high Risk

Top 100 Cities with Highest Total Trihalomethanes (TTHMs) Levels

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.

EPA Limit (MCL)

80 ppb

Health Goal (MCLG)

0 ppb

Cities Above 50% of Limit

Cities Exceeding Limit

National Statistics for Total Trihalomethanes

Cities Tested

762

Average Level

17.59 ppb

Highest Level

59.87 ppb

in Carrollton, GA

People Affected (>50% of limit)

6.0M

Health Effects of Total Trihalomethanes

Children

Potential developmental effects
Lifetime cancer risk from early exposure

Adults

Increased bladder cancer risk
Possible colon and rectal cancer risk
Liver and kidney effects
Central nervous system effects at high levels

Vulnerable Populations: Pregnant women may face increased risk of miscarriage and birth defects with high THM exposure, though research is ongoing.

Top 100 Cities by Total Trihalomethanes Level

Ranked by percentage of EPA limit. Click any city for full water quality report.

Rank	City	State	Level	EPA Limit	% of Limit	Status	Population
#1	Tucson	Arizona	59.86 ppb	80.00 ppb	74.8%	Elevated	545,677
#2	Carrollton	Georgia	59.87 ppb	80.00 ppb	74.8%	Elevated	26,337
#3	Lancaster	California	59.68 ppb	80.00 ppb	74.6%	Elevated	171,042
#4	Peachtree City	Georgia	58.91 ppb	80.00 ppb	73.6%	Elevated	38,802
#5	Blackfoot	Idaho	58.64 ppb	80.00 ppb	73.3%	Elevated	10,311
#6	Cape Coral	Florida	58.15 ppb	80.00 ppb	72.7%	Elevated	190,445
#7	Largo	Florida	58.10 ppb	80.00 ppb	72.6%	Elevated	80,565
#8	Redlands	California	58.04 ppb	80.00 ppb	72.5%	Elevated	68,132
#9	Alexandria	Louisiana	58.02 ppb	80.00 ppb	72.5%	Elevated	46,654
#10	Antioch	California	57.84 ppb	80.00 ppb	72.3%	Elevated	120,083
#11	Woodland	California	57.28 ppb	80.00 ppb	71.6%	Elevated	65,033
#12	Hanover Park	Illinois	56.15 ppb	80.00 ppb	70.2%	Elevated	41,216
#13	Peachtree Corners	Georgia	55.62 ppb	80.00 ppb	69.5%	Elevated	42,595
#14	National City	California	54.87 ppb	80.00 ppb	68.6%	Elevated	58,660
#15	Aurora	Colorado	54.55 ppb	80.00 ppb	68.2%	Elevated	386,506
#16	Hammond	Indiana	54.31 ppb	80.00 ppb	67.9%	Elevated	76,263
#17	Kenai	Alaska	54.27 ppb	80.00 ppb	67.8%	Elevated	8,065
#18	Garden Grove	California	53.98 ppb	80.00 ppb	67.5%	Elevated	176,920
#19	Moreno Valley	California	53.43 ppb	80.00 ppb	66.8%	Elevated	204,716
#20	Germantown	Maryland	53.41 ppb	80.00 ppb	66.8%	Elevated	95,954
#21	Evansville	Indiana	53.06 ppb	80.00 ppb	66.3%	Elevated	118,111
#22	San Marcos	California	52.34 ppb	80.00 ppb	65.4%	Elevated	100,051
#23	South Portland	Maine	52.12 ppb	80.00 ppb	65.1%	Elevated	24,490
