The History of 1,4-Dioxane: A Concern in Environmental Science

As you take a flight across the country, watching a movie on your phone and enjoying an in-flight meal, the people, materials, and chemicals that make these services possible feel like minor details. Modern industry has afforded the world fast travel, communication, and food. However, the synthetic chemicals used to deliver these conveniences have had disastrous consequences on water quality worldwide.

High-profile water contamination events like the PFAS contamination in North Carolina’s Cape Fear River, have raised public awareness and concern regarding drinking water safety. Even with airports, businesses, and drinking water providers complying with environmental regulations, the presence of emerging contaminants like PFAS and 1,4-dioxane in our water supplies remains a significant issue.  

Amid industry, utilities, airports, and agriculture grappling with the evolving landscape of PFAS regulations, another contaminant — 1,4-dioxane — is increasingly coming under scrutiny. Given the health hazards it poses, the ease at which it spreads, and its resistance to biodegradation, there is potential for 1,4-dioxane to follow a similar regulatory path as PFAS did, at both state and federal levels.

In the case of PFAS, the growing public concern influenced a comprehensive and strategic response from regulatory bodies. Initially, several states took the lead by enacting Maximum Contaminant Levels (MCLs) for PFAS chemicals. In 2021 EPA released its PFAS Strategic Roadmap, which culminated in the 2024 establishment of federal drinking water standards for six PFAS chemicals and the designation of PFOA and PFOS as hazardous substances under CERCLA.  

This multifaceted approach underscores the significant developments that can occur in these situations, highlighting the potential for a similar path for 1,4-dioxane. While a national MCL for this emerging contaminant may be years away, substantial regulatory progress at the state level could occur in the interim.

What is 1,4-Dioxane?

1,4-dioxane is a colorless liquid primarily used as a stabilizer in various industrial applications, such as solvents, greases, waxes and detergents, and enters the environment when these products are used or disposed of. A highly flammable chemical, its aversion to being absorbed by soil and high solubility in water make it pervasive in groundwater.

1,4-dioxane is sometimes labeled as a “forever chemical” alongside PFAS due to their bio-persistence, solubility in water, and resistance to evaporation, requiring specialized treatment technology to treat them. As a result, 1,4-dioxane persists in the environment for long periods, continuously threatening water sources and public health. After decades of improper discharge to water bodies from industrial processes and landfills receiving dioxane-laden consumer products, it has been detected widely in groundwater and surface water supplies.

Historical Context and the Discovery of 1,4-Dioxane

While 1,4-dioxane was first synthesized in 1863, its production exploded in the 1980s when it was mass-produced to stabilize the active chemicals found in aluminum aerosol cans products, particularly 1,1,1-Trichloroethane (1,1,1-TCA).  

1,1,1-TCA was eventually banned by the Montreal Protocol, due to its impact on the ozone layer. Still, the legacy of 1,4-dioxane’s parallel production and its more recent applications have created an ongoing contamination loop in the groundwater that many American communities rely on for drinking water, industry, and agriculture.

1,4-dioxane contamination arose from unregulated industrial discharge practices, where spent solvents were legally dumped into unlined ponds or leaked from underground storage tanks. Its contamination sources are as vast as its applications, including plane engine cleaner, pesticides and herbicides, and contaminated landfill leachate.

Common Sources of 1,4-Dioxane

The chemical’s widespread use has created multiple entry points for it to enter the environment. 1,4-dioxane does not stick to wastewater sludge, soil sediment, or carbon filters, allowing it to flow through underequipped water and wastewater treatment plants untouched. 1,4-dioxane contamination can come from, but is not limited to:

Industrial applications

• Paint strippers

• Adhesives

• Degreasing solvents

• Dyes

• Greases

• Varnishes and waxes

Personal Products

• Shampoo

• Makeup

• Detergents

• Cleaning products

• Deodorants

• Perfumes

• Toothpaste and Mouthwash

Airports

• Deicing fluids

• Industrial aviation cleaners

Agriculture

• Contaminated irrigation water 

• Pesticides and herbicides

The discharge of contaminated wastewater effluent continuously contributes to surface water and groundwater contamination of 1,4-dioxane, which are usually water sources for downstream communities. Once present in groundwater, the lack of UV light and abundance of water offer 1,4-dioxane the perfect safe haven to reside indefinitely, concerning affected community groups, lawmakers, and farms.

