Production to Pollution: 1,4-Dioxane and its Environmental Footprint

The products we buy have stories. Take a pair of jeans - starting its journey from cotton fields to factory floors, followed by years of wear. Like anything, jeans reach the end of their usefulness and are eventually replaced and discarded. They leave our homes, but their material lives on at a landfill or secondhand store.

1,4-dioxane is no different. Produced to stabilize chlorinated chemicals and discharged into landfills and waterways, this chemical continues to exist in the environment well after its useful life in a factory.

1,4-dioxane is a colorless liquid, primarily used to stabilize active chemicals in solvents, greases, and detergents. It is sometimes categorized as a “forever chemical” alongside PFAS due to their bio-persistence, solubility in water, and resistance to evaporation, requiring specialized treatment technologies to remove them from water. After decades of improper discharge to water bodies from dioxane-laden industrial processes and landfill leachate, it has contaminated groundwater and surface water, continuously threatening drinking water and public health.

1,4-dioxane is a tenacious contaminant. Coupled with a lack of regulations to treat it at industrial sites and landfills, 1,4-dioxane has continuously spread from its industrial origins and entered our air, water, and soil. Oxygen and sunlight degrade the contaminant quickly, minimizing its air pollution hazards. The stable characteristics that make it an industrial superstar also prevent it from interacting with soil. This leaves one place for 1,4-dioxane to extend its life: our groundwater.

The Lifecycle of 1,4-Dioxane

We typically hear news about pollution after it’s entered our environment and caused damage to ecosystems and human health. But the story of how it arrived in our streams, soil, and air is sometimes neglected. In the case of 1,4-dioxane, production is simple: it improves many industrial processes and consumer products and, up until recently, there were few regulations to prevent it from entering the environment.

Industrial Production and Uses

Producing 1,4-dioxane is like making a panini. A chemical called diethylene glycol (the sandwich) is mixed with an acid (the toaster). The reaction dehydrates (cooks) the diethylene glycol — yielding 1,4-dioxane (the panini). On an industrial scale, this process happens in large metal vats, applying heat and acid to thousands of gallons of diethylene glycol and harvesting the resulting 1,4-dioxane.

In some instances, 1,4-dioxane is manufactured accidentally, particularly during ethoxylation. Ethoxylation is the mixing of ethylene oxide, a diethylene glycol precursor, with other chemicals to make new ones. These novel chemicals are often active ingredients in laundry detergents, cosmetics, agricultural products, clothes dye, and other household products.  

1,4-dioxane is a workhorse. Widely used as a laboratory reagent, solvent, and stabilizer for chlorinated solvents, it can be found in adhesives, sealants, and electronic components. Other industrial applications include:

• Stabilizing volatile chemicals: Particularly chlorine-based solvents, preventing corrosion during storage and use.

• Pharmaceuticals: Acting as a purifying agent in the production of medicines.

• Manufacturing processes: Supporting the production of dyes, adhesives, plastics, and lubricants.

• Textiles: Used to dye fabrics and ensure uniform color application.

• Semiconductor production: Where its stability supports precision manufacturing.

• Food processing: Assisting in oil extraction and other processes.

Once it leaves the manufacturing floor, 1,4-dioxane finds its way into an array of industrial and consumer applications. Its high solubility, stability, and effectiveness as a solvent make it an essential component in countless products and processes.  

Distribution and Applications

Coming home from the grocery store, you may have a number of products that were touched by 1,4-dioxane. Of particular concern are detergents for laundry and dishwashing, shampoos, soaps, and cosmetics, where the contaminant emerges accidentally via ethoxylation. Consumer brands have made strides in reducing 1,4-dioxane levels in these products, but its persistent presence means it continues to enter the environment when these items are discarded.

The industries that benefit from 1,4-dioxane’s properties are as varied as its applications, spanning pharmaceuticals, cosmetics, electronics, and agriculture. Its inclusion in so many products and processes ensures its pervasive footprint in both the economy and the environment.

Whether through direct use, accidental production, or inclusion in finished products, 1,4-dioxane ultimately makes its way into landfills, wastewater, and the air. From there, it often leaches into groundwater or flows into surface water, creating a persistent contamination challenge.

