Carcinogenic Volatile Organic Compounds
Many tap water contaminants can move from water into air, and also enter the body through the skin when you’re showering or bathing. The federal government classifies such substances as volatile organic compounds, or VOCs. These pollutants originate from multiple sources, including gasoline, solvents, paints, cars, carpets and shower curtains.
Between 1987 and 1992, the federal government set legal limits for 21 different VOCs in tap water. No new or updated federal standards for VOCs have been published since. The legal limits allow much greater VOC exposure than the amounts public health agencies consider to pose minimal harm to human health.
The full range of potential VOC contaminants in everyday environments probably includes hundreds of chemicals. Most worrisome are those that harm developing fetuses and increase the risk of cancer. This report highlights 12 carcinogenic VOCs that EWG believes should be regulated as a group of tap water contaminants.
Carcinogenic VOCs in tap water
In 2011 the EPA recommended the establishment of a single regulatory standard for a group of carcinogenic VOCs. So far, this initiative has not resulted in an official proposal for a new drinking water standard. Of the 12 VOCs listed in table below, the EPA had recommended to include nine in a potential carcinogenic VOC group. EWG believes that three additional chemicals should be added to the list of VOCs that should be regulated as a single group of drinking water contaminants: 1,4-dioxane, styrene and 1,1,2-trichloroethane.
|Carcinogenic VOC*||Federal legal limit, ppb||One-in-a-million cancer risk1||Reference||Carcinogenicity classification2|
|1,2,3-Trichloropropane||N/A||0.0007||California public health goal||Likely to be carcinogenic to humans|
|Vinyl chloride||2||0.05||California public health goal||Known human carcinogen|
|Tetrachloroethylene (PCE or PERC)||5||0.06||California public health goal||Likely to be carcinogenic to humans|
|Carbon tetrachloride||5||0.1||California public health goal||Likely to be carcinogenic to humans|
|Benzene||5||0.15||California public health goal||Known human carcinogen|
|1,1,2-Trichloroethane||5||0.3||California public health goal||Possible human carcinogen|
|1,4-Dioxane||N/A||0.35||EPA one-in-a-million cancer risk level||Likely to be carcinogenic to humans|
|1,2-Dichloroethane||5||0.4||California public health goal||Probable human carcinogen|
|Styrene||100||0.5||California public health goal||Reasonably anticipated to be a human carcinogen|
|1,2-Dichloropropane||5||0.5||California public health goal||Carcinogenic to humans|
|Trichloroethylene (TCE)||5||1.7||California public health goal||Carcinogenic to humans|
|Dichloromethane (methylene chloride)||5||4||California public health goal||Likely to be carcinogenic to humans|
* Click on a contaminant above to see its nationwide testing results.
1 Concentration that corresponds to one-in-a-million cancer risk, as defined by the California Office of Environmental Health Hazard Assessment and the EPA Integrated Risk Information System, or IRIS.
2 Carcinogenicity classifications come from the EPA IRIS program, except for two contaminants, styrene and 1,2-dichloropropane, which have not been assessed by IRIS for carcinogenicity. In 2011, the National Toxicology Program classified styrene as “reasonably anticipated to be a human carcinogen.” In 2016, the International Agency for Research on Cancer classified 1,2-dichloropropane as “carcinogenic to humans.”
What are the health effects of VOC exposures?
VOCs have gained notoriety as carcinogens and chemicals that harm the nervous system and fetal development during pregnancy. For example:
- Benzene, a petrochemical, increases the risk of leukemia and lymphoma;
- Carbon tetrachloride, a solvent, increases the risk of non-Hodgkin’s lymphoma;
- PERC (tetrachloroethylene), a dry cleaning chemical, can cause bladder cancer;
- TCE (trichloroethylene), a solvent and dry cleaning chemical, can cause cancers of the liver, kidneys and blood.
There are several VOCs that are not known to cause cancer, but can cause other serious health problems. For example, the petrochemicals toluene, ethylbenzene and xylene are toxic to the liver, kidneys and nervous system. Toluene is reported to harm the hormone system.
How do VOCs get in water?
VOCs are used in a wide variety of industrial and commercial products and processes. Commercial and residential applications, as well as disposal at municipal and industrial landfills across the country, have contributed to VOC contamination of drinking water supplies.
A 2006 U.S. Geological Survey study of groundwater and drinking water wells found VOCs in 90 of 98 aquifers tested nationwide, with the most frequent detections in California, Nevada, Florida, and the New England and mid-Atlantic states. Multiple VOCs co-occurred in groundwater samples.