#24	Fort Dodge	Iowa	51.92 ppb	80.00 ppb	64.9%	Elevated	21,031
#25	Topeka	Kansas	51.75 ppb	80.00 ppb	64.7%	Elevated	123,414
#26	El Mirage	Arizona	51.67 ppb	80.00 ppb	64.6%	Elevated	32,910
#27	Deltona	Florida	49.93 ppb	80.00 ppb	62.4%	Elevated	95,468
#28	Pooler	Georgia	49.50 ppb	80.00 ppb	61.9%	Elevated	23,913
#29	Safety Harbor	Florida	49.51 ppb	80.00 ppb	61.9%	Elevated	12,419
#30	Hagerstown	Maryland	49.48 ppb	80.00 ppb	61.8%	Elevated	42,034
#31	Mount Prospect	Illinois	49.27 ppb	80.00 ppb	61.6%	Elevated	57,546
#32	Juneau	Alaska	47.94 ppb	80.00 ppb	59.9%	Elevated	31,466
#33	Kaneohe	Hawaii	47.53 ppb	80.00 ppb	59.4%	Elevated	32,542
#34	Westminster	Colorado	47.11 ppb	80.00 ppb	58.9%	Elevated	116,011
#35	Cabot	Arkansas	47.01 ppb	80.00 ppb	58.8%	Elevated	24,877
#36	Cerritos	California	46.91 ppb	80.00 ppb	58.6%	Elevated	46,952
#37	Manteca	California	45.71 ppb	80.00 ppb	57.1%	Elevated	82,653
#38	Oswego	Illinois	45.30 ppb	80.00 ppb	56.6%	Elevated	32,956
#39	Hoover	Alabama	45.18 ppb	80.00 ppb	56.5%	Elevated	90,476
#40	San Jose	California	44.82 ppb	80.00 ppb	56.0%	Elevated	1,012,356
#41	Lenexa	Kansas	44.62 ppb	80.00 ppb	55.8%	Elevated	56,572
#42	Englewood	Colorado	44.53 ppb	80.00 ppb	55.7%	Elevated	37,600
#43	Nogales	Arizona	44.50 ppb	80.00 ppb	55.6%	Elevated	22,856
#44	Melbourne	Florida	44.35 ppb	80.00 ppb	55.4%	Elevated	88,368
#45	Scottsdale	Arizona	44.15 ppb	80.00 ppb	55.2%	Elevated	244,541
#46	Baton Rouge	Louisiana	43.62 ppb	80.00 ppb	54.5%	Elevated	224,800
#47	Danbury	Connecticut	43.03 ppb	80.00 ppb	53.8%	Elevated	90,841
#48	DeKalb	Illinois	42.96 ppb	80.00 ppb	53.7%	Elevated	46,012
#49	Honolulu	Hawaii	42.52 ppb	80.00 ppb	53.2%	Elevated	343,284
#50	Lafayette	Colorado	41.58 ppb	80.00 ppb	52.0%	Elevated	31,100
#51	Parkland	Florida	41.39 ppb	80.00 ppb	51.7%	Elevated	39,147
#52	Ammon	Idaho	40.41 ppb	80.00 ppb	50.5%	Elevated	22,275
#53	Pleasanton	California	40.37 ppb	80.00 ppb	50.5%	Elevated	83,447
#54	Belleville	Illinois	40.40 ppb	80.00 ppb	50.5%	Elevated	39,285
#55	Indio	California	40.43 ppb	80.00 ppb	50.5%	Elevated	96,735
#56	Seaford	Delaware	39.63 ppb	80.00 ppb	49.5%	Within Limit	10,965
#57	Encinitas	California	39.21 ppb	80.00 ppb	49.0%	Within Limit	66,157
#58	Sulphur	Louisiana	38.66 ppb	80.00 ppb	48.3%	Within Limit	15,987
#59	Sarasota	Florida	38.52 ppb	80.00 ppb	48.2%	Within Limit	58,717
#60	Augusta	Georgia	37.80 ppb	80.00 ppb	47.3%	Within Limit	197,376
#61	Miramar	Florida	37.65 ppb	80.00 ppb	47.1%	Within Limit	136,668
#62	Margate	Florida	37.66 ppb	80.00 ppb	47.1%	Within Limit	54,305
#63	Wheat Ridge	Colorado	37.69 ppb	80.00 ppb	47.1%	Within Limit	33,790
