Addressing Forever Chemicals PFAS and 1,4 Dioxane

In the 1970s through the 1990s, 1,4-dioxane was used primarily as a stabilizer for chlorinated solvents, especially methyl chloroform. Methyl chloroform is associated with chlorinated solvent releases from industrial facilities, dry cleaners, landfills, and other sources. Until recently, the chemical often went undetected because it was not a required analyte at these kinds of facilities, and so it was often not considered when assessing release incidents.

The use of 1,4-dioxane as a solvent stabilizer has decreased since methyl chloroform was phased out by the Montreal Protocol in 1996, which aimed to reduce the production of chlorofluorocarbons (CFCs) that depleted the ozone layer.

We also see 1,4-dioxane in many manufacturing applications, from paints and varnishes to pharmaceuticals. It is also a byproduct in the manufacturing process of the plastic used in most drinking water bottles. While 1,4-dioxane is not intentionally added into consumer products in the United States, it has been found as a byproduct or contaminant in many everyday household products, including cosmetics, deodorants, detergents, shampoos, and other cleaning products (ATSDR, 2012). It has even been found in some food products from packaging residues or from pesticides used in food production.

The most common source of 1,4-dioxane in groundwater has been from spills or leaks of chlorinated solvents, either from industrial activities, manufacturing processes, or dry cleaning facilities. Unlined solid waste landfills have also been found to be sources of 1,4-dioxane in groundwater. 1,4-Dioxane has been identified in at least 34 of the 1,689 US EPA National Priorities List (NPL) hazardous waste sites (US EPA 2016b); however, the number of those sites that remain unevaluated for 1,4-dioxane is not known.

According to the California State Water Resources Control Board (SWRCB, May 2019), 194 active and standby public water wells out of 1,539 sampled had at least one detection of 1,4-dioxane well above the EPA advisory number. Results of a 2006 U.S. Geological Survey study of 1,208 domestic wells detected the presence of potential 1,4-dioxane co-contaminants in as many as 102 wells (Zogorski et al., 2006).

1,4-Dioxane is considered a persistent and recalcitrant compound; it completely dissolves in water, it does not easily sorb onto soil or other particulates, and it does not readily biodegrade in the environment. As a result, it is very mobile in groundwater and can travel great distances with little change in its concentration.  Most chlorinated solvents, like 1,4-dioxane, readily degrade under anaerobic conditions so natural attenuation will often reduce the size and concentrations in a chlorinated solvent plume over time. However, since 1,4-dioxane does not degrade, not only can the 1,4-dioxane plume extend much farther than the solvent plume, but it is often left behind, even decades after a release.

Due to its physical and chemical properties, 1,4-dioxane is very hard to treat in groundwater. Although 1,4-dioxane is classified as a volatile organic compound (VOC), most of the conventional methods for treating other VOCs do not work well on 1,4-dioxane (Myers et al., 2018 and Chiang, 2016).

In general, the most effective treatments require the impacted groundwater to be removed from the subsurface, treated above ground, and then discharged. However, there are some potentially effective technologies that do not require the removal of groundwater from the subsurface. The challenge with most of these effective or potentially effective technologies is that they are costly. Most plumes associated with unlined landfills have low-level concentrations of contaminants that are not large. Implementing these expensive technologies is cost-prohibitive for these types of plumes. They are more feasible to apply to a large Superfund site.

An even bigger challenge is treating residential supply wells that are found to be impacted by 1,4-dioxane. Most commercial home water filters do not remove 1,4-dioxane effectively. The most practical solution may be to install a two-stage granular activated carbon (GAC) filter system on the home, sample it frequently (at least quarterly), and then replace the first filter as soon as there is breakthrough. Breakthrough will happen much more quickly for 1,4-dioxane than for most other VOCs, so the filters will need to be changed often. Eventually, it may be necessary to replace the well with a new one farther from the 1,4-dioxane source; however, that is not always possible, especially given how far 1,4-dioxane can travel.

Researchers are continuing to study the human toxicology of 1,4-dioxane to give the EPA the data they need to establish consistent standards and policies. Federal, state, and local regulatory agencies are requiring more testing of groundwater, surface water, and drinking water supplies for 1,4-dioxane at many facilities and release sites. In addition, many industries and manufacturers are removing 1,4-dioxane from their processes and products, as well as developing better management practices to prevent its release into the environment. Moreover, new treatment technologies and approaches are being developed and tested to help clean up 1,4-dioxane contamination sites.

In August 2020, New York adopted first-in-nation drinking water standards for 1,4-dioxane and approved a treatment standard. Scroll down for more.