Completed Exposure Pathway (CEP) Site Count Report
What is the CEP Site Count Report?
Exposure to hazardous substances is of significant concern to ATSDR. Therefore, ATSDR’s Division of Toxicology and Human Health Sciences publishes the following Completed Exposure Pathway Site Count Report along with the Priority List of Hazardous Substances (also called the Substance Priority List). A completed exposure pathway (CEP) links a contaminant source to a receptor population, and people are likely to have been exposed to the substance. The CEP ranking presented here is based on a site frequency count, and thus lists the number of sites at which a substance has been found in a CEP. This information is derived from ATSDR public health assessments and health consultations. The CEP report therefore focuses on documented exposure, and lists hazardous substances according to exposure frequency.
How does the CEP report differ from the Substance Priority List?
This CEP ranking is similar to a subcomponent in the substance priority list algorithm called “Exposure to Contaminant”. This subcomponent is part of the potential-for-human-exposure component of the listing algorithm, and is a count of the number of completed exposure pathways that substances appeared in, not the number of sites where it was in a CEP. (A substance can appear in more than one pathway at a given site.) A pathway count, rather than a site count, is more appropriate for the substance priority list because it adds more discrimination to the less-frequent substances on the list. Another difference between the two exposure counts is that since the substance priority list is mandated by CERCLA, it only uses data from CERCLA sites on the National Priorities List (NPL), whereas this CEP report uses data from all ATSDR-activity sites at which a CEP has been detected.
The substances in the CEP report are similar to the substances on the substance priority list. However, some substances in the CEP report have a very low toxicity (e.g., sodium) and as a result are not included in the substance priority list. Since the substance priority list uses toxicity, frequency of occurrence, and potential for human exposure to determine its priority substances, other low-toxicity substances will not appear on the list and, consequently, will not become subjects of toxicological profiles. Also, the CEP report includes substance groups, process wastes, and other environmental hazards at hazardous waste sites that do not have a Chemical Abstracts Service Registry Number (CAS number). Substances without CAS numbers have been excluded from the substance priority list in order to focus the development of toxicological profiles on well identified substances. Substances without CAS numbers appear on this report with a “pseudo-CAS” assigned by ATSDR that begins with HZ.
What is the utility of the CEP report?
The CEP Report presents a straightforward measure of the extent to which the public is being exposed to particular substances. Public health officials can use the CEP Report for a quick overview of the substances most frequently involved in exposures at ATSDR sites and events.
For past CEP Reports and a spreadsheet with substances past the top 100, including pathway counts, see the CEP Report Archive.
ATSDR 2017 Completed Exposure Pathway Site Count Report
2017 Rank | Substance Name | All Sites/Events | NPL Sites | CAS RN |
1 | LEAD | 544 | 292 | 7439-92-1 |
2 | ARSENIC | 495 | 262 | 7440-38-2 |
3 | TRICHLOROETHYLENE | 442 | 312 | 79-01-6 |
4 | TETRACHLOROETHYLENE | 345 | 226 | 127-18-4 |
5 | BENZENE | 278 | 143 | 71-43-2 |
6 | CADMIUM | 267 | 164 | 7440-43-9 |
7 | CHROMIUM | 226 | 140 | 7440-47-3 |
8 | MERCURY | 223 | 103 | 7439-97-6 |
9 | POLYCHLORINATED BIPHENYLS | 208 | 128 | 1336-36-3 |
10 | MANGANESE | 201 | 110 | 7439-96-5 |
11 | COPPER | 191 | 107 | 7440-50-8 |
12 | ZINC | 167 | 97 | 7440-66-6 |
13 | VOLATILE ORGANIC COMPOUNDS N.O.S. | 155 | 93 | HZ1900-01-T |
14 | BENZO(A)PYRENE | 143 | 69 | 50-32-8 |
15 | CHLOROFORM | 142 | 94 | 67-66-3 |
16 | VINYL CHLORIDE | 137 | 99 | 75-01-4 |
17 | ANTIMONY | 136 | 79 | 7440-36-0 |
18 | NICKEL | 131 | 77 | 7440-02-0 |