Pathways to Environmental Contamination

1,4-dioxane’s journey from manufacturing wonder child to discarded environmental pollutant is paved with multiple paths. Its chemical properties, combined with decades of inadequate disposal practices, have allowed it to infiltrate groundwater, surface water, and soil. Manufacturing facilities that produce or use the chemical in solvents, adhesives, and detergents often release it through:

• Wastewater discharges: Where it flows untreated into water bodies due to its resistance to conventional treatment methods and lack of regulation.

• Air emissions: During production or disposal, allowing 1,4-dioxane to settle back into soil or water.

• Unregulated disposal: Historical practices, such as dumping solvents into unlined ponds or landfills, have left behind a legacy of contamination.

Landfills are a significant source of 1,4-dioxane contamination as well. Consumer products containing trace amounts of the chemical are discarded, and over time, rainfall and decomposition create leachate that carries the compound out of landfills and into groundwater. Studies show that 1,4-dioxane is present in 70% of landfills receiving incinerator waste and 38% of those handling other types of waste​​.

Due to its pervasiveness, water discharged from wastewater treatment plants often contains 1,4-dioxane as well, as traditional treatment methods like carbon filtration fail to capture it. Groundwater recharge using treated effluent can further compound the issue, directly introducing the contaminant into aquifers relied upon for drinking water.

The combination of these pathways has resulted in a widespread presence of 1,4-dioxane in drinking water supplies. Understanding how the chemical reaches water systems is the first step toward effective remediation and prevention strategies.

1,4-Dioxane Water Contamination in the US

The contamination of groundwater and surface water with 1,4-dioxane is extensive. Results from the EPA’s Third Unregulated Contaminant Monitoring Rule (UCMR3) revealed the presence of 1,4-dioxane in 7% of public water systems sampled across the country, with concentrations exceeding the health-based reference level of 0.35 µg/L. At some sites, levels soared as high as 2,400 µg/L, far beyond thresholds considered safe for human health​.

When comparing UCMR 3 results, only 4.02% of systems tested had any detections of PFAS, with 1.32% above the reference concentration. In contrast, 21.92% of systems tested had detections of 1,4-dioxane, with 7.02% above the reference concentration. Despite the limited scope of UCMR 3 testing, the significant prevalence of 1,4-dioxane contamination suggests it could follow a similar regulatory path as PFAS at the federal level. Its ability to evade conventional treatment methods exacerbates the problem, requiring advanced technologies for effective removal.

Some states have experienced severe contamination due to local industrial activity and legacy pollution. These hotspots underscore the regional variability of 1,4-dioxane contamination and the need for location-specific strategies to address it. As a result, the following states have either passed regulations or are actively in the process of developing them:

• New York: Long Island is the epicenter of 1,4-dioxane pollution in the state of New York, where over 90% of the state’s contaminations occurs.

• California: Home to hundreds of contaminated sites, with some utilities reporting concentrations far above regulatory thresholds.

• New Jersey: Where contamination from industrial solvents has led to state-specific drinking water guidelines and increased testing requirements.

The presence of 1,4-dioxane in drinking water raises significant health concerns. Classified by the EPA as a likely human carcinogen, prolonged exposure is linked to liver and kidney damage and an increased risk of cancer. Its persistence in water supplies makes it an ongoing hazard, particularly for vulnerable populations such as children, pregnant women, and individuals with compromised immune systems.

Regulatory and Remediation Efforts

After discovering widespread 1,4-dioxane contamination in its groundwater, New York became the first state to set a drinking water limit of one part per billion for this contaminant in 2020. In addition to its water regulation, New York State also passed a bill banning the sale of contaminated cosmetics, household cleaning, and personal care products, which went into effect at the end of 2022. New Jersey, California, and Virginia are following suit, all in the process of developing drinking water regulations to limit 1,4-dioxane concentrations in drinking water sources.  

These regulations aim to protect consumers’ health but come with a price tag. Water utilities that discover 1,4-dioxane in their water, whether now or in the future, may experience disruptions to their planning and budgets, from having to hire consulting engineers, purchase new treatment solutions, and manage public concerns based on the severity of the contamination. Applying for grants to fund remediation costs might be an option, however it does not always cover all expenses, often leading water systems to think that they have no other choice than raising rates or taking out loans. Fortunately, there are other innovative funding strategies that agencies can pursue, such as water contamination litigation, which allows utilities to cover the clean-up costs by holding accountable the chemical manufacturers responsible for the pollution. In fact, many public and private agencies have already successfully pursued litigation against the polluters that produced the legacy contamination we see today.  

To learn more about water contamination and how some communities are fighting back, read one of our guides.