EWG rated big city (population over 250,000) water utilities based on three factors: the total number of chemicals detected since 2004; the percentage of chemicals found of those tested; and the highest average level for an individual pollutant, relative to legal limits or national average amounts, including for the most common pollutants (disinfection byproducts, nitrate and arsenic). [read more on rating methodology]

RANK	WATER UTILITY	CHEMICALS FOUND	TOP CONCERN ***	NATIONAL POLLUTANTS
1	Arlington, TX (Arlington Water Utilities serves 290,000 people)	7 *	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 6.7 ppb HAAs: 2.3 ppb nitrate: 0.4 ppm arsenic: 0.0 ppb
2	Providence, RI (Providence Water serves 295,700 people)	4 *	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 22.5 ppb HAAs: 16.4 ppb nitrate: 0.0 ppm arsenic: 0.0 ppb
3	Fort Worth, TX (Fort Worth Water Department serves 501,954 people)	7 *	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 22.6 ppb HAAs: 11.9 ppb nitrate: 0.2 ppm arsenic: 0.0 ppb
4	Charleston, SC (Charleston Water System serves 327,620 people)	5 *	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid.	THMs: 23.7 ppb HAAs: 21.3 ppb nitrate: 0.4 ppm arsenic: 0.0 ppb
5	Boston, MA (Massachusetts Water Resources Authority serves 2,000,000 people)	14 *	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid. **	THMs: 3.7 ppb HAAs: 3.7 ppb nitrate: 0.1 ppm arsenic: 0.0 ppb
6	Honolulu, HI (Board of Water Supply (Honolulu/Windward/Pearl Harbor) serves 661,004 people)	8 *	DieldrinDieldrin is a banned insecticide that is persistent and bioaccumulative, and was historically used on corn, cotton and citrus; it also forms in the environment as a breakdown product of the pesticide aldrin.	THMs: 0.8 ppb HAAs:<0.1 ppb nitrate: 0.3 ppm arsenic: 0.0 ppb
7	Austin, TX (Austin Water Utility serves 669,693 people)	5 *	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 30.6 ppb HAAs: 14.8 ppb nitrate: 0.3 ppm arsenic: 0.0 ppb
8	Fairfax County, VA (Fairfax Water serves 823,216 people)	8 *	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform. **	THMs: 23.0 ppb HAAs: 16.0 ppb nitrate: 1.0 ppm arsenic: 0.0 ppb
9	St. Louis, MO (City of St. Louis Water Division serves 370,000 people)	7	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid. **	THMs: 15.4 ppb HAAs: 19.2 ppb nitrate: 2.7 ppm arsenic: 0.0 ppb
10	Minneapolis, MN (City of Minneapolis Water Department serves 382,618 people)	6 *	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid. **	THMs: 29.6 ppb HAAs: 27.3 ppb nitrate: 0.4 ppm arsenic: 0.0 ppb
11	Richmond, VA (Henrico County Public Utilities serves 289,000 people)	9 *	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid.	THMs: 15.0 ppb HAAs: 21.5 ppb nitrate: 0.3 ppm arsenic: 0.0 ppb
12	Dallas, TX (Dallas Water Utilities serves 1,188,580 people)	9 *	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 32.1 ppb HAAs: 24.0 ppb nitrate: 0.3 ppm arsenic: 0.0 ppb
13	New York, NY (New York City Department of Environmental Protection- Jamaica serves 518,000 people)	4 *	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid.	THMs: 30.8 ppb HAAs: 32.0 ppb nitrate: n/a arsenic: 0.0 ppb
14	Oklahoma City, OK (Oklahoma City Water Utilities Trust serves 598,000 people)	5	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 40.0 ppb HAAs: 23.5 ppb nitrate: 0.1 ppm arsenic: 2.8 ppb
15	Buffalo, NY (Buffalo Water Authority serves 345,974 people)	9 *	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 32.3 ppb HAAs: 18.9 ppb nitrate: 0.2 ppm arsenic: 0.0 ppb
