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PFAS Chemicals and Thornton’s Drinking Water

Link to Thornton’s public notice letter for PFAS exceeding the Health Advisory Level (en español

Link to the USEPA PFAS page

Updates:

EPA releases final National Primary Drinking Water Regulation for PFAS (4/10/24): On April 10th, 2024 the US EPA released the final National Primary Drinking Water Regulation (NPDWR) for six per- and polyfluoroalkyl substances (PFAS). Much of the final rule remains similar to the draft NPDWR released in March 2023. Substantive changes from the draft rule include newly set Maximum Contaminant Levels (MCLs) for three PFAS compounds, monitoring and notification requirements, and an increased compliance schedule of 5 years. Please see the table below for the MCLs of the regulated PFAS compounds; compliance will be based on the average concentration of the previous 12 months of data (Running Annual Average or RAA). Thornton remains on pace to meet these regulations prior to the compliance deadline. The graphs below show how Thornton has compared to the final rule since the city began monitoring for PFAS. The city has been working with engineering consultants to design and build new treatment processes to remove PFAS from the drinking water. City staff are currently evaluating PFAS removal effectiveness and cost considerations of preliminary engineering designs for treatment options. Other steps Thornton has taken to protect our customers include blending water sources when available to reduce PFAS concentrations, shutting down groundwater wells that have high concentrations of PFAS, increasing Powdered Activated Carbon doses to reduce PFAS concentrations, and installing a new laboratory instrument to increase our ability to monitor PFAS compounds in our source and drinking waters.  

Background:
Per- and poly-fluoroalkyl substances (PFAS) are a group of manufactured chemicals that have been used in industry and consumer products since the 1940s. PFAS have characteristics that make them useful in various products, including nonstick cookware, waterproof clothing, stain-resistant carpets and fabrics, firefighting foam, and certain manufacturing processes. There are thousands of different PFAS. The domestic production or use of some PFAS (like PFOA and PFOS) has been largely phased out, but others continue to be used. 

PFAS tend to break down extremely slowly in the environment and can build up in people, animals, and the environment over time. PFAS have been found in water, air, and soil across the nation and around the globe. Because of this, PFAS can end up in the water sources communities rely on for drinking water. Scientific studies show links between certain levels of PFAS exposure and harmful health effects in humans and animals.

EPA NPDWR:

The final rule that the US EPA released in April 2024 will establish Maximum Contaminant Levels (MCLs) for six PFAS compounds: PFOS, PFOA, PFHxS, GenX, PFNA, and PFBS. The table below summarizes the regulation. Compliance with the rule will be based on the average concentration of the previous 12 months of data (Running Annual Average or RAA).

Compound MCLG (ng/L) MCL (ng/L)​Thornton Treatment Plant RAA
Wes Brown Water Treatment Plant RAA
PFOS
0
4​3.5
1.0​
PFOA04​2.4
1.2​
PFHxS​10
​10
2.2​​0.9
GenX
​10
10​​Not Detected
​Not Detected
PFNA
10​10​​0.2
​Not Detected
​Hazard Index
(Unitless. Evaluates PFHxS, PFNA, PFBS, and GenX as a mixture)
1
​1
0.3​​0.1


Thornton’s PFAS Status (updated 4/10/24):
Thornton has been actively monitoring for PFAS and adjusting treatment processes to lower PFAS in our customer’s drinking water. We fully expect to be able to comply with the proposed rule when it takes effect. 



PFAS FAQs

What are Thornton’s latest PFAS sampling results (updated 3/8/2024)?

The table below summarizes Thornton's drinking water's most recent PFAS sampling results. Wes Brown WTP is off for the winter season.

Date Site PFOS (ng/L) PFOA (ng/L) Hazard Index
10/10/23
​Wes Brown Treatment Plant
1.3
1.1
​0.1
2/27/24
Thornton Treatment Plant
1.7
2.2
0.2
US EPA Draft MCL:
4
4
1

ND - Not Detected

~ approximate value, result is below the lab reporting limit

* Hazard Index evaluates the concentrations of PFBS, PFNA, PFHxS, and GenX as a group


 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 expect 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 the treatment system removes PFAS.

