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Drinking Water Contaminants

Health-based violations by contaminant type across community water systems in all 50 states, drawn from the EPA Safe Drinking Water Information System (SDWIS) under the Safe Drinking Water Act, from EPA Safe Drinking Water Information System (SDWIS) data. Click any contaminant to see which water systems and states are affected.

Summary: EPA records show 196,329 health-based violations across 90 distinct contaminant types in U.S. drinking water. The most commonly violated standards involve disinfection byproducts (TTHM, HAA5), microbial contaminants (E. coli, Total Coliform), and naturally occurring minerals (nitrate, arsenic, radium). PFAS contamination has emerged as a critical concern, with the EPA finalizing new federal limits in 2024.

Contaminant Types
90
Total Health Violations
196,329
Systems Affected
27,215

All Contaminants with Violations

Ranked by number of health-based violations. Click any contaminant to see state-by-state data and affected water systems.

# Contaminant Violations Systems
1 Total Trihalomethanes (TTHM) 53,036 2,715
2 Haloacetic Acids (HAA5) 21,348 1,585
3 Barium 19,993 779
4 Fluoride 14,728 3,142
5 Nitrate 8,701 610
6 Lead & Copper Rule 8,150 395
7 Arsenic 6,671 1,155
8 Combined Radium 226/228 6,345 2,938
9 Turbidity 6,319 703
10 Copper 5,767 305
11 Total Coliform (RTCR) 5,765 1,942
12 E. coli 5,491 2,276
13 Gross Alpha 5,201 4,950
14 Manganese 5,169 133
15 Lead (Action Level) 4,571 188
16 Chloroform 3,763 308
17 Chlorine 3,407 1,107
18 Atrazine 2,745 380
19 Nitrite 2,326 142
20 Total Coliform 1,847 614
21 Selenium 608 52
22 Thallium 578 66
23 Chromium 502 84
24 Di(2-ethylhexyl) phthalate 318 36
25 Mercury 231 60
26 Dibutyl phthalate 226 39
27 PFOA + PFOS 210 22
28 Contaminant 4030 168 6
29 Antimony 152 46
30 Benzene 138 27
31 Contaminant 1094 134 9
32 Contaminant 1009 123 36
33 Contaminant 2977 117 3
34 Contaminant 1041 114 30
35 Contaminant 1008 108 20
36 Uranium 108 20
37 Contaminant 2982 107 10
38 Contaminant 1030 81 48
39 Contaminant 2987 75 15
40 Contaminant 1022 70 25
41 Contaminant 1074 69 12
42 Contaminant 2990 63 4
43 Contaminant 1006 45 12
44 Contaminant 1010 44 13
45 Contaminant 1085 39 7
46 Contaminant 2946 38 13
47 Contaminant 1075 38 6
48 Contaminant 2976 31 2
49 Contaminant 1920 31 7
50 Contaminant 2931 30 6
51 Contaminant 1015 30 6
52 Contaminant 1011 29 9
53 Contaminant 1020 28 2
54 Contaminant 2414 26 6
55 Contaminant 2380 26 3
56 Contaminant 2964 23 3
57 Contaminant 1925 23 12
58 Contaminant 2984 21 5
59 Contaminant 2216 18 1
60 Contaminant 2214 18 4
61 Contaminant 4020 12 3
62 Contaminant 2983 12 1
63 Contaminant 2257 12 5
64 Contaminant 4002 11 5
65 Contaminant 2306 11 2
66 Contaminant 1905 11 6
67 Contaminant 2326 8 1
68 Contaminant 1055 8 3
69 Contaminant 1930 7 3
70 Contaminant 2210 6 3
71 Contaminant 1002 6 3
72 Contaminant 1039 5 4
73 Contaminant 1024 5 1
74 Contaminant 4100 4 1
75 Contaminant 2980 4 1
76 Contaminant 3014 3 3
77 Contaminant 2650 3 1
78 Contaminant 2590 3 2
79 Contaminant 2251 2 1
80 Contaminant 2050 2 1
81 Contaminant 2049 2 2
82 Contaminant 1095 2 1
83 Contaminant 1035 2 1
84 Contaminant 3001 1 1
85 Contaminant 2991 1 1
86 Contaminant 2476 1 1
87 Contaminant 2424 1 1
88 Contaminant 2263 1 1
89 Contaminant 1013 1 1
90 Contaminant 1000 1 1

About This Data

Contaminant violation data is from the EPA Safe Drinking Water Information System (SDWIS). Only health-based violations are counted, these include Maximum Contaminant Level (MCL) and Treatment Technique (TT) violations that may pose direct health risks. Monitoring and reporting violations are excluded.

Source: U.S. Environmental Protection Agency, SDWIS Federal Reporting Services U.S. Environmental Protection Agency, SDWIS Federal Reporting Services