June 16, 2022

Environmental, Natural Resources, & Energy Law Blog

1,4-Dioxane: Why Drinking Water Regulations Won’t Work to Mitigate This Carcinogenic “Forever Chemical” - Scott Hudson


The water you are drinking and using to cook, bathe and clean is likely contaminated with carcinogens. If you are like most Americans, you take clean, fresh drinking water for granted. However, recent studies show that municipal drinking water and groundwater in the United States and other industrialized countries is increasingly contaminated with 1,4-dioxane, a known carcinogen. 1,4-Dioxane and other “forever chemicals” constitute an overlooked environmental health hazard that is not addressed by current drinking water regulations. This blog will discuss the sources of 1,4-dioxane, how it is getting into our ground and drinking water and its adverse environmental and health effects. The blog will also discuss the limitations of using drinking water statutes to mitigate these impacts and recommend a comprehensive regulatory approach as a solution.



1,4-Dioxane is a by-product of industrial processes found in many common goods including dyes, anti-freeze, deicers and paint stripper, and alarmingly, in much-used consumer products such as shampoos and deodorants.[1] It is often referred to as a “forever chemical” meaning that it can last for thousands of years and is resistant to water, heat and normal biodegradation.[2]

Historically, 1,4-dioxane was primarily a stabilizer in chlorinated solvents, which were used in wafer fabrication and cleaning for components of the semiconductor and printed circuit board industry.[3] Regulatory agencies required these solvents and solvent wastes to be stored in underground storage tanks, which leaked or were the source of spills, contaminating nearby groundwater.[4] Due to its stability and reluctance to react with other substances, 1,4-dioxane was later used in a wide range of processes, which created new sources of contamination, such as leachate from landfills, detergent manufacturing plants and metal manufacturing/chroming facilities.[5] 1,4-Dioxane is also a by-product of manufacturing polyethylene terephthalate (PET) plastic and is used as a purifying agent in manufacturing pharmaceuticals.[6] Although it was widely used, disposal methods varied and in some cases the technical guidance for disposal involved nothing more than pouring 1,4-dioxane into open trenches so it could evaporate.[7]

These lax methods along with 1,4-dioxane’s unique chemical properties and broad use have resulted in widespread environmental contamination of ground and surface water. 1,4-Dioxane is highly soluble in water and is not easily absorbed by soils.[8] It also does not react with oxygen nor do soil micro-organisms degrade it.[9] Therefore, it remains ever present in the environment until removed.[10] Studies have also shown that because of its properties, 1,4-dioxane easily migrates to other areas.[11] 1,4-Dioxane is also a major contaminate in drinking water derived from surface water.[12] The source of these contaminates is likely industrial wastewater, either directly from industrial wastewater treatment plants or from sewer collection systems, released into municipal wastewater treatment facilities.[13]

Municipalities identified 1,4-dioxane in their drinking water as early as the 1970s.[14] But, the chemical only received regulatory attention when the Environmental Protection Agency (EPA) included it on the Drinking Water Contaminant Candidate Lists in 2009 and the Third Unregulated Contaminant Monitoring Rule in 2016.[15] This prompted additional research on human exposure and impacts on the environment. The International Agency for Research on Cancer and EPA classified 1,4-dioxane as a probable human carcinogen.[16] This classification was based primarily on animal studies which focus on individual, singular pathways of exposure. However, humans are exposed to 1,4-dioxane through multiple pathways by ingestion, inhalation and contact with the skin.[17] Therefore, it is unclear what level of exposure humans actually receive and what effects it may cause.[18] Obviously, exposure from multiple pathways and from multiple chemicals could cause increased risk of cancer or other health issues, but there is limited research with this methodology.[19] The Center for Disease Control said that more research is needed to determine the effect of 1,4-dioxane and “forever chemicals” on human health.[20]

