Contaminants and rules in Mississippi water systems
45 different rules and contaminants appear in the past three years of violation records for Mississippi's 1,196 active public water systems. The tables show how many systems each one affected and how many of those violations are still unresolved. Most entries are monitoring, reporting, or notification lapses rather than confirmed contamination.
Microbial
Bacteria and the rules that test for them. Health-based when a sample is positive.
| Rule or contaminant | Code | Mississippi systems with violations, 3 yr | Share | In violation, latest quarter |
|---|---|---|---|---|
| Revised Total Coliform Rule (RTCR) | 8000 | 179 | 15% | 25 |
Inorganic Chemical
Naturally occurring or from fertilizer and industry. Each has a maximum contaminant level.
| Rule or contaminant | Code | Mississippi systems with violations, 3 yr | Share | In violation, latest quarter |
|---|---|---|---|---|
| Nitrate-Nitrite (Combined) | 1038 | 52 | 4% | 0 |
| Nitrate | 1040 | 52 | 4% | 0 |
| Nitrite | 1041 | 52 | 4% | 0 |
| Cyanide | 1024 | 10 | 1% | 0 |
| Arsenic | 1005 | 8 | 1% | 0 |
| Mercury | 1035 | 8 | 1% | 0 |
| Barium | 1010 | 7 | 1% | 0 |
| Cadmium | 1015 | 7 | 1% | 0 |
| Chromium | 1020 | 7 | 1% | 0 |
| Selenium | 1045 | 7 | 1% | 0 |
| Antimony | 1074 | 7 | 1% | 0 |
| Beryllium | 1075 | 7 | 1% | 0 |
| Thallium | 1085 | 7 | 1% | 0 |
| Fluoride | 1025 | 6 | 1% | 0 |
Disinfection Byproduct
Formed when chlorine reacts with organic matter in the water.
| Rule or contaminant | Code | Mississippi systems with violations, 3 yr | Share | In violation, latest quarter |
|---|---|---|---|---|
| TTHM (Total Trihalomethanes) | 2950 | 501 | 42% | 11 |
| Total Haloacetic Acids (HAA5) | 2456 | 490 | 41% | 10 |
Treatment Technique
Rules that require a process, such as corrosion control or disinfection, rather than a measured limit.
| Rule or contaminant | Code | Mississippi systems with violations, 3 yr | Share | In violation, latest quarter |
|---|---|---|---|---|
| Chlorine (MRDL) | 0999 | 171 | 14% | 0 |
| Lead and Copper Rule (LCR) | 5000 | 71 | 6% | 71 |
| Groundwater Rule (GWR) | 0700 | 23 | 2% | 23 |
Monitoring and Reporting
Administrative requirements. No direct health risk from the violation itself.
| Rule or contaminant | Code | Mississippi systems with violations, 3 yr | Share | In violation, latest quarter |
|---|---|---|---|---|
| Public Notification Rule | 7500 | 75 | 6% | 75 |
| Consumer Confidence Rule (CCR) | 7000 | 6 | 1% | 6 |
Volatile Organic Compound
Solvents and fuel components, usually monitored as a group, which is why the counts are similar.
| Rule or contaminant | Code | Mississippi systems with violations, 3 yr | Share | In violation, latest quarter |
|---|---|---|---|---|
| 1,2,4-Trichlorobenzene | 2378 | 3 | 0% | 1 |
| cis-1,2-Dichloroethylene | 2380 | 3 | 0% | 1 |
| Xylenes, Total | 2955 | 3 | 0% | 1 |
| Dichloromethane (Methylene Chloride) | 2964 | 3 | 0% | 1 |
| o-Dichlorobenzene | 2968 | 3 | 0% | 1 |
| p-Dichlorobenzene | 2969 | 3 | 0% | 1 |
| Vinyl Chloride | 2976 | 3 | 0% | 1 |
| 1,1-Dichloroethylene | 2977 | 3 | 0% | 1 |
| trans-1,2-Dichloroethylene | 2979 | 3 | 0% | 1 |
| 1,2-Dichloroethane | 2980 | 3 | 0% | 1 |
| 1,1,1-Trichloroethane | 2981 | 3 | 0% | 1 |
| Carbon Tetrachloride | 2982 | 3 | 0% | 1 |
| 1,2-Dichloropropane | 2983 | 3 | 0% | 1 |
| Trichloroethylene (TCE) | 2984 | 3 | 0% | 1 |
| 1,1,2-Trichloroethane | 2985 | 3 | 0% | 1 |
| Tetrachloroethylene (PCE) | 2987 | 3 | 0% | 1 |
| Chlorobenzene | 2989 | 3 | 0% | 1 |
| Benzene | 2990 | 3 | 0% | 1 |
| Toluene | 2991 | 3 | 0% | 1 |
| Ethylbenzene | 2992 | 3 | 0% | 1 |
| Styrene | 2996 | 3 | 0% | 1 |
Radionuclide
Naturally occurring radioactive elements in groundwater.
| Rule or contaminant | Code | Mississippi systems with violations, 3 yr | Share | In violation, latest quarter |
|---|---|---|---|---|
| Combined Uranium | 4006 | 2 | 0% | 0 |
Other rules
| Rule or contaminant | Code | Mississippi systems with violations, 3 yr | Share | In violation, latest quarter |
|---|---|---|---|---|
| Carbon, Total | 2920 | 1 | 0% | 0 |
About this data
A system is counted once per rule if any of its violations in the past three years involved that rule, including monitoring and reporting lapses. In violation, latest quarter counts systems whose contaminant list for the latest official quarter in EPA's data, or new violations reported since, includes this entry. Share is of the 1,196 active Mississippi systems.
Source: the U.S. EPA's Enforcement and Compliance History Online system (ECHO), which publishes the federal Safe Drinking Water Information System. EPA's terms and values are shown as published. The Mississippi records are from EPA's data refresh of Oct 7, 2026; EPA refreshes this data quarterly, and states report to EPA with a lag of three to six months, so the newest violations may not appear yet. Retrieved from ECHO on Oct 11, 2026.