes |
| Chromium (PM10) | Chromium compounds in PM10 sample | (None) | 82112 | Yes |
| Chromium (PM2.5) | Chromium compounds in PM2.5 sample | (None) | 88112 | Yes |
| Chromium (TSP) | Chromium compounds in total particulate sample | (None) | 12112 | Yes |
| Chromium VI (TSP) | Hexavalent chromium compounds in total particulate sample | 18540-29-9 | 12115 | Yes |
| Cobalt (TSP) | Cobalt compounds in total particulate sample | (None) | 12113 | Yes |
| Coke Oven Emissions | Coke Oven Emissions | (None) | 17200 | No |
| m-Cresol | m-Cresol | 108-39-4 | 17302 | No |
| o-Cresol | o-Cresol | 95-48-7 | 17301 | No |
| p-Cresol | p-Cresol | 106-44-5 | 17303 | No |
| Cresol/Cresylic acid (mixed isomers) | Cresols; Cresylol; Toluenol | 1319-77-3 | 17320 | No |
| Cumene | Isopropyl Benzene | 98-82-8 | 45210 | Yes |
| Cyanide Compounds | X-CN where X = any group where formal dissociation may occur, such as KCN or Ca(CN)2. | (None) | 12349 | No |
| 2,4-D (salts and esters) | 2,4-D (2,4-Dichlorophenoxyacetic Acid) (including salts and esters) | 94-75-7 | 54103 | No |
| DDE (1,1-dichloro-2,2-bis(p-chlorophenyl) ethylene) | DDE | 3547-04-4 | 51118 | No |
| Diazomethane | Azimethylene | 334-88-3 | 16229 | No |
| Dibenzofurans | Furans | 132-64-9 | 18202 | No |
| 1,2-Dibromo-3-chloropropane | 3-Chloro-1,2-dibromopropane | 96-12-8 | 51623 | No |
| Dibutyl phthalate | Di-n-butylphthalate | 84-74-2 | 43455 | No |
| 1,4-Dichlorobenzene(p) | p-Dichlorobenzene | 106-46-7 | 45807 | Yes |
| 3,3'-Dichlorobenzidene | 4,4'-Diamino-3,3'-dichlorobiphenyl | 91-94-1 | 17716 | No |
| Dichloroethyl ether (Bis[2-chloroethyl]ether) | Bis(2-chloroethyl)ether | 111-44-4 | 43352 | No |
| 1,3-Dichloropropene | Includes cis and trans isomers | 542-75-6 | 43841 | No |
| Dichlorvos | Phosphoric acid 2,2-dichloroethenyl dimethyl ester | 62-73-7 | 51307 | No |
| Diethanolamine | 2,2'-Iminobisethanol | 111-42-2 | 16709 | No |
| N,N-Diethyl aniline (N,N-Dimethylaniline) | N,N-Dimethylbenzenamine | 121-69-7 | 17720 | No |
| Diethyl sulfate | Sulfuric acid diethyl ester | 64-67-5 | 16909 | No |
| 3,3'-Dimethoxybenzidine | o,o-Diansidine | 119-90-4 | 17721 | No |
| Dimethyl aminoazobenzene | 4-Dimethylaminoazobenzene | 60-11-7 | 17722 | No |
| Dimethyl carbamoyl chloride | Dimethyl carbamic acid | 79-44-7 | 16825 | No |
| Dimethyl formamide | N,N-Dimethylformamide | 68-12-2 | 43454 | No |
| Dimethyl phthalate | 1,2-Benzenedicarboxylic acid dimethy ester | 131-11-3 | 43519 | No |
| Dimethyl sulfate | Sulfuric acid dimethyl ester | 77-78-1 | 16231 | No |
| 3,3'-Dimethylbenzidine | o-Tolidine | 119-93-7 | 17723 | No |
| 1,1-Dimethylhydrazine | N,N-Dimethylhydrazine | 57-14-7 | 16230 | No |
| 4,6-Dinitro-o-cresol (and salts) | 4,6-Dinitro-o-cresol (and salts) | 534-52-1 | 17322 | No |
| 2,4-Dinitrophenol | Aldifen; 2,4-DNP | 51-28-5 | 17313 | No |
| 2,4-Dinitrotoluene | DNT; 1-Methyl-2,4-dinitrobenzene | 121-14-2 | 17724 | No |
| 1,4-Dioxane | 1,4-Diethyleneoxide | 123-91-1 | 46201 | No |
| 1,2-Diphenylhydrazine | Hydrazobenzene | 122-66-7 | 16232 | No |
