Contaminants and rules

Every violation in EPA's database is tied to a rule or a specific contaminant. This index lists the ones that appear in the past three years of records, with how many active systems were affected nationally. Most violations are monitoring or reporting lapses rather than confirmed contamination; each entry explains what the rule requires and what the health effects are.

Microbial

Bacteria and the rules that test for them. Health-based when a sample is positive.

Rule or contaminant	Code	Systems with violations, 3 yr	Unresolved	States
Revised Total Coliform Rule (RTCR)	8000	30,005	7,820	50
E. coli (Escherichia coli)	3014	3,834	2,209	44
Total Coliform Rule (TCR)	3100	2	0	1

Inorganic Chemical

Naturally occurring or from fertilizer and industry. Each has a maximum contaminant level.

Rule or contaminant	Code	Systems with violations, 3 yr	Unresolved	States
Nitrate	1040	10,272	396	40
Nitrite	1041	1,821	48	33
Arsenic	1005	1,798	234	47
Nitrate-Nitrite (Combined)	1038	1,387	41	18
Mercury	1035	885	15	43
Barium	1010	867	15	44
Beryllium	1075	862	16	43
Selenium	1045	861	21	44
Thallium	1085	859	14	43
Cadmium	1015	857	15	43
Antimony	1074	856	15	43
Chromium	1020	851	15	43
Fluoride	1025	850	56	41
Cyanide	1024	793	8	38
Nickel	1036	672	9	37
Asbestos	1094	182	2	20
Lead	1030	1	1	1

Disinfection Byproduct

Formed when chlorine reacts with organic matter in the water.

Rule or contaminant	Code	Systems with violations, 3 yr	Unresolved	States
TTHM (Total Trihalomethanes)	2950	6,250	784	50
Total Haloacetic Acids (HAA5)	2456	5,721	486	50
Stage 1 Disinfectants and DBP Rule	0400	126	126	23
Stage 2 Disinfectants and Disinfection Byproducts Rule	0600	100	100	12
Chlorite	1009	63	6	20

Treatment Technique

Rules that require a process, such as corrosion control or disinfection, rather than a measured limit.

Rule or contaminant	Code	Systems with violations, 3 yr	Unresolved	States
Lead and Copper Rule (LCR)	5000	7,623	7,203	51
Chlorine (MRDL)	0999	4,173	432	41
Lead and Copper Rule Revisions (LCRR)	5200	3,848	3,848	39
Groundwater Rule (GWR)	0700	2,821	1,720	43
Surface Water Treatment Rule (SWTR)	0200	1,357	341	40
Interim Enhanced Surface Water Treatment Rule	0300	952	173	43
Long Term 2 Enhanced Surface Water Treatment Rule (LT2)	0800	221	146	32

Monitoring and Reporting

Administrative requirements. No direct health risk from the violation itself.

Rule or contaminant	Code	Systems with violations, 3 yr	Unresolved	States
Public Notification Rule	7500	10,051	10,051	49
Consumer Confidence Rule (CCR)	7000	4,766	4,766	48

Volatile Organic Compound

Solvents and fuel components, usually monitored as a group, which is why the counts are similar.

Rule or contaminant	Code	Systems with violations, 3 yr	Unresolved	States
Benzene	2990	2,000	87	42
Tetrachloroethylene (PCE)	2987	1,966	86	42
Trichloroethylene (TCE)	2984	1,960	90	42
Dichloromethane (Methylene Chloride)	2964	1,958	86	42
Toluene	2991	1,958	88	42
Ethylbenzene	2992	1,955	88	42
1,1-Dichloroethylene	2977	1,949	88	42
Carbon Tetrachloride	2982	1,949	87	42
cis-1,2-Dichloroethylene	2380	1,949	88	42
1,1,1-Trichloroethane	2981	1,947	86	42
Styrene	2996	1,947	86	42
o-Dichlorobenzene	2968	1,946	86	42
p-Dichlorobenzene	2969	1,946	87	42
trans-1,2-Dichloroethylene	2979	1,946	86	42
1,1,2-Trichloroethane	2985	1,945	87	42
1,2-Dichloroethane	2980	1,945	87	42
1,2-Dichloropropane	2983	1,945	86	42
Chlorobenzene	2989	1,945	86	42
1,2,4-Trichlorobenzene	2378	1,944	86	42
Vinyl Chloride	2976	1,776	80	41
Xylenes, Total	2955	1,764	72	41
Ethylene Dibromide (EDB)	2946	1,034	47	33