Date Site PFOS (ng/L) PFOA (ng/L) Hazard Index
​2/21/24
Thornton Treatment Plant​2.2​​3.2
0.2​
1/29/24​
Thornton Treatment Plant​​2.0
​3.0
0.2​
1/11/24​
Thornton Treatment Plant​1.6​​1.6
​0.1
12/21/24​
Thornton Treatment Plant​1.3​
​3.8
​0.1
​11/28/23
Thornton Treatment Plant​​2.1
3.0​
0.2​
10/31/23​
Thornton Treatment Plant​1.2​0.9​0.1​
​10/10/23
Wes Brown Treatment Plant​​1.3
1.1​0.1​
​10/10/23
​Thornton Treatment Plant
​2.5
3.6​0.2​
9/26/23
Wes Brown Treatment Plant​1.1​2.4​0.1​
​9/26/23
Thornton Treatment Plant​​2.4
3.4​0.3​
9/7/23
Wes Brown Treatment Plant​1.4
1.2
0.1
9/7/23
Thornton Treatment Plant​2.6
3.5​
0.3
​8/29/23
​Wes Brown Treatment Plant
​1.7
​1.3
0.1​
8/29/23​
Thornton Treatment Plant​​2.4
​2.8
0.3​
​8/14/23
Wes Brown Treatment Plant​​1.7
1.4​0.1​
8/14/23
​Thornton Treatment Plant2.3​​2.6
0.3​
​7/18/23
Wes Brown Treatment Plant​1.8
​1.6
0.2​
​7/18/23
​Thornton Treatment Plant​1.8
2.1​
0.2​
6/27/23​
Wes Brown Treatment Plant1.8​2.0​0.2​
6/27/23
​Thornton Treatment Plant​2.0
2.1​0.2​
​6/15/23
Wes Brown Treatment Plant1.4​1.8​0.1​
​6/15/23
​Thornton Treatment Plant1.5​1.5​0.1​
​5/30/23
​Wes Brown Treatment Plant
​<1.9
​<1.9
​0
​5/30/23
​Thornton Treatment Plant
​4.5
​6.5
​0.5
​4/17/23
Wes Brown Treatment Plant​<1.9​​<1.9
​0
​4/17/23
Thornton Treatment Plant​5.6​​8.6
​0.7
​2/14/23
​Thornton Treatment Plant
​5.0
​7.1
0.7
​01/10/23
​Thornton Treatment Plant
​2.8
​4.5
0.4
​12/6/2022
​Thornton Treatment Plant
​2.4
​3.9
0.3
​11/15/2022
​Thornton Treatment Plant
​2.2
​3.7
0.3
​10/3/2022
​Wes Brown Treatment Plant
​~1.3
​~0.85

0.1
​10/3/2022
​Thornton Treatment Plant
​3.5
​6.3
0.5
​9/15/2022
​Wes Brown Treatment Plant
​~1.6
​~1.0
​0.1
​9/15/2022
​Thornton Treatment Plant
​3.0
​4.6
​0.4
​8/15/2022
Wes Brown Treatment Plant​​2.2
​3.8
0.3
​8/15/2022
​Thornton Treatment Plant
​3.0
​5.1
​0.4
7/26/2022Wes Brown Treatment Plant2.12.50.2
7/26/2022Thornton Treatment Plant3.25.0
0.3
5/5/2022Wes Brown Treatment Plant2.05.40.3
5/5/2022Thornton Treatment Plant3.57.10.6
4/27/2021Wes Brown Treatment Plant2.44.00.4
4/27/2021
Thornton Treatment Plant<2.03.00.0
US EPA Draft MCL: ​
4
4
1

ND - Not Detected

~ approximate value, result is below the lab reporting limit

* Hazard Index evaluates PFBS, PFNA, PFHxS, and GenX as a group

 Is my water safe to drink?

There is no immediate public health risk; people need not stop drinking their water now. Water systems are taking steps to lower the levels of PFAS in light of the NPDWR from the EPA. The state health department will keep providing facts to help inform the public about the latest science. Notably, the MCLs have not yet become enforceable, and utilities are not required to meet those limits until 2029. However, Thornton believes in protecting public health, and the Water Treatment and Quality group is performing temporary measures to reduce PFAS levels to meet the MCL while pursuing more permanent solutions. 

What are PFAS?

Per- and poly-fluoroalkyl substances (PFAS) are a group of manufactured chemicals that have been used in industry and consumer products since the 1940s. PFAS have characteristics that make them useful in various products, including nonstick cookware, waterproof clothing, stain-resistant carpets and fabrics, firefighting foam, and certain manufacturing processes. There are thousands of different PFAS. The domestic production or use of some PFAS (like PFOA and PFOS) has been largely phased out, but others continue to be used. 

