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Vinyl Chloride (VC)

What is Vinyl Chloride?

Vinyl chloride (VC), also known as chloroethene, is a chlorinated hydrocarbon primarily used in the production of polyvinyl chloride (PVC) plastics. In environmental remediation, vinyl chloride is most commonly encountered as a breakdown product of other chlorinated solvents, including perchloroethylene (PCE), trichloroethylene (TCE), and cis-1,2-dichloroethylene (cis-DCE).

Vinyl chloride is a colorless gas at room temperature and is highly volatile. Although it is rarely released directly to the environment, it is frequently detected at chlorinated solvent remediation sites where biological degradation of PCE and TCE is occurring.

Due to its toxicity and carcinogenicity, vinyl chloride often becomes the primary risk driver at contaminated sites and is closely scrutinized by regulators during site investigation and remediation.

Chemical Properties

Property Value
Chemical Name Chloroethene
Common Name Vinyl Chloride (VC)
Chemical Formula C₂H₃Cl
CAS Number 75-01-4
Molecular Weight 62.50 g/mol
Density Gas at ambient conditions
Solubility in Water Approximately 2,700 mg/L at 25°C

Because vinyl chloride is highly volatile, it readily partitions from groundwater into soil gas and can pose vapor intrusion risks to overlying buildings.

Common Sources of Vinyl Chloride

Vinyl chloride may be present due to:

  • Biological degradation of PCE
  • Biological degradation of TCE
  • Biological degradation of cis-DCE
  • Historical PVC manufacturing operations
  • Industrial chemical production facilities

At most remediation sites, vinyl chloride is encountered as a daughter product resulting from reductive dechlorination of chlorinated solvents.

Environmental Concerns

Vinyl chloride is often considered one of the most significant chlorinated solvent contaminants because it is more toxic than many of its parent compounds.

Vinyl chloride is typically formed through the following degradation pathway:

  • Perchloroethylene (PCE)
  • Trichloroethylene (TCE)
  • cis-1,2-Dichloroethylene (cis-DCE)
  • Vinyl Chloride (VC)
  • Ethene (the desired non-toxic end product)

The presence of vinyl chloride may indicate that reductive dechlorination is occurring; however, elevated vinyl chloride concentrations can also indicate that biodegradation has stalled before reaching complete detoxification.

Because vinyl chloride is highly volatile, it is also a common vapor intrusion concern.

Behavior in Soil and Groundwater

Vinyl chloride behaves differently than PCE and TCE because it does not typically exist as a Dense Non-Aqueous Phase Liquid (DNAPL).

Instead, vinyl chloride is generally encountered as:

  • Dissolved contamination in groundwater
  • Vapor-phase contamination within soil gas
  • A degradation product of other chlorinated solvents

Due to its volatility and mobility, vinyl chloride plumes can migrate beyond source areas and may require evaluation of both groundwater and vapor intrusion pathways.

Human Health Effects

Exposure to elevated concentrations of vinyl chloride may affect the:

  • Central nervous system
  • Liver
  • Immune system

Long-term exposure has been associated with increased cancer risk. Vinyl chloride is classified as a known human carcinogen and is subject to stringent regulatory standards.

Because of its toxicity, vinyl chloride frequently becomes the primary contaminant of concern during risk assessments and remedial decision-making.

Regulatory Standards

Regulatory criteria vary by jurisdiction; however, the United States Environmental Protection Agency has established a Maximum Contaminant Level (MCL) for vinyl chloride in drinking water of 2 µg/L.

Many states have additional groundwater, soil gas, indoor air, vapor intrusion, and risk-based screening criteria.

Because of its carcinogenicity and volatility, vapor intrusion screening levels are often particularly stringent.

Remediation Technologies for Vinyl Chloride

Several remediation technologies may be applied depending on site conditions, contaminant concentrations, geology, and cleanup objectives.

Common treatment approaches include:

  • Enhanced Reductive Dechlorination (ERD): ERD stimulates microorganisms that convert vinyl chloride to harmless ethene as part of the final stage of reductive dechlorination.
  • Enhanced Anaerobic Bioremediation: Bioaugmentation cultures containing specialized microorganisms may be added to promote complete dechlorination and prevent accumulation of vinyl chloride.
  • In Situ Chemical Reduction (ISCR): ISCR technologies utilize reactive materials such as zero-valent iron to chemically reduce chlorinated contaminants and accelerate destruction.
  • Source Area Treatment: Because vinyl chloride is frequently generated from upstream contaminants, treatment often focuses on addressing source areas containing PCE, TCE, or cis-DCE.

Tersus Solutions for Vinyl Chloride Remediation

Tersus Environmental provides a range of technologies to support the remediation of TCE and other chlorinated solvents in soil and groundwater.

Commonly utilized products include:

Electron Donors

  • EDS-ER™ – emulsified vegetable oil substrate for Enhanced Reductive Dechlorination.
  • EDS-ME™ – alcohol co-substrate for enhanced biological activity.
  • EDS-QR™ – a high-purity, quick-release soluble electron donor that rapidly establishes anaerobic conditions for fast-track bioremediation projects.

Activators & Alkaline Reagents

  • EDS-Activator™ – a proprietary remediation catalyst that accelerates fatty acid release, enhances hydrogen generation, and supports efficient reductive dechlorination as part of the EDS-Advanced™ platform.

Bioaugmentation Cultures

  • Specialized microbial cultures may be added to accelerate reductive dechlorination where native dechlorinating populations are limited.

Abiotic Amendments

  • BioBoost™ GeoChem – geochemical amendment designed to support reducing conditions and enhance biological treatment.
  • mZVI™ – micron-scale sulfidated zero-valent iron for In Situ Chemical Reduction applications.
  • ZVI-IronGel™ – injectable colloidal iron technology for treatment of chlorinated solvents.

Surfactants & Solvents

  • EDS-Substrate Shuttle™ – a targeted substrate delivery amendment designed to improve distribution of remediation amendments in low-permeability formations and areas impacted by residual DNAPL.
  • TASK™ Anionic Surfactant Blend – a site-tailored surfactant system used in surfactant-enhanced aquifer remediation (SEAR) applications to improve recovery of DNAPL source areas containing chlorinated solvents.

Tersus also provides site characterization, contaminant flux measurement, compound-specific isotope analysis (CSIA), microbial diagnostic testing, and remedial design support to help optimize treatment performance.

Frequently Asked Questions

Is vinyl chloride more toxic than PCE or TCE?
Yes. Vinyl chloride is generally considered more toxic than its parent compounds and is classified as a known human carcinogen.

Is vinyl chloride a DNAPL?
No. Vinyl chloride is a gas at ambient conditions and is not classified as a Dense Non-Aqueous Phase Liquid (DNAPL).

Why is vinyl chloride found at remediation sites?
Vinyl chloride is commonly formed during the biological degradation of PCE, TCE, and cis-DCE through reductive dechlorination.

How is vinyl chloride removed from groundwater?
Common remediation approaches include enhanced reductive dechlorination, bioaugmentation, in situ chemical reduction, source treatment, and vapor intrusion mitigation where necessary.

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