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)?

2019 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 revised and published on a 2-year basis, with a yearly informal review and revision. (No list was published in 2009 while ATSDR transitioned to a new agency science database.) 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 2019 Substance Priority List

The ATSDR 2019 Substance Priority List
2019 Rank Substance Name Total Points CAS RN
1 ARSENIC 1676 7440-38-2
2 LEAD 1531 7439-92-1
3 MERCURY 1458 7439-97-6
4 VINYL CHLORIDE 1356 75-01-4
5 POLYCHLORINATED BIPHENYLS 1345 1336-36-3
6 BENZENE 1327 71-43-2
7 CADMIUM 1318 7440-43-9
8 BENZO(A)PYRENE 1307 50-32-8
9 POLYCYCLIC AROMATIC HYDROCARBONS 1278 130498-29-2
10 BENZO(B)FLUORANTHENE 1253 205-99-2
11 CHLOROFORM 1201 67-66-3
12 AROCLOR 1260 1191 11096-82-5
13 DDT, P,P’- 1181 50-29-3
14 AROCLOR 1254 1172 11097-69-1
15 DIBENZO(A,H)ANTHRACENE 1160 53-70-3
16 TRICHLOROETHYLENE 1155 79-01-6
17 CHROMIUM, HEXAVALENT 1149 18540-29-9
18 DIELDRIN 1143 60-57-1
19 PHOSPHORUS, WHITE 1141 7723-14-0
20 HEXACHLOROBUTADIENE 1127 87-68-3
21 DDE, P,P’- 1126 72-55-9
22 CHLORDANE 1125 57-74-9
23 AROCLOR 1242 1125 53469-21-9
24 COAL TAR CREOSOTE 1124 8001-58-9
25 ALDRIN 1115 309-00-2
26 DDD, P,P’- 1113 72-54-8
27 AROCLOR 1248 1106 12672-29-6
28 HEPTACHLOR 1101 76-44-8
29 AROCLOR 1101 12767-79-2
30 BENZIDINE 1092 92-87-5
31 ACROLEIN 1090 107-02-8
32 TOXAPHENE 1089 8001-35-2
33 TETRACHLOROETHYLENE 1077 127-18-4
34 HEXACHLOROCYCLOHEXANE, GAMMA- 1076 58-89-9
35 CYANIDE 1069 57-12-5
36 HEXACHLOROCYCLOHEXANE, BETA- 1054 319-85-7
37 DISULFOTON 1048 298-04-4
38 BENZO(A)ANTHRACENE 1048 56-55-3
39 1,2-DIBROMOETHANE 1043 106-93-4
40 ENDRIN 1038 72-20-8
41 DIAZINON 1038 333-41-5
42 HEXACHLOROCYCLOHEXANE, DELTA- 1035 319-86-8
43 BERYLLIUM 1030 7440-41-7
44 ENDOSULFAN 1029 115-29-7
45 AROCLOR 1221 1028 11104-28-2
46 1,2-DIBROMO-3-CHLOROPROPANE 1027 96-12-8
47 HEPTACHLOR EPOXIDE 1021 1024-57-3
48 ENDOSULFAN, ALPHA 1019 959-98-8
49 CIS-CHLORDANE 1017 5103-71-9
50 CARBON TETRACHLORIDE 1013 56-23-5
51 AROCLOR 1016 1012 12674-11-2
52 COBALT 1011 7440-48-4
53 DDT, O,P’- 1009 789-02-6
54 METHOXYCHLOR 1007 72-43-5
55 PENTACHLOROPHENOL 1007 87-86-5
56 ENDOSULFAN SULFATE 1004 1031-07-8
57 DI-N-BUTYL PHTHALATE 993 84-74-2
58 NICKEL 993 7440-02-0
59 ENDRIN KETONE 993 53494-70-5
60 DIBROMOCHLOROPROPANE 984 67708-83-2
61 BENZO(K)FLUORANTHENE 974 207-08-9
62 TRANS-CHLORDANE 969 5103-74-2
63 ENDOSULFAN, BETA 968 33213-65-9
64 CHLORPYRIFOS 965 2921-88-2
