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EPA-Expo-Box (A Toolbox for Exposure Assessors)

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Other Organics

Perfluorinated Compounds (PFCs)

Perfluorinated Compounds (PFCs) contain a carbon chain with fluorine atoms attached in the place of hydrogen atoms and one or more atom or functional groups attached to the end. These compounds are synthetic and used in a variety of manufacturing and industrial applications, including fire resistance and non-stick surfaces. A wide variety of consumer products contain varying levels of PFCs. These chemicals have been used for many decades in products that resist or repel oil, grease, and water-based liquids. These include products advertised as stain resistant or non-stick, such as cookware, carpets, upholstered furniture, or other fabrics, as well as non-advertised products that have repellent qualities, such as microwave popcorn bags and food packaging.

Example PFC Structures
8:2 Fluorotelomer Alcohol (8:2 FTOH)
FTOH
Perfluorooctanoic acid (PFOA)
PFOA
Perfluorooctanesulfonic acid (PFOS)
PFOS

Physicochemical Properties

PFCs are generally resistant to further degradation in the environment or within biota (Olsen et al., 2007; Harada et al., 2004). The carbon-fluorine bonds that characterize PFCs are very strong and stable in air at high temperatures; are not readily degradable by strong acids, alkalis, or oxidizing agents; and generally do not undergo photolysis (Lau et al., 2007). In general, the atmospheric lifespan of long-chain PFCs (LCPFCs) (i.e., 8 or more carbons) is on the order of days to weeks under most atmospheric conditions (Lau et al., 2007). The compounds tend to partition into other environmental media. The half-lives in soil of the C6 through C11 alkylates range from about 1 to 3 years and increase with increasing chain length (Washington et al., 2010). Based on the physicochemical characteristics of these compounds, the half-lives of LCPFCs and precursors in water also are expected to be very long.

The table below provides a summary of key physicochemical factors that are likely to affect partitioning and fate of select PFCs in the environment. For chemical-specific values, consult the resources provided in the introduction to this module.

Property Fate and Transport Implications
Vapor pressure at 25°C (atm)

Vapor pressure varies depending on the alkyl chain-length of the PFC. Low vapor pressure of some PFCs contributes to the phenomenon of Long-Range Atmopsheric Transport (LRAT). PFCs remain in the vapor state for extended periods and move readily through the atmosphere, resulting in PFC contamination in areas far from the source of release.

Solubility in water (mg/L)

While PFCs are lipid soluble, they are also moderately water-soluble. Many PFCs are acids that will dissociate in freshwater, which increases their solubility. This allows them to remain in the water column.

Octanol-Water Partition Coefficient (log value)

PFCs are specifically designed to be hydrophobic and oleophobic, making it difficult to determine a Kow value. However, biomonitoring studies have indicated a tendency to partition into organic fractions (biota), where they bind to proteins in blood serum rather than partition to fats. PFCs with longer alkyl chains are more likely to bioaccumulate and biomagnify than those with shorter chains.

Summary: PFCs are a unique type of compound in that they are both hydrophobic and oleophobic. They can be measured in the water column, but will also bioaccumulate in biota. They move readily out of products into the air, and can spread long distances through the atmosphere due to their low vapor pressure, meaning exposure can occur far from the source.

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Routes

Ingestion is the primary pathway identified for human exposures to PFCs. Exposures from inhalation and dermal contact can also occur. The Routes Tool Set of EPA-Expo-Box provides additional information and resources organized by route.

Route Potential Sources of PFC Exposure
Inhalation
  • Inhalation of contaminated dust.
Ingestion
  • Because PFCs partition readily to aquatic systems and bioaccumulate, fish consumption represents a common exposure route and food consumption is an important exposure pathway for PFOS and PFOA (Egeghy and Lorber, 2011; Trudel et al., 2008), two of the major PFCs.
  • PFCs can migrate from food packaging to food (with concentrations occurring in high-fat foods, such as microwave popcorn and fast food), resulting in unintentional ingestion.
  • Traditional drinking water treatment techniques do not remove LCPFCs, so contamination of ground water or surface water, or both, can lead to contamination of drinking water.
  • Dust ingestion is an important route of exposure, particularly because of the high number of household and consumer products that contain PFCs. Vapor-phase materials can sorb to dust or dust can be contaminated with PFCs from direct contact with consumer products containing PFCs, such as carpet or textiles. This pathway is of greatest concern for young children, who spend a high percentage of time on the floor and have high hand-to-mouth contact.
Dermal Contact

Although exposure from dermal contact to PFCs is not considered a dominant route of exposure, people could be exposed via uptake from carpets or other surfaces such as clothing.