| Epichlorohydrin | l-Chloro-2,3-epoxypropane | 106-89-8 | 16901 | No |
| 1,2-Epoxybutane | 1,2-Butylene Oxide; 1,2-Butene oxide | 106-88-7 | 16601 | No |
| Ethyl acrylate | 2-Propenoic acid ethyl ester | 140-88-5 | 43438 | Yes |
| Ethyl carbamate (Urethane) | Urethane; Chloroethane | 51-79-6 | 16233 | No |
| Ethyl Chloride (Chloroethane) | Chloroethane | 75-00-3 | 43812 | Yes |
| Ethylbenzene | Ethylbenzol; Phenylethane | 100-41-4 | 45203 | Yes |
| Ethylene dibromide (Dibromoethane) | 1,2-Dibromoethane | 106-93-4 | 43843 | Yes |
| Ethylene dichloride (1,2-Dichloroethane) | 1,2-Dichloroethane | 107-06-2 | 43815 | Yes |
| Ethylene glycol | 1,2-Ethanediol | 107-21-1 | 43370 | No |
| Ethylene imine (Aziridine) | Aziridine | 151-56-4 | 43601 | No |
| Ethylene oxide | Oxirane | 75-21-8 | 16719 | No |
| Ethylene thiourea | 2-Mercaptoimidazoline | 96-45-7 | 43773 | No |
| Ethylidene dichloride (1,1-Dichloroethane) | 1,1-Dichloroethane | 75-34-3 | 43813 | Yes |
| Fine mineral fibers | Fine mineral fibers | (None) | 11117 | No |
| Formaldehyde | Methanal | 50-00-0 | 43502 | Yes |
| Glycol ethers | See Note 1. | (None) | 16363 | No |
| Heptachlor | 3-Chlorochlordene; Heptachlorane | 76-44-8 | 51109 | No |
| Hexachlorobenzene | Perchlorobenzene; HCB | 118-74-1 | 17804 | No |
| Hexachlorobutadiene | Hexachloro-1,3-Butadiene | 87-68-3 | 43844 | Yes |
| Hexachlorocyclopentadiene | Hexachloro-1,3-Cyclopentadiene | 77-47-4 | 16826 | No |
| Hexachloroethane | Carbon hexachloride; Ethane hexachloride | 67-72-1 | 16807 | No |
| Hexamethylene-1,6-diisocyanate | Hexamethylene diisocyanate | 822-06-0 | 16714 | No |
| Hexamethylphosphoramide | Hexamethylphosphoric acid triamide | 680-31-9 | 16720 | No |
| Hexane | n-Hexane | 110-54-3 | 43231 | Yes |
| Hydrazine | Hydrazine anhydrous | 302-01-2 | 42606 | No |
| Hydrochloric acid | Hydrogen Chloride; gas only | 7647-01-0 | 42302 | No |
| Hydrogen fluoride (Hydrofluoric acid) | Hydrofluoric Acid | 7664-39-3 | 42303 | No |
| Hydroquinone | Dihydroquinone | 123-31-9 | 17316 | No |
| Isophorone | Isoacetophorone | 78-59-1 | 16914 | No |
| Lead (PM10) | Lead compounds in PM10 sample | (None) | 82128 | Yes |
| Lead (PM2.5) | Lead compounds in PM2.5 sample | (None) | 88128 | Yes |
| Lead (TSP) | Lead compounds in total particulate sample | (None) | 12128 | Yes |
| Lindane (all isomers) | Hexachlorocyclohexane | 58-89-9 | 51110 | No |
| Maleic anhydride | 2,5-Furandione | 108-31-6 | 16452 | No |
| Manganese (PM10) | Manganese compounds in PM10 sample | (None) | 82132 | Yes |
| Manganese (PM2.5) | Manganese compounds in PM2.5 sample | (None) | 88132 | Yes |
| Manganese (TSP) | Manganese compounds in total particulate sample | (None) | 12132 | Yes |
| Mercury (PM10) | Mercury compounds in PM10 sample | (None) | 82142 | Yes |
| Mercury (PM2.5) | Mercury compounds in PM2.5 sample | (None) | 88142 | Yes |
| Mercury (TSP) | Mercury compounds in total particulate sample | 7439-97-6 | 12142 | Yes |
| Mercury Compounds | Mercury Compounds | (None) | 92142 | No |
| Methanol | Methyl alcohol | 67-56-1 | 43301 | No |
