Health Canada (1987) indicates that manganese is regarded as one of the least toxic elements to mammals; only exposure to extremely high concentrations from human-made sources has resulted in adverse health effects. There is currently no health-related maximum acceptable concentration set for this element. The aesthetic objective for manganese in drinking water is less than or equal to 0.05 mg/L. Manganese at this recommended limit is not considered to represent a threat to health, and drinking water with much higher concentrations has been safely consumed.
In 2016, Health Canada led a public consultation process on proposed updates to the manganese in drinking water guidelines. The proposed change included:
“A maximum acceptable concentration (MAC) of 0.1 mg/L is proposed for total manganese in drinking water. An aesthetic objective (AO) of 0.02 mg/L is also proposed for total manganese in drinking water.”
At this point in time, this proposed guideline is draft only and the existing guideline is still in effect. It is not known if or when changes to the existing guideline will occur.
The average manganese level in City of White Rock’s water system remains above the aesthetic objective for manganese of 0.05mg/L. In some instances it is above the proposed MAC, but below the World Health Organization's health-based guideline level of 0.4mg/L for daily use. Levels of manganese in the discoloured water are typically higher than the aesthetic objective, but lower than the World Health Organization's guideline.