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PFAS Chemicals and Thornton's Drinking Water

EPA releases drinking water health advisories for PFAS:  PFAS are a family of chemicals used in firefighting foams, non-stick cook wear, stain and water resistant fabrics, and a number of other everyday products. These chemicals have made their way into the environment. To learn more about PFAS, the updated Health Advisories, what the city of Thornton is doing in response, as well as actions you can take to lower your risk, please read the PFAS Letter.

La EPA publica avisos de salud del agua potable para PFAS:
Los PFAS son un grupo de productos químicos utilizados en espumas contra-incendios, sartenes y articulos de cocina antiadherentes, telas resistentes a manchas y agua, ademas de varios otros productos cotidianos. Consequentemente, estos productos químicos estan presentes en el medio ambiente. Para obtener más información sobre los quimicos PFAS, o los mas actuales Avisos de salud, ademas de lo que la ciudad de Thornton está haciendo al respecto, así como las acciones que puede tomar para reducir su riesgo, por favor lea la Carta de PFAS.


What are Thornton’s latest PFAS sampling results (updated 09/28/2022)?

The table below summarizes the most recent PFAS sampling results in Thornton’s drinking water. 

8/15/2022Wes Brown Treatment Plant2.2
8/15/2022Thornton Treatment Plant3.0
US EPA Health Advisory:

All units in parts per trillion (ng/L)
ND = Not Detected  

What are Thornton’s historical PFAS results and why is there variability in those results?

The table below summarizes Thornton’s PFAS sampling results. Thornton is actively reducing PFAS concentrations in our customer’s drinking water, however we do expect there to be variability in these results due to differences between Thornton’s various raw water sources, seasonal variability within each raw water source, and variability of water treatment plant performance. Thornton has optimized the existing treatment processes where possible, but water quality coming into the treatment plant can vary and may affect how much PFAS is removed by the treatment system.


Wes Brown Treatment Plant​​2.2
​Thornton Treatment Plant
7/26/2022Wes Brown Treatment Plant2.12.53.9ND
7/26/2022Thornton Treatment Plant3.25.04.8ND
5/5/2022Wes Brown Treatment Plant2.05.45.8ND
5/5/2022Thornton Treatment Plant3.57.18.0ND
4/27/2021Wes Brown Treatment Plant2.44.07.1ND
Thornton Treatment Plant<
US EPA Health Advisory: ​

All units in parts per trillion (ng/L)

ND = Not Detected 

Is my water safe to drink?

There is not an immediate public health risk, and people do not need to stop drinking their water at this time. Water systems are taking steps to lower the levels of PFAS in light of the new health advisories from the EPA. The state health department will keep providing facts to help inform the public on the latest science. 

What are PFAS?

Per- and polyfluoroalkyl substances (PFAS) are a large group of chemicals used since the 1940s in common household and commercial products. PFAS have unique chemical properties and are often used to keep food from sticking to cookware. They also make clothes, carpets, and furniture more fire, water, and stain resistant.

Why is EPA releasing Health Advisories (HA) for PFAS in drinking water

PFAS are slow to break down in the environment and can move far from their original use areas. The manufacturing and use of products with PFAS puts PFAS into the environment, where, over time, they may end up in drinking water supplies.

When will EPA issue Maximum Contaminate Levels (MCL) for PFAS?

The Agency expects to release the draft Maximum Contaminate Levels (MCL) at the end of calendar year 2022.

What is the difference between a PFAS MCL and the new HA?

The EPA frequently uses HAs in the development of MCLs. HAs are theoretical levels of exposure at which no health effects are anticipated. MCLs are developed with practical constraints such as treatability and analytical capability. MCLs are also based on probability of an adverse health effect based on 70 years of consumption above the MCL.

What are the health risks of ingesting PFAS?

Scientists are studying the health effects of elevated PFAS blood levels. Preliminary research indicates that health effects may include certain types of cancer, high cholesterol, and decreased vaccine response in children. Because of their prevalence in our homes from products we purchase, as well as environmental exposure via the air, water, and dust, virtually every person in America has a detectable level of PFAS in their blood.

What is Thornton Water doing now about PFAS?

In the next three years, all drinking water systems larger than 3,300 customers will need to sample for PFAS, under the Fifth Unregulated Contaminant Monitoring Rule (UCMR5). In advance of the UCMR5, we have begun testing for PFAS, and have discovered trace amounts. We are taking steps to inform residents, undertake additional monitoring to assess the level, scope, and source of contamination, and examine steps to reduce exposure.

What can customers do about PFAS?

Customers who are concerned and would like to reduce their risk associated with PFAS in their drinking water may install water filters at their home. Visit the CDPHE website for a list of filters approved for PFAS removal:

Customers may also want to consider reducing exposure to PFAS from consumer products such as non-stick pans, take-out food, waterproof clothing/outdoor gear, and cosmetics.

I’m concerned and would like to purchase a water filter, but a company gave me a quote that costs thousands of dollars. Do I really need to spend that much?

Thornton has received reports of companies using predatory sales tactics to scare customers into paying more than they need to on water treatment options. The filters recommended by CDPHE for PFAS removal range from $50-200:

What products are PFAS-free?

There is an available list of common items that have PFAS, and which brands are PFAS-free:

Additional Water Quality questions?

If you have any questions or concerns about your tap water that were not answered here, please email or call the Water Quality Line at 303-255-7770.

Additional Information