The Latest ATSDR Substance Priority List of Chemicals and Elements Posing the Most Significant Risk at NPL sites
The rankings are out and three metals top the chart: arsenic, lead, and mercury. The Agency for Toxic Substances and Disease Registry (ATSDR) has released its 2017 list of substances at EPA-managed contamination sites posing the most significant risk to human health.
CERCLA/SARA (Superfund) 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) that 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.
ATSDR typically publishes the substance priority list every two years, in addition to performing an annual informal review and revision. The total points ranking is determined using an algorithm that prioritizes substances based on frequency of occurrence at NPL sites, toxicity, and potential for human exposure to the substances found at NPL sites. ATSDR notes that this priority list is not a list of “most toxic” substances, but instead is a prioritization of substances based on the ranking algorithm.
A total of 275 substances are listed on the entire ATSDR 2017 Substance Priority list. Here are the Top 50 substances listed.
Rank, Substance Name, Total Points, CAS #
1. Arsenic 1674 points 7440-38-2
2. Lead 1531 points 7439-92-1
3. Mercury 1458 points 7439-97-6
4. Vinyl Chloride 1358 points 75-01-4
5. Polychlorinated Biphenyls 1345 points 1336-36-3
6. Benzene 1329 points 71-43-2
7. Cadmium 1320 points 7440-43-9
8. Benzo(a)pyrene 1306 points 50-32-8
9. PAHs (PNAs) 1279 points 130498-29-2
10. Benzo(b)fluoranthene 1251 points 205-99-2
11. Chloroform 1203 points 67-66-3
12. Arolcor 1260 1191 points 11096-82-5
13. DDT, P,P’ 1183 points 50-29-3
14. Arolcor 1254 1172 points 11097-69-1
15. Dibenzo(a,h)anthracene 1156 points 53-70-3
16. Trichloroethylene 1155 points 79-01-6
17. Hexavalent Chromium 1148 points 18540-29-9
18. Dieldrin 1144 points 60-57-1
19. Phosphorus, White 1141 points 7723-14-0
20. Hexachlorobutadiene 1130 points 87-68-3
21. DDE, P,P’ 1127 points 72-55-9
22. Chlordane 1126 points 57-74-9
23. Arolcor 1242 1126 points 53469-21-9
24. Coal Tar Creosote 1124 points 8001-58-9
25. Aldrin 1116 points 309-00-2
26. DDD, P,P’ 1114 points 72-54-8
27. Arolcor 1248 1105 points 12672-29-6
28. Heptachlor 1102 points 76-44-8
29. Arolcor 1101 points 12767-79-2
30. Benzidine 1093 points 92-87-5
31. Acrolein 1090 points 107-02-8
32. Toxaphene 1089 points 8001-35-2
33. Tetrachloroethylene 1078 points 127-18-4
34. Hexachlorocyclohexane, Gamma 1076 points 58-89-9
35. Cyanide 1071 points 57-12-5
36. Hexachlorocyclohexane, Beta 1054 points 319-85-7
37. Disulfoton 1049 points 298-04-4
38. Benzo(a)anthracene 1047 points 56-55-3
39. 1,2-Dibromoethane 1043 points 106-93-4
40. Endrin 1039 points 72-20-8
41. Diazinon 1038 points 333-41-5
42. Hexachlorocyclohexane, Delta 1036 points 319-86-8
43. Beryllium 1031 points 7440-41-7
44. Endosulfan 1029 points 115-29-7
45. Arolcor 1221 1028 points 11104-28-2
46. 1,2-Dibromo-3-Chloropropane 1027 points 96-12-8
47. Heptachlor Epoxide 1022 points 1024-57-3
48. Endosulfan Alpha 1019 points 959-98-8
49. Cis-Chlordane 1017 points 5103-71-9
50. Carbon Tetrachloride 1014 points 56-23-5
According to ATSDR, the ranking of hazardous substances on the substance priority list is based on three criteria, which are combined to result in the total score. The three criteria are:
• Frequency of Occurrence at NPL sites: A substance has to be identified at three or more NPL hazardous waste sites or facilities to be considered a candidate for this list.
• Toxicity: Final Reportable Quantities (RQs) are used to assess the toxicity of candidate substances during the listing activity. If a final RQ is not available, the RQ methodology is applied to candidate substances to establish a Toxicity/Environmental Score (TES). This process is only used in scoring the substances with respect to their toxicity, and does not represent regulatory values.
• Potential for Human Exposure The exposure component is based on two parts: (1) the concentration of the substances in environmental media at sites, and (2) the exposure status of populations at sites. ATSDR’s science database is the source of this data with concentration and exposure data obtained from ATSDR public health assessments and health consultations.
Using these three criteria, the hazard potential of each candidate substance is ranked according to the following algorithm:
Total Score (1,800 point max.) = NPL Frequency (600 point max.) + Toxicity (600 point max.) + Potential for Human Exposure (300 concentration + 300 exposure points max.)
The algorithm generates a candidate list of substances based on their total score. The top 275 scoring substances becomes the Priority List of Hazardous Substances. There are currently 857 candidate substances for the priority list.
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