65 XYLENES, TOTAL 962 1330-20-7
66 CHROMIUM(VI) TRIOXIDE 961 1333-82-0
67 AROCLOR 1232 959 11141-16-5
68 ENDRIN ALDEHYDE 959 7421-93-4
69 METHANE 952 74-82-8
70 3,3′-DICHLOROBENZIDINE 941 91-94-1
71 2-HEXANONE 940 591-78-6
72 2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN 940 1746-01-6
73 BENZOFLUORANTHENE 937 56832-73-6
74 TOLUENE 914 108-88-3
75 ZINC 913 7440-66-6
76 PENTACHLOROBENZENE 907 608-93-5
77 DI(2-ETHYLHEXYL)PHTHALATE 905 117-81-7
78 CHROMIUM 893 7440-47-3
79 AROCLOR 1240 889 71328-89-7
80 2,4,6-TRINITROTOLUENE 878 118-96-7
81 NAPHTHALENE 878 91-20-3
82 1,1-DICHLOROETHENE 873 75-35-4
83 BROMODICHLOROETHANE 868 683-53-4
84 DDD, O,P’- 867 53-19-0
85 2,4,6-TRICHLOROPHENOL 867 88-06-2
86 BIS(2-CHLOROETHYL)ETHER 867 111-44-4
87 HYDRAZINE 862 302-01-2
88 2,4-DINITROPHENOL 859 51-28-5
89 4,4′-METHYLENEBIS(2-CHLOROANILINE) 859 101-14-4
90 METHYLENE CHLORIDE 857 75-09-2
91 1,2-DICHLOROETHANE 852 107-06-2
92 THIOCYANATE 847 302-04-5
93 HEXACHLOROBENZENE 844 118-74-1
94 ASBESTOS 840 1332-21-4
95 RADIUM-226 833 13982-63-3
96 RDX (Cyclonite) 833 121-82-4
97 URANIUM 833 7440-61-1
98 2,4-DINITROTOLUENE 831 121-14-2
99 ETHION 831 563-12-2
100 4,6-DINITRO-O-CRESOL 828 534-52-1
101 RADIUM 827 7440-14-4
102 THORIUM 824 7440-29-1
103 DIMETHYLARSINIC ACID 822 75-60-5
104 CHLORINE 821 7782-50-5
105 1,3,5-TRINITROBENZENE 820 99-35-4
106 RADON 818 10043-92-2
107 HEXACHLOROCYCLOHEXANE, ALPHA- 816 319-84-6
108 RADIUM-228 815 15262-20-1
109 THORIUM-230 813 14269-63-7
110 URANIUM-235 812 15117-96-1
111 THORIUM-228 810 14274-82-9
112 RADON-222 810 14859-67-7
113 URANIUM-234 809 13966-29-5
114 COAL TARS 808 8007-45-2
115 N-NITROSODI-N-PROPYLAMINE 808 621-64-7
116 METHYLMERCURY 808 22967-92-6
117 CHRYSOTILE ASBESTOS 806 12001-29-5
118 PLUTONIUM-239 806 15117-48-3
119 POLONIUM-210 805 13981-52-7
120 COPPER 805 7440-50-8
121 PLUTONIUM-238 805 13981-16-3
122 LEAD-210 805 14255-04-0
123 AMOSITE ASBESTOS 804 12172-73-5
123 PLUTONIUM 804 7440-07-5
123 STRONTIUM-90 804 10098-97-2
126 RADON-220 804 22481-48-7
127 1,1,1-TRICHLOROETHANE 804 71-55-6
128 AMERICIUM-241 804 86954-36-1
129 HYDROGEN CYANIDE 803 74-90-8
130 AZINPHOS-METHYL 802 86-50-0
131 CHLOROBENZENE 802 108-90-7
132 CHLORDECONE 802 143-50-0
133 NEPTUNIUM-237 802 13994-20-2
134 PLUTONIUM-240 801 14119-33-6
135 1,2,3-Trichlorobenzene 801 87-61-6
136 BARIUM 800 7440-39-3
137 ETHYLBENZENE 800 100-41-4
138 S,S,S-TRIBUTYL PHOSPHOROTRITHIOATE 799 78-48-8
139 FLUORANTHENE 799 206-44-0
140 MANGANESE 797 7439-96-5
