Water splashing against a white background

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:

Bench scale testing begins (2/8/24): The City of Thornton has started design of new treatment processes to remove PFAS from the drinking water. This week the city's engineering consultant collected finished water from Thornton Water Treatment Plant to perform Rapid Small Scale Column Testing (RSSCT). These tests will compare Granular Activated Carbon and Ion Exchange Resin to determine the best PFAS removal technology for our water.  

Legislative Priorities (2/8/24): Staff have briefed Thornton City Council on legislative priorities to support during state and federal legislative sessions this year. Those priorities include holding polluters accountable for the cost of PFAS removal, removing PFAS from consumer products, and requests for additional federal funding for PFAS removal. 

Lawsuit against PFAS manufacturers (7/14/23): The City of Thornton is a current plaintiff in a lawsuit against chemical manufacturers over the contamination of drinking water with per- and polyfluoroalkyl substances (PFAS). A recent USGS study indicated that PFAS could be detected in about 45% of U.S. drinking water. Some of these companies, the 3M Company, Dupont, Chemours, and Corteva have tentatively agreed to settle the ongoing multi-district litigation (MDL). 3M agreed to pay $12.5 billion, and Dupont, Chemours, Corteva agreed to $1.185 billion. A Special Master and Claims Administrator will oversee the allocation of settlement funds to be paid to water utilities with PFAS contamination. These funds can only be used for PFAS removal treatment.

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.

Draft EPA Rule:

The draft rule that the US EPA released in March 2023 will establish standards for six PFAS compounds. The table below summarizes those draft standards.

Compound MCLG (ng/L) MCL (ng/L)
PFOS0
4
PFOA04
PFBS



Hazard Index = 1.0 (unitless)
​ ​
​ ​
PFHxS
PFNA
GenX


Thornton’s PFAS Status (updated 12/29/23):
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 Status.PNG



PFAS FAQs

What are Thornton’s latest PFAS sampling results (updated 12/29/2023)?

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
11/28/23
Thornton Treatment Plant
2.1
3.0
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
​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 draft NPDWR from the EPA. The state health department will keep providing facts to help inform the public about the latest science. Notably, the draft MCLs have not yet become regulated, and utilities are not required to meet those limits. 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 draft 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 March 14th, 2023, the US EPA released the National Primary Drinking Water Regulation (NPDWR) draft for PFAS. There will be a 60-day public comment period. The EPA considers all public comments informing the final regulation's development. The EPA expects to finalize the PFAS NPDWR by the end of 2023 or early in the first quarter 2024. Once completed, drinking water utilities like Thornton must meet the regulations within three years. 

What is the difference between MCLG and MCL? 

In the proposed rule, 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.