16	Cinncinnati, OH (Greater Cincinnati Water Works serves 775,000 people)	8 *	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 33.0 ppb HAAs: 8.1 ppb nitrate: 1.4 ppm arsenic: 0.0 ppb
17	St. Paul, MN (Saint Paul Regional Water Services serves 414,735 people)	11 *	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 31.1 ppb HAAs: 18.2 ppb nitrate: 0.3 ppm arsenic: 0.0 ppb
18	Sacramento, CA (City of Sacramento Department of Utilities serves 407,018 people)	14 *	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid. **	THMs: 1.4 ppb HAAs: 17.7 ppb nitrate: 1.3 ppm arsenic: 2.9 ppb
19	Milwaukee, WI (Milwaukee Water Works serves 647,290 people)	14 *	BromateBromate is a carcinogenic disinfection byproduct of ozonation formed when source waters contain high levels of natural bromide; it can also form following water treatment with chlorine dioxide or hypochlorite.	THMs: 5.4 ppb HAAs: 1.1 ppb nitrate: 0.3 ppm arsenic: 0.0 ppb
20	Odessa, FL (St. Petersburg Water Resources Department serves 300,075 people)	13 *	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid.	THMs: 16.4 ppb HAAs: 14.0 ppb nitrate: 0.2 ppm arsenic: 0.0 ppb
21	Bridgeport, CT (Aquarion Water Company serves 341,421 people)	6	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid. **	THMs: 40.0 ppb HAAs: 31.0 ppb nitrate: 1.2 ppm arsenic: 0.0 ppb
22	Louisville, KY (Louisville Water Company serves 836,926 people)	12	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 22.8 ppb HAAs: 13.9 ppb nitrate: 1.0 ppm arsenic: 0.0 ppb
23	Hartfort, CT (Metropolitan District Commission serves 388,700 people)	9	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform. **	THMs: 33.2 ppb HAAs: 23.5 ppb nitrate: 0.1 ppm arsenic: 0.0 ppb
24	Springfield, MA (Springfield Water & Sewer Commission serves 250,000 people)	4 *	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid.	THMs: 50.8 ppb HAAs: 38.4 ppb nitrate: 0.1 ppm arsenic: 0.0 ppb
25	Seattle, WA (Seattle Public Utilities serves 629,000 people)	9 *	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid.	THMs: 31.5 ppb HAAs: 25.2 ppb nitrate: 0.1 ppm arsenic: 0.0 ppb
26	Greensboro, NC (City of Greensboro Department of Water Resources serves 250,000 people)	5 *	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid.	THMs: 42.6 ppb HAAs: 36.6 ppb nitrate: 0.4 ppm arsenic: 0.0 ppb
27	Newport News, VA (Newport News Water Works serves 406,000 people)	10 *	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid.	THMs: 24.6 ppb HAAs: 23.5 ppb nitrate: 0.0 ppm arsenic: 0.0 ppb
28	Winston-Salem, NC (Winston-Salem/Forsyth County Utility Commission serves 286,028 people)	10 *	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid.	THMs: 29.4 ppb HAAs: 27.9 ppb nitrate: 1.9 ppm arsenic: 0.0 ppb
29	San Antonio, TX (San Antonio Water System serves 1,219,113 people)	20 *	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid. **	THMs: 15.4 ppb HAAs: 11.6 ppb nitrate: 1.7 ppm arsenic: 0.0 ppb
30	Kent, OH (Akron Public Utilities Bureau serves 320,000 people)	6 *	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 45.8 ppb HAAs: 34.2 ppb nitrate: 0.6 ppm arsenic: 0.0 ppb
31	Birmingham, AL (Birmingham Water Works & Sewer Board serves 585,000 people)	10 *	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 30.5 ppb HAAs: 23.2 ppb nitrate: 0.3 ppm arsenic: 0.0 ppb
32	Pittsburgh, PA (Pennsylvania American Water Company- Pittsburgh serves 660,000 people)	4	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 54.0 ppb HAAs: 13.1 ppb nitrate: 0.7 ppm arsenic: 0.0 ppb
