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

Written by Craig "The Water Guy" Phillips

In the complex world of water contamination, countless chemicals threaten the safety of our drinking water supply, yet many remain invisible to the average consumer. Among these lesser-known but potentially dangerous contaminants is cis-1,2-dichloroethylene, a volatile organic compound that has been quietly infiltrating water systems across the globe. This industrial chemical, often abbreviated as cis-1,2-DCE, represents a significant concern for public health officials and environmental scientists who understand its potential to cause serious health complications when consumed over extended periods.

While most people focus on well-publicized contaminants like lead or chlorine, cis-1,2-dichloroethylene operates in the shadows, contaminating groundwater and municipal water supplies through various industrial processes and environmental degradation. Understanding this contaminant is crucial for anyone concerned about their water quality, as its presence often goes undetected without proper testing and monitoring.

Understanding cis-1,2-Dichloroethylene and Its Chemical Properties

cis-1,2-Dichloroethylene is a colorless liquid with a slightly sweet odor that belongs to the family of chlorinated hydrocarbons.
This synthetic chemical compound consists of two carbon atoms, two hydrogen atoms, and two chlorine atoms arranged in a specific geometric configuration that gives it the "cis" designation. The molecular formula C₂H₂Cl₂ represents a structure where the 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 exhibits high volatility, meaning it readily evaporates at room temperature, which contributes to both its industrial usefulness and its potential for environmental contamination. Its solubility in water is moderate, allowing it to persist in aquatic environments while also enabling it to partition between water and air phases. These properties make cis-1,2-dichloroethylene particularly concerning from an environmental perspective, as it can migrate through soil and groundwater systems relatively easily.

In industrial applications, this compound serves as an intermediate in chemical manufacturing processes and as a solvent in various operations. Its stability under certain conditions makes it valuable for specific industrial purposes, but this same stability contributes to its persistence in environmental systems once released.

Primary Sources and Pathways of Water Contamination

The contamination of water supplies with cis-1,2-dichloroethylene typically occurs through multiple industrial and environmental pathways.
Manufacturing facilities that produce or use chlorinated solvents represent the most significant direct source of contamination, particularly when improper waste disposal practices or accidental spills occur. Chemical plants, metal degreasing operations, and facilities involved in the production of plastics and synthetic materials often generate this compound as either a primary product or a byproduct.

One of the most common contamination scenarios involves the biodegradation of other chlorinated compounds, particularly tetrachloroethylene (PCE) and trichloroethylene (TCE). When these more heavily chlorinated solvents undergo anaerobic biodegradation in groundwater, they often break down sequentially, with cis-1,2-dichloroethylene appearing as an intermediate degradation product. This process means that areas previously contaminated with dry cleaning solvents or industrial degreasers may continue to show contamination with cis-1,2-dichloroethylene long after the original source has been removed.

Landfills and waste disposal sites represent another significant source of contamination, particularly older facilities that accepted industrial waste before modern environmental regulations were implemented. Leachate from these sites can carry dissolved cis-1,2-dichloroethylene into surrounding groundwater, creating plumes of contamination that may extend considerable distances from the original source.

Underground storage tanks, particularly those used for storing industrial solvents, pose additional contamination risks. Corrosion, improper installation, or poor maintenance can lead to leaks that directly introduce the chemical into soil and groundwater systems.

Health Effects and Medical Concerns

Exposure to cis-1,2-dichloroethylene through contaminated drinking water can result in a range of adverse health effects, both acute and chronic.
The severity and type of health impacts depend largely on the concentration of the contaminant, duration of exposure, and individual susceptibility factors such as age, overall health status, and genetic variations in metabolism.

Short-term exposure to elevated levels of cis-1,2-dichloroethylene can cause immediate neurological symptoms including dizziness, drowsiness, and headaches. Some individuals may experience nausea, vomiting, and respiratory irritation when exposed to higher concentrations. These acute effects typically resolve once exposure ceases, but they serve as warning signs of potentially dangerous contamination levels.

**What are the long-term health risks associated with chronic exposure?** Prolonged consumption of water contaminated with cis-1,2-dichloroethylene raises more serious health concerns, particularly regarding liver and kidney function. Studies have indicated that chronic exposure may lead to hepatic toxicity, manifesting as elevated liver enzymes, impaired liver function, and potential liver damage over time.

The central nervous system represents another target for toxicity, with chronic exposure potentially causing persistent neurological symptoms, cognitive impairment, and mood changes. Some research suggests that long-term exposure may contribute to developmental issues in children, including potential impacts on neurological development and learning capabilities.

**Is cis-1,2-dichloroethylene considered carcinogenic?** While the evidence for carcinogenicity remains limited, some studies have suggested potential links between exposure to chlorinated hydrocarbons and increased cancer risk. The Environmental Protection Agency continues to evaluate the carcinogenic potential of this compound, maintaining a cautious approach to exposure limits and regulatory standards.

