cis-1,2-Dichloroethylene: The Contaminant in Tap Water You Didn't Know Was Harming Your Health

Written by Craig "The Water Guy" Phillips

When you turn on your tap for a glass of water, you expect it to be clean and safe. However, lurking beneath the surface of what appears to be crystal-clear water could be cis-1,2-dichloroethylene, a volatile organic compound that poses significant health risks. This industrial chemical, often abbreviated as cis-1,2-DCE, represents one of the most concerning yet overlooked contaminants in modern water supplies. As communities across the nation grapple with aging infrastructure and industrial pollution, understanding the presence and impact of this chemical compound becomes crucial for protecting public health.

Understanding cis-1,2-Dichloroethylene: What Exactly Is This Chemical?

cis-1,2-Dichloroethylene is a colorless liquid with a slightly sweet odor that belongs to a family of chemicals known as volatile organic compounds (VOCs).
This synthetic chemical doesn't occur naturally in the environment but is created through various industrial processes and can form as a breakdown product of other chlorinated compounds. The "cis" designation refers to the specific molecular structure where chlorine atoms are positioned on the same side of the carbon-carbon double bond, distinguishing it from its isomer, trans-1,2-dichloroethylene.

The chemical formula C₂H₂Cl₂ represents a relatively simple molecular structure, but its simplicity doesn't diminish its potential for causing harm. **What makes cis-1,2-dichloroethylene particularly concerning is its persistence in groundwater and its ability to migrate through soil and contaminate drinking water sources.** The compound's volatility means it can easily evaporate from contaminated water, potentially creating indoor air quality issues in homes and buildings supplied by affected water sources.

Historically, this chemical has been used in the production of other chemicals, as a solvent, and in various industrial applications. While direct industrial use has decreased over the years, it continues to appear in water supplies as a degradation product of more commonly used chemicals like tetrachloroethylene (PCE) and trichloroethylene (TCE), which were extensively used in dry cleaning and degreasing operations.

Sources and Pathways: How Does This Contaminant Enter Our Water Supply?

The primary pathway for cis-1,2-dichloroethylene contamination in drinking water stems from groundwater pollution caused by industrial activities and improper waste disposal practices.
Manufacturing facilities that produce or use chlorinated solvents represent the most significant source of contamination. When these chemicals are spilled, leaked, or improperly disposed of, they can seep into soil and eventually reach groundwater aquifers that supply drinking water wells.

Dry cleaning operations have historically been major contributors to this type of contamination. **The solvents used in dry cleaning, particularly tetrachloroethylene, can break down in groundwater to form cis-1,2-dichloroethylene through a process called reductive dechlorination.** This natural degradation process, while reducing the concentration of the original contaminant, creates new compounds that can be equally or more problematic for human health.

Military installations and former defense facilities represent another significant source of contamination. Decades of using chlorinated solvents for equipment maintenance and degreasing have left many of these sites with contaminated groundwater plumes that continue to affect surrounding communities. **Legacy contamination from these sites can persist for decades, slowly releasing chemicals into water supplies long after the original activities have ceased.**

Underground storage tanks, particularly older ones that may have developed leaks, can also contribute to groundwater contamination. Gas stations, industrial facilities, and even some residential properties with heating oil tanks have the potential to release chemicals that can degrade into cis-1,2-dichloroethylene over time.

Health Effects and Medical Concerns: The Hidden Dangers to Human Health

Exposure to cis-1,2-dichloroethylene can cause both immediate and long-term health effects, with the severity depending on the concentration and duration of exposure.
Short-term exposure to high concentrations can result in nervous system depression, causing symptoms such as dizziness, drowsiness, and headaches. Some individuals may also experience nausea, vomiting, and respiratory irritation when exposed to elevated levels of this chemical.

**The most concerning aspect of cis-1,2-dichloroethylene exposure relates to its potential long-term health effects, particularly its impact on the liver and nervous system.** Chronic exposure has been associated with liver damage, including fatty liver disease and potential liver toxicity. The compound's ability to cross the blood-brain barrier raises concerns about neurological effects, including potential impacts on cognitive function and nervous system development.

Pregnant women and developing fetuses face particular risks from exposure to this contaminant. **Studies have suggested that exposure during pregnancy may be associated with developmental problems and birth defects.** The chemical's ability to cross the placental barrier means that fetal exposure can occur when pregnant women consume contaminated water, potentially affecting critical stages of development.

Children are especially vulnerable to the effects of cis-1,2-dichloroethylene contamination due to their developing organ systems and higher water consumption relative to body weight. **Research indicates that children exposed to this chemical may experience developmental delays, learning difficulties, and increased susceptibility to other health problems.**

The carcinogenic potential of cis-1,2-dichloroethylene remains a subject of ongoing research. While definitive conclusions about cancer risk in humans haven't been established, animal studies have shown increased rates of certain cancers following exposure to this chemical, leading regulatory agencies to treat it as a potential human carcinogen.

