What are perfluoroalkylated substances, or PFAS?

Some homes inthe Mississippi Mills, Ont., community of South Ramsayare showing levels of potentially toxic chemicals calledperfluoroalkylatedsubstancesin well water near a governmentfire safety testing facility.

Perfluoroalkylatedsubstances, or PFAS for short, is the termused to describe afamily of nine substances.

They are used in a wide variety of industrial and consumer products, including adhesives, cosmetics, cleaning products and firefighting foams, "as well as water-, stain-, and oil-repellent coatings for fabrics and paper," according to a Health Canada fact sheet about drinking water screening values forPFAS.

According to Mississippi Mills Mayor ShaunMcLaughlin, well water for21 of thehomes near the National Research Council fire research testing facilitythat have been screened so far showed noPFASat all, 17 showedPFASamounts that are under the screening level of concern, and one home showed a "slightly elevated level."

Drinking water screening levels

The chemicals are not considered to pose a risk to humans if levels fall below the screening level, which varies depending on the specific chemical:

• Perfluorooctanoic acid: 0.0002 milligrams/litre.
• Perfluorooctane sulfonate: 0.0006milligrams/litre.
• Perfluorobutanoate: 0.03milligrams/litre.
• Perfluorobutane sulfonate: 0.015milligrams/litre.
• Perfluorohexanesulfonate: 0.0006milligrams/litre.
• Perfluoropentanoate: 0.0002milligrams/litre.
• Perfluorohexanoate:0.0002milligrams/litre.
• Perfluoroheptanoate:0.0002milligrams/litre.
• Perfluorononanoate:0.0002milligrams/litre.

Scientific information is limited on the human health risks ofPFAS exposure, Health Canada says, but in studies done on animals, "high levels of PFAS have been linked with negative health effects ... including liver damage and impacts on neurological development," the agency's fact sheet says.

In humans, short-term exposure to PFAS at levels slightly above the safety threshold isn't expected to have health effects, according to Health Canada, but the agency does not define what constitutes short- or long-term exposure.

It'snot yet known how long the chemicals have been present in the groundwater of the affected area. The fire testing facility has been on Ramsay Concession Road 8 in Mississippi Millssince 1981.

Bathing, showering, washing dishes, brushing teeth and doing laundry do not pose risks. The chemicals stay in water and can't be breathed in or absorbed through skin, Health Canada says.

Read entire Health Canada fact sheet on PFAS