#64	Jacksonville	Florida	37.28 ppb	80.00 ppb	46.6%	Within Limit	952,495
#65	Cedar Rapids	Iowa	36.49 ppb	80.00 ppb	45.6%	Within Limit	137,324
#66	Harvey	Louisiana	36.05 ppb	80.00 ppb	45.1%	Within Limit	17,430
#67	Garden City	Idaho	35.97 ppb	80.00 ppb	45.0%	Within Limit	10,792
#68	Baldwin Park	California	35.94 ppb	80.00 ppb	44.9%	Within Limit	74,178
#69	Paradise Valley	Arizona	35.88 ppb	80.00 ppb	44.9%	Within Limit	17,473
#70	North Miami	Florida	35.94 ppb	80.00 ppb	44.9%	Within Limit	65,145
#71	Jeffersonville	Indiana	35.76 ppb	80.00 ppb	44.7%	Within Limit	47,390
#72	Coral Gables	Florida	35.72 ppb	80.00 ppb	44.7%	Within Limit	50,118
#73	Sunnyvale	California	35.76 ppb	80.00 ppb	44.7%	Within Limit	160,723
#74	Shenandoah	Louisiana	35.69 ppb	80.00 ppb	44.6%	Within Limit	16,946
#75	Houma	Louisiana	35.65 ppb	80.00 ppb	44.6%	Within Limit	37,535
#76	Bettendorf	Iowa	35.61 ppb	80.00 ppb	44.5%	Within Limit	34,831
#77	Hoffman Estates	Illinois	35.64 ppb	80.00 ppb	44.5%	Within Limit	47,459
#78	Covina	California	35.55 ppb	80.00 ppb	44.4%	Within Limit	48,616
#79	South Laurel	Maryland	35.50 ppb	80.00 ppb	44.4%	Within Limit	30,059
#80	Gardena	California	35.26 ppb	80.00 ppb	44.1%	Within Limit	57,874
#81	Titusville	Florida	35.22 ppb	80.00 ppb	44.0%	Within Limit	51,951
#82	Olathe	Kansas	35.05 ppb	80.00 ppb	43.8%	Within Limit	143,182
#83	Beverly	Massachusetts	34.79 ppb	80.00 ppb	43.5%	Within Limit	40,115
#84	Chubbuck	Idaho	34.69 ppb	80.00 ppb	43.4%	Within Limit	16,674
#85	Sugar Hill	Georgia	34.76 ppb	80.00 ppb	43.4%	Within Limit	29,449
#86	Covington	Kentucky	34.63 ppb	80.00 ppb	43.3%	Within Limit	38,552
#87	Buena Park	California	34.33 ppb	80.00 ppb	42.9%	Within Limit	81,383
#88	Clearwater	Florida	34.35 ppb	80.00 ppb	42.9%	Within Limit	114,409
#89	Palm Bay	Florida	34.33 ppb	80.00 ppb	42.9%	Within Limit	124,351
#90	Evans	Colorado	34.23 ppb	80.00 ppb	42.8%	Within Limit	22,513
#91	Fresno	California	34.27 ppb	80.00 ppb	42.8%	Within Limit	538,556
#92	Fairbanks	Alaska	34.07 ppb	80.00 ppb	42.6%	Within Limit	29,207
#93	Berwyn	Illinois	34.02 ppb	80.00 ppb	42.5%	Within Limit	50,288
#94	Bradenton	Florida	33.79 ppb	80.00 ppb	42.2%	Within Limit	54,398
#95	Athens	Alabama	33.48 ppb	80.00 ppb	41.9%	Within Limit	26,489
#96	San Francisco	California	33.45 ppb	80.00 ppb	41.8%	Within Limit	876,036
#97	Kenner	Louisiana	33.40 ppb	80.00 ppb	41.8%	Within Limit	66,094
#98	Leavenworth	Kansas	33.46 ppb	80.00 ppb	41.8%	Within Limit	38,532
#99	Enfield	Connecticut	33.35 ppb	80.00 ppb	41.7%	Within Limit	38,265
#100	Medford	Massachusetts	33.24 ppb	80.00 ppb	41.6%	Within Limit	65,507