PFAS tend to break down extremely slowly in the environment and can build up in people, animals, and the environment over time. PFAS have been found in water, air, and soil across the nation and around the globe. Because of this, PFAS can end up in the water sources communities rely on for drinking water. Scientific studies show links between certain levels of PFAS exposure and harmful health effects in humans and animals.

What is the timeline for regulating PFAS?

On April 10th, 2024 the US EPA released the final National Primary Drinking Water Regulation (NPDWR) for six per- and polyfluoroalkyl substances (PFAS). There is a five year compliance schedule associated with this regulation. For the first three years, the city must monitor for PFAS. Between years 3-5, the city must monitor and report PFAS results in our Consumer Confidence Report. After year 5 (April 2029), the city must meet the PFAS MCLs listed in the table at the top of this webpage. Thornton is on pace to meet this regulation within the compliance timeframe. 

What is the difference between MCLG and MCL? 

In the NPDWR, EPA proposes a Maximum Contaminant Level Goal (MCLG) and a Maximum Contaminant Level (MCL) for these six PFAS. MCLGs are non-enforceable public health goals. An MCLG is the level of a contaminant in drinking water at which no known or anticipated adverse health effects occur and which allows an adequate margin of safety. MCLGs consider only public health risks for sensitive populations like pregnant people, developing babies and infants, children, the elderly, and immunocompromised individuals. MCLGs do not consider limits of detection or treatment technology effectiveness. Therefore, MCLGs are sometimes set at levels water systems cannot meet because of current technological limitations. For example, if a contaminant is a known or likely carcinogen, EPA sets the MCLG at 0. MCLs are enforceable standards. An MCL protects public health by setting a maximum level of contaminant allowed in drinking water, which can be delivered to public water system users. The EPA must establish an enforceable MCL as close to the MCLG as is feasible. The EPA evaluates feasibility according to several factors, including costs and benefits, the ability to measure the regulated chemicals in drinking water, and whether proven treatment technologies capable of removing these chemicals under laboratory and field conditions exist. 

What is a Hazard Index?

EPA proposes to regulate four PFAS – PFHxS, GenX Chemicals, PFNA, and PFBS – as a mixture, using an established approach called a hazard index. The Hazard Index is a tool used to evaluate health risks from simultaneous exposure to mixtures of certain chemicals. Many PFAS are found together and in different levels and combinations. Estimating risk by considering one chemical at a time may underestimate the health risks associated with exposure to many PFAS simultaneously. 

To prevent health risks from mixtures of certain PFAS in drinking water, EPA proposes using this Hazard Index calculation to regulate PFHxS, GenX Chemicals, PFNA, and PFBS in public water systems. To determine the Hazard Index for these four PFAS, water systems would monitor and compare the amount of each PFAS in drinking water to its associated Health-Based Water Concentration (HBWC), which is the level below which no health effects are expected for that PFAS. Water systems would add the comparison values for each PFAS contained within the mixture. If the value exceeds 1.0, it will exceed the proposed Hazard Index MCL for PFHxS, GenX Chemicals, PFNA, and PFBS.

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?

Since the release of the updated Health Advisory Levels in June 2022, Thornton has been a leader in the state in addressing the risks of PFAS. 

  • Transparently inform the public on PFAS levels in the drinking water and our strategy to address the new regulations.
  • Procuring laboratory instrumentation to conduct further monitoring of PFAS in our system
  • Improving current treatment processes and source water blending strategies to reduce PFAS in the drinking water
  • Procuring engineering and construction consultants to evaluate the effectiveness of preliminary PFAS treatment designs
  • Entered a multijurisdictional lawsuit against the manufacturers of PFAS for costs related to PFAS treatment
  • Pursuing grant funding through CDPHE’s State Revolving Fund for PFAS monitoring and treatment
  • Supporting legislation that removes PFAS from entering the water source and holding polluters accountable

What can customers do about PFAS?

Customers concerned about reducing the risk associated with PFAS in their drinking water may install water filters at their homes. Visit the CDPHE website for a list of filters approved for PFAS removal: https://cdphe.colorado.gov/pfas-health.

Customers may also want to consider reducing exposure to PFAS from consumer products such as nonstick 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 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 for water treatment options. The filters recommended by CDPHE for PFAS removal range from $50-200: https://cdphe.colorado.gov/pfas-health.

What products are PFAS-free?

There is a list of everyday items with PFAS and which brands are PFAS-free: https://pfascentral.org/pfas-free-products/.

Additional Water Quality questions?

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