The Lake Simcoe Region Conservation Authority

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Perfluoroalkyl Substances

Perfluoroalkyl substances

Perfluoroalkyl substances (PFASs) are used to resist stains and repel water on items such as furniture, carpets and clothing, and provide non-s​tick capabilities for cookware and other Teflon products. They have also been used in fire-fighting foam. They are a broad class of chemicals comprised of thousands of different man-made compounds used in many personal, commercial, and industrial applications.

Some PFASs are chemically stable and resistant to breaking down by weathering processes (degradation) and last for a very long time in the environment. Living things absorb PFASs faster than they can naturally break them down or expel them, such that the contaminant builds up in their tissue over time, a process known as bioaccumulation. PFASs toxins can also travel up the food chain when organisms ingest other plants or animals which have consumed the chemicals, a process known as biomagnification, where there is a greater amount of the contaminant in the organisms higher on the food chain.

The current scientific concern is the identification, measurement and determination of the long-term effects of the countless number of PFAS compounds in the environment.

In a recent study of the Lake Simcoe watershed, PFAS compounds were measured in the sediment of several streams and rivers.

What are perfluoroalkyl substances (PFASs)?

Perfluoroalkyl substances (PFASs) are a broad class of more than 6000 synthetic fluorinated organic chemicals used extensively in personal, commercial, and industrial applications, often to provide protective coating for surfaces or as additives in certain products.

​​PFASs are used to resist stains and repel water on items such as furniture, carpets and clothing. They can provide non-stick capabilities in cookware and deter grease absorption in food packaging.  They are used in fire-fighting foam, surfactants and lubricants (Suthersan et al., 2016) and in the aerospace, medical, construction, electronic, aviation and automotive industries, often because of the ability to reduce friction and the increased resistance to the extremes of high and low temperatures.

PFASs can be grouped into two categories, including perfluorosulfonic acids (PFSAs) and perfluorocarboxylic acids (PFCAs), containing perfluorinated compounds of varying chain lengths (chemical structures). PFSAs include perfluoro -hexane, -octane and -decane sulfonates (PFHxS, PFOS and PFDS, respectively) and PFCAs include perfluoro -octanoic, -nonanoic, -decanoic, -undecanoic, -dodecanoic, -tetradecanoic acids (PFOA, PFNA, PFDA, PFUA, PFdoA, PFTA, respectively).

One of the more well-known compounds listed above, PFOS, was used primarily as a repellent to water, oil, soil and grease for various products and was also used in fire-fighting foams against fuel-based fires. Production of PFOS is highly restricted by the Stockholm Convention, an international treaty, as a persistent organic pollutant (POP; Stockholm Convention, 2008) and PFOS is prohibited in Canada [Environment and Climate Change Canada (ECCC), 2017a]. The Stockholm Convention (that includes Canada as a member; ECCC, 2017c) is considering adding PFOA as well, which is used in the manufacture of Teflon and similar chemicals.

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Mobility and fate of PFASs in the environment

Emissions to the environment can occur during the production and use of certain products (such as carpets), through the treatment of waste (including incineration, in landfills and from water pollution control plants), from fire extinguishing foams and from the metalworking industry.

PFASs are very resistant to degradation in the environment, possibly transforming to dead end products that can remain unaltered in soil and groundwater indefinitely. PFASs are both hydrophobic and lipophobic (Chaudhuri et al., 2017). Adverse biological effects can occur upon exposure and they may bioaccumulate and biomagnify in the food web (Giesy et al., 2006).

The main scientific concern now is identification, measurement and toxicological assessment of the myriad of PFAS compounds and their biodegradation products (Suthersan et al., 2016).

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PFASs in Ontario and the Lake Simcoe watershed

In Ontario, PFASs were measured in sediment as part of the Southern Ontario Stream Sediment Project (SOSSP). The study found that there was a greater density of sites with elevated concentrations of PFSAs (perfluorosulfonic acids) in the central and southwest portions of southern Ontario, whereas higher concentrations of PFCAs (perfluorocarboxylic acids) were found near Niagara and also the eastern region of Ontario (Chaudhuri, 2017).

