On this page (10 sections)
Vinyl chloride is a colorless gas used to make PVC plastic. Near the soil surface it evaporates quickly [1]. Deeper down, and in groundwater, it can last until microbes break it down, and two groups of them do that. With oxygen present, aerobic bacteria, mostly Mycobacterium, eat it [2]. Without oxygen, anaerobic bacteria led by Dehalococcoides convert it to ethene [4]. Both groups have turned up in the field without anyone adding them [2][4].
This general explainer covers where vinyl chloride comes from, how it moves through soil and water, and what research shows about each biological route. For one derailment site in detail, see our primary-source soil guide. Related compounds are covered in chlorinated solvents and VOCs.
What it is and where it comes from
ATSDR describes vinyl chloride as a colorless gas with a mild, sweet odor. It is manufactured, doesn’t occur naturally, and goes into polyvinyl chloride (PVC) for pipes, wire coatings and packaging [1]. It also forms underground when other chlorinated solvents, such as trichloroethylene (TCE) and tetrachloroethylene (PCE), partly break down [1].
That second source explains why it turns up at dry cleaners, metal-degreasing shops and industrial sites. A review of the chloroethene literature says vinyl chloride in groundwater is primarily a consequence of incomplete anaerobic breakdown of the more highly chlorinated ethenes [3]. The solvent sheds chlorine atoms one at a time, and vinyl chloride is one of the last steps.
Health agencies classify vinyl chloride as a known human carcinogen [1]. For health risk at a specific property, go to the state health department and ATSDR. This post gives no verdict on any site.
How it behaves in soil and groundwater
According to ATSDR [1]:
- Liquid vinyl chloride evaporates easily, and vinyl chloride in water or soil evaporates rapidly near the surface.
- Small amounts dissolve in water.
- Vapor can get into the indoor air of buildings on contaminated ground.
Depth changes the picture completely: a surface spill may lose much of its vinyl chloride to the air within days. A groundwater plume has no easy way out, and biological breakdown is often what removes it.
Two ways microbes break it down
| Route | Oxygen | Main organisms | Field marker | Result |
|---|---|---|---|---|
| Aerobic | Present | Mycobacterium, Nocardioides | Genes etnC and etnE [5] | Vinyl chloride used as sole carbon source [2] |
| Anaerobic | Absent | Dehalococcoides, Dehalogenimonas | Gene vcrA [4] | Vinyl chloride converted to ethene [4] |
Aerobic
In 2002, researchers tested samples from contaminated sites and found aerobic vinyl chloride biodegradation in 23 of 37 microcosms and enrichments. They isolated twelve bacteria that grew on vinyl chloride as their only carbon source: eleven Mycobacterium and one Nocardioides (strain JS614) [2]. The authors concluded these organisms are widespread at chlorinated-solvent sites and likely responsible for natural attenuation of vinyl chloride [2]. An oxygen half-velocity constant of 0.03 to 0.3 mg/L means they can work at low oxygen but need some [2].
Anaerobic
Without oxygen, Dehalococcoides bacteria carrying a vinyl chloride reductase gene (vcrA) strip the chlorine and leave ethene [4]. That is why vcrA counts serve as a biomarker at sites treated by enhanced reductive dechlorination.
A field demonstration
A 2008 demonstration in a contaminated aquifer tracked the anaerobic route directly [4]. The aquifer held cis-1,2-dichloroethene (about 150 micromolar) and vinyl chloride (about 80 micromolar). The team recirculated groundwater with added lactate as food for 201 days and added a mixed culture containing Dehalococcoides with vcrA on day 69. Ethene appeared within four weeks of the food addition and rose to 10 to 25 micromolar by day 145, while vcrA gene copies climbed to 10^7 to 10^8 per liter [4].
The site already had some Dehalococcoides with vcrA before the test began, and the test ran seven months at plot scale. It shows the route works in a real aquifer under managed conditions. It sets no timeline for any other site.
A watershed example
After the East Palestine, Ohio derailment, university researchers sampled stream sediment, surface water and private-well water at 128 and 276 days after the accident to see whether vinyl chloride and butyl acrylate could break down naturally [5]. The aerobic marker genes etnC and etnE turned up in about 40% and 27% of sediment samples. Dehalococcoides and Dehalogenimonas appeared in 50% and 64% of samples at 128 days, rising to 63% and 88% at 276 days. Every sediment microcosm degraded vinyl chloride aerobically, with matching increases in etnC/etnE genes and Mycobacterium. The authors concluded the watershed’s microbiomes can naturally attenuate these compounds [5].
