Drinking waterThe EPA has established that exposure to manganese in drinking water at concentrations of 1 mg/L for 1 or 10 days is not expected to cause any adverse effects in a child.

The EPA has established that lifetime exposure to 0.3 mg/L manganese is not expected to cause any adverse effects.
Bottled waterThe FDA has established that the manganese concentration in bottled drinking water should not exceed 0.05 mg/L.
Workplace airOSHA set a legal limit of 5 mg/m3 manganese in air averaged over an 8-hour work day.

From: 1, PUBLIC HEALTH STATEMENT

Cover of Toxicological Profile for Manganese
Toxicological Profile for Manganese.
Williams M, Todd GD, Roney N, et al.

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