| Methoxychlor | 1,1'-(2,2,2-Trichloroethylidene)-bis[4-methoxybenzene] | 72-43-5 | 43153 | No |
| Methyl bromide (Bromomethane) | Bromomethane | 74-83-9 | 43819 | Yes |
| Methyl chloride (Chloromethane) | Chloromethane | 74-87-3 | 43801 | Yes |
| Methyl chloroform (1,1,1-Trichloroethane) | 1,1,1-Trichloroethane | 71-55-6 | 43814 | Yes |
| Methyl ethyl ketone (2-Butanone) | MEK; 2-Butanone | 78-93-3 | 43552 | Yes |
| Methyl hydrazine | Monomethylhydrazine | 60-34-4 | 16234 | No |
| Methyl iodide (Iodomethane) | Iodomethane | 74-88-4 | 43808 | No |
| Methyl isobutyl ketone (Hexone) | MIK; Hexone | 108-10-1 | 43560 | Yes |
| Methyl isocyanate | Isocyanic acid, methyl ester | 624-83-9 | 16235 | No |
| Methyl methacrylate | Methyl ester methacrylic acid | 80-62-6 | 43441 | Yes |
| Methyl tert-butyl ether | MTBE | 1634-04-4 | 43372 | Yes |
| Methylene chloride (Dichloromethane) | Dichloromethane | 75-09-2 | 43802 | Yes |
| Methylene diphenyl diisocyanate (MDI) | MDI; MethyleneBis (Phenylisosyanate); Methylene Biphenyl Isocyanate | 101-68-8 | 45732 | No |
| 4,4'-Methylenebis(2-chloroaniline) | 4,4'-Methylenebis[2-chlorobenzenamine] | 101-14-4 | 17718 | No |
| 4,4'-Methylenedianiline | 4-(4-Aminobenzyl)aniline; MDA | 101-77-9 | 45704 | No |
| Naphthalene | White tar; Camphor tar | 91-20-3 | 17141 | Yes |
| Nickel (PM10) | Nickel compounds in PM10 sample | (None) | 82136 | Yes |
| Nickel (PM2.5) | Nickel compounds in PM2.5 sample | (None) | 88136 | Yes |
| Nickel (TSP) | Nickel compounds in total particulate sample | (None) | 12136 | Yes |
| Nitrobenzene | Nitrobenzol | 98-95-3 | 45705 | No |
| 4-Nitrobiphenyl | p-Nitrobiphenyl | 92-93-3 | 17323 | No |
| 4-Nitrophenol | p-Nitrophenol, 4-Hydroxynitrobenzene, | 100-02-7 | 17312 | No |
| 2-Nitropropane | 2-NP; Dimethylnitromethane | 79-46-9 | 43756 | No |
| N-Nitroso-N-methylurea | NMU; N-nitroso-n-methylcarbamide | 684-93-5 | 16721 | No |
| N-Nitrosodimethylamine | N-Methyl-N-nitroso-methanamine | 62-75-9 | 16722 | No |
| N-Nitrosomorpholine | 4-Nitrosomorpholine | 59-89-2 | 16723 | No |
| Parathion | O,O-diethyl O-(4-nitrophenyl) phosphorothioate | 56-38-2 | 51421 | No |
| Pentachloronitrobenzene (Quintobenzene) | Quintobenzene; Quintozene | 82-68-8 | 17725 | No |
| Pentachlorophenol | Penta; PCP | 87-86-5 | 17808 | No |
| Phenol | Carbolic acid | 108-95-2 | 45300 | No |
| p-Phenylenediamine | 1,4-Benzenediamine | 106-50-3 | 17704 | No |
| Phosgene | Carbonic dichloride | 75-44-5 | 43850 | No |
| Phosphine | Hydrogen phosphide | 7803-51-2 | 42610 | No |
| Phosphorous | Phosphorous | 7723-14-0 | 12152 | Yes |
| Phthalic anhydride | 1,3-Isobenzenofurandione | 85-44-9 | 16462 | No |
| Polychlorinated biphenyls (Aroclors) | Arochlors | 1336-36-3 | 17833 | No |
| Polycyclic Organic Matter | POM | (None) | 17199 | No |
| 1,3-Propane sultone | 1,2-Oxathiolane 2,2-dioxide | 1120-71-4 | 16528 | No |
| beta-Propiolactone | 2-Oxetanone | 57-57-8 | 16529 | No |
| Propionaldehyde | Propanal | 123-38-6 | 43504 | Yes |
| Propoxur (Baygon) | 2-(1-Methylethoxy)phenol methyl carbamate; Baygon | 114-26-1 | 51504 | No |