33	San Francisco, CA (San Francisco Public Utilities Commission serves 800,000 people)	14 *	NitrateNitrate enters drinking water sources from fertilizer runoff, leaching septic tanks, and erosion of natural deposits; it is also emitted by chemical, petrochemical and metal-finishing industries.	THMs: 8.6 ppb HAAs: 24.9 ppb nitrate: 4.2 ppm arsenic: 0.0 ppb
34	Chicago, IL (Chicago Department of Water Management serves 2,896,016 people)	15 *	Combined Radium (-226 & -228)Radium is a radioactive element usually found around uranium deposits.	THMs: 16.1 ppb HAAs: 8.2 ppb nitrate: 0.3 ppm arsenic: 0.0 ppb
35	Toledo, OH (City of Toledo Division of Water serves 380,000 people)	10 *	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 35.7 ppb HAAs: 11.9 ppb nitrate: 1.2 ppm arsenic: 0.0 ppb
36	Oakland, CA (East Bay Municipal Utility District serves 1,300,000 people)	14	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform. **	THMs: 28.0 ppb HAAs: 16.0 ppb nitrate: 0.0 ppm arsenic: 0.1 ppb
37	New Haven, CT (South Central Connecticut Regional Water Authority serves 389,300 people)	10	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform. **	THMs: 37.0 ppb HAAs: 26.0 ppb nitrate: 1.4 ppm arsenic: 0.0 ppb
38	Manatee County, FL (Manatee County Utilities Department serves 253,263 people)	17 *	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 22.8 ppb HAAs: 14.1 ppb nitrate: 0.2 ppm arsenic: 0.0 ppb
39	Monroe County, NY (Monroe County Water Authority- Shoremont Water Treatment Plant serves 490,000 people)	6	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 53.8 ppb HAAs: 6.0 ppb nitrate: 0.4 ppm arsenic: 0.0 ppb
40	Long Beach, CA (Long Beach Water Department serves 452,905 people)	15 *	Arsenic (total)Arsenic contaminates drinking water due to mining runoff, erosion of natural deposits, emissions from glass and electronics processing and the use of arsenical compounds as wood preservatives and pesticides. **	THMs: 2.6 ppb HAAs: 10.5 ppb nitrate: 0.0 ppm arsenic: 4.2 ppb
41	New York, NY (New York City Department of Environmental Protection- Catskill/Delaware serves 6,552,718 people)	5 *	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid.	THMs: 37.3 ppb HAAs: 42.6 ppb nitrate: 0.2 ppm arsenic: 0.0 ppb
42	Layton, UT (Weber Basin Water Conservancy District serves 298,000 people)	13 *	Thallium (total)Thallium is a highly toxic metal that contaminates the environment due to leaching from ore-processing sites, discharge from electronics, glass, and drug factories and historical use as rodenticide	THMs: 18.2 ppb HAAs: 15.6 ppb nitrate: 0.8 ppm arsenic: 0.0 ppb
43	Fort Wayne, IN (Fort Wayne City Utilities- Three Rivers Filtration Plant serves 250,000 people)	16 *	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 22.8 ppb HAAs: 14.4 ppb nitrate: 1.9 ppm arsenic: 0.0 ppb
44	Corpus Christi, TX (City of Corpus Christi Water Department serves 270,000 people)	13 *	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 38.0 ppb HAAs: 26.5 ppb nitrate: 0.3 ppm arsenic: 0.0 ppb
45	Tacoma, WA (City of Tacoma Water Division serves 305,000 people)	19 *	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid.	THMs: 6.5 ppb HAAs: 20.6 ppb nitrate: 2.5 ppm arsenic: 0.6 ppb
46	Miami, FL (Miami-Dade Water & Sewer Department serves 2,100,000 people)	14 *	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid.	THMs: 18.7 ppb HAAs: 22.4 ppb nitrate: 0.8 ppm arsenic: 0.0 ppb
47	Palm Beach County, CA (Palm Beach County Water Utilities Department serves 416,303 people)	16 *	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid. **	THMs: 24.7 ppb HAAs: 17.8 ppb nitrate: 0.0 ppm arsenic: 0.0 ppb