Studies about how 1,4-dioxane impacts the environment primarily focus on aquatic animals.[21] Some studies indicate that 1,4-dioxane does not bioaccumulate and has a low order of toxicity to aquatic animals.[22] However, other studies have shown that there is bioaccumulation in polar bears, birds and dolphins.[23]

Despite the health risks from 1,4-dioxane, EPA has not set a federal maximum contamination level for drinking water.[24] Nor has it delineated any guidelines for surface water/groundwater or soil contamination. EPA has calculated a screening level of 0.46 μg/L for tap water, based on a 1 in 10-6 lifetime excess cancer risk.[25] It also promulgated a risk assessment, stating a drinking water concentration representing a 1 x 10-6 cancer risk level is 0.35 μg/L.[26] In the meantime, more municipalities are recognizing 1,4-dioxane contamination in their water treatment or drinking water systems.[27] This has prompted several states to finally set drinking water and groundwater guidelines on their own.[28]

However, state guidelines and efforts may not be very impactful, since 1,4-dioxane is difficult to remove from water, especially drinking water.[29] Studies show that 1,4-dioxane is not removed from drinking water through normal conventional surface water treatment plants.[30] Other common water treatment processes, such as granular-activated carbon absorption or packed-tower aeration, have also proven to be ineffective.[31] Wastewater treatment plants cannot effectively remove 1,4-dioxane either.[32] Most municipal wastewater facilities and water treatment plants are unable to remove “forever chemicals” like 1,4-dioxane with their current technology, which makes drinking water regulation ineffective in controlling them.

All of this prompts the question of what should be done to control 1,4-dioxane. I believe the current efforts to regulate solely through drinking water systems and regulations is misguided and that a more comprehensive effort would be more effective.


Legal Analysis and Argument:

States and municipalities currently focus on controlling 1,4-dioxane by attempting to remove it from drinking water. This is primarily because that is where contamination was originally discovered, and because state and local officials answer directly to the public, so they are under pressure to take quick action to correct drinking water issues. As discussed above, this approach is ineffective and will not be successful in controlling drinking water contamination from 1,4-dioxane and other “forever chemicals.” Instead, a comprehensive regulatory approach is needed that tracks 1,4-dioxane from cradle to grave, controls disposal, monitors for unauthorized releases and remediates existing contamination.

Fortunately, federal environmental and pollution control statutes provide the necessary tools for this comprehensive approach. The Toxic Substances Control Act (TSCA) and Resource Conservation and Recovery Act (RCRA) allow EPA and states to regulate chemicals when generated, sold, distributed or converted to waste products from manufacturing or industrial processes. The Clean Water Act (CWA) provides regulatory authority when these chemicals are released into the waters of the United States. The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) allows EPA and the states to clean up current and past releases of the chemicals, thereby eliminating the source of contamination. Together, these statutes provide the regulatory framework necessary to control 1,4-dioxane and “forever chemicals.” However, not all of these statutes have been updated to adequately respond to the threat of these substances.


Safe Drinking Water Act

Drinking water is regulated under the Safe Drinking Water Act (SDWA), which is administered by EPA.[33] The Act gives EPA authority to either set maximum contaminate levels (MCLs) based on national health standards for a number of substances or require methods to treat water to remove contaminates through the National Primary Drinking Water Regulations (NPDWRs).[34] EPA can then either enforce these standards or delegate to the states. Once EPA and states set the MCL or required treatment for a particular contaminate, public water systems and utilities are responsible for implementing the regulations and treating the water to meet required standards.[35] Public water systems must also monitor contaminate levels and report these to the state or EPA.[36] Although EPA has set national standards on 89 chemicals, it listed nearly all of them between 1986 and 1996, when Congress forced EPA to evaluate and regulate drinking water contaminants on a regular basis.[37] During this period, Congress and EPA regularly added new contaminates that public systems had to monitor and remove, which caused utilities to constantly upgrade their systems.[38] Congress significantly amended the Act in 1996 after municipalities and water utilities complained they could not keep up with the growing list of contaminants.[39]

