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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 2011 Completed Exposure Pathway Site Count Report

Rank Substance Name All Sites/
Events
NPL Sites CAS RN
1 LEAD 510 271 007439-92-1
2 ARSENIC 453 234 007440-38-2
3 TRICHLOROETHYLENE 405 291 000079-01-6
4 TETRACHLOROETHYLENE 320 213 000127-18-4
5 BENZENE 261 138 000071-43-2
6 CADMIUM 247 149 007440-43-9
7 MERCURY 225 99 007439-97-6
8 CHROMIUM 213 130 007440-47-3
9 POLYCHLORINATED BIPHENYLS 193 120 001336-36-3
10 MANGANESE 187 102 007439-96-5
11 COPPER 175 96 007440-50-8
12 ZINC 165 94 007440-66-6
13 VOLATILE ORGANIC COMPOUNDS N.O.S. 157 93 HZ1900-01-T
14 CHLOROFORM 133 91 000067-66-3
15 BENZO(A)PYRENE 132 63 000050-32-8
16 ANTIMONY 128 76 007440-36-0
17 VINYL CHLORIDE 127 93 000075-01-4
18 NICKEL 124 71 007440-02-0
19 1,1,1-TRICHLOROETHANE 123 97 000071-55-6
20 1,1-DICHLOROETHENE 120 96 000075-35-4
21 METHYLENE CHLORIDE 118 67 000075-09-2
22 POLYCYCLIC AROMATIC HYDROCARBONS 116 74 130498-29-2
23 TOLUENE 112 65 000108-88-3
24 BARIUM 109 56 007440-39-3
25 1,2-DICHLOROETHANE 104 78 000107-06-2
26 VANADIUM 104 54 007440-62-2
27 IRON 103 60 007439-89-6
28 CARBON TETRACHLORIDE 100 64 000056-23-5
29 BENZO(A)ANTHRACENE 97 45 000056-55-3
30 DI(2-ETHYLHEXYL)PHTHALATE 91 59 000117-81-7
31 CHRYSENE 90 42 000218-01-9
32 BENZO(B)FLUORANTHENE 90 34 000205-99-2
33 1,1-DICHLOROETHANE 88 71 000075-34-3
34 PHENANTHRENE 88 36 000085-01-8
35 NAPHTHALENE 85 41 000091-20-3
36 BERYLLIUM 85 39 007440-41-7
37 METALS N.O.S. 83 52 HZ0900-01-T
38 INDENO(1,2,3-CD)PYRENE 79 32 000193-39-5
39 BENZO(K)FLUORANTHENE 78 32 000207-08-9
40 ALUMINUM 77 44 007429-90-5
41 DIELDRIN 77 41 000060-57-1
42 XYLENES, TOTAL 76 38 001330-20-7
43 THALLIUM 73 39 007440-28-0
44 ETHYLBENZENE 71 39 000100-41-4
45 DIBENZO(A,H)ANTHRACENE 67 26 000053-70-3
46 PENTACHLOROPHENOL 66 43 000087-86-5
47 COBALT 65 27 007440-48-4
48 DDT, P,P'- 64 39 000050-29-3
49 BENZO(GHI)PERYLENE 64 24 000191-24-2
50 SELENIUM 60 23 007782-49-2
51 SODIUM 59 30 007440-23-5
52 DDE, P,P'- 58 34 000072-55-9
53 1,2-DICHLOROETHENE, CIS- 53 38 000156-59-2
54 1,2-DICHLOROETHENE, TRANS- 50 46 000156-60-5
55 DDD, P,P'- 50 28 000072-54-8
56 HEPTACHLOR EPOXIDE 49 23 001024-57-3
57 2-METHYLNAPHTHALENE 49 22 000091-57-6
58 FLUORANTHENE 49 18 000206-44-0
59 PYRENE 48 19 000129-00-0
60 1,2-DICHLOROETHYLENE 46 38 000540-59-0
61 CHLOROBENZENE 45 33 000108-90-7
62 AROCLOR 1260 45 27 011096-82-5
63 CYANIDE 45 23 000057-12-5
64 DIBENZOFURAN 43 20 000132-64-9
65 ASBESTOS 43 13 001332-21-4
66 CHLORDANE 42 29 000057-74-9
67 BROMODICHLOROMETHANE 41 27 000075-27-4
68 SILVER 41 18 007440-22-4
69 MAGNESIUM 39 21 007439-95-4
70 ALDRIN 38 16 000309-00-2
71 PESTICIDES N.O.S. 36 19 HZ1200-01-T
72 FLUORENE 36 13 000086-73-7
73 AROCLOR 1254 35 23 011097-69-1
74 ACETONE 35 18 000067-64-1
75 1,2,4-TRIMETHYLBENZENE 34 6 000095-63-6
76 HEPTACHLOR 33 14 000076-44-8
77 ACENAPHTHYLENE 33 12 000208-96-8
78 CARBAZOLE 33 10 000086-74-8
79 2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN 32 23 001746-01-6
80 2-BUTANONE 32 21 000078-93-3
80 DIOXINS N.O.S. 32 21 HZ0400-05-T
82 ANTHRACENE 32 9 000120-12-7
82 1,4-DICHLOROBENZENE 32 9 000106-46-7
84 NITRATE 31 20 014797-55-8
85 CALCIUM 30 21 007440-70-2
86 DIBROMOCHLOROMETHANE 29 18 000124-48-1
87 CHROMIUM, HEXAVALENT 29 14 018540-29-9
88 ACENAPHTHENE 29 9 000083-32-9
89 BUTYL BENZYL PHTHALATE 28 7 000085-68-7
90 1,1,2,2-TETRACHLOROETHANE 27 19 000079-34-5
91 DI-N-BUTYL PHTHALATE 27 10 000084-74-2
92 HYDROGEN SULFIDE 27 4 007783-06-4
93 1,1,2-TRICHLOROETHANE 26 20 000079-00-5
94 HEXACHLOROCYCLOHEXANE, GAMMA- 26 14 000058-89-9
94 PHENOL 26 14 000108-95-2
94 TCDD EQUIVALENTS 26 14 HZ0400-03-T
97 BORON 26 13 007440-42-8
98 STYRENE 25 11 000100-42-5
99 METHYL-T-BUTYL ETHER 25 9 001634-04-4
100 1,2-DICHLOROPROPANE 24 17 000078-87-5

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 2011 CEP and SPL Generation
(Run date Sept. 26, 2011)
All Sites/Events NPL Sites
Number of Sites/Events 6096 1777
Number of Sites/Events with Public Health Assessments (PHAs) 1838 1621
Number of Sites/Events with CEPs 1686 802
Number of CEP records (incidents) 17573 10187
Number of CEP records (incidents) from PHAs 11031 9152
Total number of substances in CEPs 697 500

 

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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