Drinking water contaminants
EPA-verified legal limits, health effects, and removal technologies for 23 contaminants commonly found in US drinking water — from lead and PFAS to nitrate and arsenic.
1,4-Dioxane
Volatile organic compounds
No numeric federal limit — see page for details
0 recorded violations nationally
Arsenic
Metals
EPA limit: 0.01 mg/L
79,748 recorded violations nationally
Atrazine
Pesticides
EPA limit: 0.003 mg/L
28,364 recorded violations nationally
Benzene
Volatile organic compounds
EPA limit: 0.005 mg/L
51,220 recorded violations nationally
Chlorine (residual disinfectant)
Disinfectants
EPA limit: 4 mg/L
92,396 recorded violations nationally
Chromium-6 (Hexavalent chromium)
Metals
No numeric federal limit — see page for details
0 recorded violations nationally
Combined Radium-226/228
Radionuclides
EPA limit: 5 pCi/L
44,563 recorded violations nationally
Copper
Metals
No numeric federal limit — see page for details
100 recorded violations nationally
E. coli
Microbial
No numeric federal limit — see page for details
46,739 recorded violations nationally
Fluoride
Inorganic chemicals
EPA limit: 4 mg/L
47,811 recorded violations nationally
GenX Chemicals (HFPO-DA)
PFAS ("forever chemicals")
EPA limit: 10 ppt
0 recorded violations nationally
Haloacetic Acids (HAA5)
Disinfection byproducts
EPA limit: 60 ppb
69,754 recorded violations nationally
Lead
Metals
No numeric federal limit — see page for details
137 recorded violations nationally
Manganese
Metals
No numeric federal limit — see page for details
0 recorded violations nationally
Nitrate
Inorganic chemicals
EPA limit: 10 mg/L
318,803 recorded violations nationally
Perchlorate
Inorganic chemicals
No numeric federal limit — see page for details
0 recorded violations nationally
PFHxS (Perfluorohexane sulfonic acid)
PFAS ("forever chemicals")
EPA limit: 10 ppt
0 recorded violations nationally
PFNA (Perfluorononanoic acid)
PFAS ("forever chemicals")
EPA limit: 10 ppt
0 recorded violations nationally
PFOA (Perfluorooctanoic acid)
PFAS ("forever chemicals")
EPA limit: 4 ppt
0 recorded violations nationally
PFOS (Perfluorooctane sulfonic acid)
PFAS ("forever chemicals")
EPA limit: 4 ppt
0 recorded violations nationally
Total Coliform Bacteria
Microbial
No numeric federal limit — see page for details
1,151,686 recorded violations nationally
Total Trihalomethanes (TTHM)
Disinfection byproducts
EPA limit: 80 ppb
98,123 recorded violations nationally
Uranium
Radionuclides
EPA limit: 30 ug/L
57,976 recorded violations nationally
Source: EPA National Primary Drinking Water Regulations · Data as of 2026-07-16