48	Bryn Mawr, PA (Aqua Pennsylvania Inc. (Aqua) serves 820,000 people)	14	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 31.7 ppb HAAs: 22.3 ppb nitrate: 3.8 ppm arsenic: 0.0 ppb
49	Erie County, NY (Erie County Water Authority serves 402,180 people)	8 *	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 53.7 ppb HAAs: 21.7 ppb nitrate: 0.1 ppm arsenic: 0.0 ppb
50	Plano, TX (City of Plano Utility Operations Department serves 291,144 people)	6 *	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 58.3 ppb HAAs: 22.0 ppb nitrate: 0.1 ppm arsenic: 0.0 ppb
51	Albuquerque, NM (Albuquerque Bernalillo County Water Authority serves 453,000 people)	9 *	Arsenic (total)Arsenic contaminates drinking water due to mining runoff, erosion of natural deposits, emissions from glass and electronics processing and the use of arsenical compounds as wood preservatives and pesticides. **	THMs: 6.2 ppb HAAs: 2.3 ppb nitrate: 0.4 ppm arsenic: 7.0 ppb
52	St. Louis County, MO (Missouri American Water- St. Louis County/ St. Charles County serves 1,049,600 people)	14 *	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid. **	THMs: 12.0 ppb HAAs: 24.8 ppb nitrate: 0.9 ppm arsenic: 0.6 ppb
53	Phoenix, AZ (City of Phoenix Water Services Department serves 1,200,000 people)	13	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 38.5 ppb HAAs: 16.3 ppb nitrate: 1.7 ppm arsenic: 0.0 ppb
54	Stockton, CA (Stockton East Water District serves 250,000 people)	15 *	Arsenic (total)Arsenic contaminates drinking water due to mining runoff, erosion of natural deposits, emissions from glass and electronics processing and the use of arsenical compounds as wood preservatives and pesticides.	THMs: 27.1 ppb HAAs: 8.9 ppb nitrate: 0.6 ppm arsenic: 0.0 ppb
55	New York, NY (New York City Department of Environmental Protection- Croton serves 1,000,000 people)	5 *	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid.	THMs: 46.5 ppb HAAs: 47.9 ppb nitrate: 0.2 ppm arsenic: 0.0 ppb
56	Mobile, AL (Mobile Area Water & Sewer System serves 274,995 people)	13 *	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 72.2 ppb HAAs: 26.2 ppb nitrate: 0.0 ppm arsenic: 0.0 ppb
57	Pinellas County, FL (Pinellas County Utilities serves 426,877 people)	16 *	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 30.1 ppb HAAs: 16.1 ppb nitrate: 0.1 ppm arsenic: 0.0 ppb
58	Los Angeles Suburbs, CA (Metropolitan Water District of Southern California serves 17,000,000 people)	22 *	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 30.8 ppb HAAs: 14.0 ppb nitrate: 0.2 ppm arsenic: 2.3 ppb
59	Portland, OR (Portland Water Bureau serves 539,200 people)	15	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid.	THMs: 20.2 ppb HAAs: 26.1 ppb nitrate: 0.2 ppm arsenic: 0.0 ppb
60	Philadelphia, PA (Philadelphia Water Department serves 1,600,000 people)	12	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 44.6 ppb HAAs: 31.4 ppb nitrate: 2.7 ppm arsenic: 0.0 ppb
61	Santa Ana, CA (City of Santa Ana Public Works serves 293,700 people)	20	NitrateNitrate enters drinking water sources from fertilizer runoff, leaching septic tanks, and erosion of natural deposits; it is also emitted by chemical, petrochemical and metal-finishing industries.	THMs: 15.0 ppb HAAs: 4.2 ppb nitrate: 4.6 ppm arsenic: 1.1 ppb
62	Totowa Borough, NJ (Passaic Valley Water Commission serves 314,900 people)	19 *	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 38.1 ppb HAAs: 26.5 ppb nitrate: 1.7 ppm arsenic: 0.0 ppb
