Loading water data...
Chlorine byproducts linked to bladder cancer. Below are US cities ranked by their measured Total Trihalomethanes levels compared to EPA limits. Higher percentages indicate greater concern.
Vulnerable Populations: Pregnant women may face increased risk of miscarriage and birth defects with high THM exposure, though research is ongoing.
Ranked by percentage of the EPA limit, using one real EPA measurement per water system (2012–2019 (SYR4)). Click any city for its full report.
Historical data. Figure shown is the average of the system's 2012–2019 finished-water compliance samples (EPA Six-Year Review 4), non-detects counted as zero. Treat as history, not today's tap water.
| Rank | City | State | Level | Period | EPA Limit | % of Limit | Status | Population |
|---|---|---|---|---|---|---|---|---|
| #1 | Daytona Beach | Florida | 66.64 ppbAverage of 128 samples | 2012–2019 | 80.00 ppb | 83.3% | Elevated | 87,534 |
| #2 | Norwich | Connecticut | 65.68 ppbAverage of 234 samples | 2012–2019 | 80.00 ppb | 82.1% | Elevated | 36,163 |
| #3 | Lake Havasu City | Arizona | 65.42 ppbAverage of 114 samples | 2012–2019 | 80.00 ppb | 81.8% | Elevated | 54,610 |
| #4 | Ashland | Kentucky | 63.57 ppbAverage of 134 samples | 2012–2019 | 80.00 ppb | 79.5% | Elevated | 44,402 |
| #5 | Junction City | Kansas | 63.61 ppbAverage of 107 samples | 2012–2019 | 80.00 ppb | 79.5% | Elevated | 19,167 |
| #6 | Winter Springs | Florida | 62.70 ppbAverage of 130 samples | 2012–2019 | 80.00 ppb | 78.4% | Elevated | 34,657 |
| #7 | Burlington | Iowa | 60.81 ppbAverage of 24 samples | 2012–2019 | 80.00 ppb | 76.0% | Elevated | 26,015 |
| #8 | Urbandale | Iowa | 60.75 ppbAverage of 4 samples | 2012–2019 | 80.00 ppb | 75.9% | Elevated | 45,605 |
| #9 | Deltona | Florida | 60.27 ppbAverage of 135 samples | 2012–2019 | 80.00 ppb | 75.3% | Elevated | 81,006 |
| #10 | Bella Vista | Arkansas | 59.76 ppbAverage of 136 samples | 2012–2019 | 80.00 ppb | 74.7% | Elevated | 39,419 |
| #11 | Jacksonville | Florida | 59.68 ppbAverage of 307 samples | 2012–2019 | 80.00 ppb | 74.6% | Elevated | 826,664 |
| #12 | Mount Dora | Florida | 59.40 ppbAverage of 113 samples | 2012–2019 | 80.00 ppb | 74.2% | Elevated | 39,710 |
| #13 | New Iberia | Louisiana | 58.95 ppbAverage of 120 samples | 2012–2019 | 80.00 ppb | 73.7% | Elevated | 59,928 |
| #14 | Hawthorne | California | 58.12 ppbAverage of 371 samples | 2012–2019 | 80.00 ppb | 72.6% | Elevated | 44,718 |
| #15 | Lafayette | Colorado | 57.11 ppbAverage of 128 samples | 2012–2019 | 80.00 ppb | 71.4% | Elevated | 28,700 |
| #16 | Tamarac | Florida | 56.86 ppbAverage of 204 samples | 2012–2019 | 80.00 ppb | 71.1% | Elevated | 63,793 |
| #17 | Orlando | Florida | 56.42 ppbAverage of 175 samples | 2012–2019 | 80.00 ppb | 70.5% | Elevated | 536,466 |
| #18 | San Luis | Arizona | 56.04 ppbAverage of 148 samples | 2012–2019 | 80.00 ppb | 70.1% | Elevated | 39,705 |
| #19 | El Centro | California | 56.02 ppbAverage of 92 samples | 2012–2019 | 80.00 ppb | 70.0% | Elevated | 43,772 |
| #20 | Akron | Ohio | 55.96 ppbAverage of 384 samples | 2012–2019 | 80.00 ppb | 69.9% | Elevated | 280,000 |
| #21 | Madisonville | Kentucky | 55.92 ppbAverage of 129 samples | 2012–2019 | 80.00 ppb | 69.9% | Elevated | 28,102 |
