The Priority List of Hazardous Substances That Will Be the Subject of Toxicological Profiles

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ATSDR’s Substance Priority List

What is the Substance Priority List (SPL)?

2022 Substance Priority List

The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) section 104 (i), as amended by the Superfund Amendments and Reauthorization Act (SARA), requires ATSDR and the EPA to prepare a list, in order of priority, of substances that are most commonly found at facilities on the National Priorities List (NPL) and which are determined to pose the most significant potential threat to human health due to their known or suspected toxicity and potential for human exposure at these NPL sites. CERCLA also requires this list to be revised periodically to reflect additional information on hazardous substances. In CERCLA, it is called the priority list of hazardous substances that will be candidates for toxicological profiles.

This substance priority list is generally revised and published every two years, with an informal review and revision each year. Each substance on the list is a candidate to become the subject of a toxicological profile prepared by ATSDR. The listing algorithm prioritizes substances based on frequency of occurrence at NPL sites, toxicity, and potential for human exposure to the substances found at NPL sites.

It should be noted that this priority list is not a list of “most toxic” substances, but rather a prioritization of substances based on a combination of their frequency, toxicity, and potential for human exposure at NPL sites.

Thus, it is possible for substances with low toxicity but high NPL frequency of occurrence and exposure to be on this priority list. The objective of this priority list is to rank substances across all NPL hazardous waste sites to provide guidance in selecting which substances will be the subject of toxicological profiles prepared by ATSDR.

Where can I find more information on the Substance Priority List?

Substantial additional information can be found on the SPL Resource page, including:

  • Past Substance Priority Lists
  • A Support Document describing the algorithm in detail
  • A comprehensive SPL spreadsheet with data for all current and past lists, including candidate substances that did not make the top of the list