63	Mahwah, NJ (United Water New Jersey serves 773,458 people)	19 *	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid.	THMs: 34.6 ppb HAAs: 26.9 ppb nitrate: 1.5 ppm arsenic: 0.0 ppb
64	Norfolk, VA (Norfolk Department of Utilities serves 755,617 people)	11 *	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 49.5 ppb HAAs: 30.0 ppb nitrate: 0.1 ppm arsenic: 0.0 ppb
65	Hillsborough County, FL (Hillsborough County Water Resource Services- South Hillsborough serves 303,000 people)	18 *	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 27.7 ppb HAAs: 13.4 ppb nitrate: 0.6 ppm arsenic: 0.0 ppb
66	Tucson, AZ (Tucson Water serves 675,000 people)	19 *	Arsenic (total)Arsenic contaminates drinking water due to mining runoff, erosion of natural deposits, emissions from glass and electronics processing and the use of arsenical compounds as wood preservatives and pesticides.	THMs: 5.7 ppb HAAs: 0.2 ppb nitrate: 1.9 ppm arsenic: 0.0 ppb
67	Lexington, KY (Kentucky-American Water serves 354,473 people)	12	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 48.9 ppb HAAs: 26.8 ppb nitrate: 0.2 ppm arsenic: 0.0 ppb
68	Tampa, FL (Tampa Water Department serves 550,000 people)	19 *	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 26.4 ppb HAAs: 16.2 ppb nitrate: 0.2 ppm arsenic: 0.0 ppb
69	Baltimore, MD (Baltimore City Department of Public Works serves 1,600,000 people)	12 *	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid.	THMs: 44.5 ppb HAAs: 42.1 ppb nitrate: 1.8 ppm arsenic: 0.0 ppb
70	Alameda County, CA (Alameda County Water District serves 271,000 people)	27 *	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid.	THMs: 14.2 ppb HAAs: 20.9 ppb nitrate: 1.3 ppm arsenic: 0.0 ppb
71	Tulsa, OK (City of Tulsa Water Supply System serves 471,000 people)	13 *	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 48.4 ppb HAAs: 18.9 ppb nitrate: 0.5 ppm arsenic: 0.0 ppb
72	Cleveland OH (Cleveland Division of Water serves 1,500,000 people)	19 *	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid.	THMs: 22.5 ppb HAAs: 22.3 ppb nitrate: 0.4 ppm arsenic: 0.0 ppb
73	Pittsburgh City, PA (Pittsburgh Water & Sewer Authority serves 250,000 people)	11	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 57.5 ppb HAAs: 15.4 ppb nitrate: 1.2 ppm arsenic: 7.0 ppb
74	Raleigh, NC (City of Raleigh Public Utilities Department serves 409,542 people)	19 *	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 42.2 ppb HAAs: 31.4 ppb nitrate: 0.0 ppm arsenic: 0.0 ppb
75	Columbus, OH (City of Columbus Department of Public Utilities serves 897,213 people)	8 *	PhosphorusPhosphorus is a component of fertilizer and manure, and a common pollutant in municipal wastewater discharges.	THMs: 32.5 ppb HAAs: 27.3 ppb nitrate: 1.6 ppm arsenic: 0.0 ppb
76	Mesa, AZ (City of Mesa Utilities Department serves 350,000 people)	21 *	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 33.3 ppb HAAs: 13.7 ppb nitrate: 1.3 ppm arsenic: 0.0 ppb
77	Charlotte, NC (Charlotte-Mecklenburg Utilities serves 761,830 people)	20 *	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 43.1 ppb HAAs: 17.1 ppb nitrate: 0.0 ppm arsenic: 0.0 ppb
78	Little Rock, AR (Central Arkansas Water serves 323,212 people)	13 *	Dibenz[a,h]anthraceneDibenz[a,h]anthracene a polycyclic aromatic hydrocarbon (PAH) released from the incomplete combustion of fossil fuels.	THMs: 49.8 ppb HAAs: 29.7 ppb nitrate: 0.0 ppm arsenic: 0.0 ppb
