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Substances Most Frequently Found in
Completed Exposure Pathways at Hazardous Waste Sites


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.

ATSDR 2015 Completed Exposure Pathway Site Count Report

Rank Substance Name All Sites/
Events
NPL Sites CAS RN
1 LEAD 536 287 007439-92-1
2 ARSENIC 486 257 007440-38-2
3 TRICHLOROETHYLENE 430 306 000079-01-6
4 TETRACHLOROETHYLENE 339 222 000127-18-4
5 BENZENE 274 143 000071-43-2
6 CADMIUM 263 161 007440-43-9
7 CHROMIUM 225 140 007440-47-3
8 MERCURY 222 102 007439-97-6
9 POLYCHLORINATED BIPHENYLS 208 128 001336-36-3
10 MANGANESE 198 110 007439-96-5
11 COPPER 188 107 007440-50-8
12 ZINC 166 97 007440-66-6
13 VOLATILE ORGANIC COMPOUNDS N.O.S. 154 93 HZ1900-01-T
14 BENZO(A)PYRENE 142 68 000050-32-8
15 CHLOROFORM 139 93 000067-66-3
16 ANTIMONY 136 79 007440-36-0
17 VINYL CHLORIDE 134 98 000075-01-4
18 NICKEL 129 76 007440-02-0
19 1,1,1-TRICHLOROETHANE 123 98 000071-55-6
20 1,1-DICHLOROETHENE 121 96 000075-35-4
21 METHYLENE CHLORIDE 119 67 000075-09-2
22 POLYCYCLIC AROMATIC HYDROCARBONS 115 74 130498-29-2
23 TOLUENE 112 65 000108-88-3
24 BARIUM 111 60 007440-39-3
25 1,2-DICHLOROETHANE 110 80 000107-06-2
26 IRON 107 62 007439-89-6
27 VANADIUM 107 59 007440-62-2
28 CARBON TETRACHLORIDE 102 64 000056-23-5
29 BENZO(A)ANTHRACENE 101 48 000056-55-3
30 DI(2-ETHYLHEXYL)PHTHALATE 93 61 000117-81-7
31 BENZO(B)FLUORANTHENE 93 37 000205-99-2
32 CHRYSENE 92 44 000218-01-9
33 1,1-DICHLOROETHANE 89 73 000075-34-3
34 BERYLLIUM 88 42 007440-41-7
35 PHENANTHRENE 87 36 000085-01-8
36 NAPHTHALENE 86 41 000091-20-3
37 METALS N.O.S. 83 52 HZ0900-01-T
38 DIELDRIN 83 44 000060-57-1
39 ALUMINUM 82 50 007429-90-5
40 INDENO(1,2,3-CD)PYRENE 82 35 000193-39-5
41 BENZO(K)FLUORANTHENE 81 35 000207-08-9
42 THALLIUM 77 40 007440-28-0
43 XYLENES, TOTAL 76 38 001330-20-7
44 ETHYLBENZENE 73 39 000100-41-4
45 DIBENZO(A,H)ANTHRACENE 71 28 000053-70-3
46 DDT, P,P'- 68 42 000050-29-3
47 COBALT 68 32 007440-48-4
48 PENTACHLOROPHENOL 67 44 000087-86-5
49 BENZO(GHI)PERYLENE 65 24 000191-24-2
50 SODIUM 60 31 007440-23-5
51 1,2-DICHLOROETHENE, CIS- 59 42 000156-59-2
52 SELENIUM 59 25 007782-49-2
53 DDE, P,P'- 57 35 000072-55-9
54 DDD, P,P'- 51 30 000072-54-8
55 HEPTACHLOR EPOXIDE 51 24 001024-57-3
56 1,2-DICHLOROETHENE, TRANS- 50 46 000156-60-5
57 FLUORANTHENE 49 18 000206-44-0
58 AROCLOR 1260 48 31 011096-82-5
59 CYANIDE 48 24 000057-12-5
60 2-METHYLNAPHTHALENE 48 22 000091-57-6
61 PYRENE 48 19 000129-00-0
62 1,2-DICHLOROETHYLENE 45 38 000540-59-0
63 CHLOROBENZENE 45 33 000108-90-7
64 CHLORDANE 45 30 000057-74-9
65 ASBESTOS 45 13 001332-21-4
66 DIBENZOFURAN 43 20 000132-64-9
67 BROMODICHLOROMETHANE 42 27 000075-27-4
68 SILVER 41 18 007440-22-4
69 ALDRIN 40 17 000309-00-2
70 MAGNESIUM 39 21 007439-95-4
71 1,2,4-TRIMETHYLBENZENE 37 6 000095-63-6
72 AROCLOR 1254 36 26 011097-69-1
73 FLUORENE 36 13 000086-73-7
74 BENZO(A)PYRENE EQUIVALENTS 35 19 HZ1500-50-T
74 PESTICIDES N.O.S. 35 19 HZ1200-01-T
76 ACETONE 35 18 000067-64-1
77 HEPTACHLOR 35 15 000076-44-8
78 CARBAZOLE 35 12 000086-74-8
79 TCDD EQUIVALENTS 34 18 HZ0400-03-T
80 2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN 33 24 001746-01-6
81 ACENAPHTHYLENE 33 12 000208-96-8
82 2-BUTANONE 32 21 000078-93-3
82 DIOXINS N.O.S. 32 21 HZ0400-05-T
82 NITRATE 32 21 014797-55-8
85 CHROMIUM, HEXAVALENT 32 16 018540-29-9
86 1,4-DICHLOROBENZENE 32 10 000106-46-7
87 ANTHRACENE 32 9 000120-12-7
88 HEXACHLOROCYCLOHEXANE, GAMMA- 31 17 000058-89-9
89 CALCIUM 30 21 007440-70-2
90 DIBROMOCHLOROMETHANE 30 18 000124-48-1
91 ACENAPHTHENE 29 9 000083-32-9
92 1,1,2-TRICHLOROETHANE 27 21 000079-00-5
93 1,1,2,2-TETRACHLOROETHANE 27 19 000079-34-5
94 HEXACHLOROCYCLOHEXANE, ALPHA- 27 15 000319-84-6
95 DI-N-BUTYL PHTHALATE 27 10 000084-74-2
96 BUTYL BENZYL PHTHALATE 27 7 000085-68-7
97 HYDROGEN SULFIDE 27 4 007783-06-4
98 1,2-DICHLOROPROPANE 26 18 000078-87-5
99 PHENOL 26 14 000108-95-2
100 BORON 26 13 007440-42-8

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.

 

Summary Statistics for 2015 CEP and SPL Generation
(Run date 9/16/2015)
All Sites/Events NPL Sites
Number of Sites/Events 6318 1832
Number of Sites/Events with Public Health Assessments (PHAs) 1870 1630
Number of Sites/Events with CEPs 1820 848
Number of CEP records (incidents) 18315 10584
Number of CEP records (incidents) from PHAs 11277 9374
Total number of substances in CEPs 708 505

 

Contact Information

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 30333
Phone: 1-800-CDC-INFO 888-232-6348 (TTY)
Email: Contact CDC-INFO

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