| #22 | Salem | Massachusetts | 55.84 ppbAverage of 220 samples | 2012–2019 | 80.00 ppb | 69.8% | Elevated | 90,330 |
| #23 | Beverly | Massachusetts | 55.84 ppbAverage of 220 samples | 2012–2019 | 80.00 ppb | 69.8% | Elevated | 90,330 |
| #24 | Springfield | Massachusetts | 55.76 ppbAverage of 327 samples | 2012–2019 | 80.00 ppb | 69.7% | Elevated | 169,170 |
| #25 | Salina | Kansas | 55.32 ppbAverage of 129 samples | 2012–2019 | 80.00 ppb | 69.1% | Elevated | 46,481 |
| #26 | Clearwater | Florida | 55.19 ppbAverage of 235 samples | 2012–2019 | 80.00 ppb | 69.0% | Elevated | 115,000 |
| #27 | Casselberry | Florida | 54.84 ppbAverage of 126 samples | 2012–2019 | 80.00 ppb | 68.6% | Elevated | 54,747 |
| #28 | Las Vegas | Nevada | 54.70 ppbAverage of 511 samples | 2012–2019 | 80.00 ppb | 68.4% | Elevated | 1,539,277 |
| #29 | Coralville | Iowa | 54.50 ppbAverage of 2 samples | 2012–2019 | 80.00 ppb | 68.1% | Elevated | 22,318 |
| #30 | Thibodaux | Louisiana | 54.42 ppbAverage of 144 samples | 2012–2019 | 80.00 ppb | 68.0% | Elevated | 14,862 |
| #31 | Russellville | Arkansas | 54.27 ppbAverage of 121 samples | 2012–2019 | 80.00 ppb | 67.8% | Elevated | 29,260 |
| #32 | Dunedin | Florida | 53.99 ppbAverage of 146 samples | 2012–2019 | 80.00 ppb | 67.5% | Elevated | 46,161 |
| #33 | Brockton | Massachusetts | 53.73 ppbAverage of 253 samples | 2012–2019 | 80.00 ppb | 67.2% | Elevated | 105,788 |
| #34 | Braintree | Massachusetts | 53.77 ppbAverage of 108 samples | 2012–2019 | 80.00 ppb | 67.2% | Elevated | 39,143 |
| #35 | Kissimmee | Florida | 53.64 ppbAverage of 179 samples | 2012–2019 | 80.00 ppb | 67.1% | Elevated | 110,102 |
| #36 | Texarkana | Arkansas | 53.69 ppbAverage of 128 samples | 2012–2019 | 80.00 ppb | 67.1% | Elevated | 50,815 |
| #37 | Hot Springs | Arkansas | 53.53 ppbAverage of 257 samples | 2012–2019 | 80.00 ppb | 66.9% | Elevated | 75,343 |
| #38 | Sioux City | Iowa | 53.25 ppbAverage of 8 samples | 2012–2019 | 80.00 ppb | 66.6% | Elevated | 85,791 |
| #39 | Attleboro | Massachusetts | 53.10 ppbAverage of 140 samples | 2012–2019 | 80.00 ppb | 66.4% | Elevated | 46,461 |
| #40 | Galesburg | Illinois | 52.92 ppbAverage of 107 samples | 2012–2019 | 80.00 ppb | 66.2% | Elevated | 31,620 |
| #41 | Pittsburgh | Pennsylvania | 52.70 ppbAverage of 380 samples | 2012–2019 | 80.00 ppb | 65.9% | Elevated | 686,000 |
| #42 | Sunrise | Florida | 52.69 ppbAverage of 131 samples | 2012–2019 | 80.00 ppb | 65.9% | Elevated | 79,550 |
| #43 | San Luis Obispo | California | 52.64 ppbAverage of 117 samples | 2012–2019 | 80.00 ppb | 65.8% | Elevated | 47,788 |
| #44 | Nicholasville | Kentucky | 52.65 ppbAverage of 134 samples | 2012–2019 | 80.00 ppb | 65.8% | Elevated | 35,266 |
| #45 | Auburn | Alabama | 52.54 ppbAverage of 281 samples | 2012–2019 | 80.00 ppb | 65.7% | Elevated | 74,292 |
| #46 | Napa | California | 52.45 ppbAverage of 378 samples | 2012–2019 | 80.00 ppb | 65.6% | Elevated | 84,804 |
| #47 | Evans | Colorado | 52.52 ppbAverage of 120 samples | 2012–2019 | 80.00 ppb | 65.6% | Elevated | 19,369 |
| #48 | Lawrence | Massachusetts | 52.39 ppbAverage of 244 samples | 2012–2019 | 80.00 ppb | 65.5% | Elevated | 89,143 |
| #49 | Leominster | Massachusetts | 52.35 ppbAverage of 205 samples | 2012–2019 | 80.00 ppb | 65.4% | Elevated | 41,683 |
| #50 | Shelton | Connecticut | 51.79 ppbAverage of 384 samples | 2012–2019 | 80.00 ppb | 64.7% | Elevated | 351,756 |
