9Cl-PF3ONS
9-chlorohexadecafluoro-3-oxanonane-1-sulfonic acid
- EPA federal limit
- No federal limit
- Detected in
- 10,289 systems
- Regulatory status
- Unregulated (UCMR 5)
What is 9Cl-PF3ONS?
9-chlorohexadecafluoro-3-oxanonane-1-sulfonic acid, known as 9Cl-PF3ONS, is a man-made chemical that belongs to the PFAS family, a group of thousands of chemicals often called "forever chemicals." Like other PFAS, 9Cl-PF3ONS is built with extremely strong chemical bonds that make it nearly impossible for nature to break down. This means it can build up in the environment and in living things over time.
Where does it come from?
9Cl-PF3ONS is an industrial chemical that has been used mainly in manufacturing processes, particularly in China as a replacement for other restricted PFAS compounds. It can enter the environment through industrial wastewater discharge and may also appear in some consumer products that use PFAS-based coatings or treatments. It has been detected in surface water and drinking water near industrial sites.
Health concerns
Research on 9Cl-PF3ONS is still in early stages, and published data in humans is very limited. Some animal studies have associated this compound with effects on the liver and thyroid function, but these findings have not yet been confirmed in large human studies. Because evidence is limited, scientists cannot draw firm conclusions, and more research is needed. If you have specific health concerns, consult a healthcare provider.
EPA standard
The EPA has not established a Maximum Contaminant Level (MCL) — a legal limit for how much of a chemical is allowed in drinking water — for 9Cl-PF3ONS. Without a federal limit, public water systems are not required to test for or remove it. This means there is currently no regulatory safety net for this specific compound.
What you can do
If you are concerned about 9Cl-PF3ONS in your water, consider using a certified reverse osmosis filter or an ion exchange filter, both of which research studies show can effectively reduce PFAS compounds in drinking water. Granular activated carbon filters may also help, though they are generally less effective than reverse osmosis. Remember, boiling water does not remove PFAS — it can actually concentrate them.
About this summary: Narrative text on this page was drafted by an AI model (claude-sonnet-4-6) from EPA UCMR 5 data and reviewed before publication. The numeric data above is reported by water utilities directly to the EPA. If you spot an error, email data@checkyourwater.org.