The Canadian Council of Ministers of the Environment (CCME) has published soil and groundwater quality guidelines for perfluoroalkyl substances, widely known as PFOS.
The guidelines can be used as the basis for consistent assessment and remediation of soils and groundwater at contaminated sites. While no longer manufactured, imported, sold, offered for sale or used in Canada, PFOS is still found in the environment because of its extremely persistent nature, according to Health Canada.
The anthropogenic compounds were commonly used in products such as firefighting foams, insecticides, grease repellants, coatings used for textiles and paper, and cleaning products. From 1997 to 2000, approximately 600 tonnes of PFOS compounds were imported into Canada, primarily from the U.S.
PFOS can exist as an anion, an acid, or various salts and polymers. They were produced using the Simons electrochemical fluorination, or ECF, method.
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The chemicals can be released directly into the environment as a result of its production, use and disposal, or it may result indirectly from the biodegradation, photo-oxidation, photolysis and hydrolysis of precursor per- and polyfluoroalkyl substances known as PFAS.
The drinking water guideline for PFOS is a maximum acceptable concentration of 0.0006 mg/L (0.6 µg/L). The final environmental groundwater quality guideline for PFOS is a concentration in groundwater that considers the protection of soil-dependent organisms such as plants; the protection of surface freshwater aquatic life; livestock watering; and the solubility of PFOS.
For soil, the guideline is 0.01 mg/kg for all land use types, according to CCME. Soil quality guidelines for PFOS were derived by considering organisms (plants and invertebrates) in direct contact with soil.
Many toxic effects have been observed in humans and animals from PFOS exposure, the new guidelines state. These include altered immune response, hepatic effects, altered lipid and glucose homeostasis, endocrine and neuroendocrine disruption, neurotoxicity, reproductive and developmental effects, and tumours. The new guidelines look at the effects of PFOS on terrestrial plants and invertebrates, birds, humans and lab animals.
