What Are PFASs?

A group of unregulated chemicals called perfluoroalkyl substances (PFASs), which are sometimes found in drinking water, have been in the news a lot lately. This is your place for information regarding these substances and how the City of Sioux Falls works to keep your drinking water safe.


Perfluoroalkyl substances, or PFASs, are a group of manmade chemicals that repel oil, grease, and water. Because of this, they may be used by manufacturers to keep food from sticking to cookware (Teflon), to make sofas and carpets resistant to stains (Scotchguard), to make clothes and mattresses more waterproof, and may also be used in some food packaging, as well as in some firefighting materials such as firefighting foam. Some products that use or previously used PFASs include dental floss, non-stick cookware, microwave popcorn bags, pizza boxes, fast food wrappers, outdoor gear with durable water resistant coatings, shampoo, nail polish, facial moisturizers, and eye make-up. Drinking water is only one of many potential sources where a consumer may be exposed to PFASs.

Sometimes chemicals that had not previously been detected (or were previously found in far lesser concentrations) are discovered in a water supply. The U.S. Environmental Protection Agency (EPA) refers to these chemicals as “contaminants of emerging concern” or simply “emerging contaminants.”

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) are only two of many known PFASs. EPA has studied these two chemicals extensively. On May 19, 2016, the EPA published new drinking water Health Advisories for PFOA and PFOS. The new guidelines reduced the acceptable levels of PFOA and PFOS in drinking water from 600 parts per trillion (ppt) to 70 ppt. The Health Advisories recommend that when PFOA and/or PFOS are found individually or combined in drinking water above 70 ppt, the water should not be consumed. An example of one part per trillion is equal to one drop of detergent in enough dishwater to fill a string of railroad tank cars ten miles long.

The EPA reports that concentrations below these recommended drinking water levels should be safe.

Yes, very low levels of PFASs have been previously detected in the City of Sioux Falls water. No sample ever exceeded the Health Advisory Level of 70 parts per trillion. Since August 2016 monthly samples have been collected from the treated water at the water plant and from the treated water purchased from the Lewis and Clark Regional Water System and analyzed for PFASs. No PFASs have been detected in any of the samples. The Sioux Falls drinking water is safe to consume.

As part of a 2011/2012 survey, drinking water samples were collected, and results showed very low levels of PFOA and PFOS. The results ranged from 3.10 to 4.45 parts per trillion. 

In 2013 additional testing was conducted to identify potential sources of the PFASs. On a voluntary basis, the City discontinued use of wells when PFASs were found. 

Additional water testing was performed in 2014, 2015, and 2016. 

After the EPA finalized the PFOS and PFOA Health Advisory levels in May 2016, additional water samples were collected. Very low levels of PFOS were detected, which resulted in the discontinued use of additional wells.

The federal Safe Drinking Water Act requires testing of a number of unregulated substances every five years. The purpose of this testing, known as the Unregulated Contaminant Monitoring Rule (UCMR), is to collect data for substances suspected to be present in drinking water but that do not have established health-based standards under the Safe Drinking Water Act. This process provides a source of data used by the EPA in setting regulatory actions to protect public health. (EPA. 25, August 2016, retrieved from

The City continues to monitor for this unregulated substance by testing well water, treated water, and the water it purchases from Lewis and Clark water on a monthly basis.

Sioux Falls drinking water is safe to consume. The PFASs that were detected were at levels far below the EPA Health Advisory guidelines. The research to date does not demonstrate that there is a human health risk due to the very low levels that were found in the Sioux Falls water system.

The Sioux Falls Water Division has implemented a monitoring program that includes monthly tests of treated water for PFASs. The City also tests water received from the Lewis and Clark Regional Water System on a monthly basis. To date, no PFASs have been detected in the water purchased from the Lewis and Clark system.

The City has proactively and temporarily discontinued the use of any well where PFASs have been detected. The City is working with the State Department of Environment and Natural Resources’ Drinking Water Program to further understand the new health advisory. In addition, all currently operating wells are being tested to ensure they are free of PFASs.


Because they are emerging contaminants, the EPA has NOT established national primary drinking water regulations for PFOA and PFOS. EPA is currently determining if a maximum contaminant levels should be developed for PFOA and PFOS in drinking water.

While PFASs have recently been detected in the drinking water of several cities, there are no established state or federal regulations. Water systems are not required to routinely test or treat drinking water that contains PFAs.

EPA Health Advisories are non-enforceable, non-regulatory advisories that are used to provide public health officials with information on health effects associated with drinking water contamination.

People are most likely to be exposed to PFASs by consuming foods that contain high levels of PFASs (some fish and shellfish), drinking contaminated water, eating foods contaminated by packaging materials containing PFASs, or by eating foods prepared on certain “non-stick” cooking surfaces containing PFASs. Hand-to-mouth transfer may occur from surfaces treated with PFAS-containing stain protectants, such as carpets, which is thought to be most significant for infants and toddlers. 

People can also be exposed by breathing air that contains dust contaminated with PFASs (from carpets, upholstery, clothing, etc.), or from fabric sprays that contain PFASs. Skin contact with PFASs does not cause significant absorption. Infants may be exposed to PFASs through breast milk, but PFASs do not appear to be highly concentrated in breast milk. An unborn child can be exposed to PFASs from the mother’s blood because PFASs also can cross the placenta. 

Workers in the chemical industry who manufacture certain types of products may be exposed to PFASs at much greater amounts than the general public.

Studies show that nearly all people have some PFASs in their blood, regardless of age. PFASs build up and remain in the human body, and the amount reduces very slowly over time.

Limited studies in humans have shown that certain PFASs may be associated with:

  • Developmental delays in the fetus and child, including possible changes in growth, learning, and behavior
  • Decreased fertility and changes to the body’s natural hormones
  • Increased cholesterol
  • Changes to the immune system
  • Increased uric acid levels
  • Changes in liver enzymes
  • Prostate, kidney, and testicular cancer

More research is needed to confirm or rule out possible links between health outcomes and exposure to PFASs. Overall, the scientific evidence linking PFAS exposures with specific health effects in people is mixed and inconclusive.

(ATSDR (June 8, 2016). 24, August 2016, retrieved from

PFASs are found in the blood of people and animals all over the world and are present at low levels in a variety of food products and in the environment (air, water, soil, etc.). Therefore, completely preventing exposure to PFASs is unlikely. 

Fortunately, many companies are now reducing the use of PFASs in the manufacturing process. However, older products and imported materials may still contain these substances. People may choose to use products that do not contain pre-treated stain repellent products or grease-resistant food packaging.