That is a lab microcosm result on native organisms in the sediment tested, and it says nothing about any treatment.
What controls the outcome
- The aerobic route needs oxygen and the anaerobic route runs only without it, so site chemistry decides which dominates.
- Labs can test for the organisms and their genes by qPCR for etnC, etnE and vcrA, and measure ethene as an end product, so nobody has to guess.
- The breakdown chain has to run to the end, because the plume holds vinyl chloride if upstream steps stall and vinyl chloride piles up if the last step is missing.
- Projects track vinyl chloride, ethene and marker genes over many sampling rounds.
Reading a monitoring report on a vinyl chloride plume
A single concentration says little, and a report you can make decisions from usually has several kinds of evidence:
- A trend over several sampling rounds for vinyl chloride and its parent compounds, across wells.
- End products show whether breakdown is complete, and in the 2008 demonstration, ethene rose as the chlorinated compounds fell, the signature of complete anaerobic dechlorination [4].
- Gene counts from qPCR for etnC, etnE and vcrA show whether the organisms are present and growing. In the Ohio derailment sediments, etnC reached about 10^5 gene copies per gram and Dehalococcoides about 10^7 cells per gram [5].
- Oxygen and redox readings, which show the route the site favors.
- Indoor air belongs in the report where buildings sit over a plume, since ATSDR notes vapor can enter indoor air of buildings on contaminated ground [1].
Check which of these a report includes, and which it leaves out.
Microbes in Elm Dirt’s products and vinyl chloride
A Nocardioides species is among the 291 microbial species identified in Elm Dirt’s Plant Juice by independent lab analysis (Biome Makers, 29 May 2024) [6]. Nocardioides is one of the two genera among the twelve vinyl-chloride-growing isolates in the 2002 study [2]. The match is at genus level; the degradation genes are studied strain by strain, and site results are confirmed by lab testing.
Open questions
How a given plume, soil and oxygen profile would respond is something no test of ours has addressed, and it is unclear how well the aerobic route holds at the very low oxygen of a deep plume. A treatability study on site water and soil answers both. If you have a site with vinyl chloride or other volatile organic compounds, contact us.
Sources
All links checked 2026-10-01.
- Agency for Toxic Substances and Disease Registry. Vinyl Chloride, ToxFAQs (January 2024). atsdr.cdc.gov/toxfaqs/tfacts20.pdf
- Coleman NV, Mattes TE, Gossett JM, Spain JC. Phylogenetic and kinetic diversity of aerobic vinyl chloride-assimilating bacteria from contaminated sites. Applied and Environmental Microbiology 68(12):6162 to 6171 (2002). doi:10.1128/AEM.68.12.6162-6171.2002
- Mattes TE, Alexander AK, Coleman NV. Aerobic biodegradation of the chloroethenes: pathways, enzymes, ecology, and evolution. FEMS Microbiology Reviews 34(4):445 to 475 (2010). doi:10.1111/j.1574-6976.2010.00210.x
- Scheutz C, Durant ND, Dennis P, Hansen MH, Jorgensen T, Jakobsen R, Cox EE, Bjerg PL. Concurrent ethene generation and growth of Dehalococcoides containing vinyl chloride reductive dehalogenase genes during an enhanced reductive dechlorination field demonstration. Environmental Science & Technology 42(24):9302 to 9309 (2008). doi:10.1021/es800764t
- Chen G, Rosolina S, Padilla-Crespo E, He G, Chen Q, Arosemena A, Rosado-Maldonado BE, Swift CM, Coelho PB, Whelton AJ, Taggart D, Loffler FE. Natural attenuation potential of vinyl chloride and butyl acrylate released in the East Palestine, Ohio train derailment accident. Environmental Science & Technology 58(40):17743 to 17755 (2024). doi:10.1021/acs.est.4c04198
- Biome Makers (BeCrop). Independent lab analysis of Elm Dirt Plant Juice (Biome Makers lab profile), 29 May 2024. Report disclaimer: results are an interpretation of the potential function of the sample microbiome and are for research purposes.