The ATSDR 2022 Substance Priority List

The ATSDR 2022 Substance Priority List
2022 Rank Substance Name Total Points CAS RN
1 ARSENIC 1675 7440-38-2
2 LEAD 1531 7439-92-1
3 MERCURY 1455 7439-97-6
4 VINYL CHLORIDE 1355 75-01-4
5 POLYCHLORINATED BIPHENYLS 1342 1336-36-3
6 BENZENE 1328 71-43-2
7 CADMIUM 1317 7440-43-9
8 BENZO(A)PYRENE 1306 50-32-8
9 POLYCYCLIC AROMATIC HYDROCARBONS 1277 130498-29-2
10 BENZO(B)FLUORANTHENE 1255 205-99-2
11 CHLOROFORM 1202 67-66-3
12 AROCLOR 1260 1191 11096-82-5
13 DDT, P,P’- 1182 50-29-3
14 AROCLOR 1254 1172 11097-69-1
15 DIBENZO(A,H)ANTHRACENE 1163 53-70-3
16 TRICHLOROETHYLENE 1153 79-01-6
17 CHROMIUM, HEXAVALENT 1151 18540-29-9
18 DIELDRIN 1142 60-57-1
19 PHOSPHORUS, WHITE 1141 7723-14-0
20 AROCLOR 1242 1126 53469-21-9
21 DDE, P,P’- 1125 72-55-9
22 CHLORDANE 1125 57-74-9
23 COAL TAR CREOSOTE 1124 8001-58-9
24 HEXACHLOROBUTADIENE 1122 87-68-3
25 ALDRIN 1115 309-00-2
26 DDD, P,P’- 1113 72-54-8
27 AROCLOR 1248 1107 12672-29-6
28 HEPTACHLOR 1102 76-44-8
29 AROCLOR 1102 12767-79-2
30 BENZIDINE 1093 92-87-5
31 ACROLEIN 1090 107-02-8
32 TOXAPHENE 1089 8001-35-2
33 TETRACHLOROETHYLENE 1081 127-18-4
34 HEXACHLOROCYCLOHEXANE, GAMMA- 1074 58-89-9
35 CYANIDE 1068 57-12-5
36 HEXACHLOROCYCLOHEXANE, BETA- 1054 319-85-7
37 DISULFOTON 1049 298-04-4
38 BENZO(A)ANTHRACENE 1048 56-55-3
39 1,2-DIBROMOETHANE 1044 106-93-4
40 DIAZINON 1038 333-41-5
41 HEXACHLOROCYCLOHEXANE, DELTA- 1035 319-86-8
42 ENDRIN 1035 72-20-8
43 BERYLLIUM 1033 7440-41-7
44 AROCLOR 1221 1029 11104-28-2
45 1,2-DIBROMO-3-CHLOROPROPANE 1027 96-12-8
46 ENDOSULFAN 1022 115-29-7
47 ENDOSULFAN, ALPHA 1019 959-98-8
48 HEPTACHLOR EPOXIDE 1019 1024-57-3
49 CIS-CHLORDANE 1017 5103-71-9
50 CARBON TETRACHLORIDE 1015 56-23-5
51 COBALT 1015 7440-48-4
52 AROCLOR 1016 1013 12674-11-2
53 DDT, O,P’- 1010 789-02-6
54 PENTACHLOROPHENOL 1007 87-86-5
55 ENDOSULFAN SULFATE 1005 1031-07-8
56 METHOXYCHLOR 1004 72-43-5
57 NICKEL 994 7440-02-0
58 ENDRIN KETONE 994 53494-70-5
59 DI-N-BUTYL PHTHALATE 993 84-74-2
60 DIBROMOCHLOROPROPANE 985 67708-83-2
61 BENZO(K)FLUORANTHENE 975 207-08-9
62 TRANS-CHLORDANE 969 5103-74-2
63 ENDOSULFAN, BETA 969 33213-65-9
64 CHLORPYRIFOS 965 2921-88-2
65 XYLENES, TOTAL 962 1330-20-7
66 CHROMIUM(VI) TRIOXIDE 962 1333-82-0
67 AROCLOR 1232 959 11141-16-5
68 ENDRIN ALDEHYDE 959 7421-93-4
69 METHANE 952 74-82-8
70 2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN 943 1746-01-6
71 3,3′-DICHLOROBENZIDINE 942 91-94-1
72 2-HEXANONE 940 591-78-6
73 BENZOFLUORANTHENE 937 56832-73-6
74 ZINC 916 7440-66-6
75 TOLUENE 912 108-88-3
76 PENTACHLOROBENZENE 907 608-93-5
77 DI(2-ETHYLHEXYL)PHTHALATE 903 117-81-7
78 CHROMIUM 892 7440-47-3
79 2,4,5-TRICHLOROPHENOL 892 95-95-4
80 AROCLOR 1240 890 71328-89-7
81 2,4,6-TRINITROTOLUENE 879 118-96-7
82 NAPHTHALENE 878 91-20-3
83 1,1-DICHLOROETHENE 873 75-35-4
84 BROMODICHLOROETHANE 868 683-53-4
85 DDD, O,P’- 868 53-19-0
86 BIS(2-CHLOROETHYL)ETHER 868 111-44-4
87 2,4,6-TRICHLOROPHENOL 867 88-06-2
88 HYDRAZINE 863 302-01-2
89 2,4-DINITROPHENOL 860 51-28-5
90 4,4′-METHYLENEBIS(2-CHLOROANILINE) 859 101-14-4
91 METHYLENE CHLORIDE 858 75-09-2
92 1,2-DICHLOROETHANE 854 107-06-2
93 N-NITROSODIMETHYLAMINE 849 62-75-9
94 THIOCYANATE 848 302-04-5
95 HEXACHLOROBENZENE 845 118-74-1
96 ASBESTOS 840 1332-21-4
