Arsenic Contamination

Arsenic in Colorado Drinking Water

Ranked by arsenic violation count · Data from EPA SDWIS & UCMR

135

Cities Tested

135

Has Violations

100%

% Has Violations

4.2 violations

State Avg

▼ 0% vs national

vs National

205

Health Violations

Analysis

Arsenic in Colorado: what the data shows

Colorado has 135 cities with arsenic-related violations on record. Arsenic contamination is a federal MCL violation at levels above 10 µg/L (10 ppb). The state has 135 cities with at least one arsenic violation. Arsenic enters drinking water primarily through erosion of natural deposits, particularly in western states with arsenite-bearing geology. Industrial sources include mining runoff, glass manufacturing, and semiconductor production. Groundwater systems are significantly more likely to have arsenic issues than surface water systems. Long-term arsenic exposure above the MCL increases the risk of bladder, lung, and skin cancer, as well as cardiovascular disease and diabetes. Reverse osmosis and specialized arsenic-removal media are the most effective point-of-use treatment options.

Comparison

Cities exceeding 10 µg/L EPA MCL

Colorado

100%

135 of 135 cities

← = Exactly at national rate

National avg

100%

5270 of 5270 cities

City Map

Arsenic data across Colorado

Each dot is a city with arsenic violation data. Cities with at least one arsenic-related violation are highlighted. Size reflects population served.

Worst Offenders

Top 10 cities by arsenic level in Colorado

Highest Arsenic levels (violations)