Organic Chemical

Industrial and synthetic organic chemicals with a maximum contaminant level.

Rule or contaminant	Code	Systems with violations, 3 yr	Unresolved	States
Di(2-ethylhexyl) Phthalate	2039	1,357	77	40
Benzo(a)pyrene	2306	1,250	61	37
Hexachlorocyclopentadiene	2042	1,236	65	38
Di(2-ethylhexyl) Adipate	2035	1,235	64	39
Hexachlorobenzene	2274	1,203	60	37
Pentachlorophenol	2326	1,180	56	39
Polychlorinated Biphenyls (PCBs)	2383	940	46	34
1,2-Dibromo-3-Chloropropane (DBCP)	2931	913	48	30
2,3,7,8-TCDD (Dioxin)	2063	354	21	16

Pesticide

Pesticides and herbicides, monitored as a group.

Rule or contaminant	Code	Systems with violations, 3 yr	Unresolved	States
Atrazine	2050	1,284	62	42
Alachlor (Lasso)	2051	1,265	63	42
Simazine	2037	1,261	60	41
BHC-Gamma (Lindane)	2010	1,240	64	40
Heptachlor Epoxide	2067	1,233	63	38
Methoxychlor	2015	1,232	62	40
Heptachlor	2065	1,231	63	38
Chlordane	2959	1,210	58	38
2,4-D	2105	1,205	51	40
Endrin	2005	1,196	59	37
Picloram	2040	1,183	59	40
Toxaphene	2020	1,176	56	37
2,4,5-TP (Silvex)	2110	1,175	55	36
Dinoseb	2041	1,146	55	36
Oxamyl (Vydate)	2036	1,141	50	39
Carbofuran	2046	1,139	50	38
Dalapon	2031	1,111	53	34
Diquat	2032	839	45	30
Endothall	2033	793	41	28
Glyphosate	2034	758	33	31
Aldicarb Sulfone	2044	348	10	11
Aldicarb	2047	347	10	11
Aldicarb Sulfoxide	2043	347	10	11

Radionuclide

Naturally occurring radioactive elements in groundwater.

Rule or contaminant	Code	Systems with violations, 3 yr	Unresolved	States
Gross Alpha, Excl. Radon and U	4000	1,149	89	41
Combined Radium (-226 and -228)	4010	970	96	38
Combined Uranium	4006	909	61	38
Radium-228	4030	463	27	25
Radium-226	4020	401	23	23
Gross Beta Particle Activity	4100	129	0	4

Other rules

Rule or contaminant	Code	Systems with violations, 3 yr	Unresolved	States
Carbon, Total	2920	367	70	38
Coliphage	3028	227	5	2
Chloramine	1006	118	15	8
Not applicable		79	71	4
Bromate	1011	47	13	15
Chlorine dioxide	1008	36	3	12
Enterococci	3002	7	6	2
Tritium	4102	7	0	4
Strontium-90	4174	6	0	3
Iodine-131	4264	5	0	2
Cryptosporidium	3015	4	0	3
Turbidity	0100	2	0	2
Copper, Free	1022	1	1	1
Epichlorohydrin	2257	1	0	1

Contaminants and rules

Microbial

Inorganic Chemical

Disinfection Byproduct

Treatment Technique

Monitoring and Reporting

Volatile Organic Compound

Organic Chemical

Pesticide

Radionuclide

Other rules

Compliant

Violations in the past 3 years

Serious violator

Health flag

Inactive system