97 RADIUM-226 834 13982-63-3
98 RDX (Cyclonite) 833 121-82-4
99 URANIUM 833 7440-61-1
100 2,4-DINITROTOLUENE 832 121-14-2
101 ETHION 832 563-12-2
102 4,6-DINITRO-O-CRESOL 829 534-52-1
103 RADIUM 827 7440-14-4
104 THORIUM 823 7440-29-1
105 DIMETHYLARSINIC ACID 823 75-60-5
106 CHLORINE 822 7782-50-5
107 1,3,5-TRINITROBENZENE 820 99-35-4
108 HEXACHLOROCYCLOPENTADIENE 820 77-47-4
109 RADON 818 10043-92-2
110 HEXACHLOROCYCLOHEXANE, ALPHA- 816 319-84-6
111 RADIUM-228 815 15262-20-1
112 THORIUM-230 814 14269-63-7
113 URANIUM-235 812 15117-96-1
114 THORIUM-228 810 14274-82-9
115 RADON-222 810 14859-67-7
116 URANIUM-234 809 13966-29-5
117 N-NITROSODI-N-PROPYLAMINE 809 621-64-7
118 METHYLMERCURY 808 22967-92-6
119 COAL TARS 808 8007-45-2
120 COPPER 807 7440-50-8
121 CHRYSOTILE ASBESTOS 806 12001-29-5
122 PLUTONIUM-239 806 15117-48-3
123 POLONIUM-210 805 13981-52-7
124 PLUTONIUM-238 805 13981-16-3
125 LEAD-210 805 14255-04-0
126 1,1,1-TRICHLOROETHANE 804 71-55-6
127 AMOSITE ASBESTOS 804 12172-73-5
127 PLUTONIUM 804 7440-07-5
127 STRONTIUM-90 804 10098-97-2
130 RADON-220 804 22481-48-7
131 BARIUM 804 7440-39-3
132 AMERICIUM-241 804 86954-36-1
133 HYDROGEN CYANIDE 803 74-90-8
134 AZINPHOS-METHYL 802 86-50-0
134 CHLORDANE, TECHNICAL 802 12789-03-6
136 CHLORDECONE 802 143-50-0
137 MERCURIC CHLORIDE 802 7487-94-7
137 NEPTUNIUM-237 802 13994-20-2
139 ACTINIUM-227 801 14952-40-0
139 PLUTONIUM-240 801 14119-33-6
141 CHLOROBENZENE 801 108-90-7
142 S,S,S-TRIBUTYL PHOSPHOROTRITHIOATE 799 78-48-8
143 MANGANESE 799 7439-96-5
144 ETHYLBENZENE 798 100-41-4
145 FLUORANTHENE 797 206-44-0
146 CHRYSENE 794 218-01-9
147 PERFLUOROOCTANE SULFONIC ACID 790 1763-23-1
148 1,2,3-TRICHLOROBENZENE 786 87-61-6
149 POLYBROMINATED BIPHENYLS 786 67774-32-7
150 DICOFOL 785 115-32-2
151 SELENIUM 779 7782-49-2
152 1,3-BUTADIENE 778 106-99-0
153 1,1,2,2-TETRACHLOROETHANE 776 79-34-5
154 PARATHION 775 56-38-2
155 HEPTACHLORODIBENZO-P-DIOXIN 775 37871-00-4
156 HEXACHLOROCYCLOHEXANE, TECHNICAL GRADE 774 608-73-1
157 TRICHLOROFLUOROETHANE 774 27154-33-2
158 BROMINE 772 7726-95-6
159 AROCLOR 1268 766 11100-14-4
160 PERFLUOROOCTANOIC ACID 761 335-67-1
161 HEPTACHLORODIBENZOFURAN 756 38998-75-3
162 TRIFLURALIN 756 1582-09-8
163 PERFLUOROHEXANESULFONIC ACID 750 355-46-4
164 1,2,3,4,6,7,8,9-OCTACHLORODIBENZOFURAN 744 39001-02-0
165 AMMONIA 742 7664-41-7
166 1,4-DICHLOROBENZENE 727 106-46-7
167 2-METHYLNAPHTHALENE 727 91-57-6
168 2,3,4,7,8-PENTACHLORODIBENZOFURAN 724 57117-31-4
169 NALED 722 300-76-5
170 1,1,2-TRICHLOROETHANE 719 79-00-5
171 1,2-DIPHENYLHYDRAZINE 719 122-66-7
172 1,1-DICHLOROETHANE 718 75-34-3
173 PHORATE 717 298-02-2
174 PERFLUORODECANOIC ACID 712 335-76-2
175 TRICHLOROETHANE 711 25323-89-1
176 ACENAPHTHENE 711 83-32-9
177 TETRACHLOROBIPHENYL 711 26914-33-0
178 PALLADIUM 707 7440-05-3
179 INDENO(1,2,3-CD)PYRENE 705 193-39-5
180 OXYCHLORDANE 705 27304-13-8
181 CRESOL, PARA- 703 106-44-5
182 GAMMA-CHLORDENE 702 56641-38-4
183 TETRACHLOROPHENOL 699 25167-83-3
184 1,2-DICHLOROBENZENE 696 95-50-1
185 1,2-DICHLOROETHENE, TRANS- 691 156-60-5
186 P-XYLENE 687 106-42-3
187 CHLOROETHANE 686 75-00-3
188 ALUMINUM 685 7429-90-5
189 CARBON MONOXIDE 684 630-08-0
190 PHENOL 682 108-95-2
191 CARBON DISULFIDE 681 75-15-0
192 2,4-DIMETHYLPHENOL 679 105-67-9