19 | 1,1,1-TRICHLOROETHANE | 123 | 98 | 71-55-6 |
20 | 1,1-DICHLOROETHENE | 121 | 96 | 75-35-4 |
21 | METHYLENE CHLORIDE | 119 | 67 | 75-09-2 |
22 | POLYCYCLIC AROMATIC HYDROCARBONS | 115 | 74 | 130498-29-2 |
23 | 1,2-DICHLOROETHANE | 112 | 80 | 107-06-2 |
24 | TOLUENE | 112 | 65 | 108-88-3 |
25 | BARIUM | 112 | 60 | 7440-39-3 |
26 | IRON | 108 | 62 | 7439-89-6 |
27 | VANADIUM | 107 | 59 | 7440-62-2 |
28 | CARBON TETRACHLORIDE | 105 | 65 | 56-23-5 |
29 | BENZO(A)ANTHRACENE | 101 | 48 | 56-55-3 |
30 | DI(2-ETHYLHEXYL)PHTHALATE | 96 | 63 | 117-81-7 |
31 | BENZO(B)FLUORANTHENE | 93 | 37 | 205-99-2 |
32 | CHRYSENE | 92 | 44 | 218-01-9 |
33 | 1,1-DICHLOROETHANE | 89 | 73 | 75-34-3 |
34 | BERYLLIUM | 88 | 42 | 7440-41-7 |
35 | PHENANTHRENE | 87 | 36 | 85-01-8 |
36 | NAPHTHALENE | 86 | 41 | 91-20-3 |
37 | METALS N.O.S. | 83 | 53 | HZ0900-01-T |
38 | ALUMINUM | 83 | 50 | 7429-90-5 |
39 | DIELDRIN | 83 | 44 | 60-57-1 |
40 | INDENO(1,2,3-CD)PYRENE | 82 | 35 | 193-39-5 |
41 | BENZO(K)FLUORANTHENE | 81 | 35 | 207-08-9 |
42 | THALLIUM | 77 | 40 | 7440-28-0 |
43 | XYLENES, TOTAL | 77 | 38 | 1330-20-7 |
44 | ETHYLBENZENE | 74 | 39 | 100-41-4 |
45 | DIBENZO(A,H)ANTHRACENE | 71 | 28 | 53-70-3 |
46 | DDT, P,P’- | 68 | 42 | 50-29-3 |
47 | COBALT | 68 | 32 | 7440-48-4 |
48 | PENTACHLOROPHENOL | 67 | 44 | 87-86-5 |
49 | BENZO(GHI)PERYLENE | 65 | 24 | 191-24-2 |
50 | SODIUM | 64 | 32 | 7440-23-5 |
51 | 1,2-DICHLOROETHENE, CIS- | 60 | 43 | 156-59-2 |
52 | SELENIUM | 59 | 25 | 7782-49-2 |
53 | DDE, P,P’- | 57 | 35 | 72-55-9 |
54 | 1,2-DICHLOROETHENE, TRANS- | 51 | 46 | 156-60-5 |
55 | DDD, P,P’- | 51 | 30 | 72-54-8 |
56 | HEPTACHLOR EPOXIDE | 51 | 24 | 1024-57-3 |
57 | FLUORANTHENE | 49 | 18 | 206-44-0 |
58 | AROCLOR 1260 | 48 | 31 | 11096-82-5 |
59 | CYANIDE | 48 | 24 | 57-12-5 |
60 | 2-METHYLNAPHTHALENE | 48 | 22 | 91-57-6 |
61 | PYRENE | 48 | 19 | 129-00-0 |
62 | 1,2-DICHLOROETHYLENE | 45 | 38 | 540-59-0 |
63 | CHLOROBENZENE | 45 | 33 | 108-90-7 |
64 | CHLORDANE | 45 | 30 | 57-74-9 |
65 | ASBESTOS | 45 | 13 | 1332-21-4 |
66 | DIBENZOFURAN | 44 | 20 | 132-64-9 |
67 | BROMODICHLOROMETHANE | 43 | 28 | 75-27-4 |
68 | SILVER | 41 | 18 | 7440-22-4 |
69 | MAGNESIUM | 40 | 21 | 7439-95-4 |
70 | ALDRIN | 40 | 17 | 309-00-2 |
71 | 1,2,4-TRIMETHYLBENZENE | 38 | 6 | 95-63-6 |
72 | AROCLOR 1254 | 36 | 26 | 11097-69-1 |
73 | BENZO(A)PYRENE EQUIVALENTS | 36 | 19 | HZ1500-50-T |
74 | FLUORENE | 36 | 13 | 86-73-7 |
75 | PESTICIDES N.O.S. | 35 | 19 | HZ1200-01-T |
75 | TCDD EQUIVALENTS | 35 | 19 | HZ0400-03-T |
77 | ACETONE | 35 | 18 | 67-64-1 |
78 | HEPTACHLOR | 35 | 15 | 76-44-8 |
79 | CARBAZOLE | 35 | 12 | 86-74-8 |
80 | 2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN | 33 | 24 | 1746-01-6 |
81 | ACENAPHTHYLENE | 33 | 12 | 208-96-8 |
82 | 2-BUTANONE | 32 | 21 | 78-93-3 |
82 | DIOXINS N.O.S. | 32 | 21 | HZ0400-05-T |
82 | NITRATE | 32 | 21 | 14797-55-8 |
85 | CHROMIUM, HEXAVALENT | 32 | 16 | 18540-29-9 |
86 | 1,4-DICHLOROBENZENE | 32 | 10 | 106-46-7 |
87 | ANTHRACENE | 32 | 9 | 120-12-7 |
88 | CALCIUM | 31 | 21 | 7440-70-2 |
89 | DIBROMOCHLOROMETHANE | 31 | 19 | 124-48-1 |
90 | HEXACHLOROCYCLOHEXANE, GAMMA- | 31 | 17 | 58-89-9 |
91 | ACENAPHTHENE | 29 | 9 | 83-32-9 |
92 | HYDROGEN SULFIDE | 29 | 4 | 7783-06-4 |
93 | 1,1,2-TRICHLOROETHANE | 27 | 21 | 79-00-5 |
94 | 1,1,2,2-TETRACHLOROETHANE | 27 | 19 | 79-34-5 |
95 | HEXACHLOROCYCLOHEXANE, ALPHA- | 27 | 15 | 319-84-6 |
96 | BORON | 27 | 14 | 7440-42-8 |
97 | DI-N-BUTYL PHTHALATE | 27 | 10 | 84-74-2 |
98 | BUTYL BENZYL PHTHALATE | 27 | 7 | 85-68-7 |
99 | 1,2-DICHLOROPROPANE | 26 | 18 | 78-87-5 |
100 | PHENOL | 26 | 14 | 108-95-2 |
All Sites/Events = all sites and events with ATSDR activity; NPL Sites = current and former sites on the National Priorities List (EPA NPL status of Final, Proposed, Removed, and Deleted); CAS RN = Chemical Abstracts Service Registry Number; CEP = Completed Exposure Pathway.
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
1600 Clifton Road NE, Mailstop F-57
Atlanta, GA 30329
Phone: 1-800-CDC-INFO 888-232-6348 (TTY)
Email: Contact CDC-INFO
- Page last reviewed: August 10, 2017
- Page last updated: September 25, 2017
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