Detection, Testing, and Regulatory Standards

Detecting cis-1,2-dichloroethylene in drinking water requires specialized analytical techniques due to its volatile nature and relatively low odor threshold.
Professional water testing laboratories typically employ gas chromatography-mass spectrometry (GC-MS) or other advanced analytical methods to accurately measure concentrations of this contaminant. These sophisticated techniques can detect the compound at very low levels, often in the parts per billion range, which is necessary given the stringent regulatory standards.

The Environmental Protection Agency has established a Maximum Contaminant Level (MCL) of 70 parts per billion (ppb) for cis-1,2-dichloroethylene in public drinking water systems. This standard represents the maximum allowable concentration that regulatory agencies consider safe for lifelong consumption. Public water utilities are required to regularly monitor for this contaminant and take corrective action if levels exceed the MCL.

**How often should private well water be tested for this contaminant?** Private well owners face additional challenges since they are not subject to the same monitoring requirements as public water systems. Environmental health experts recommend testing private wells for volatile organic compounds, including cis-1,2-dichloroethylene, at least annually, or more frequently if the well is located near potential contamination sources such as industrial facilities, landfills, or known contamination sites.

Home testing kits for volatile organic compounds are available, though their accuracy and reliability may vary significantly compared to professional laboratory analysis. For accurate results and proper interpretation, professional testing by certified laboratories remains the gold standard for detecting this contaminant.

Treatment Options and Prevention Strategies

Several proven treatment technologies can effectively remove cis-1,2-dichloroethylene from contaminated drinking water.
Activated carbon filtration represents one of the most widely used and effective methods for removing this contaminant from residential water supplies. High-quality activated carbon systems can achieve removal efficiencies exceeding 95% when properly maintained and operated within their design parameters.

Air stripping technology offers another effective treatment approach, particularly for larger-scale applications. This process involves forcing air through contaminated water, causing volatile compounds like cis-1,2-dichloroethylene to transfer from the water phase to the air phase, where they can be captured and treated. Air stripping systems are commonly used in municipal water treatment facilities and larger residential applications.

Advanced oxidation processes, including ultraviolet light combined with hydrogen peroxide, can break down cis-1,2-dichloroethylene into harmless byproducts. These systems are becoming increasingly popular for treating multiple contaminants simultaneously, though they typically require more sophisticated operation and maintenance.

**What preventive measures can communities implement?** Prevention strategies focus primarily on source control and proper industrial waste management. Communities can advocate for stricter oversight of industrial facilities, improved waste disposal practices, and regular environmental monitoring of potential contamination sources. Proper siting of new industrial facilities away from drinking water sources and implementation of protective buffer zones can help prevent future contamination.

Individual property owners can contribute to prevention by properly disposing of household chemicals, avoiding the use of chlorinated solvents when possible, and maintaining any underground storage tanks according to regulatory requirements. Regular inspection and maintenance of septic systems and private wells also helps prevent cross-contamination.

Frequently Asked Questions

Q: Can boiling water remove cis-1,2-dichloroethylene?
A: Boiling water can reduce concentrations of cis-1,2-dichloroethylene due to its volatile nature, but this method is not reliable for complete removal. The compound may not be entirely eliminated through boiling, and some may remain in the water. Professional treatment systems like activated carbon filtration are much more effective and reliable.

Q: How long does cis-1,2-dichloroethylene persist in groundwater?
A: The persistence of cis-1,2-dichloroethylene in groundwater varies significantly depending on environmental conditions. In anaerobic groundwater conditions, it can persist for many years or even decades. However, under the right conditions with appropriate microorganisms present, it may undergo biodegradation to less harmful compounds like vinyl chloride and ultimately to non-toxic end products.

Q: Are certain populations more vulnerable to the effects of this contaminant?
A: Yes, certain populations face higher risks from exposure to cis-1,2-dichloroethylene. Pregnant women, infants, young children, elderly individuals, and people with compromised liver or kidney function are generally more susceptible to the toxic effects. Children are particularly vulnerable due to their developing organ systems and higher water consumption relative to body weight.

Q: Can this contaminant be detected by taste or smell?
A: cis-1,2-Dichloroethylene has a slightly sweet odor, but it is not reliably detectable by taste or smell at the concentrations typically found in contaminated drinking water. The odor threshold is higher than levels that may cause health effects, so water may be contaminated at harmful levels without any noticeable sensory indicators.

Q: What should I do if my water tests positive for this contaminant?
A: If testing reveals the presence of cis-1,2-dichloroethylene above safe levels, immediately stop using the water for drinking and cooking. Contact local health authorities and consider installing an appropriate treatment system such as activated carbon filtration. Seek professional advice on the best treatment options for your specific situation and have the water retested after treatment installation.

Q: How does this contaminant compare to other chlorinated solvents in terms of health risks?
A: cis-1,2-Dichloroethylene is generally considered less toxic than some other chlorinated solvents like tetrachloroethylene or trichloroethylene, but it still poses significant health risks with chronic exposure. Its health effects are similar to other members of this chemical family, primarily affecting the liver, kidneys, and central nervous system. However, each compound has unique toxicological properties that require specific consideration in risk assessment and treatment planning.