| #51 | Champaign | Illinois | 51.70 ppbAverage of 189 samples | 2012–2019 | 80.00 ppb | 64.6% | Elevated | 150,000 |
| #52 | Fitchburg | Massachusetts | 51.68 ppbAverage of 219 samples | 2012–2019 | 80.00 ppb | 64.6% | Elevated | 41,946 |
| #53 | Laurel | Maryland | 51.55 ppbAverage of 2071 samples | 2012–2019 | 80.00 ppb | 64.4% | Elevated | 1,900,000 |
| #54 | Springdale | Arkansas | 51.52 ppbAverage of 217 samples | 2012–2019 | 80.00 ppb | 64.4% | Elevated | 98,948 |
| #55 | Fall River | Massachusetts | 51.55 ppbAverage of 220 samples | 2012–2019 | 80.00 ppb | 64.4% | Elevated | 94,000 |
| #56 | Fountain | Colorado | 51.43 ppbAverage of 133 samples | 2012–2019 | 80.00 ppb | 64.3% | Elevated | 25,130 |
| #57 | Fort Dodge | Iowa | 51.33 ppbAverage of 6 samples | 2012–2019 | 80.00 ppb | 64.2% | Elevated | 25,874 |
| #58 | Haverhill | Massachusetts | 51.25 ppbAverage of 198 samples | 2012–2019 | 80.00 ppb | 64.1% | Elevated | 61,277 |
| #59 | Kokomo | Indiana | 51.11 ppbAverage of 252 samples | 2012–2019 | 80.00 ppb | 63.9% | Elevated | 59,313 |
| #60 | Boca Raton | Florida | 51.02 ppbAverage of 140 samples | 2012–2019 | 80.00 ppb | 63.8% | Elevated | 130,000 |
| #61 | Oklahoma City | Oklahoma | 50.92 ppbAverage of 634 samples | 2012–2019 | 80.00 ppb | 63.7% | Elevated | 644,000 |
| #62 | Winter Haven | Florida | 50.87 ppbAverage of 177 samples | 2012–2019 | 80.00 ppb | 63.6% | Elevated | 87,537 |
| #63 | Paducah | Kentucky | 50.91 ppbAverage of 259 samples | 2012–2019 | 80.00 ppb | 63.6% | Elevated | 65,004 |
| #64 | Chandler | Arizona | 50.84 ppbAverage of 390 samples | 2012–2019 | 80.00 ppb | 63.5% | Elevated | 247,328 |
| #65 | Yuma | Arizona | 50.45 ppbAverage of 256 samples | 2012–2019 | 80.00 ppb | 63.1% | Elevated | 103,264 |
| #66 | Apopka | Florida | 50.47 ppbAverage of 133 samples | 2012–2019 | 80.00 ppb | 63.1% | Elevated | 71,917 |
| #67 | Rockville | Maryland | 50.21 ppbAverage of 162 samples | 2012–2019 | 80.00 ppb | 62.8% | Elevated | 52,000 |
| #68 | Charlotte | North Carolina | 50.12 ppbAverage of 406 samples | 2012–2019 | 80.00 ppb | 62.7% | Elevated | 1,163,701 |
| #69 | Oakland Park | Florida | 49.88 ppbAverage of 120 samples | 2012–2019 | 80.00 ppb | 62.4% | Elevated | 38,905 |
| #70 | Groton | Connecticut | 49.83 ppbAverage of 128 samples | 2012–2019 | 80.00 ppb | 62.3% | Elevated | 30,200 |
| #71 | Muncie | Indiana | 49.53 ppbAverage of 231 samples | 2012–2019 | 80.00 ppb | 61.9% | Elevated | 74,030 |
| #72 | Middletown | Connecticut | 49.43 ppbAverage of 182 samples | 2012–2019 | 80.00 ppb | 61.8% | Elevated | 41,019 |
| #73 | Bloomington | Indiana | 49.37 ppbAverage of 343 samples | 2012–2019 | 80.00 ppb | 61.7% | Elevated | 83,000 |
| #74 | Kodiak | Alaska | 49.34 ppbAverage of 32 samples | 2012–2019 | 80.00 ppb | 61.7% | Elevated | 9,547 |
| #75 | Waterbury | Connecticut | 49.26 ppbAverage of 255 samples | 2012–2019 | 80.00 ppb | 61.6% | Elevated | 107,271 |
| #76 | Frederick | Maryland | 49.12 ppbAverage of 266 samples | 2012–2019 | 80.00 ppb | 61.4% | Elevated | 54,000 |
| #77 | New Haven | Connecticut | 48.97 ppbAverage of 400 samples | 2012–2019 | 80.00 ppb | 61.2% | Elevated | 418,900 |
| #78 | Prichard | Alabama | 48.93 ppbAverage of 120 samples | 2012–2019 | 80.00 ppb | 61.2% | Elevated | 29,190 |