79	Anaheim, CA (Anaheim Public Utilities serves 345,556 people)	28 *	Alpha particle activityAlpha particles are a form of radiation released from mining waste pollutants and natural sources.	THMs: 3.2 ppb HAAs: 18.0 ppb nitrate: 3.1 ppm arsenic: 1.7 ppb
80	Salt Lake City, UT (Salt Lake City Department of Public Utilities serves 312,000 people)	24 *	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid.	THMs: 12.2 ppb HAAs: 26.7 ppb nitrate: 1.5 ppm arsenic: 0.0 ppb
81	Orlando, FL (Orlando Utilities Commission serves 414,500 people)	17	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 50.4 ppb HAAs: 20.1 ppb nitrate: 0.0 ppm arsenic: 0.0 ppb
82	Montgomery & Prince George's Counties, MD (Washington Suburban Sanitary Commission serves 1,800,000 people)	22 *	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid.	THMs: 31.8 ppb HAAs: 34.6 ppb nitrate: 1.5 ppm arsenic: 0.0 ppb
83	Los Angeles, CA (Los Angeles Department of Water and Power serves 3,828,700 people)	25 *	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid. **	THMs: 34.4 ppb HAAs: 29.0 ppb nitrate: 1.5 ppm arsenic: 2.6 ppb
84	San Jose, CA (San Jose Water Company serves 979,000 people)	30 *	NitrateNitrate enters drinking water sources from fertilizer runoff, leaching septic tanks, and erosion of natural deposits; it is also emitted by chemical, petrochemical and metal-finishing industries.	THMs: 1.8 ppb HAAs: 10.0 ppb nitrate: 4.7 ppm arsenic: 0.4 ppb
85	Haworth Boro, NJ (United Water- New Jersey serves 253,045 people)	32 *	DieldrinDieldrin is a banned insecticide that is persistent and bioaccumulative, and was historically used on corn, cotton and citrus; it also forms in the environment as a breakdown product of the pesticide aldrin.	THMs: 13.3 ppb HAAs: 3.4 ppb nitrate: 0.6 ppm arsenic: 0.0 ppb
86	Cocoa, FL (City of Cocoa- Claude H. Dyal Water Treatment Plant serves 260,887 people)	19	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 49.8 ppb HAAs: 25.4 ppb nitrate: 0.2 ppm arsenic: 0.0 ppb
87	West Milford (City of Newark Department of Water serves 273,000 people)	18 *	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid.	THMs: 48.4 ppb HAAs: 51.4 ppb nitrate: 0.3 ppm arsenic: 0.0 ppb
88	Chino Hills, CA (Chino Hills Water & Sewer serves 520,000 people)	18 *	NitrateNitrate enters drinking water sources from fertilizer runoff, leaching septic tanks, and erosion of natural deposits; it is also emitted by chemical, petrochemical and metal-finishing industries.	THMs: 0.4 ppb HAAs: 7.9 ppb nitrate: 8.4 ppm arsenic: 7.5 ppb
89	Fresno, CA (City of Fresno Water Division serves 390,350 people)	30 *	NitrateNitrate enters drinking water sources from fertilizer runoff, leaching septic tanks, and erosion of natural deposits; it is also emitted by chemical, petrochemical and metal-finishing industries.	THMs: 0.1 ppb HAAs: 1.7 ppb nitrate: 5.0 ppm arsenic: 2.6 ppb
90	Indianapolis, IN (Indianapolis Water serves 805,431 people)	23 *	Total haloacetic acids (HAAs)Total haloacetic acids refers to the sum of the concentrations of five related disinfection byproducts in a water sample: dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid.	THMs: 33.6 ppb HAAs: 36.6 ppb nitrate: 1.2 ppm arsenic: 0.0 ppb
91	Jacksonville, FL (JEA serves 800,000 people)	23	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.	THMs: 48.0 ppb HAAs: 13.3 ppb nitrate: 0.1 ppm arsenic: 0.0 ppb
92	San Diego, CA (San Diego Water Department serves 1,281,400 people)	24 *	Gross beta particle activity (pCi/L)Beta particles are a form of radiation frequently associated with nuclear testing and radioactive mineral deposits.	THMs: 41.0 ppb HAAs: 17.8 ppb nitrate: 0.5 ppm arsenic: 0.0 ppb
