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

Written by Craig "The Water Guy" Phillips

Water contamination remains one of the most pressing public health concerns of our time, with countless chemicals finding their way into our drinking water supplies. Among these concerning pollutants is cis-1,2-dichloroethylene, a volatile organic compound that many homeowners have never heard of but may be consuming daily through their tap water. This industrial solvent and its presence in drinking water systems across the country represents a significant yet often overlooked threat to public health, making awareness and action more critical than ever.

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

cis-1,2-Dichloroethylene is a colorless liquid with a sweet, ether-like odor that belongs to the family of volatile organic compounds (VOCs).
This chemical compound, also known as 1,2-DCE, consists of two carbon atoms, two hydrogen atoms, and two chlorine atoms arranged in a specific geometric configuration. The "cis" designation refers to the spatial arrangement of the chlorine atoms on the same side of the carbon-carbon double bond, which distinguishes it from its isomer, trans-1,2-dichloroethylene.

The compound is highly volatile, meaning it easily evaporates at room temperature, and it's also relatively soluble in water. These properties make it particularly concerning when it comes to water contamination, as it can persist in groundwater systems and easily transfer from water to air during everyday activities like showering, cooking, or even drinking. What makes this chemical particularly insidious is its ability to remain undetected without proper testing?

Originally developed for industrial applications, cis-1,2-dichloroethylene has been widely used as a solvent in various manufacturing processes, including the production of other chemicals, cleaning agents, and as an intermediate in chemical synthesis. Its stability and effectiveness as a solvent have made it valuable in industrial settings, but these same properties contribute to its persistence in the environment and potential for widespread contamination.

Primary Sources and Pathways of Contamination

Industrial facilities represent the most significant source of cis-1,2-dichloroethylene contamination in drinking water supplies.
Chemical manufacturing plants, metal degreasing operations, and facilities that produce or use chlorinated solvents are primary contributors to environmental releases. These facilities may discharge the compound directly into surface waters through permitted or accidental releases, or it may seep into groundwater through improper waste disposal practices or underground storage tank leaks.

Groundwater contamination often occurs through a process called natural attenuation, where other chlorinated compounds like trichloroethylene (TCE) and tetrachloroethylene (PCE) break down in the subsurface environment. This biodegradation process, while reducing more toxic parent compounds, creates cis-1,2-dichloroethylene as a persistent byproduct that can contaminate aquifers for decades:

• Leaking underground storage tanks containing industrial solvents
• Improper disposal of industrial waste at contaminated sites
• Runoff from manufacturing facilities and chemical plants
• Historical contamination from closed or abandoned industrial sites
• Cross-contamination from nearby polluted groundwater sources

The compound's mobility in groundwater systems means that contamination can spread far from the original source, potentially affecting drinking water wells and municipal water supplies miles away from the initial point of release. This widespread distribution capability makes cis-1,2-dichloroethylene contamination a regional rather than localized concern?

Health Effects and Medical Concerns

Exposure to cis-1,2-dichloroethylene through contaminated drinking water poses several significant health risks that can affect multiple organ systems.
The compound is readily absorbed through the gastrointestinal tract when consumed in drinking water, and it can also be inhaled when it volatilizes from water during household activities. Once in the body, it can affect the central nervous system, liver, and potentially other organs through various mechanisms of toxicity.

Short-term exposure to elevated levels of cis-1,2-dichloroethylene can cause immediate health effects including dizziness, drowsiness, headaches, and nausea. These acute symptoms often mirror those of other solvent exposures and may be misattributed to other causes if water contamination isn't suspected: Higher concentrations can lead to more severe neurological effects, including confusion, loss of coordination, and in extreme cases, unconsciousness.

Long-term exposure concerns are particularly troubling, as chronic consumption of contaminated water may lead to more serious health consequences. Studies have suggested potential liver damage, as the organ works to metabolize and eliminate the chemical from the body. The Environmental Protection Agency has classified cis-1,2-dichloroethylene as a possible human carcinogen, meaning there is limited evidence suggesting it may cause cancer in humans.

Vulnerable populations, including pregnant women, children, and individuals with compromised immune systems or pre-existing liver conditions, may be at higher risk for adverse effects. Children may be particularly susceptible due to their smaller body size and developing organ systems? Pregnant women face additional concerns as the compound may cross the placental barrier, potentially affecting fetal development.

Detection Methods and Testing Protocols

Detecting cis-1,2-dichloroethylene in drinking water requires specialized analytical techniques due to its volatile nature and the low concentrations at which it can cause health concerns.
The most commonly used method for detection is gas chromatography-mass spectrometry (GC-MS), which can accurately identify and quantify the compound at the parts-per-billion level. This sophisticated analytical technique separates the chemical from other compounds in the water sample and provides definitive identification through its unique molecular signature.