| #79 | Topeka | Kansas | 48.88 ppbAverage of 252 samples | 2012–2019 | 80.00 ppb | 61.1% | Elevated | 125,963 |
| #80 | Stamford | Connecticut | 48.91 ppbAverage of 254 samples | 2012–2019 | 80.00 ppb | 61.1% | Elevated | 119,214 |
| #81 | Rogers | Arkansas | 48.84 ppbAverage of 225 samples | 2012–2019 | 80.00 ppb | 61.1% | Elevated | 81,443 |
| #82 | Ketchikan | Alaska | 48.80 ppbAverage of 75 samples | 2012–2019 | 80.00 ppb | 61.0% | Elevated | 8,937 |
| #83 | Baltimore | Maryland | 48.45 ppbAverage of 732 samples | 2012–2019 | 80.00 ppb | 60.6% | Elevated | 1,600,000 |
| #84 | Greensboro | North Carolina | 48.46 ppbAverage of 407 samples | 2012–2019 | 80.00 ppb | 60.6% | Elevated | 319,588 |
| #85 | Hopkinsville | Kentucky | 48.48 ppbAverage of 129 samples | 2012–2019 | 80.00 ppb | 60.6% | Elevated | 41,350 |
| #86 | Inglewood | California | 48.22 ppbAverage of 227 samples | 2012–2019 | 80.00 ppb | 60.3% | Elevated | 80,824 |
| #87 | Scottsdale | Arizona | 48.18 ppbAverage of 268 samples | 2012–2019 | 80.00 ppb | 60.2% | Elevated | 241,361 |
| #88 | Fayetteville | Arkansas | 48.19 ppbAverage of 220 samples | 2012–2019 | 80.00 ppb | 60.2% | Elevated | 116,398 |
| #89 | Santa Cruz | California | 48.07 ppbAverage of 472 samples | 2012–2019 | 80.00 ppb | 60.1% | Elevated | 94,626 |
| #90 | Jacksonville | Arkansas | 48.04 ppbAverage of 129 samples | 2012–2019 | 80.00 ppb | 60.1% | Elevated | 32,875 |
| #91 | North Port | Florida | 48.00 ppbAverage of 132 samples | 2012–2019 | 80.00 ppb | 60.0% | Elevated | 61,163 |
| #92 | West Sacramento | California | 47.97 ppbAverage of 29 samples | 2012–2019 | 80.00 ppb | 60.0% | Elevated | 53,355 |
| #93 | Wellington | Florida | 47.93 ppbAverage of 142 samples | 2012–2019 | 80.00 ppb | 59.9% | Elevated | 56,475 |
| #94 | Fort Lauderdale | Florida | 47.81 ppbAverage of 183 samples | 2012–2019 | 80.00 ppb | 59.8% | Elevated | 185,163 |
| #95 | Bartlett | Illinois | 47.84 ppbAverage of 120 samples | 2012–2019 | 80.00 ppb | 59.8% | Elevated | 41,500 |
| #96 | Mountain View | California | 47.73 ppbAverage of 252 samples | 2012–2019 | 80.00 ppb | 59.7% | Elevated | 81,501 |
| #97 | Conway | Arkansas | 47.76 ppbAverage of 236 samples | 2012–2019 | 80.00 ppb | 59.7% | Elevated | 64,008 |
| #98 | Ottumwa | Iowa | 47.58 ppbAverage of 24 samples | 2012–2019 | 80.00 ppb | 59.5% | Elevated | 25,529 |
| #99 | Indianapolis | Indiana | 47.50 ppbAverage of 517 samples | 2012–2019 | 80.00 ppb | 59.4% | Elevated | 880,345 |
| #100 | Winston-Salem | North Carolina | 47.49 ppbAverage of 381 samples | 2012–2019 | 80.00 ppb | 59.4% | Elevated | 391,900 |
Standard carbon filters very effective for THMs. Pitchers, faucet-mount, or whole-house.
Effective but carbon pre-filter does most THM removal.
THMs are volatile and can be reduced by aeration, but not a primary treatment.
THMs are chemicals formed when chlorine disinfectant reacts with natural organic matter in water. The main ones are chloroform, bromoform, dibromochloromethane, and bromodichloromethane.
THMs are volatile and can be inhaled during showering and bathing. Whole-house carbon filtration addresses this exposure route.
Chlorine prevents deadly waterborne diseases. The risk from THMs is much lower than the risk from untreated water. Filtration at point of use is the solution.