| Propylene dichloride (1,2-Dichloropropane) | 1,2-Dichloropropane | 78-87-5 | 43829 | Yes |
| Propylene oxide | Methyloxirane | 75-56-9 | 43602 | No |
| 1,2-Propylenimine (2-Methylaziridine) | 2-Methylaziridine; Methylethylenimine | 75-55-8 | 16715 | No |
| Quinoline | Leucoline; chinoleine | 91-22-5 | 18105 | No |
| Quinone | p-Benzoquinone; 2,5-Cyclohexadiene-1,4-dione | 106-51-4 | 18125 | No |
| Radionuclides (including radon) | Radionuclides (including radon) | (None) | 11300 | No |
| Selenium (TSP) | Selenium compounds in total particulate sample | (None) | 12154 | Yes |
| Styrene | Ethenylbenzene, Cinnamene, Phenylethylene, Vinyl benzene, Vinylbenzol | 100-42-5 | 45220 | Yes |
| Styrene oxide | Epoxystyrene | 96-09-3 | 17601 | No |
| 2,3,7,8-Tetrachlorodibenzo-p-dioxin | TCDD; 2,3,7,8-TCDD | 1746-01-6 | 17902 | No |
| 1,1,2,2-Tetrachloroethane | Tetrachloroethane | 79-34-5 | 43818 | Yes |
| Tetrachloroethylene (Perchloroethylene) | Perchloroethylene; Perc | 127-18-4 | 43817 | Yes |
| Titanium tetrachloride | Titanium chloride | 7550-45-0 | 12278 | No |
| Toluene | Methylbenzene | 108-88-3 | 45202 | Yes |
| 2,4-Toluene diamine | Toluene-2,4-diamine; TDA; 2,4-Diaminotoluene | 95-80-7 | 17726 | No |
| 2,4-Toluene diisocyanate | 2,4-Diisocyanatotoluene; Toluene 2,4-Diisocynate; TDI | 584-84-9 | 17906 | No |
| o-Toluidine | 2-Aminotoluene | 95-53-4 | 17710 | No |
| Toxaphene (chlorinated camphene) | Chlorinated camphene; camphechlor | 8001-35-2 | 51117 | No |
| 1,2,4-Trichlorobenzene | 1,2,4-Trichlorobenzol | 120-82-1 | 45810 | Yes |
| 1,1,2-Trichloroethane | Vinyl Trichloride | 79-00-5 | 43820 | Yes |
| Trichloroethylene | Trichloroethene; TCE | 79-01-6 | 43824 | Yes |
| 2,4,5-Trichlorophenol | Dowicide 2; Dowicide B | 95-95-4 | 17324 | No |
| 2,4,6-Trichlorophenol | Dowicide 2S; Phenachlor | 88-06-2 | 17325 | No |
| Triethylamine | N,N-Diethylethanamine | 121-44-8 | 43741 | No |
| Trifluralin | 2,6-Dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine | 1582-09-8 | 54426 | No |
| 2,2,4-Trimethylpentane | Isooctane | 540-84-1 | 43250 | Yes |
| Vinyl acetate | Acetic acid ethenyl ester; acetic acid vinyl ester | 108-05-4 | 43447 | No |
| Vinyl bromide | Bromoethene; Bromoethylene | 593-60-2 | 43861 | No |
| Vinyl chloride | Chloroethylene | 75-01-4 | 43860 | Yes |
| Vinylidene chloride (1,1-Dichloroethylene) | 1,1-Dichloroethylene; 1,1-Dichloroethene | 75-35-4 | 43826 | Yes |
| m-Xylene | 1,3-Dimethyl benzene | 108-38-3 | 45205 | Yes |
| o-Xylene | 1,2-Dimethyl benzene | 95-47-6 | 45204 | Yes |
| p-Xylene | 1,4-Dimethyl benzene | 106-42-3 | 45206 | Yes |
| Xylenes (mixed isomers) | Dimethyl benzenes | 1330-20-7 | 45102 | No |
Note 1: "Glycol ethers" include mono- and di-ethers of ethylene glycol [R-O-CH2-CH2-O-R'], diethylene glycol [R-O-CH2-CH2-O-CH2-CH2-O-R'], and triethylene glycol [R-O-CH2-CH2-O-CH2-CH2-O-CH2-CH2-O-R'], where
R = alkyl or aryl group, and
R' = R, H, or groups that yield H when removed.
Surfactant alcohol ethoxylates and their derivatives (SAED) are excluded.