Common Sources of Total Trihalomethanes

Formed when chlorine reacts with organic matter in water
Higher in surface water systems with more organic material
Increases with water age in distribution system
Warmer temperatures increase formation

How to Remove Total Trihalomethanes from Drinking Water

Activated Carbon

95-99% effective

Standard carbon filters very effective for THMs. Pitchers, faucet-mount, or whole-house.

Reverse Osmosis

90-95% effective

Effective but carbon pre-filter does most THM removal.

Aeration

50-70% effective

THMs are volatile and can be reduced by aeration, but not a primary treatment.

View Filter Recommendations

Frequently Asked Questions About Total Trihalomethanes

What are trihalomethanes?

THMs are chemicals formed when chlorine disinfectant reacts with natural organic matter in water. The main ones are chloroform, bromoform, dibromochloromethane, and bromodichloromethane.

Are THMs dangerous to inhale in the shower?

THMs are volatile and can be inhaled during showering and bathing. Whole-house carbon filtration addresses this exposure route.

Why not just stop using chlorine?

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.

Browse Other Contaminants

Lead Arsenic PFAS (Forever Chemicals)Nitrates Chromium-6 (Hexavalent Chromium)Fluoride Chlorine Copper View All Contaminants

Back to All Contaminant Rankings

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Rank

City

State

Level

EPA Limit

% of Limit

Status

Population

Tucson

Arizona

59.86 ppb

80.00 ppb

74.8%

Elevated

545,677

Carrollton

Georgia

59.87 ppb

80.00 ppb

74.8%

Elevated

26,337

Lancaster

California

59.68 ppb

80.00 ppb

74.6%

Elevated

171,042

Peachtree City

Georgia

58.91 ppb

80.00 ppb

73.6%

Elevated

38,802

Blackfoot

Idaho

58.64 ppb

80.00 ppb

73.3%

Elevated

10,311

Cape Coral

Florida

58.15 ppb

80.00 ppb

72.7%

Elevated

190,445

Largo

Florida

58.10 ppb

80.00 ppb

72.6%

Elevated

80,565

Redlands

California

58.04 ppb

80.00 ppb

72.5%

Elevated

68,132

Alexandria

Louisiana

58.02 ppb

80.00 ppb

72.5%

Elevated

46,654

#10

Antioch

California

57.84 ppb

80.00 ppb

72.3%

Elevated

120,083

#11

Woodland

California

57.28 ppb

80.00 ppb

71.6%

Elevated

65,033

#12

Hanover Park

Illinois

56.15 ppb

80.00 ppb

70.2%

Elevated

41,216

#13

Peachtree Corners

Georgia

55.62 ppb

80.00 ppb

69.5%

Elevated

42,595

#14

National City

California

54.87 ppb

80.00 ppb

68.6%

Elevated

58,660

#15

Aurora

Colorado

54.55 ppb

80.00 ppb

68.2%

Elevated

386,506

#16

Hammond

Indiana

54.31 ppb

80.00 ppb

67.9%

Elevated

76,263

#17

Kenai

Alaska

54.27 ppb

80.00 ppb

67.8%

Elevated

8,065

#18

Garden Grove

California

53.98 ppb

80.00 ppb

67.5%

Elevated

176,920

#19

Moreno Valley

California

53.43 ppb

80.00 ppb

66.8%

Elevated

204,716

#20

Germantown

Maryland

53.41 ppb

80.00 ppb

66.8%

Elevated

95,954

#21

Evansville

Indiana

53.06 ppb

80.00 ppb