Water Pollution Findings and Impacts

Between 2013 and 2015, the EPA called on thousands of American water providers to monitor thirty water contaminants under UCMR3 (Third Unregulated Contaminant Monitoring Rule). This list of contaminants included 1,4-dioxane and the six PFAS chemicals recently added to the federal drinking water standard.

As part of the two-year study, 4,915 public water systems tested for 1,4-dioxane (for reference 4,920 systems tested for PFAS). Out of these, 1,077 systems (21.91%) had 1,4-dioxane detections, and 345 systems (7.02%) reported concentrations above the reference concentration of 0.35 ppb, which is the level the EPA considers hazardous to human health. The highest 1,4-dioxane detection in this dataset was 34 ppb.

To put this into perspective, the same study also assessed the presence of PFOS and PFOA, two well-known PFAS compounds. It found that 198 systems out of 4,920 participating water systems (4.02%) had any detection of PFAS, with 65 total systems (1.32%) reporting PFOS and PFOA levels above the 2016 reference concentration of 70 ppt. Given today's stricter MCL of 4 ppt for PFOS and PFOA, 3.60% of systems would have exceeded this limit, assuming today's detection limits were applied.

This comparison highlights a troubling trend: the percentage of water systems exceeding the reference concentration for 1,4-dioxane (7.02%) is significantly higher than those exceeding the 2016 reference concentration for PFOS and PFOA (1.32%). Given that the findings regarding PFAS concentrations prompted the EPA to take a closer look at regulations and safety measures, the higher prevalence of 1,4-dioxane detections above its reference concentration could signal a similar need for regulatory action regarding this emerging contaminant.

Health Impact of 1,4-Dioxane

The widespread contamination of 1,4-dioxane is particularly alarming because it is classified as likely to be a carcinogen. The EPA recently updated its risk assessment for this chemical, estimating that daily consumption of 1,4-dioxane in drinking water poses a cancer risk greater than one in a million for the general population.

Beyond cancer risks, research has shown that prolonged exposure to 1,4-dioxane can adversely affect organ function, including the liver, kidneys, and the central nervous system. Additionally, pregnant women, infants, and individuals with compromised immune systems may face more severe risks.

Decades of exposure through occupational proximity and inadvertent consumption have taken a toll on public health. As water systems wait to see what action the EPA and the various states may take to regulate 1,4-dioxane, lessons may be learned from those who took early action to manage their PFAS situations.

Looking Forward

After discovering numerous cases of 1,4-dioxane contamination in its groundwater, New York became the first state to set a 1,4-dioxane drinking water limit of one part per billion in 2020. In addition to its water regulation, New York State passed a bill to ban the sale of cosmetics, household cleaning, and personal care products containing 1,4-dioxane by the end of 2022. New Jersey has proposed a Maximum Contaminant Level (MCL) for 1,4-dioxane, while California has established a notification level of 1 ppb and a response level of 35 ppb.

In addition to this regulatory progress in the above-mentioned states, Virginia has enacted legislation mandating its State Board of Health to establish a maximum contaminant level (MCL). Similarly, Illinois has introduced comparable legislation. The EPA's recent update to the risk evaluation for 1,4-Dioxane indicates further regulatory advancement and is expected to impact forthcoming federal regulatory decisions.

Whether 1,4-dioxane will follow the same regulatory path as PFAS remains to be seen. However, some communities already had to invest in remediation and treatment solutions. Many others may follow. The case of contamination will likely come with costs that utilities or ratepayers will be forced to bear. Being proactive in identifying potential funding options can help mitigate future financial burdens and facilitate compliance with evolving regulations. By securing financial resources ahead of time, utilities can manage budgetary impacts more effectively and avoid the urgency and potential pitfalls of rushing to comply with any new regulations. Ultimately, urgency in seeking funding options allows water systems to plan and allocate resources efficiently.

If 1,4-dioxane is a contaminant you'd want to learn more about or if it is already on your radar, you can refer to our guides page for additional information about water contaminants, regulatory landscape, and funding options. Entities affected by contamination may have legal claims against the manufacturers of 1,4-dioxane and products that contain it and litigation can be an avenue to recoup some of these potential costs.