The amendments created a number of hurdles for listing new chemicals, weakened EPA’s ability to set standards and eliminated key provisions that required EPA to set health-based standards in specific instances.[40] Since the 1996 amendment, EPA has not regulated any new contaminants except those explicitly ordered by Congress.[41]

Despite this challenging track record, EPA has taken initial steps to regulate 1,4-dioxane under the SDWA by including it on the Drinking Water Contaminant Candidate List in 2009 and the Third Unregulated Contaminant Monitoring Rule in 2016. However, because of the 1996 amendments, EPA has a number of steps it must take, each with significant review periods, before it can set a federal limit. Therefore, EPA is not likely to set limits for 1,4-dioxane anytime soon, which keeps the SDWA from being a viable method of controlling 1,4-dioxane in the near term. Even if EPA could set immediate limits, the SDWA is not designed to control 1,4-dioxane and other “forever chemicals.”

The SDWA was enacted in 1974 after the Clean Air Act and Clean Water Act as part of a larger regulatory framework. It was not designed as a pollution control statute. Instead, it was intended to work in conjunction with the pollution control statutes by regulating conditions within drinking water systems and controlling contamination from non-pollution sources such as alkaline water.[42] This focus affects the technology used by municipal systems to remove contaminants. It is not focused on industrial chemicals such as 1,4-dioxane that come from some distances away, but instead on those contaminants normally found in drinking water systems. As discussed above, these conventional surface water treatment technologies are not successful in removing 1,4-dioxane or other “forever chemicals.” If states and municipalities want to effectively remove 1,4-dioxane, they will need to invest in new and more expensive technology, but they are unlikely to do this in the absence of a regulatory requirement.

This doesn’t mean that the SDWA shouldn’t play a role in controlling 1,4-dioxane and other “forever chemicals.” It should, but only as part of a comprehensive regulatory framework that includes pollution control statutes and only as a backstop or last barrier to protect the public. To affect that, EPA should complete the SDWA process and add 1,4-dioxane to its list of regulated chemicals, or Congress should take action to require EPA to add it, bypassing the SDWA process. Additionally, EPA should utilize the existing pollution control statutes discussed below to control the introduction of 1,4-dioxane and remove as many of the sources of contamination as possible.


Toxic Substances Control Act

The TSCA gives EPA comprehensive authority to regulate the manufacture, use, distribution and disposal of chemicals.[43] Once EPA identifies chemicals that pose a risk, it can require record-keeping requirements and impose regulations on storage and disposal.[44]

This includes not only chemicals manufactured in the United States but also those imported.[45] This authority is an important step in controlling 1,4-dioxane and the first piece of a comprehensive regulatory framework. EPA did take measures under the TSCA to evaluate 1,4-dioxane’s risk to humans and the environment, initiating a risk evaluation review in 2015.

Unfortunately, EPA determined in December 2020 that there was no unreasonable risk to the environment or general population.[46] This seems unusual considering the independent 1,4-dioxane evaluations listed above. However, on June 30, 2021, EPA announced it was reviewing its risk evaluation based on policy changes and stated that the previous administration had not taken into account the multiple pathways a person can be exposed when it made the “no unreasonable risk” assessment.[47] This is certainly a step in the right direction and in line with scientific and medical information, but it also signifies delay in regulating this “forever chemical.” EPA must finalize this process to allow it and the states to manage and monitor 1,4-dioxane prior to use and disposal.