141 CHRYSENE 793 218-01-9
142 2,4,5-TRICHLOROPHENOL 791 95-95-4
143 Perfluorooctane sulfonic acid 788 1763-23-1
144 POLYBROMINATED BIPHENYLS 785 67774-32-7
145 DICOFOL 785 115-32-2
146 1,1,2,2-TETRACHLOROETHANE 776 79-34-5
147 SELENIUM 775 7782-49-2
148 PARATHION 774 56-38-2
149 HEPTACHLORODIBENZO-P-DIOXIN 774 37871-00-4
150 HEXACHLOROCYCLOHEXANE, TECHNICAL GRADE 774 608-73-1
151 TRICHLOROFLUOROETHANE 773 27154-33-2
152 BROMINE 771 7726-95-6
153 AROCLOR 1268 765 11100-14-4
154 1,3-BUTADIENE 763 106-99-0
155 Perfluorooctanoic acid 758 335-67-1
156 HEPTACHLORODIBENZOFURAN 756 38998-75-3
157 TRIFLURALIN 755 1582-09-8
158 Perfluorohexanesulfonic acid 749 355-46-4
159 1,2,3,4,6,7,8,9-OCTACHLORODIBENZOFURAN 743 39001-02-0
160 AMMONIA 742 7664-41-7
161 2-METHYLNAPHTHALENE 725 91-57-6
162 2,3,4,7,8-PENTACHLORODIBENZOFURAN 724 57117-31-4
163 1,4-DICHLOROBENZENE 723 106-46-7
164 NALED 721 300-76-5
165 1,1,2-TRICHLOROETHANE 719 79-00-5
166 1,1-DICHLOROETHANE 719 75-34-3
167 HEXACHLOROCYCLOPENTADIENE 719 77-47-4
168 1,2-DIPHENYLHYDRAZINE 718 122-66-7
169 PHORATE 716 298-02-2
170 TRICHLOROETHANE 712 25323-89-1
171 TETRACHLOROBIPHENYL 710 26914-33-0
172 ACENAPHTHENE 710 83-32-9
173 PALLADIUM 706 7440-05-3
174 OXYCHLORDANE 705 27304-13-8
175 INDENO(1,2,3-CD)PYRENE 705 193-39-5
176 CRESOL, PARA- 703 106-44-5
177 GAMMA-CHLORDENE 702 56641-38-4
178 TETRACHLOROPHENOL 698 25167-83-3
179 1,2-DICHLOROBENZENE 696 95-50-1
180 1,2-DICHLOROETHENE, TRANS- 689 156-60-5
181 P-XYLENE 687 106-42-3
182 CHLOROETHANE 686 75-00-3
183 ALUMINUM 685 7429-90-5
184 PHENOL 684 108-95-2
185 CARBON MONOXIDE 684 630-08-0
186 CARBON DISULFIDE 681 75-15-0
187 2,4-DIMETHYLPHENOL 679 105-67-9
188 DIBENZOFURAN 675 132-64-9
189 HEXACHLOROETHANE 670 67-72-1
190 ACETONE 670 67-64-1
191 Butyl methyl phthalate 668 34006-76-3
192 CHLOROMETHANE 665 74-87-3
193 HEXACHLORODIBENZOFURAN 660 55684-94-1
194 HYDROGEN SULFIDE 657 7783-06-4
195 BUTYL BENZYL PHTHALATE 657 85-68-7
196 DICHLORVOS 656 62-73-7
197 DIBENZOFURANS, CHLORINATED 653 42934-53-2
198 CRESOL, ORTHO- 652 95-48-7
199 HEXACHLORODIBENZO-P-DIOXIN 651 34465-46-8
200 N-NITROSODIMETHYLAMINE 649 62-75-9
201 VANADIUM 648 7440-62-2
202 Perfluorononanoic acid 647 375-95-1
203 1,2,4-TRICHLOROBENZENE 646 120-82-1
204 ETHOPROP 644 13194-48-4
205 TETRACHLORODIBENZO-P-DIOXIN 641 41903-57-5
206 BROMOFORM 635 75-25-2
207 PENTACHLORODIBENZOFURAN 631 30402-15-4
208 1,3-DICHLOROBENZENE 628 541-73-1
209 PENTACHLORODIBENZO-P-DIOXIN 626 36088-22-9
210 N-NITROSODIPHENYLAMINE 625 86-30-6
