EWG's Tap Water Database — 2021 UPDATE


Mercury (inorganic)

Status: National drinking water standard exists


Mercury is a potent neurotoxin that also damages the kidneys and other internal organs. Mercury enters drinking water from industrial pollution, mining wastes and coal-fired power plants.




states detected


utilities detected

6.3 million

people served


states over health guideline


utilities over health guideline


people served over health guideline

Health concerns for mercury (inorganic)

Harm to the brain and nervous system

Harm to fetal growth and child development

Harm to the kidney

Harm to the immune system

State and national drinking water standards and health guidelines

EWG Health Guideline 1.2 ppb

The EWG Health Guideline of 1.2 ppb for mercury (inorganic) was defined by the California Office of Environmental Health Hazard Assessment as a public health goal, the level of a drinking water contaminant that does not pose a significant health risk. This health guideline protects against harm to internal organs.

EPA Maximum Contaminant
Level (MCL) 2 ppb

The legal limit for inorganic mercury, established in 1991, was based on toxicity studies conducted in laboratory animals in the 1970s and 1980s. This limit does not include any additional consideration of children’s health.

ppb = parts per billion

States reporting mercury (inorganic) in drinking water

State UtilitiesPeople Served UtilitiesPeople Served
New York0033552,512
New Jersey0041495,527
South Dakota0011188,631
South Carolina00240,343
North Carolina001238,114
West Virginia001028,319
New Mexico0048,720
New Hampshire00183,952

Filtering technologies that reduce mercury (inorganic)

carbon filter icon

Activated Carbon

reverse osmosis icon

Reverse Osmosis

Utilities with the highest amounts of mercury (inorganic), 2017-2019

UtilityLocationTestsAverage levelPeople served
Picnic Grove Mobile HomesMalaga, NJ4 of 41.63 ppb250
Murrieta/hernandez FarmsKerman, CA17 of 181.52 ppb29
Bethel Heights Water SystemBethel, AK1 of 11.29 ppb2,220
Town of Trophy Club Public Improvement DTrophy Club, TX1 of 21.13 ppb3,589
Trophy Club Municipal Utility District 1*Trophy Club, TX1 of 21.13 ppb8,577
Hidden Valley Light AssociationColdwater, MS2 of 21.05 ppb59
Grays Harbor Co. Water District 2Montesano, WA1 of 11.000 ppb3,507
Knoll EnterprisesLudlow, CA4 of 80.875 ppb500
Cassatt Water Kershaw-lee Company RWACassatt, SC21 of 430.871 ppb25,061
Western GreeneWalcott, AR24 of 320.788 ppb7,342
Mount Charleston Water CompanyLas Vegas, NV1 of 20.730 ppb20
Vineland Water & Sewer UtilityVineland, NJ22 of 280.718 ppb36,250
Deberry Water Supply CorporationDe Berry, TX1 of 20.710 ppb1,071
Garcia Domestic WuaSan Luis, CO2 of 20.700 ppb100
Choctaw Valley Mutual Water CompanyBakersfield, CA1 of 20.700 ppb44
Green Acres Subdivision WsWest Monroe, LA2 of 60.667 ppb150
Pg&e Helms Support FacilityShaver Lake, CA1 of 20.650 ppb40
Lakeview Estates Mobile Home CommunityMt. Gilead, OH1 of 20.650 ppb145
Daggett Community Services DistrictDaggett, CA1 of 30.633 ppb795
Oak Forest Mobile Home ParkSeaville, NJ2 of 20.573 ppb300
San Acacio Domestic WaSan Luis, CO1 of 20.550 ppb40
MO American Rogue Creek UtilitiesPotosi, MO5 of 50.550 ppb200
Wattenburg Improvement AssociationFort Lupton, CO1 of 30.533 ppb350
Lake Tarpon Mobile Home VillagPalm Harbor, FL1 of 60.517 ppb1,285
Hardy County Psd Marvin ChapelMoorefield, WV1 of 20.500 ppb90
J & T Water CompanyTerre Haute, IN1 of 20.500 ppb25
Oak Mountain Country EstatesSturgis, SD1 of 20.500 ppb70
Wardensville, Town Of*Wardensville, WV1 of 20.500 ppb788
Hardy County Psd-trout RunMoorefield, WV1 of 20.500 ppb245
Viejo San AcacioSan Luis, CO2 of 20.500 ppb45
City of Log CabinLog Cabin, TX1 of 20.500 ppb1,098
West Terre Haute WaterWest Terre Haute, IN2 of 20.500 ppb4,028
Webb Mobile Home ParkReno, NV1 of 10.500 ppb30
Stoney Field Mobile Home ParkPittsford, NJ2 of 20.489 ppb200
Marquez RentalFirebaugh, CA1 of 10.480 ppb50
Cowanshannock M A Sagamore SystemNu Mine, PA1 of 30.467 ppb300
Craig Public WorksCraig, AK1 of 10.459 ppb1,475
Plum Point Community Water AssociationPope, MS1 of 20.450 ppb135
Sun Desert Inc.Moses Lake, WA1 of 20.450 ppb25
Friendship Water DepartmentFriendship, ME2 of 20.435 ppb85
Meadows Mobile Home EstatesMontross, VA1 of 60.417 ppb105
Rainier TerracePort Orchard, WA1 of 10.400 ppb125
Twin Pines Health Care CenterWest Grove, PA1 of 20.400 ppb120
Colorado Mountain College SvcGlenwood Springs, CO1 of 20.385 ppb715
Chapman Manufactured HousingVineland, NJ2 of 20.362 ppb375
Manderly Mobile Home ParkFestus, MO1 of 20.360 ppb220
Indian Hills EstatesNikiski, AZ1 of 10.360 ppb30
Sherwood Retirement and Personal Care HomeCanton, PA1 of 20.360 ppb32
East End WaLa Junta, CO1 of 20.350 ppb70
Ponderosa Basin Mutual Water CompanyMariposa, CA6 of 140.343 ppb665

* This water utility supplies finished drinking water to at least one other water utility. The purchasing utility is not required to test for or report Mercury (inorganic), but it likely has the contaminant in its water supply.

