Manitoba cautions on manganese in well water

A significant number of wells in Manitoba may be carrying water with manganese levels well above new health standards, particularly for infants.

The province on May 3 issued an advisory for owners of private wells that their water “may exceed a new health-based guideline” for the trace element.

The element occurs naturally, and commonly, in well water throughout Canada. It’s often associated with discoloured (that is, brown or blackish) water, which can stain laundry and/or plumbing fixtures, and which some well owners deal with through water treatment.

Up until recently, the province said, manganese was thought to have only “aesthetic impacts” on well water.

However, the province added, based on “new evidence,” Health Canada in its 2019 Guidelines for Canadian Drinking Water Quality (GCDWQ) put a health-based “maximum acceptable concentration” of 0.12 milligrams per litre on total manganese in drinking water.

To reduce complaints of discoloured water, the federal guideline also set an “aesthetic objective” at 0.02 mg/L or lower.

Health Canada’s 2019 GCDWQ for manganese was adopted in December 2020 as the drinking water standard in Manitoba.

Manganese is an essential element and consumption of small amounts is part of a healthy diet, the province said. In solid food, manganese is “usually not a concern.”

But the new evidence indicates drinking water with high levels of manganese “may harm brain development in infants and young children,” the province said. Infants fed with formula mixed with water are considered to be “the most sensitive population.”

As the health basis for the new standards, Health Canada cited “effects on neurological development and behaviour (and) deficits in memory, attention, and motor skills.”

For adults and older children, the province said, short-term exposure to manganese in drinking water slightly above the guideline is “unlikely to cause negative health effects.”

However, the province added, long-term exposure of adults and older children to levels above the federal guideline is “not recommended.”

If manganese levels test above the maximum at the well or the tap, users of the well should either seek out an alternate water source for drinking and “all other consumptive purposes,” or install water treatment devices, either where the water enters the house or at the tap.

In its evaluation of manganese in well water, the province reviewed groundwater samples collected via regional groundwater quality surveys, its well sampling program and data collected through its regulation of public and “semi-public” water systems.

The evaluation showed naturally-occurring manganese can be found within “a wide range of concentrations” throughout the province, at “all kinds of well depths, aquifer types, and geological settings.”

It found about 56 per cent of wells sampled were above the 0.02 mg/L aesthetic objective for manganese, and 34 per cent above the 0.12 mg/L health limit.

On average, the province said, the manganese concentration per well throughout Manitoba ran at 0.5 mg/L.

At the 0.12 mg/L level, the province said, water is often discoloured and may have a “bitter, metallic taste,” but may not be apparent by taste or colour of the water in all cases. “The only way to determine manganese levels is to test the water.”

Manganese makes its way into groundwater mainly through “dissolution of naturally-occurring minerals commonly found in soil and rock,” Health Canada said, while other sources may include industrial discharge, mining activities or leaching from landfills. — Glacier FarmMedia Network