66.3%

Elevated

118,111

#22

San Marcos

California

52.34 ppb

80.00 ppb

65.4%

Elevated

100,051

#23

South Portland

Maine

52.12 ppb

80.00 ppb

65.1%

Elevated

24,490

#24

Fort Dodge

Iowa

51.92 ppb

80.00 ppb

64.9%

Elevated

21,031

#25

Topeka

Kansas

51.75 ppb

80.00 ppb

64.7%

Elevated

123,414

#26

El Mirage

Arizona

51.67 ppb

80.00 ppb

64.6%

Elevated

32,910

#27

Deltona

Florida

49.93 ppb

80.00 ppb

62.4%

Elevated

95,468

#28

Pooler

Georgia

49.50 ppb

80.00 ppb

61.9%

Elevated

23,913

#29

Safety Harbor

Florida

49.51 ppb

80.00 ppb

61.9%

Elevated

12,419

#30

Hagerstown

Maryland

49.48 ppb

80.00 ppb

61.8%

Elevated

42,034

#31

Mount Prospect

Illinois

49.27 ppb

80.00 ppb

61.6%

Elevated

57,546

#32

Juneau

Alaska

47.94 ppb

80.00 ppb

59.9%

Elevated

31,466

#33

Kaneohe

Hawaii

47.53 ppb

80.00 ppb

59.4%

Elevated

32,542

#34

Westminster

Colorado

47.11 ppb

80.00 ppb

58.9%

Elevated

116,011

#35

Cabot

Arkansas

47.01 ppb

80.00 ppb

58.8%

Elevated

24,877

#36

Cerritos

California

46.91 ppb

80.00 ppb

58.6%

Elevated

46,952

#37

Manteca

California

45.71 ppb

80.00 ppb

57.1%

Elevated

82,653

#38

Oswego

Illinois

45.30 ppb

80.00 ppb

56.6%

Elevated

32,956

#39

Hoover

Alabama

45.18 ppb

80.00 ppb

56.5%

Elevated

90,476

#40

San Jose

California

44.82 ppb

80.00 ppb

56.0%

Elevated

1,012,356

#41

Lenexa

Kansas

44.62 ppb

80.00 ppb

55.8%

Elevated

56,572

#42

Englewood

Colorado

44.53 ppb

80.00 ppb

55.7%

Elevated

37,600

#43

Nogales

Arizona

44.50 ppb

80.00 ppb

55.6%

Elevated

22,856

#44

Melbourne

Florida

44.35 ppb

80.00 ppb

55.4%

Elevated

88,368

#45

Scottsdale

Arizona

44.15 ppb

80.00 ppb

55.2%

Elevated

244,541

#46

Baton Rouge

Louisiana

43.62 ppb

80.00 ppb

54.5%

Elevated

224,800

#47

Danbury

Connecticut

43.03 ppb

80.00 ppb

53.8%

Elevated

90,841

#48

DeKalb

Illinois

42.96 ppb

80.00 ppb

53.7%

Elevated

46,012

#49

Honolulu

Hawaii

42.52 ppb

80.00 ppb

53.2%

Elevated

343,284

#50

Lafayette

Colorado

41.58 ppb

80.00 ppb

52.0%

Elevated

31,100

#51

Parkland

Florida

41.39 ppb

80.00 ppb

51.7%

Elevated

39,147

#52

Ammon

Idaho

40.41 ppb

80.00 ppb

50.5%

Elevated

22,275

#53

Pleasanton

California

40.37 ppb

80.00 ppb

50.5%

Elevated

83,447

#54

Belleville

Illinois

40.40 ppb

80.00 ppb

50.5%

Elevated

39,285

#55

Indio

California

40.43 ppb

80.00 ppb

50.5%

Elevated

96,735

#56

Seaford

Delaware

39.63 ppb

80.00 ppb

49.5%

Within Limit

10,965

#57

Encinitas

California

39.21 ppb

80.00 ppb

49.0%

Within Limit

66,157

#58

Sulphur

Louisiana

38.66 ppb

80.00 ppb

48.3%

Within Limit

15,987

#59

Sarasota

Florida

38.52 ppb

80.00 ppb

48.2%

Within Limit

58,717

#60

Augusta

Georgia

37.80 ppb

80.00 ppb

47.3%

Within Limit

197,376

#61

Miramar

Florida

37.65 ppb

80.00 ppb

47.1%

Within Limit

136,668

#62

Margate

Florida

37.66 ppb