Within the Lake Simcoe watershed for the SOSSP study, detectable levels of PFSAs (mainly as PFOS) were found in the Tannery Creek branch of the East Holland River and in some rural/agricultural tributaries (including Beaver, Black and Talbot Rivers and a creek of the Ramara subwatershed). PFCAs was found above the detection limit (mainly PFOA) at Tannery Creek, Beaver River, Uxbridge Brook and the creek in Ramara. Provincial and federal sediment guidelines are not currently available for PFAS compounds, for comparison of the results (Chaudhuri, 2017).

Though PFOS are now prohibited in Canada, they were widely used and are believed to be ubiquitous in our environment (found virtually everywhere). Monitoring of background levels of PFOS in Etobicoke Creek, a tributary of Lake Ontario, showed a decline since 2000 possibly from the phasing out of these substances in consumer products. Trends of the levels of PFOS in Lake Ontario are not as clear, but over time, concentrations are expected to decline. The Ministry of Environment, Conservation and Parks (MECP) continues to monitor PFOS in some parts of Ontario (MOE, 2013; MECP, 2018).

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Actions to reduce PFASs in the environment

In 2009, PFOS was added to the Virtual Elimination List, which essentially states that no levels of PFOS should enter the Canadian environment [Environment Canada (EC), 2013 and 2017b]. The manufacture, use, sale and import of PFOS were prohibited in Canada starting in 2016 under the Perfluorooctane Sulfonate and Its Salts and Certain Other Compounds Regulations (with some exemptions; ECCC, 2017a).

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Chaudhuri SR, Dyer RD, Fletcher R, Helm P, Millar M, Reiner EJ and Welsh PG. 2017. Southern Ontario Stream Sediment Project (SOSSP) summary report—Organic contaminants (Ontario Geological Survey, Open File Report 6335). Toronto, Ontario: Queen’s Printer for Ontario.

Environment Canada (EC). 2013, March 7. Virtual elimination list. Retrieved from:

Environment and Climate Change Canada (ECCC). 2017a, January 17. Toxic substances list: PFOS. Retrieved from:

ECCC. 2017b, June 5. CEPA: Virtual elimination. Retrieved from:

ECCC. 2017c, August 10. Stockholm Convention on persistent organic pollutants (POPs). Retrieved from:

Giesy JP, Mabury SA, Martin JW, Kannan K, Jones PD, Newsted JL and Coady K. 2006. Perfluorinated compounds in the Great Lakes. In: RA Hites (Ed.), Persistent organic pollutants in the Great Lakes. The handbook of environmental chemistry, vol. 5N. Berlin, Heidelberg, Germany: Springer.

Ministry of the Environment (MOE). 2013. Water quality in Ontario report, 2012. Toronto, Ontario: Queen’s Printer for Ontario.

Ministry of the Environment, Conservation and Parks (MECP). 2018, July 17. Water quality in Ontario report, 2014. Retrieved from:

Stockholm Convention. 2008. The new POPs under the Stockholm Convention. Retrieved from:

Suthersan S, Quinnan J, Horst J, Ross I, Kalve E, Bell C, Pancras T. 2016. Making strides in the management of “Emerging Contaminants”. Groundwater Monit. Rem. 36: 15-25.

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Chemical Contaminants in Lake Simcoe and its Tributaries

in 2015, a study was undertaken to investigate levels of chemical contaminants in the surface water and sediments of Lake Simcoe and its tributaries. The contaminants included in this study were chosen based on historical use within the watershed, previous research undertaken (such as the LSRCA 2004 study), and literature from similar areas in the Great Lakes Region. 

Read Chemical Contaminants in Lake Simcoe and its Tributaries

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