Resource Conservation and Recovery Act

Congress enacted the RCRA to properly manage hazardous waste, thereby reducing the need for corrective action due to improper practices or disposal.[48] RCRA establishes a rigorous regulatory program which manages hazardous waste from generation until disposal.[49] The program imposes management controls on owners and operators of hazardous waste treatment, storage and disposal facilities and those that generate and transport the material.[50] EPA promulgates regulations defining which chemicals are waste and hazardous, which then obligates industry to manage them.[51] States can also regulate hazardous waste in lieu of the federal program if their regulatory regime is approved by EPA.[52]

RCRA is the second piece of a comprehensive regulatory framework for 1,4-dioxane, allowing EPA and the states to control disposal and storage of “forever chemicals.” EPA listed 1,4-dioxane in 1980 as a hazardous waste under RCRA[53] Therefore, EPA and the states can use RCRA to control improper disposal of 1,4-dioxane and prevent it from getting into ground and surface waters. However, it appears the Act has been ineffectively implemented, since much of 1,4-dioxane contamination is the result of improper storage of chlorinated solvents in leaking underground storage tanks. This could mean that EPA and the states are not adequately inspecting facilities or that spills and leakage are not being reported. It is also challenging since 1,4-dioxane is often only a component of a compound or by-product of an industrial process. However, EPA and the states will need to begin vigorously enforcing RCRA and its associated regulations in order to reduce 1,4-dioxane releases into the environment.


Clean Water Act

The Clean Water Act serves as the primary federal statute for addressing water pollution.[54] The Act makes it unlawful to discharge any pollutant into the navigable waters of the United States without a permit.[55] EPA identifies pollutants and must set the appropriate levels and surface water quality criteria in order to regulate industry discharges.[56]

The CWA is the third piece of a comprehensive regulatory framework for controlling 1,4-dioxane, allowing EPA and the states to prevent releases of 1,4-dioxane and other “forever chemicals” from wastewater treatment facilities and industrial sources into waters that provide the source of drinking water. However, EPA has failed to develop recommended surface water quality criteria under Section 304(a) of the Clean Water Act for 1,4-dioxane to protect aquatic life or human health.[57] Interestingly, it has required monitoring for the chemical in some National Pollutant Discharge Elimination System (NPDES) permits, and some permits containing effluent limits.[58] Not regulating 1,4-dioxane under the CWA is a significant gap in the regulatory framework, since contamination in drinking water comes from surface and groundwater sources. EPA must develop and promulgate water-quality criteria to control release of 1,4-dioxane to close this gap.


Comprehensive Environmental Response, Compensation and Liability Act

CERCLA is a remediation statute designed to provide a unified federal response to past and ongoing releases of hazardous substances.[59] It allows EPA to clean-up or force those responsible to clean-up releases of hazardous substances. This is the final piece of a comprehensive regulatory framework for 1,4-dioxane. EPA can use CERCLA to address the large number of spills, leaks and industrial sites that are the ultimate sources of 1,4-dioxane and forever chemicals in drinking water.

EPA does list 1,4-dioxane as a hazardous substance under CERCLA, subjecting it to regulation and clean-up. EPA promulgated a memorandum in 2019, providing procedures and guidance for addressing it at Superfund sites.[60] The memo notes that it is now possible to reliably analyze 1,4-dioxane at Superfund sites and provides guidance on characterization and remediation.[61] This is recent guidance and has not been applied extensively to other sites. However, this is the best method for addressing contaminated sites that are the source of 1,4-dioxane contamination. Tracing drinking water contamination to its source and then using CERCLA to remediate these areas is key to reducing 1,4-dioxane in the environment and eventually in drinking water.



EPA and the states are currently focusing on the SDWA to address 1,4-dioxane contamination of drinking water systems. However, a better approach would utilize multiple federal pollution control statutes in conjunction with the SDWA to provide a comprehensive regulatory framework. This would result in cradle-to-grave management and monitoring of the chemical, address spills and leakage and provide authority for remediation of contaminated sites, greatly reducing the amount of 1,4-dioxane in surface and groundwater. Only a comprehensive approach will successfully combat challenging “forever chemicals” such as 1,4-dioxane.



[1] EPA Technical Fact Sheet - 1,4-Dioxane 2 (November 2017).