80.00 ppb

47.1%

Within Limit

54,305

#63

Wheat Ridge

Colorado

37.69 ppb

80.00 ppb

47.1%

Within Limit

33,790

#64

Jacksonville

Florida

37.28 ppb

80.00 ppb

46.6%

Within Limit

952,495

#65

Cedar Rapids

Iowa

36.49 ppb

80.00 ppb

45.6%

Within Limit

137,324

#66

Harvey

Louisiana

36.05 ppb

80.00 ppb

45.1%

Within Limit

17,430

#67

Garden City

Idaho

35.97 ppb

80.00 ppb

45.0%

Within Limit

10,792

#68

Baldwin Park

California

35.94 ppb

80.00 ppb

44.9%

Within Limit

74,178

#69

Paradise Valley

Arizona

35.88 ppb

80.00 ppb

44.9%

Within Limit

17,473

#70

North Miami

Florida

35.94 ppb

80.00 ppb

44.9%

Within Limit

65,145

#71

Jeffersonville

Indiana

35.76 ppb

80.00 ppb

44.7%

Within Limit

47,390

#72

Coral Gables

Florida

35.72 ppb

80.00 ppb

44.7%

Within Limit

50,118

#73

Sunnyvale

California

35.76 ppb

80.00 ppb

44.7%

Within Limit

160,723

#74

Shenandoah

Louisiana

35.69 ppb

80.00 ppb

44.6%

Within Limit

16,946

#75

Houma

Louisiana

35.65 ppb

80.00 ppb

44.6%

Within Limit

37,535

#76

Bettendorf

Iowa

35.61 ppb

80.00 ppb

44.5%

Within Limit

34,831

#77

Hoffman Estates

Illinois

35.64 ppb

80.00 ppb

44.5%

Within Limit

47,459

#78

Covina

California

35.55 ppb

80.00 ppb

44.4%

Within Limit

48,616

#79

South Laurel

Maryland

35.50 ppb

80.00 ppb

44.4%

Within Limit

30,059

#80

Gardena

California

35.26 ppb

80.00 ppb

44.1%

Within Limit

57,874

#81

Titusville

Florida

35.22 ppb

80.00 ppb

44.0%

Within Limit

51,951

#82

Olathe

Kansas

35.05 ppb

80.00 ppb

43.8%

Within Limit

143,182

#83

Beverly

Massachusetts

34.79 ppb

80.00 ppb

43.5%

Within Limit

40,115

#84

Chubbuck

Idaho

34.69 ppb

80.00 ppb

43.4%

Within Limit

16,674

#85

Sugar Hill

Georgia

34.76 ppb

80.00 ppb

43.4%

Within Limit

29,449

#86

Covington

Kentucky

34.63 ppb

80.00 ppb

43.3%

Within Limit

38,552

#87

Buena Park

California

34.33 ppb

80.00 ppb

42.9%

Within Limit

81,383

#88

Clearwater

Florida

34.35 ppb

80.00 ppb

42.9%

Within Limit

114,409

#89

Palm Bay

Florida

34.33 ppb

80.00 ppb

42.9%

Within Limit

124,351

#90

Evans

Colorado

34.23 ppb

80.00 ppb

42.8%

Within Limit

22,513

#91

Fresno

California

34.27 ppb

80.00 ppb

42.8%

Within Limit

538,556

#92

Fairbanks

Alaska

34.07 ppb

80.00 ppb

42.6%

Within Limit

29,207

#93

Berwyn

Illinois

34.02 ppb

80.00 ppb

42.5%

Within Limit

50,288

#94

Bradenton

Florida

33.79 ppb

80.00 ppb

42.2%

Within Limit

54,398

#95

Athens

Alabama

33.48 ppb

80.00 ppb

41.9%

Within Limit

26,489

#96

San Francisco

California

33.45 ppb

80.00 ppb

41.8%

Within Limit

876,036

#97

Kenner

Louisiana

33.40 ppb

80.00 ppb

41.8%

Within Limit

66,094

#98

Leavenworth

Kansas

33.46 ppb

80.00 ppb

41.8%

Within Limit

38,532

#99

Enfield

Connecticut

33.35 ppb

80.00 ppb

41.7%

Within Limit

38,265

#100

Medford

Massachusetts

33.24 ppb

80.00 ppb

41.6%

Within Limit

65,507