UtilityLocationTestsAverage levelPeople served
Cassatt Water Kershaw-lee Company RWACassatt, SC21 of 430.871 ppb25,061
Vineland Water & Sewer UtilityVineland, NJ22 of 280.718 ppb36,250
Monroe Twp MUAWilliamstown, NJ97 of 1520.292 ppb26,179
Hamilton Township MUA*Mays Landing, NJ6 of 100.268 ppb21,720
Harrison City PWSHarrison, OH1 of 20.250 ppb10,000
City of Albemarle*Albemarle, NC3 of 120.223 ppb17,874
Epcor Water - MohaveYoungtown, AZ6 of 160.218 ppb36,330
Hammonton Water DepartmentHammonton, NJ4 of 60.210 ppb12,153
Sioux Falls*Sioux Falls, SD1 of 10.200 ppb158,800
Chambersburg Boro Water Sys*Chambersburg, PA1 of 60.200 ppb31,048
Peoples Water Service CompanyPensacola, FL1 of 100.180 ppb24,081
City of Sulphur Springs*Sulphur Springs, TX1 of 60.167 ppb15,449
Belforest Water SystemDaphne, AL3 of 60.161 ppb13,380
Onalaska WaterworksOnalaska, WI4 of 90.156 ppb18,000
City of Lynn Haven Water SystemLynn Haven, FL1 of 40.150 ppb19,045
Millville Water DepartmentMillville, NJ8 of 90.144 ppb27,500
City of ClermontClermont, FL1 of 50.120 ppb11,628
City of Trinidad*Trinidad, CO1 of 10.120 ppb11,400
California American Water Company - MontereyMonterey, CA8 of 1900.111 ppb96,754
Granger - Hunter Improvement DistrictWest Valley City, UT9 of 230.1000 ppb121,083
University of West FloridaPensacola, FL1 of 40.1000 ppb13,285
City of Corsicana*Corsicana, TX3 of 120.0958 ppb23,770
Breezy Hill WDGraniteville, SC7 of 360.0839 ppb15,282
City of Cocoa*Cocoa, FL1 of 60.0833 ppb294,039
City of Lawrence UtilitiesIndianapolis, IN2 of 60.0833 ppb46,100
Brownsburg Water WorksBrownsburg, IN1 of 40.0750 ppb26,000
City of Zephyrhills*Zephyrhills, FL4 of 160.0750 ppb23,097
Montclair Water Bureau*Montclair, NJ3 of 30.0723 ppb37,669
NJ American Water - Atlantic CountyEgg Harbor, NJ5 of 310.0710 ppb120,146
Town of Elkton*Elkton, MD2 of 120.0667 ppb15,625
Municipal Authority of Westmoreland County - Yough Plant*Greensburg, PA1 of 60.0667 ppb140,000
City of LexingtonLexington, NE1 of 150.0665 ppb10,230
Winslow Township DMU*Braddock, NJ7 of 140.0645 ppb39,174
EurekaEureka, MO2 of 110.0636 ppb10,574
Northeast*Davenport, FL5 of 130.0615 ppb60,557
Highland S & W Authority Beaverdam*Johnstown, PA1 of 60.0560 ppb23,140
Albion Village*Waterport, NY1 of 60.0550 ppb17,206
Northern Kentucky Water District*Ft Thomas, KY3 of 210.0524 ppb199,460
Frankfort Water WorksFrankfort, IN1 of 40.0500 ppb16,422
La Crosse WaterworksLa Crosse, WI6 of 220.0500 ppb53,000
Seven SpringsNew Port Richey, FL1 of 20.0500 ppb32,834
City of Temple Terrace UtilityTemple Terrace, FL2 of 40.0500 ppb31,250
Hardin County Water District #2Elizabethtown, KY2 of 120.0500 ppb76,326
Ozark Utilities BoardOzark, AL4 of 160.0491 ppb14,907
West Escambia Utilities Inc.Atmore, AL2 of 140.0479 ppb12,060
Columbia Water CompanyColumbia, PA1 of 80.0475 ppb25,200
Willingboro MUA*Riverside, NJ3 of 70.0471 ppb35,000
Long Neck Water CompanyLong Neck, DE3 of 430.0465 ppb11,180
Schuylkill County. Municipal Authority*Pottsville, PA1 of 200.0465 ppb31,850
Livingston Twp Div of WaterLivingston Twp, NJ10 of 210.0464 ppb27,391

* This water utility supplies finished drinking water to at least one other water utility. The purchasing utility is not required to test for or report Mercury (inorganic), but it likely has the contaminant in its water supply.