Water quality
by state and county

Under its UCMR 5 programme, EPA sampled public water systems across the country for PFAS — industrial chemicals that EPA describes as breaking down only very slowly in the environment. In April 2024 it set the first enforceable national limits: 4 ng/L for PFOA and PFOS, 10 ng/L for PFHxS, PFNA and GenX.

Of the 3,108 counties covered here, 596 have a reading above a federal limit. Pick a state to see every county in it, or search your ZIP code on the map.

StateOver the limit
Delaware3of 3
Connecticut8of 8
New Jersey20of 21
Rhode Island4of 5
Massachusetts9of 14
California35of 58
Arizona9of 15
South Carolina27of 46
Florida33of 67
North Carolina46of 100
Alabama27of 67
New Hampshire4of 10
Pennsylvania26of 67
Maryland8of 24
Maine5of 16
New York17of 62
Ohio24of 88
Washington10of 39
Wisconsin18of 72
Tennessee23of 95
Nevada4of 17
Georgia33of 159
Oregon7of 36
West Virginia10of 55
Illinois18of 102
Kentucky20of 120
Texas39of 254
Indiana14of 92
Colorado9of 64
Utah4of 29
Minnesota11of 87
New Mexico4of 33
Oklahoma9of 77
Louisiana6of 64
Michigan7of 83
Iowa8of 99
Missouri9of 115
Mississippi6of 82
Vermont1of 14
Kansas5of 105
Idaho2of 44
Virginia6of 133
Wyoming1of 23
Nebraska4of 93
Montana1of 56
South Dakota1of 66
Arkansas1of 75
District of Columbianone
North Dakotanone

Ordered by the share of counties with a reading over a federal limit. A county with no reading has not necessarily got clean water — EPA samples every system serving more than 3,300 people and only a national sample of smaller ones, so rural counties are frequently unsampled. That is an absence of evidence, not evidence of absence.