Detection and Testing Methods: Identifying the Invisible Threat

Detecting cis-1,2-dichloroethylene in drinking water requires sophisticated analytical techniques, as this contaminant is colorless, odorless at low concentrations, and can't be detected through basic sensory evaluation.
The most commonly used method for detection is gas chromatography-mass spectrometry (GC-MS), which can identify and quantify even trace amounts of the chemical in water samples.

**Public water systems are required to test for volatile organic compounds, including cis-1,2-dichloroethylene, under the Safe Drinking Water Act regulations.** However, testing frequency varies depending on the system size and previous detection history. Large water systems typically test more frequently than smaller ones, and systems with no previous detection may test less often, potentially missing intermittent contamination events.

Private well owners face unique challenges in detecting this contaminant, as they're responsible for their own water testing. **Many private well owners remain unaware of potential contamination because routine testing for volatile organic compounds can be expensive and isn't automatically included in basic water quality tests.** State health departments and local environmental agencies often provide guidance on testing protocols and may offer reduced-cost testing programs for residents in known contamination areas.

**The detection limit for cis-1,2-dichloroethylene in drinking water is typically set at very low levels, often measured in parts per billion (ppb).** The Environmental Protection Agency has established a Maximum Contaminant Level (MCL) of 70 ppb for this chemical, though some states have set even more stringent standards based on updated health research.

Emerging testing technologies, including portable field testing equipment, are making it easier and more cost-effective to screen for volatile organic compounds. However, confirmation testing using certified laboratory methods remains necessary for accurate quantification and regulatory compliance purposes.

Treatment and Prevention: Protecting Your Family from Contamination

Several effective treatment technologies can remove cis-1,2-dichloroethylene from drinking water, with activated carbon filtration being one of the most widely used and effective methods.
Granular activated carbon (GAC) systems can achieve very high removal rates for this contaminant, though the carbon media requires regular replacement to maintain effectiveness. Point-of-use carbon filters, such as those installed under kitchen sinks, can provide effective protection for drinking and cooking water.

**Air stripping technology represents another highly effective treatment option, particularly for larger water systems dealing with significant contamination levels.** This process involves forcing air through contaminated water, causing volatile compounds like cis-1,2-dichloroethylene to transfer from the water to the air phase, where they can be captured and treated before release.

Advanced oxidation processes (AOPs) offer a newer approach to treating this type of contamination. **These systems use combinations of ozone, hydrogen peroxide, and ultraviolet light to break down chemical contaminants into harmless byproducts.** While effective, AOP systems tend to be more expensive and complex than carbon filtration, making them more suitable for larger treatment facilities.

Prevention strategies focus on source protection and proper handling of chemicals that can degrade into cis-1,2-dichloroethylene. **Community efforts to identify and remediate contaminated sites, implement proper waste disposal practices, and upgrade aging infrastructure can help prevent new contamination events.** Individuals can contribute by properly disposing of household chemicals, supporting local environmental protection initiatives, and staying informed about potential contamination sources in their area.

For households concerned about potential contamination, installing a whole-house carbon filtration system can provide comprehensive protection. **These systems treat all water entering the home, protecting against both ingestion and inhalation exposure that can occur during showering, cooking, and other daily activities.**

Frequently Asked Questions About cis-1,2-Dichloroethylene in Drinking Water

Q: How do I know if my water contains cis-1,2-dichloroethylene?
A: The only way to definitively determine if your water contains this contaminant is through laboratory testing. Contact a certified water testing laboratory or your local health department for testing information. Public water system customers can request water quality reports from their utility company.

Q: Is boiling water effective at removing cis-1,2-dichloroethylene?
A: Boiling can reduce concentrations of this volatile compound, but it's not a reliable long-term solution. Boiling may actually increase exposure in enclosed spaces by releasing the chemical into indoor air. Professional water treatment systems are more effective and safer.

Q: What should I do if my water tests positive for this contaminant?
A: Contact your local health department immediately for guidance. Consider using bottled water for drinking and cooking until a treatment system can be installed. Work with water treatment professionals to select appropriate filtration technology for your specific situation.

Q: Are certain areas more likely to have this type of contamination?
A: Areas near former or current industrial facilities, dry cleaners, military installations, and gas stations have higher risk. Communities with older infrastructure and those relying on groundwater sources may also face increased risk.

Q: How often should I test my private well for this contaminant?
A: Annual testing is recommended for private wells, with more frequent testing if you're in a high-risk area or if contamination has been detected previously. Consult with local environmental health officials for specific recommendations based on your location.

Q: Can exposure to small amounts of this chemical cause health problems?
A: While regulatory limits are set to protect public health, some individuals may be more sensitive than others. Pregnant women, children, and people with compromised immune systems should be particularly cautious about any exposure to chemical contaminants.