193 DIBENZOFURAN 676 132-64-9
194 PERFLUORONONANOIC ACID 671 375-95-1
195 PERFLUORODODECANOIC ACID 671 307-55-1
196 ACETONE 671 67-64-1
197 HEXACHLOROETHANE 671 67-72-1
198 BUTYL METHYL PHTHALATE 669 34006-76-3
199 PERFLUOROUNDECANOIC ACID 668 2058-94-8
200 CHLOROMETHANE 664 74-87-3
201 HEXACHLORODIBENZOFURAN 661 55684-94-1
202 HYDROGEN SULFIDE 658 7783-06-4
203 DICHLORVOS 657 62-73-7
204 MONOCHLORODIBENZOFURAN 654 42934-53-2
205 CRESOL, ORTHO- 652 95-48-7
206 HEXACHLORODIBENZO-P-DIOXIN 652 34465-46-8
207 BUTYL BENZYL PHTHALATE 650 85-68-7
208 VANADIUM 650 7440-62-2
209 1,2,4-TRICHLOROBENZENE 647 120-82-1
210 ETHOPROP 645 13194-48-4
211 TETRACHLORODIBENZO-P-DIOXIN 642 41903-57-5
212 BROMOFORM 635 75-25-2
213 PENTACHLORODIBENZOFURAN 632 30402-15-4
214 1,3-DICHLOROBENZENE 628 541-73-1
215 PENTACHLORODIBENZO-P-DIOXIN 626 36088-22-9
216 N-NITROSODIPHENYLAMINE 624 86-30-6
217 2,4-DICHLOROPHENOL 620 120-83-2
218 2,3-DIMETHYLNAPHTHALENE 620 581-40-8
219 2,3,7,8-TETRACHLORODIBENZOFURAN 618 51207-31-9
220 1,4-DIOXANE 617 123-91-1
221 FLUORINE 613 7782-41-4
222 NITRITE 611 14797-65-0
223 DIBROMOCHLOROMETHANE 611 124-48-1
224 CESIUM-137 610 10045-97-3
225 CHROMIC ACID 610 7738-94-5
226 POTASSIUM-40 608 13966-00-2
227 SILVER 608 7440-22-4
228 DINITROTOLUENE 607 25321-14-6
229 FORMALDEHYDE 607 50-00-0
230 COAL TAR PITCH 605 65996-93-2
231 1,2-DICHLOROETHYLENE 605 540-59-0
232 2-BUTANONE 605 78-93-3
233 THORIUM-227 605 15623-47-9
234 ARSENIC ACID 604 7778-39-4
235 NITRATE 604 14797-55-8
236 ANTIMONY 604 7440-36-0
237 ARSENIC TRIOXIDE 604 1327-53-3
238 BENZOPYRENE 603 73467-76-2
239 STROBANE 602 8001-50-1
240 4-AMINOBIPHENYL 602 92-67-1
240 PYRETHRUM 602 8003-34-7
242 ARSINE 602 7784-42-1
242 DIMETHOATE 602 60-51-5
244 BIS(CHLOROMETHYL)ETHER 602 542-88-1
244 CARBOPHENOTHION 602 786-19-6
246 ALPHA-CHLORDENE 601 56534-02-2
246 IODINE-131 601 10043-66-0
246 SODIUM ARSENITE 601 7784-46-5
246 URANIUM-233 601 13968-55-3
250 CRESOLS 598 1319-77-3
251 2,4-D 596 94-75-7
252 DICHLOROBENZENE 596 25321-22-6
253 BUTYLATE 592 2008-41-5
254 2-CHLOROPHENOL 591 95-57-8
255 DIMETHYL FORMAMIDE 585 68-12-2
256 PHENANTHRENE 583 85-01-8
257 DIURON 580 330-54-1
258 4-NITROPHENOL 580 100-02-7
259 TETRACHLOROETHANE 578 25322-20-7
260 DICHLOROETHANE 568 1300-21-6
261 ETHYL ETHER 566 60-29-7
262 DIMETHYLANILINE 563 121-69-7
263 1,3-DICHLOROPROPENE, CIS- 562 10061-01-5
264 ACRYLONITRILE 560 107-13-1
265 1,2,3,4,6,7,8-HEPTACHLORODIBENZO-P-DIOXIN 560 35822-46-9
266 PYRENE 557 129-00-0
267 PHOSPHINE 557 7803-51-2
268 TRICHLOROBENZENE 556 12002-48-1
269 2,6-DINITROTOLUENE 555 606-20-2
270 FLUORIDE ION 550 16984-48-8
271 1,2,3,4,6,7,8-HEPTACHLORODIBENZOFURAN 550 67562-39-4
272 PENTAERYTHRITOL TETRANITRATE 550 78-11-5
273 1,3-DICHLOROPROPENE, TRANS- 549 10061-02-6
274 BIS(2-ETHYLHEXYL)ADIPATE 544 103-23-1
275 CARBAZOLE 544 86-74-8

CAS RN = Chemical Abstracts Service Registry Number

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Further information can be obtained by contacting the ATSDR Information Center at:

Agency for Toxic Substances and Disease Registry
Division of Toxicology and Human Health Sciences
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Phone: 1-800-CDC-INFO 888-232-6348 (TTY)
Email: Contact CDC-INFO