What are perfluoroalkylated substances, or PFAS?

Perfluoroalkylated substances, or PFAS, have been discovered in the drinking water of some homes west of Ottawa near a federal government fire research facility. What exactly are PFAS?

PFAS found in well water of multiple homes in Mississippi Mills, Ont.

Perfluoroalkylated substances are used in firefighting foams, adhesives, cosmetics, cleaning products, protective coatings for fabrics and paper, and more. (AP Photo/News Tribune/Julie Smith)

Some homes in the Mississippi Mills, Ont., community of South Ramsay are showing levels of potentially toxic chemicals ​called perfluoroalkylated substances in well water near a government fire safety testing facility.

​Perfluoroalkylated substances, or PFAS for short, is the term used to describe a family 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 for PFAS.

According to Mississippi Mills Mayor Shaun McLaughlin, well water for 21 of the homes near the National Research Council fire research testing facility that have been screened so far showed no PFAS at all, 17 showed PFAS amounts 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: 0.0006 milligrams/litre.
  • Perfluorobutanoate: 0.03 milligrams/litre.
  • Perfluorobutane sulfonate: 0.015 milligrams/litre.
  • Perfluorohexanesulfonate: 0.0006 milligrams/litre.
  • Perfluoropentanoate: 0.0002 milligrams/litre.
  • Perfluorohexanoate: 0.0002 milligrams/litre.
  • Perfluoroheptanoate: 0.0002 milligrams/litre.
  • Perfluorononanoate: 0.0002 milligrams/litre.

Scientific information is limited on the human health risks of PFAS 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.

The National Fire Laboratory is located on Ramsay Concession Road 8, and has been there since 1981. (CBC)

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's not 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 Mills since 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