City seeks dismissal of lawsuit over dioxane levels

Three months after two environmental groups sued Asheboro and plastics maker StarPet Inc. over 1,4-dioxane pollution, the case has become a fight over whether federal courts should step in now or wait for legal battles North Carolina to play out.

The lawsuit filed in June of this year — by Cape Fear River Watch and Haw River Assembly — accuses Asheboro’s wastewater treatment plant of illegally releasing 1,4-dioxane, a likely human carcinogen, into Haskett Creek for more than a decade. StarPet, a plastics manufacturer that discharges into the city’s system, is named as the leading source.

Because the chemical 1,4-dioxane passes through treatment plants untouched, it flows into the Cape Fear River basin and into downstream drinking water supplies serving nearly 900,000 people. Federal health officials say long-term exposure to even trace amounts can increase cancer risks.

City seeks dismissal or delay

In July, Asheboro asked a federal judge to throw out the case — or at least put it on hold — arguing that the same issues are already being fought in state court.  Lawyers for the city say North Carolina’s Department of Environmental Quality (DEQ) is “diligently prosecuting” the matter and that citizen suits are barred when regulators are already in court.

Lawyers for the city also invoked protections under the Clean Water Act’s “permit shield,” claiming its 2012 wastewater permit — reinstated earlier this year — did not include limits on 1,4-dioxane. City attorneys argue that without an enforceable standard, Asheboro cannot be sued. 

The City of Asheboro questioned the science behind 1,4-dioxane’s carcinogenicity, arguing that the environmental groups bringing the suit “incorrectly describe 1,4-dioxane as a ‘cancer-causing chemical’ about which the science is well-settled.”

To support this claim, the city pointed to a challenge filed by Union Carbide, a subsidiary of Dow Chemical. In late 2024, Union Carbide petitioned EPA to reconsider its risk evaluation of 1,4-dioxane, contending that the agency overstated the evidence linking the chemical to cancer in humans and relied on flawed methods in its calculations. 

That petition led EPA to reopen its review of 1,4-dioxane’s carcinogenicity, a process expected to take at least another year. 

Currently, the EPA classifies the chemical as probable human carcinogen while HHS labels it reasonably anticipated to be carcinogenic. StarPet joined Asheboro’s filings, saying plaintiffs have not identified any industrial permit terms or pretreatment standards that the company actually violated.

Suing groups push back

In August, the conservation groups urged the judge in the case to reject dismissal. They argue neither DEQ nor the EPA is prosecuting violations, leaving around 900,000 residents downstream exposed to an ongoing health threat from what is currently classified as a probable human carcinogen by the EPA.

Their lawyers say Asheboro cannot hide behind its permit because the city never disclosed dioxane discharges when it applied for the permit, arguing that courts have repeatedly held that permit holders must know and disclose all pollutants they release.

They also reject the city’s claim that EPA’s lack of a specified limit in the 2012 permit excuses pollution, noting the Clean Water Act covers all pollutants — not just those with listed guidelines.

A back-and-forth in court

On Aug. 28, Asheboro filed a reply brief doubling down on its dismissal request, insisting state litigation over dioxane limits makes the federal suit redundant. The city said the proper place to decide the issue is state — not federal court.

StarPet echoed the argument in its own filing the same day, stressing that no enforceable 1,4-dioxane limit exists under its current permits. A week later, on Sept. 4, the environmental groups sought permission to file a supplemental reply, responding to what they called new arguments from the city — chiefly Asheboro’s claim that it did not know about dioxane in 2012 and that EPA had not yet issued guidelines. The groups say ignorance is no defense and that the Clean Water Act prohibits discharge of any pollutant, regardless of whether EPA has set specific rules.

Parallel fight in state court

At the same time, Asheboro is also battling the state’s Department of Environmental Quality (DEQ) in state court over its wastewater permit. NC DEQ added dioxane limits to a 2023 permit, but Asheboro challenged them. Last September, an administrative law judge sided with the city, declaring the limits void and questioning DEQ’s authority to treat dioxane as a carcinogen without going through the state’s rule-adoption process. That decision garnered a letter from the EPA which objected because the state-issued permit let Asheboro discharge unlimited 1,4-dioxane, which EPA says violates the Clean Water Act and poses cancer risks.

DEQ appealed to Wake County Superior Court, where the case is pending. In January, the parties agreed to let Asheboro keep operating under its old 2012 permit while the appeal proceeds. State lawyers maintain that under existing rules, dioxane is a carcinogen and enforceable limits are needed to protect public health. Asheboro and allied cities counter that regulators skipped required rule-making and relied on unsettled science.

What’s next

The federal judge has not yet ruled on Asheboro’s motion to dismiss or delay the case. Meanwhile, the state appeal is moving toward a hearing later this year, and EPA’s scientific review of 1,4-dioxane is expected to take at least another year.