Is there a safe amount of VOCs in water?
For most individual VOCs, the one-in-a-million cancer risk defined by the California public health goals or by the EPA represents an appropriate health-based limit, although some VOCs, such as trichloroethylene, may have more protective, infant-specific health guidance. But even these benchmarks may fall short because people are exposed to different VOCs and other pollutants simultaneously. That’s why EWG urges federal and state health agencies to regulate carcinogenic VOCs as a group.
What can I do to reduce my exposure to VOCs in drinking water?
There are many sources of VOC exposure: drinking tap water that comes from polluted sources that have not been properly treated to remove VOCs; inhaling VOCs that got into indoor air from contaminated tap water; bathing or showering in water that carries VOCs; and inhaling indoor and outdoor air with VOCs emanating from consumer products, or from industrial and commercial facilities that use these chemicals.
For many tap water quality issues, shoppers can use EWG’s Water Filter Buying Guide to find a filter that can remove specific water contaminants. Here’s what to look for when it comes to VOCs:
- Many, although not all VOCs, can be effectively removed or minimized with basic countertop activated carbon filters. Such filters present an economically friendly option for mitigating water quality problems.
- More expensive technologies, such as reverse osmosis, offer even better water purification. Reverse osmosis systems can be installed at the tap or as a whole-house water treatment.
- Finally, certain VOCs, such as 1,4-dioxane can only be removed at the water utility level because they require specialized treatment not available for home installation.
Following the advice of federal and state public health agencies, EWG recommends that people who use private water wells test their water quality regularly. This is especially important for private well owners in areas with potential presence of underground fuel storage tanks, or those in the vicinity of gas stations, dry cleaning facilities and landfills.
EPA, Integrated Risk Information System Assessment for 1,2-Dichloroethane. 1987. Available at cfpub.epa.gov/ncea/iris2/chemicalLanding.cfm?substance_nmbr=149
EPA, Integrated Risk Information System Assessment for 1,1,2-Trichloroethane. 1987. Available at cfpub.epa.gov/ncea/iris2/chemicalLanding.cfm?substance_nmbr=198
EPA, Integrated Risk Information System Assessment for Benzene. 2000. Available at cfpub.epa.gov/ncea/iris2/chemicalLanding.cfm?substance_nmbr=276
EPA, Integrated Risk Information System Assessment for Vinyl Chloride. 2000. Available at cfpub.epa.gov/ncea/iris2/chemicalLanding.cfm?substance_nmbr=1001
EPA, Integrated Risk Information System Assessment for 1,2,3-Trichloropropane. 2009. Available at cfpub.epa.gov/ncea/iris2/chemicalLanding.cfm?substance_nmbr=200
EPA, Integrated Risk Information System Assessment for Carbon Tetrachloride. 2010. Available at cfpub.epa.gov/ncea/iris2/chemicalLanding.cfm?substance_nmbr=20
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EPA, Integrated Risk Information System Assessment for Dichloromethane. 2011. Available at cfpub.epa.gov/ncea/iris2/chemicalLanding.cfm?substance_nmbr=70
EPA, Integrated Risk Information System Assessment for Trichloroethylene. 2011. Available at cfpub.epa.gov/ncea/iris2/chemicalLanding.cfm?substance_nmbr=199
EPA, Integrated Risk Information System Assessment for Tetrachloroethylene. 2012. Available at cfpub.epa.gov/ncea/iris2/chemicalLanding.cfm?substance_nmbr=106
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National Toxicology Program, Report on Carcinogens: Styrene. 2011. Available at ntp.niehs.nih.gov/ntp/roc/content/profiles/styrene.pdf
P.J. Squillace et al., VOCs, Pesticides, Nitrate, and their Mixtures in Groundwater Used for Drinking Water in the United States. Environmental Science and Technology, 2002, 36(9):1923-1930.
U.S. Geological Survey, The Quality of Our Nation’s Waters. Volatile Organic Compounds in the Nation’s Ground Water and Drinking-Water Supply Wells. 2006. Available at pubs.usgs.gov/circ/circ1292
Water Research Foundation, Background Technical Information for Carcinogenic Volatile Organic Compounds (cVOCs). 2015. Available at www.waterrf.org/resources/Lists/ProjectPapers/Attachments/62/4457_BackgroundInfo_cVOCs.pdf