'Forever chemical' levels in Thornton's water exceed EPA's new health advisory

Luke Zarzecki
Posted 7/29/22

A new health advisory from the Environmental Protection Agency lowered the standards for PFAS composition – commonly known as “forever chemicals” – in drinking water and that …

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'Forever chemical' levels in Thornton's water exceed EPA's new health advisory


A new health advisory from the Environmental Protection Agency lowered the standards for PFAS composition – commonly known as “forever chemicals” – in drinking water and that puts Thornton and their water customers in a tough spot.

The EPA set the new advisory on June 15 at 0.0004 parts per trillion for PFOA and 0.02 parts per trillion for PFOS. 

In May 2022, the Thornton Water Treatment Plant measured 7.1 parts per trillion for PFOA and 3.5 parts per trillion for PFOS. The Wes Brown Water Treatment Plant saw 5.4 parts per trillion for PFOA and 2.0 parts per trillion for PFOS.

Although the levels are over 1,000 times higher than the health advisories, City Spokesperson Todd Barnes said residents should not worry and should not stop drinking the water.

“This is a concern, not a crisis. People do not need to stop drinking their water,” a letter sent to residents reads. 

However, even though Thornton’s levels are low, Metropolitan State University Professor Shamim Ahsan said people should still be attentive because it’s not the current amount of PFAs, but the buildup in the body.

All Thornton water customers will receive the letter, as required by the EPA. 

Barnes noted that the advisory will not only affect Thornton but other municipalities around Colorado and the U.S. Updating and upgrading water treatment plants to detect the new levels – should the health advisory turns into regulations – will be costly. He noted that most scientific equipment can’t detect levels that low.

Suprise change

The new levels took the water quality community by surprise, according to  Martin Kimmes, Thornton’s Water Treatment and Quality Manager. He knew the EPA was going to lower levels, but not by how much. 

“They pretty much went down to as close to zero as they could,” Kimmes said.

He said the amount of PFAS in the new guideline is as diffuse as one drop of detergent in enough dishwater to fill a 10-miles-long train of railroad cars.

The utility could be looking at spending tens of millions of dollars to satisfy the potential regulation, he said. Engineers have already started making conceptual designs. 

Some of that money may come from the federal government from the bipartisan Infrastructure Law that was passed last November as part of the Infrastructure Investment and Jobs Act.

Consider the source

EPA Region 8 Public Affairs Specialist Richard Mylott said the law provides $5 billion to help state agencies and utilities address PFAs and containment projects. Beyond upgrading water treatment plants, the new law will also aim to study where the cause of the pollution originates. For Thornton, that may be the South Platte River where the city receives most of its water. That river flows through Commerce City. 

Mylott said the South Platte River contains the highest amount of PFAS and mixing water from that source with the others, such as Clear Creek – which contains undetectable levels of PFAS – lowers the overall levels by dilution

Efforts to understand how the chemicals contaminate drinking water date back to the 1940s when the chemicals first started being used, according to Ahsan. 

PFAS are commonly used in multiple ways on a regular basis, he said, and they then are flushed into the water cycle. That can be from washing machines with plastic from clothes, runoff and spills from industrial sites, firefighting foams or agricultural biosolids that are spread across crops. 

The chemicals break down slowly, which makes them a persistent issue. 

“If we can replace these chemicals with less harmful chemicals, then it will prevent this contamination,” MSU’s Ahsan said. 

Health effects

Pregnant women and children under age five are most at risk, Kimmes said, since they are consuming more water and food per pound of body weight compared to others. 

The chemicals target the immune and cardiovascular systems, Ahsan said. They can lead to decreased fertility, developmental effects or delays in children, increased risk of cancer and interference with the body’s natural hormones. 

Ahsan explained that when PFAS enter the body, they stay there; they aren’t flushed out. That means even with low drinking water concentrations, they can form into large amounts within the body. 

The letter sent to Thornton residents outlined solutions for those concerned. They can reduce their exposure by using an in-home filter certified to lower PFAs or using bottled water treated with reverse osmosis for drinking, cooking and preparing baby formula. 

Kimmes noted residents need to be wary, as the city has already seen predatory filter sales and people trying to sell expensive filtration systems with scare tactics.

“There are some inexpensive alternatives and we’ve listed some of those on our webpage, ranging from $50-200,” Kimmes said. 


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