[2] The term “forever chemicals” refers to a family of chemicals of nonpolymer per-and polyfluoroalkyl substances that have a structure with a hydrophilic head and hydrophobic tail forming a carbon-fluorine bond that is one of the strongest in nature. The strong bond makes them highly persistent in nature and in the human body thus earning the nickname “forever chemicals.” For a description about the unique chemical properties of this class of substances see Philippe Grandjean et al., Perfluorinated Alkyl Substances: Emerging Insights into Health Risks, 25 NEW SOLUTIONS 147, 147-63 (2015); See also Kerri Jansen, “Forever chemicals no more? These technologies aim to destroy PFAS in water,” Chemical and Engineering News, (March 25, 2019), available at https://cen.acs.org/environment/persistent-pollutants/Forever-chemicals-technologies-aim-destroy/97/i12 (last visited April 5, 2022).

[3] T.K.G. Mohr, 1,4-Dioxane and Other Solvent Stabilizers White Paper 10 Santa Clara Valley Water District of California. San Jose, California (2001).

[4] Amie C. McElroy, Michael R. Hyman and Detlef R.U. Knappe,1,4-Dioxane In Drinking Water: Emerging For 40 Years And Still Unregulated, 7 Current Opinion in Environmental Science & Health, 117, 118 (2019).

[5] Id.

[6] EPA Technical Sheet, supra note 1, at 2.

[7] Mohr, supra note 2, at 10.

[8] Id at 12.

[9] Id at 13.

[10] Id.

[11] Id at 13-16.

[12] McElroy, supra note 5, at 119.

[13] Id.

[14] Toxicological Profile for 1,4-Dioxane, 9 Agency for Toxic Substances and Disease Registry (2012).

[15] McElroy, supra note 5, at 117 and EPA Technical Sheet, supra note 1, at 3; The Drinking Water Candidate Contaminant List (CCL) is an EPA list of drinking water contaminates that are known or anticipated to occur in public drinking water systems and are not currently subjected to EPA drinking water regulations. The SDWA requires the EPA to update and publish the list every 5 years and to place those contaminants on the list that present the greatest public health concern related to exposure from drinking water. The EPA will then determine whether to regulate these contaminates in a separate process known as Regulation Determination. See Drinking Water Contaminant Candidate List and Regulatory Determination, EPA website at: https://www.epa.gov/ccl. The Unregulated Contaminate Monitoring Rule is also a product of the SDWA and requires EPA to issue a list of unregulated contaminates every 5 years that must be monitored by public water systems. This provides EPA with scientific data on the occurrence of contaminates. Both the CCL and Unregulated Contaminate Monitoring Rule are seen as precursors to full regulation of a substance under the SDWA. See Fifth Unregulated Contaminate Monitoring Rule, EPA website at https://www.epa.gov/dwucmr/fifth-unregulated-contaminant-monitoring-rule.

[16] Mohr, supra note 2, at 31 and EPA Integrated Risk Information System (IRIS) (2013); The International Agency for Research on Cancer determined 1,4-dioxane was a probable carcinogen in 2011 and EPA made their determination in 2013.

[17] Id.

[18] See Annie Snead, Forever Chemicals are Widespread in U.S. Drinking Water, Scientific American (January, 22, 2021).

[19] See id.

[20] Center for Disease Control and Prevention Website, National Biomonitoring Program, Per- and Polyfluorinated Substances (PFAS) Factsheet, online https://www.cdc.gov/biomonitoring/PFAS_FactSheet.html (last accessed April 5, 2022)

[21] Mohr, supra note 2, at 33-34.

[22] Id at 34.

[23] Regarding forever chemical’s effect on birds see L.A. Walker, et al. Perfluorinated Compound (PFC) Concentrations in Northern Gannet Eggs 1977-2014: a Predatory Bird Monitoring Scheme (PBMS) report. Centre for Ecology & Hydrology, Lancaster, UK. (2015) available online at https://pbms.ceh.ac.uk; Regarding their effect on mammals see Julie Schneider, PFAS The Forever Chemicals, ChemTrust Report (July 2019) citing P.A. Fair and M. Houde, Chapter 5 - Poly- and Perfluoroalkyl Substances in Marine Mammals. Marine Mammals Ecotoxicology. Impacts of Multiple Stressors on Population Health. pp. 117-145.