All Cities

All Colorado cities ranked by arsenic level

#	City	Level	Violations?	Violations	Grade
1	Carbondale	60 violations	Yes	77	F
2	Alamosa	47 violations	Yes	44	D
3	Denver	35 violations	Yes	104	F
4	Colorado Springs	27 violations	Yes	117	F
5	Aurora	19 violations	Yes	22	F
6	Windsor	19 violations	Yes	51	D
7	Falcon	14 violations	Yes	1	D
8	Monte Vista	13 violations	Yes	10	D+
9	Hudson	12 violations	Yes	12	D
10	Durango	11 violations	Yes	112	F
11	Lakewood	9 violations	Yes	28	F
12	Burlington	9 violations	Yes	84	C-
13	Divide	9 violations	Yes	49	F
14	Monument	8 violations	Yes	23	F
15	Buena Vista	7 violations	Yes	13	F
16	Towoac	7 violations	Yes	5	D
17	Brighton	6 violations	Yes	18	F
18	Steamboat Springs	6 violations	Yes	57	F
19	Glenwood Springs	6 violations	Yes	17	F
20	Basalt	6 violations	Yes	6	D
21	Hotchkiss	6 violations	Yes	145	F
22	Holyoke	6 violations	Yes	8	C+
23	Winter Park	5 violations	Yes	7	D
24	La Junta	5 violations	Yes	245	F
25	Bayfield	5 violations	Yes	25	D
26	Frisco	5 violations	Yes	7	F
27	Antonito	5 violations	Yes	17	F
28	Cheyenne Wells	5 violations	Yes	11	B
29	Littleton	4 violations	Yes	16	F
30	Castle Rock	4 violations	Yes	20	F
31	Pagosa Springs	4 violations	Yes	25	F
32	Rifle	4 violations	Yes	64	D
33	Milliken	4 violations	Yes	0	B
34	Fraser	4 violations	Yes	0	C-
35	Paonia	4 violations	Yes	29	D
36	Crestone	4 violations	Yes	2	B-
37	Haxtun	4 violations	Yes	13	C
38	Montrose	3 violations	Yes	7	F
39	Peyton	3 violations	Yes	2	B-
40	Cedaredge	3 violations	Yes	67	D
41	Lamar	3 violations	Yes	14	B-
42	Leadville	3 violations	Yes	3	D
43	Rocky Ford	3 violations	Yes	325	F
44	Crested Butte	3 violations	Yes	12	C-
45	Elizabeth	3 violations	Yes	5	B
46	Administrative Contact	3 violations	Yes	9	F
47	Wiggins	3 violations	Yes	16	D+
48	South Fork	3 violations	Yes	8	D
49	Manzanola	3 violations	Yes	340	D+
50	Debeque	3 violations	Yes	3	C+
51	Nucla	3 violations	Yes	9	D
52	Rye	3 violations	Yes	69	D
53	Woody Creek	3 violations	Yes	2	D+
54	Granada	3 violations	Yes	11	D
55	Pueblo	2 violations	Yes	15	F
56	Parker	2 violations	Yes	4	F
57	Loveland	2 violations	Yes	50	F
58	Wheat Ridge	2 violations	Yes	56	D
59	Lafayette	2 violations	Yes	19	F
60	Johnstown	2 violations	Yes	6	B
61	Greenwood Village	2 violations	Yes	24	F
62	Evergreen	2 violations	Yes	57	F
63	Sterling	2 violations	Yes	29	C-
64	Morrison	2 violations	Yes	12	C+
65	Redvale	2 violations	Yes	0	D
66	Salida	2 violations	Yes	2	D
67	Granby	2 violations	Yes	9	C-
68	Walsenburg	2 violations	Yes	47	D
69	Watkins	2 violations	Yes	3	D
70	Palisade	2 violations	Yes	2	C-
71	Ignacio	2 violations	Yes	6	F
72	Woodland Park	2 violations	Yes	55	D
73	Edwards	2 violations	Yes	43	C
74	Deer Trail	2 violations	Yes	7	A-
75	Crawford	2 violations	Yes	31	F
76	Ridgway	2 violations	Yes	11	D+
77	Parachute	2 violations	Yes	1	A-
78	Pine Bluffs	2 violations	Yes	17	D+
79	Pine Bluffs	2 violations	Yes	17	D+
80	Beulah	2 violations	Yes	66	D
81	Hugo	2 violations	Yes	2	B-
82	Otis	2 violations	Yes	2	C+
83	Sedalia	2 violations	Yes	9	C+
84	Empire	2 violations	Yes	14	C+
85	Thornton	1 violations	Yes	3	F
86	Greeley	1 violations	Yes	16	F
87	Highlands Ranch	1 violations	Yes	0	B-
88	Englewood	1 violations	Yes	33	D
89	Golden	1 violations	Yes	18	B-
90	Canon City	1 violations	Yes	4	B+
91	Aspen	1 violations	Yes	2	D
92	Fountain	1 violations	Yes	4	F
93	Estes Park	1 violations	Yes	49	D
94	Fort Morgan	1 violations	Yes	5	A-
95	Superior	1 violations	Yes	5	A
96	Wellington	1 violations	Yes	4	B-
97	Fort Lupton	1 violations	Yes	35	D
98	Trinidad	1 violations	Yes	12	D
99	Silverthorne	1 violations	Yes	3	D+
100	Gunnison	1 violations	Yes	14	C
101	Craig	1 violations	Yes	0	B
102	Telluride	1 violations	Yes	21	D
103	Florence	1 violations	Yes	2	C+
104	Glendale	1 violations	Yes	3	D
105	Keenesburg	1 violations	Yes	5	A-
106	Hayden	1 violations	Yes	6	D
107	Silt	1 violations	Yes	28	F
108	Lyons	1 violations	Yes	61	D
109	Cripple Creek	1 violations	Yes	1	B
110	Grand Lake	1 violations	Yes	3	B+
111	Colorado City	1 violations	Yes	34	F
112	Mancos	1 violations	Yes	3	C
113	Meeker	1 violations	Yes	6	C+
114	Rangely	1 violations	Yes	3	C+
115	Akron	1 violations	Yes	4	B
116	Strasburg	1 violations	Yes	19	D
117	Wiley	1 violations	Yes	376	D+
118	Oak Creek	1 violations	Yes	28	D
119	Norwood	1 violations	Yes	44	B-
120	Del Norte	1 violations	Yes	4	B
121	Calhan	1 violations	Yes	3	D+
122	San Luis	1 violations	Yes	9	D
123	Fairplay	1 violations	Yes	2	C
124	Manassa	1 violations	Yes	3	B
125	Stratton	1 violations	Yes	8	C-
126	Kiowa	1 violations	Yes	0	A-
127	Dove Creek	1 violations	Yes	8	C-
128	Bailey	1 violations	Yes	1	C
129	Mulberry	1 violations	Yes	1	B-
130	Walsh	1 violations	Yes	18	D+
131	Nathrop	1 violations	Yes	14	B+
132	Naturita	1 violations	Yes	12	C-
133	Moffat	1 violations	Yes	1	B-
134	Clark	1 violations	Yes	6	C-
135	Saguache	1 violations	Yes	1	D+

FAQ

Frequently asked questions about arsenic in Colorado

Is arsenic in Colorado tap water a concern?

Yes — 135 cities in Colorado have arsenic-related violations on record. The EPA MCL for arsenic is 10 µg/L. Even at levels below the MCL, long-term arsenic exposure has been linked to cancer and cardiovascular disease.

How can I remove arsenic from my drinking water in Colorado?

Reverse osmosis (RO) systems are the most effective at removing arsenic, typically reducing it by 90% or more. Specialized arsenic-removal media (such as iron-based adsorption filters) are also highly effective. Standard carbon filters and pitcher filters do NOT effectively remove arsenic. If your water comes from a private well, have it tested for arsenic.

Where does arsenic in Colorado water come from?

Arsenic enters drinking water primarily through natural erosion of arsenic-bearing rock formations. It is most common in groundwater systems in the western United States, parts of the Midwest, and New England. Industrial sources include mining, smelting, and agricultural pesticide residues. Groundwater sources are far more likely to contain arsenic than surface water.

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