93	North Las Vegas, NV (City of North Las Vegas Utilities Department serves 282,600 people)	29	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform. **	THMs: 50.0 ppb HAAs: 18.0 ppb nitrate: 0.8 ppm arsenic: 2.1 ppb
94	Omaha, NE (Metropolitan Utilities District serves 506,420 people)	32 *	Arsenic (total)Arsenic contaminates drinking water due to mining runoff, erosion of natural deposits, emissions from glass and electronics processing and the use of arsenical compounds as wood preservatives and pesticides. **	THMs: 16.6 ppb HAAs: 17.0 ppb nitrate: 1.4 ppm arsenic: 5.6 ppb
95	Houston, TX (City of Houston Public Works serves 2,700,000 people)	37 *	Alpha particle activityAlpha particles are a form of radiation released from mining waste pollutants and natural sources.	THMs: 20.1 ppb HAAs: 22.2 ppb nitrate: 0.2 ppm arsenic: 0.0 ppb
96	Reno, NV (Truckee Meadows Water Authority serves 315,200 people)	23	Arsenic (total)Arsenic contaminates drinking water due to mining runoff, erosion of natural deposits, emissions from glass and electronics processing and the use of arsenical compounds as wood preservatives and pesticides. **	THMs: 39.6 ppb HAAs: 20.4 ppb nitrate: 0.1 ppm arsenic: 6.8 ppb
97	Riverside County, CA (Eastern Municipal Water District serves 480,000 people)	32 *	PerchloratePerchlorate is a synthetic oxygen additive in solid fuel propellant for rockets, missiles, and fireworks, and is primarily used by the military and the space industry; it may occur naturally in certain imported agricultural fertilizers.	THMs: 8.8 ppb HAAs: 14.5 ppb nitrate: 3.5 ppm arsenic: 0.0 ppb
98	Las Vegas, NV (Las Vegas Valley Water District serves 1,181,263 people)	33	Total trihalomethanes (TTHMs)Total trihalomethanes constitute the sum of four disinfection byproducts: chloroform, bromodichloromethane, dibromochloromethane, and bromoform. **	THMs: 62.0 ppb HAAs: 27.0 ppb nitrate: 0.9 ppm arsenic: 2.1 ppb
99	Riverside, CA (City of Riverside Public Utilities serves 280,832 people)	36 *	PerchloratePerchlorate is a synthetic oxygen additive in solid fuel propellant for rockets, missiles, and fireworks, and is primarily used by the military and the space industry; it may occur naturally in certain imported agricultural fertilizers.	THMs: 0.9 ppb HAAs: 0.9 ppb nitrate: 6.0 ppm arsenic: 0.0 ppb
100	Pensacola, FL (Emerald Coast Water Utility serves 307,076 people)	39 *	MTBEMTBE (methyl tert-butyl ether) is a fuel additive that had been used as an octane enhancer in unleaded gasoline; it contaminates groundwater due to spillage or leakage at gas stations, and has been banned or scheduled for phaseout in most states.	THMs: 0.2 ppb HAAs: 0.6 ppb nitrate: 1.4 ppm arsenic: 0.0 ppb

The following large utilities had insufficient data available and could not be included in the rankings:

• San Francisco County, CA (San Francisco Regional Water)
• Detroit, MI (City of Detroit Water Department)
• Kansas City, MO (Kansas City Water Department)
• Salt Lake City, UT (Metropolitan Water District of Salt Lake and Sandy)
• Virginia Beach, VA (City of Virginia Beach Water Department)
• Washington, DC (D.C. Water and Sewer Authority)
• Fairfax County, VA (Fairfax Water- Lorton Water Treatment Plant )

* The count of chemicals found treats THMs and HAAs as one chemical each, to account for differences in the various state databases that underlie this analysis. This count may differ from that shown on a utility's water quality report within this website, where individual THM and HAA chemicals are included in the total.