Regulations last checked for updates: Apr 19, 2025

Title 40 - Protection of Environment last revised: Nov 19, 2025
All TitlesTitle 40Chapter IPart 257Subpart DAppendix Appendix I - Appendix I to Part 257—Maximum Contaminant Levels (MCLs)
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Appendix Appendix I - Appendix I to Part 257—Maximum Contaminant Levels (MCLs)

Maximum Contaminant Levels (MCLs) Promulgated Under the Safe Drinking Water Act

Chemical CAS No. MCL (mg/l)
Arsenic7440-38-20.05
Barium7440-39-31.0
Benzene71-343-20.005
Cadmium7440-43-90.01
Carbon tetrachloride56-23-50.005
Chromium (hexavalent)7440-47-30.05
2,4-Dichlorophenoxy acetic acid94-75-70.1
1,4-Dichlorobenzene106-46-70.075
1,2-Dichloroethane107-06-20.005
1,1-Dichloroethylene75-35-40.007
Endrin75-20-80.0002
Fluoride74.0
Lindane58-89-90.004
Lead7439-92-10.05
Mercury7439-97-60.002
Methoxychlor72-43-50.1
Nitrate10.0
Selenium7782-49-20.01
Silver7440-22-40.05
Toxaphene8001-35-20.005
1,1,1-Trichloroethane71-55-60.2
Trichloroethylene79-01-60.005
2,4,5-Trichlorophenoxy acetic acid93-76-50.01
Vinyl chloride75-01-40.002
[56 FR 51016, Oct. 9, 1991]
authority: 42 U.S.C. 6907(a)(3), 6912(a)(1), 6927, 6944, 6945(a) and (d); 33 U.S.C. 1345(d) and (e)
source: 44 FR 53460, Sept. 13, 1979, unless otherwise noted.
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