1,4-Dioxane

Summary

1,4-dioxane is a likely human carcinogen that contaminates drinking water in nearly every state across the country. Yet there is no federal standard limiting the levels of the chemical in tap water. 

The Environmental Protection Agency has said 0.35 parts per billion, or ppb, of 1,4-dioxane in water is the amount expected to cause no more than one additional case of cancer in every million people who drink it for a lifetime.

Contamination of drinking water from 1,4-dioxane is due to releases of the chemical from solvent production, industrial spills and discharges from municipal wastewater plants. 

1,4-dioxane is also found in many household products like laundry detergent, shampoos and cosmetics as a byproduct of manufacturing.

Click here to see the nationwide testing results for 1,4-dioxane.

How does 1,4-dioxane get into tap water?

Since the 1950s, 1,4-dioxane has been used as a stabilizer in industrial solvents. Production in the United States dropped dramatically after the 1990s. The last several manufacturers stopped production in the United States, but companies still import it for industrial use. Because of prior use and disposal, it still contaminates many landfills across the country. 

Wastewater treatment plants can’t remove 1,4-dioxane, so effluent from these plants is a significant additional source of contamination in surface water, as reported in a 2016 study by scientists from North Carolina State University.

1,4-dioxane travels easily through soils to groundwater and surface water, and does not readily degrade, which is how it enters tap water systems. But conventional water treatment practices are not effective for removing it, and costly technologies like advanced oxidation may be needed to reduce levels of the chemical in tap water.

Detergents and shampoos may also contain 1,4-dioxane in small amounts. 

What are the toxic effects of 1,4-dioxane in drinking water?

In animal studies, 1,4-dioxane in drinking water increased the incidence of liver, nasal cavity, peritoneal and mammary gland tumors. In 2013, the EPA reported that 1,4-dioxane can also cause cancer when inhaled.

In 2013, the EPA classified 1,4-dioxane as a likely human carcinogen and defined a concentration of 0.35 ppb in tap water as the amount expected to cause no more than one additional case of cancer in 1 million people who drink it for a lifetime. 

There are no federal regulations limiting 1,4-dioxane in tap water, but some states have set their own criteria:

• California water utilities must notify state regulators if 1,4-dioxane is detected above 1 ppb. It is recommended that consumers are notified if there are exceedances. 
• Colorado’s standard for 1,4-dioxane in groundwater is 0.35 ppb.
• Connecticut’s action level for 1,4-dioxane in drinking water is 3 ppb. 
• Maine’s non-enforceable drinking water guideline for 1,4-dioxane is 4 ppb.
• Massachusetts’ non-enforceable drinking water guideline for 1,4-dioxane is 0.3 ppb.
• Michigan’s clean-up standard for 1,4-dioxane in groundwater is 7.2 ppb.
• Minnesota’s non-enforceable drinking water guideline for 1,4-dioxane is 1 ppb. 
• New Hampshire water utilities must report 1,4-dioxane at levels of 0.25 ppb and above.
• New Jersey’s groundwater quality standard is 0.4 ppb for 1,4-dioxane.
• New York set a first in the nation enforceable maximum contaminant limit of 1 ppb for 1,4 dioxane in drinking water. New York also finalized limits on levels in household cleaners and personal care products not to exceed 1 part per million. 
• North Carolina’s groundwater quality and surface water supply standards for 1,4-dioxane are 3 ppb and 0.35 ppb, respectively.

Reducing exposure to 1,4-dioxane in drinking water

Home water filters such as carbon filters are not effective in fully removing 1,4-dioxane from drinking water, but some reverse osmosis systems can remove a significant amount.
The most effective removal technologies are potentially expensive advanced oxidation methods that must be installed at the central water treatment plant. 

If you are concerned about 1,4-dioxane in your water, urge your community’s water system to install effective treatment technologies.

References

Agency for Toxic Substances and Disease Registry, Public Health Statement for 1,4-Dioxane. 2012. Available at www.atsdr.cdc.gov/ToxProfiles/tp187-c1-b.pdf. 

California Office of Environmental Health Hazard Assessment, 1,4-Dioxane Action Level. 1998. Available at oehha.ca.gov/media/downloads/water/chemicals/nl/pal14dioxan.pdf.

California State Water Resources Control Board, Drinking Water Notification Levels. 2024. Available at https://oehha.ca.gov/water/notification-levels-chemicals-drinking-water.

Colorado Department of Public Health and the Environment, Regulation No. 41: The Basic Standards for Ground Water (5 CCR 1002-41); Water Quality Control Commission. 2012. Available at www.sos.state.co.us/CCR/GenerateRulePdf.do?ruleVersionId=5034&fileName=5%20CCR%201002-41.

Environmental Protection Agency, Technical Fact Sheet - 1,4-Dioxane. 2014. Available at https://19january2021snapshot.epa.gov/sites/static/files/2014-03/documents/ffrro_factsheet_contaminant_14-dioxane_january2014_final.pdf.

EPA, Toxicological Review of 1,4-Dioxane. In Support of Summary Information on the Integrated Risk Information System (IRIS). 2013. Available at cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0326tr.pdf.

EPA, Superfund Site: Bally Ground Water Contamination, Bally, PA. Available at cumulis.epa.gov/supercpad/cursites/csitinfo.cfm?id=0301029.

Maine Department of Human Services, Maximum Exposure Guidelines (MEGs) for Drinking Water. 2016. Available at www.maine.gov/dhhs/mecdc/environmental-health/eohp/wells/documents/megtable2016.pdf 

Massachusetts Department of Environmental Protection, Standards and Guidelines for Contaminants in Massachusetts Drinking Waters. 2024. Available at www.mass.gov/eea/agencies/massdep/water/drinking/standards/standards-and-guidelines-for-drinking-water-contaminants.html#Guidelines.

New Hampshire Department of Environmental Services, Change in Reporting Limit for 1,4-Dioxane. 2011. Available at www.des.nh.gov/organization/divisions/waste/hwrb/sss/hwrp/documents/report-limits14dioxane.pdf.

New Jersey Department of Environmental Protection, Ground Water Quality Standard 1,4-Dioxane. 2015. Available at www.nj.gov/dep/wms/bears/docs/1,4%20dioxane%20final%20draft%20for%20posting2.pdf.

New York State Department of Health, Public Water Systems and NYS Drinking Water Standards for PFOA, PFOS and 1,4 Dioxane. Available at https://www.health.ny.gov/environmental/water/drinking/docs/water_supplier_fact_sheet_new_mcls.pdf.

North Carolina Department of Environmental Quality, North Carolina’s Surface Water Quality Standards. Available at deq.nc.gov/document/nc-stds-groundwater-02lstandards and deq.nc.gov/about/divisions/water-resources/water-resources-rules/nc-administrative-code-statutes.

D.K. Stepien et al., Fate of 1,4-Dioxane in the Aquatic Environment: From Sewage to Drinking Water. Water Research, 2014, 48:406–419.

M. Sun et al., Determination of 1,4-Dioxane in the Cape Fear River Watershed by Heated Purge-and-Trap Preconcentration and Gas Chromatography-Mass Spectrometry. Environmental Science & Technology, 2016, 50(5):2246–2254.

Water Research Foundation, 1,4-Dioxane White Paper. 2014. Available at https://www.newbrightonmn.gov/DocumentCenter/View/373/14-Dioxane-White-Paper-from-the-Water-Research-Foundation-PDF.