40 CFR § 141.51 - Maximum contaminant level goals for inorganic contaminants.

---
identifier: "/us/cfr/t40/s141.51"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "40 CFR § 141.51 - Maximum contaminant level goals for inorganic contaminants."
title_number: 40
title_name: "Protection of Environment"
section_number: "141.51"
section_name: "Maximum contaminant level goals for inorganic contaminants."
chapter_name: "ENVIRONMENTAL PROTECTION AGENCY"
subchapter_number: "D"
subchapter_name: "WATER PROGRAMS"
part_number: "141"
part_name: "NATIONAL PRIMARY DRINKING WATER REGULATIONS"
positive_law: false
currency: "2026-04-05"
last_updated: "2026-04-05"
format_version: "1.1.0"
generator: "[email protected]"
authority: "42 U.S.C. 300f, 300g-1, 300g-2, 300g-3, 300g-4, 300g-5, 300g-6, 300j-4, 300j-9, and 300j-11."
regulatory_source: "40 FR 59570, Dec. 24, 1975, unless otherwise noted."
cfr_part: "141"
---


# 141.51 Maximum contaminant level goals for inorganic contaminants.

(a) [Reserved]

(b) MCLGs for the following contaminants are as indicated:

| Contaminant | MCLG (mg/l) |
| --- | --- |
| Antimony | 0.006 |
| Arsenic | zero |
| Asbestos | 7 Million fibers/liter (longer than 10 µm). |
| Barium | 2 |
| Beryllium | .004 |
| Cadmium | 0.005 |
| Chromium | 0.1 |
| Copper | 1.3 |
| Cyanide (as free Cyanide) | .2 |
| Fluoride | 4.0 |
| Lead | zero |
| Mercury | 0.002 |
| Nitrate | 10 (as Nitrogen). |
| Nitrite | 1 (as Nitrogen). |
| Total Nitrate + Nitrite | 10 (as Nitrogen). |
| Selenium | 0.05 |
| Thallium | .0005 |
| This value for arsenic is effective January 23, 2006. Until then, there is no MCLG. |  |

[50 FR 47155, Nov. 14, 1985, as amended at 52 FR 20674, June 2, 1987; 56 FR 3593, Jan. 30, 1991; 56 FR 26548, June 7, 1991; 56 FR 30280, July 1, 1991; 57 FR 31846, July 17, 1992; 60 FR 33932, June 29, 1995; 66 FR 7063, Jan. 22, 2001]