[24] EPA Technical Fact Sheet, supra note 1, at 3.

[25] Id.

[26] 1,4-Dioxane, EPA Integrated Risk Information System (IRIS) online at https://cfpub.epa.gov/ncea/iris2/chemicallanding.cfm?substance_nmbr=326.

[27] Xindi C. Hu, et al, Detection of Poly- and Perfluoroalkyl Substances (PFASs) in U.S. Drinking Water Linked to Industrial Sites, Military Fire Training Areas, and Wastewater Treatment Plants, Environ. Sci. Technol. Lett. 2016, 3, 344−350

[28] EPA Technical Fact Sheet, supra note 1, at 4.

[29] McElroy, supra note 4, at 117.

[30] Detlef R. U. Knapp ET Al., Occurrence Of 1,4-Dioxane In The Cape Fear River Watershed And Effectiveness Of Water Treatment Options For 1,4-Dioxane Control 51 Water Resources Research Institute of The University fo North Carolina, Report No. 478 (September 2016).

[31] McElroy, supra note 4, at 119 and Mohr, supra note 2, at 35.

[32] Id.

[33] 42 U.S.C. § 300f et seq.

[34] 41 U.S.C. § 300g-1 contain national drinking water regulations. EPA SDWA regulations are found at 40 C.F.R. Parts 141-143. See also Christopher L. Bell et al., ENVIRONMENTAL LAW HANDBOOK, 463-470, 20th Ed. (2009) for an overview of the Act and a description of regulatory issues.

[35] Id; See also Understanding the Safe Drinking Water Act, EPA publication EPA 816-F-04-030 (June 2004).

[36] Id.

[37] Annie Snyder, What Broke the Safe Drinking Water Act, Politico (05/10/2017 04:49 AM EDT Updated 05/11/2017 05:02 PM EDT) https://www.politico.com/agenda/story/2017/05/10/safe-drinking-water-perchlorate-000434.

[38] Id.

[39] Id.

[40] Erik D. Olson, The Broken Safe Drinking Water Act Won’t Fix The PFAS Crisis, National Resource Defense Council (September 12, 2019) https://www.nrdc.org/experts/erik-d-olson/broken-safe-drinking-water-act-wont-fix-pfas-crisis.

[41] Id.

[42] S. Rep No 93-231, at 4 (1973).

[43] 15 U.S.C. § 2641-2644; See also Bell, supra note 31, at 633.

[44]15 U.S.C. § 2605-2607.

[45] Id.

[46] EPA Final Risk Evaluation for 1,4-Dioxane, EPA Doc# EPA-740-R1-8007 (December 2020).

[47] EPA News Release, EPA Announces Path Forward for TSCA Chemical Risk Evaluations (June 30, 2021), EPA website https://www.epa.gov/newsreleases/epa-announces-path-forward-tsca-chemical-risk-evaluations.

[48] 42 U.S.C.A. §6902(a).

[49] Jeffrey G. Miller and Craig N. Johnston, THE LAW OF HAZARDOUS WASTE DISPOSAL AND REMEDIATION, 46 (Thomson West 2nd ed. 2005).

[50] Id; See also Bell, supra note 31, at 142.

[51] Id.

[52] Id at 47.

[53] 40 CFR 261.33

[54] 33 U.S.C. § 1251.

[55] 33 U.S.C. § 1311.

[56] Id.

[57] Regulatory Framework 1,4-Dioxane, Interstate Technology Regulatory Council (February 2021)

[58] Id.

[59] 42 U.S.C. § 9601.

[60] Memorandum from Douglas Balotti, Director of EPA Superfund and Emergency Management Division on Procedures for Addressing Potential 1,4-Dioxane Contamination at Region 5 Superfund Remedial Sites (December 12, 2019).

[61] Id.