211 2,3-DIMETHYLNAPHTHALENE 619 581-40-8
212 2,4-DICHLOROPHENOL 619 120-83-2
213 2,3,7,8-TETRACHLORODIBENZOFURAN 619 51207-31-9
214 1,4-DIOXANE 617 123-91-1
215 FLUORINE 613 7782-41-4
216 NITRITE 610 14797-65-0
217 CESIUM-137 610 10045-97-3
217 Chromic Acid 610 7738-94-5
219 POTASSIUM-40 607 13966-00-2
220 DINITROTOLUENE 607 25321-14-6
221 1,2-DICHLOROETHYLENE 606 540-59-0
222 2-BUTANONE 606 78-93-3
223 FORMALDEHYDE 606 50-00-0
224 COAL TAR PITCH 605 65996-93-2
225 THORIUM-227 605 15623-47-9
226 NITRATE 605 14797-55-8
227 ARSENIC ACID 604 7778-39-4
228 ARSENIC TRIOXIDE 604 1327-53-3
229 SILVER 604 7440-22-4
230 BENZOPYRENE 603 73467-76-2
231 CHLORDANE, TECHNICAL 602 12789-03-6
232 STROBANE 602 8001-50-1
233 4-AMINOBIPHENYL 602 92-67-1
233 PYRETHRUM 602 8003-34-7
235 ARSINE 602 7784-42-1
235 DIMETHOATE 602 60-51-5
237 BIS(CHLOROMETHYL)ETHER 602 542-88-1
237 CARBOPHENOTHION 602 786-19-6
239 ALPHA-CHLORDENE 601 56534-02-2
239 IODINE-131 601 10043-66-0
239 MERCURIC CHLORIDE 601 7487-94-7
239 SODIUM ARSENITE 601 7784-46-5
239 URANIUM-233 601 13968-55-3
244 ANTIMONY 601 7440-36-0
245 DIBROMOCHLOROMETHANE 600 124-48-1
246 CRESOLS 597 1319-77-3
247 DICHLOROBENZENE 595 25321-22-6
248 2,4-D 595 94-75-7
249 2-CHLOROPHENOL 591 95-57-8
250 BUTYLATE 591 2008-41-5
251 DIMETHYL FORMAMIDE 585 68-12-2
252 PHENANTHRENE 584 85-01-8
253 DIURON 580 330-54-1
254 4-NITROPHENOL 580 100-02-7
255 TETRACHLOROETHANE 577 25322-20-7
256 DICHLOROETHANE 568 1300-21-6
257 ETHYL ETHER 566 60-29-7
258 DIMETHYLANILINE 563 121-69-7
259 1,3-DICHLOROPROPENE, CIS- 561 10061-01-5
260 PYRENE 559 129-00-0
261 1,2,3,4,6,7,8-HEPTACHLORODIBENZO-P-DIOXIN 559 35822-46-9
262 PHOSPHINE 557 7803-51-2
263 TRICHLOROBENZENE 556 12002-48-1
264 2,6-DINITROTOLUENE 555 606-20-2
265 FLUORIDE ION 550 16984-48-8
266 PENTAERYTHRITOL TETRANITRATE 549 78-11-5
267 1,2,3,4,6,7,8-HEPTACHLORODIBENZOFURAN 549 67562-39-4
268 1,3-DICHLOROPROPENE, TRANS- 548 10061-02-6
269 ACRYLONITRILE 544 107-13-1
270 BIS(2-ETHYLHEXYL)ADIPATE 543 103-23-1
271 CARBAZOLE 540 86-74-8
272 2-CHLOROANILINE 539 95-51-2
273 METOLACHLOR 539 51218-45-2
274 1,2-DICHLOROETHENE, CIS- 538 156-59-2
275 1,2,3-TRICHLOROPROPANE 537 96-18-4

Substances were assigned the same rank when two (or more) substances received equivalent total point scores.

CAS RN = Chemical Abstracts Service Registry Number

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Page last reviewed: January 17, 2020
Content source: Agency for Toxic Substances and Disease Registry