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Media

LCPFCs and precursors can be released to various environment media through multiple scenarios. PFCs can be released from manufacturing sites or from use of consumer or industrial products, and secondary releases at sites such as waste water treatment plants (WWTPs) and landfills are possible. These releases generally result in PFCs directly entering water or air, however, release to soils and sediment is also possible, particularly for secondary release scenarios such as application of biosolids to agricultural fields. The Media Tool Set of EPA-Expo-Box provides additional information and resources organized by media.

Media Sources of PFCs
Air
  • Direct emissions from manufacturing facilities to ambient air have been measured (Davis et al., 2007).
  • Indoor air may become contaminated with PFCs due to off-gassing from consumer products containing PFCs.
Water and Sediment
Soil
  • Soils can become contaminated with PFCs due to industrial releases and secondary releases.
Indoor Dust
  • PFCs have also been measured in indoor dust in residential and commercial buildings. PFCs can be emitted from consumer and industrial product use.

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Exposed Populations

PFCs may be found in consumer products, household products, and food packaging, resulting in exposure to the general population. However, some populations may be at risk of higher exposure levels:

  • PFCs are persistent in the environment and may be subject to long-range atmospheric transport, resulting in higher environmental contamination levels in certain regions. Therefore, people who live in certain regions, may be at higher risk of exposure.
  • The lipophilic nature of PFCs may contribute to the accumulation of these chemicals in breast milk. Infants who are breastfed may be exposed to the chemicals through ingestion. Additionally, in utero exposure can occur due to transfer through cord blood. Infant food and formula have also been shown to contain PFCs, probably due to migration from food packaging.
  • Because PFCs bioaccumulate, individuals who consume high amounts of fish or aquatic mammals (i.e., seal, whale), may be exposed to high levels of PFCs, particularly if the fish is sourced from contaminated waters. Fatty cuts of beef or other meats may also contain measureable PFC contamination.
  • Residents who live near certain industrial sites may be at risk of exposure through contaminated drinking water, soil, or air.

See the Lifestages and Populations Tool Set of EPA-Expo-Box for resources related to particular population groups and lifestages.

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Tools

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Measure of a substance’s volatility, or its propensity to partition to the vapor (gaseous) phase from its condensed phase (i.e., solid or liquid). This can be used to predict whether inhalation or other exposure routes are more relevant.

Related to Vapor Pressure. Reflects chemical partitioning between the aqueous, dissolved phase and the gaseous phase.

Measure of a substance’s partitioning between dissolved and insoluble phases. Depends on the solute (e.g., water, alcohol) and other substances dissolved in the solute.

Measure of a substance’s partitioning between dissolved and insoluble phases. Depends on the solute (e.g., water, alcohol) and other substances dissolved in the solute.

Ratio of a chemical that has reached equilibrium in adjacent fractions of octanol and water. This ratio is used frequently to estimate how an organic chemical will partition in the environment (e.g., between dissolved and sorbed fractions in surface water) as well as how it will behave in with respect to human tissues. A compound with a high octanol-water partition coefficient is more likely to bioaccumulate in human tissues, especially fatty tissues.

Ratio of a chemical that has reached equilibrium in adjacent fractions of octanol and air. This ratio is used frequently to estimate how an organic chemical will partition in the environment (e.g., between gaseous and particulate fractions in the atmosphere, between soil organic matter and air) as well as how it will behave with respect to human respiratory tissues. A compound with a high octanol-air partition coefficient is more likely to bioaccumulate in human respiratory tissues, particularly is the log octanol-water partition coefficient moderate.

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