Public water systems are required to monitor for volatile organic compounds, including cis-1,2-dichloroethylene, under the Safe Drinking Water Act. However, the frequency of testing may not be sufficient to catch all contamination events, particularly those resulting from new releases or changes in groundwater flow patterns: Private well owners bear the responsibility for testing their own water supplies, which often means contamination goes undetected for extended periods.

Professional water testing laboratories can perform comprehensive VOC analysis that includes cis-1,2-dichloroethylene along with other related compounds. Sample collection requires specific protocols to prevent volatilization of the compound during transport and storage. Proper sampling techniques include using specialized containers, avoiding air bubbles, and maintaining proper temperature control during transport to the laboratory?

Home testing kits for this specific compound are limited and generally less reliable than professional laboratory analysis. For accurate results, homeowners should work with certified laboratories that follow EPA-approved testing methods and can provide detailed analytical reports with detection limits well below health-based guidelines.

Treatment and Removal Solutions

Several proven treatment technologies can effectively remove cis-1,2-dichloroethylene from contaminated drinking water, ranging from point-of-use systems for individual homes to large-scale municipal treatment solutions.
The choice of treatment method depends on factors including contamination levels, water usage volume, budget considerations, and the presence of other contaminants that may require simultaneous removal.

Activated carbon filtration represents one of the most effective and widely used treatment options for removing volatile organic compounds from drinking water. Granular activated carbon (GAC) systems work through adsorption, where the cis-1,2-dichloroethylene molecules bind to the carbon surface and are removed from the water stream. These systems can achieve removal efficiencies exceeding 95% when properly designed and maintained:

• Point-of-use carbon filters for individual taps or whole-house systems
• Granular activated carbon beds for municipal treatment facilities
• Air stripping towers that volatilize and capture the compound
• Advanced oxidation processes that break down the chemical
• Reverse osmosis systems for comprehensive contaminant removal

Air stripping is another highly effective treatment method, particularly for municipal systems treating large volumes of water. This process involves aerating the contaminated water to transfer the volatile compound from the liquid phase to the gas phase, where it can be captured and treated. The effectiveness of air stripping depends on temperature, pH, and the specific design of the treatment system?

For comprehensive protection, many experts recommend a multi-barrier approach that combines different treatment technologies. Regular monitoring and maintenance of treatment systems are essential to ensure continued effectiveness, as filter media must be replaced and systems must be properly maintained to prevent breakthrough of contaminants.

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

Understanding the complexities of cis-1,2-dichloroethylene contamination requires addressing the most common questions and concerns that arise when this contaminant is discovered in drinking water supplies.
These frequently asked questions provide essential information for homeowners, community leaders, and anyone concerned about water quality and safety.

Q: What is the maximum allowable level of cis-1,2-dichloroethylene in drinking water?

A: The EPA has established a Maximum Contaminant Level (MCL) of 70 parts per billion (ppb) for cis-1,2-dichloroethylene in public drinking water systems. This level is based on health risk assessments and represents the maximum concentration considered safe for lifetime consumption. Some states have established more stringent standards, and health advocates argue for even lower limits based on emerging research.

Q: Can I smell or taste cis-1,2-dichloroethylene in my drinking water?

A: While cis-1,2-dichloroethylene has a sweet, ether-like odor, it may not be detectable by smell or taste at the concentrations typically found in contaminated drinking water. The compound's odor threshold is higher than levels that can cause health concerns, meaning water can be contaminated at harmful levels without any noticeable sensory indicators. Laboratory testing is the only reliable way to detect its presence.

Q: How long does it take for treatment systems to remove this contaminant effectively?

A: Properly designed treatment systems can remove cis-1,2-dichloroethylene almost immediately upon contact. Activated carbon systems typically achieve maximum removal efficiency within the first few minutes of contact time, while air stripping systems can remove the compound in a matter of minutes. However, it's important to note that treatment system effectiveness can decline over time as filter media becomes saturated or systems require maintenance.

Q: Is boiling water an effective way to remove cis-1,2-dichloroethylene?

A: Boiling water for an extended period can reduce cis-1,2-dichloroethylene concentrations due to its volatile nature, but this method is not recommended as a primary treatment approach. While some of the compound will evaporate during boiling, complete removal is unlikely, and the process may actually increase exposure through inhalation of vapors. Professional treatment systems are far more effective and reliable.

Q: What should I do if my water tests positive for cis-1,2-dichloroethylene?

A: If testing reveals cis-1,2-dichloroethylene contamination above safe levels, immediately switch to bottled water for drinking and cooking while implementing a long-term treatment solution. Contact your local health department and water utility if applicable, consider installing appropriate treatment systems, and arrange for follow-up testing to verify treatment effectiveness. Don't delay in taking action, as continued exposure can increase health risks?

Q: How often should I test my water for this contaminant?

A: Private well owners should test for volatile organic compounds, including cis-1,2-dichloroethylene, at least annually or more frequently if there are nearby industrial activities or known contamination sources. Public water system customers can review their utility's annual water quality reports, but additional private testing may be warranted if there are specific concerns about local contamination sources or if you live in an area with a history of groundwater contamination.