U.S. EPA Contaminated Site Cleanup Information (CLU-IN)

U.S. Environmental Protection Agency
U.S. EPA Technology Innovation and Field Services Division

Dense Nonaqueous Phase Liquids (DNAPLs)

Chemistry and Behavior

Halogenated Alkanes



 ChloroformChloroform (CAS #67-66-3) is a colorless liquid with a non-irritating odor and a slightly sweet taste. The compound is soluble in water (7,950 mg/L), has a high vapor pressure (246 mm Hg at 25oC), and a specific gravity of 1.48 at 20oC (Howard 1991). The Henry's constant is 4.06 e-3 atm-m3/mole at 25oC, and the log Kow is 1.97. The log Koc value is reported as 1.65 and 2.40 (ATSDR 1997). A useful profile of chloroform's chemical and physical properties can be found in Chapter 3Adobe PDF Logo of the toxicological profile for chloroform published by the Agency for Toxic Substances and Disease Registry (ATSDR).

The compound absorbs poorly to soil, especially to soil with low organic carbon content, and it can leach into groundwater. Due to its high vapor pressure, chloroform released to near-surface soils is expected to evaporate rapidly (Howard 1991).

Chloroform released to water will evaporate primarily into the atmosphere. Modeling studies predict a chloroform volatilization half life of 3.5 hours in a river, 4.4 days in a lake (HSDB). Chloroform discharged from municipal treatment plants to an estuarine arm of the Chesapeake Bay completely disappeared within 4 km in the spring and 11 km in the winter under icy conditions (Howard 1991).

Chloroform in the atmosphere will exist primarily in a vapor phase and will degrade slowly by reaction with hydroxyl radicals with a half life of approximately 80 days (ATSDR 1997). The slow breakdown process yields products such as phosgene dichloromethane, formyl chloride, carbon monoxide, carbon dioxide, and hydrogen chloride (Watts et al. 2004). Chloroform can travel long distances in the atmosphere and will return partially in precipitation (ATSDR 1997).

Because of chloroform's low Kow value (1.97), it is not expected to bioaccumulate significantly. Chloroform does not degrade under aerobic conditions and only slowly under anaerobic conditions (Watts et al. 2004). It can be degraded cometabolically under aerobic conditions (Semprini and Arp 2004).


Chloroform, CASRN: 67-66-3
Hazardous Substances Data Bank (HSDB)
TOXNET, National Library of Medicine Web site.

Concise International Chemical Assessment Document 58: Chloroform
Watts, P., G. Long, and M.E. Meek.
World Health Organization, Geneva, 2004

Final Report: Aerobic Cometabolism of Chloroform, 1,1,1-Trichloroethane, 1,1-Dichloroethylene, and Other Chlorinated Aliphatic Hydrocarbons by Microbes Grown on Butane and Propane
Semprini, L. and D.J. Arp.
U.S. EPA, National Center For Environmental Research, Grant R825689C019, Subproject 19, 2001

Handbook of Environmental Fate and Exposure Data for Organic Chemicals, Volume II: Solvents
Howard, P. (ed.)
Lewis Publishers, Chelsea, MI, 546 pp, 1991

Toxicological Profile for Chloroform
Agency for Toxic Substances and Disease Registry (ATSDR), 343 pp, 1997

For Further Information

DNAPL Site EvaluationAdobe PDF Logo
Cohen, R. and J. Mercer
EPA 600-R-93-022, 369 pp, 1993

This document has a broad discussion of DNAPL site evaluation and contains a comprehensive table of physical properties of selected DNAPL chemicals, including chloroform, in its Appendix A.

Evaluation of Functional Groups Responsible for Chloroform Formation during Water Chlorination Using Compound Specific Isotope Analysis
Arnold, W.A., J. Bolotin, U. von Gunten, and T.B. Hofstetter.
Environmental Science & Technology 42(21):7778-7785(2008)
View abstract

Factors Associated with Sources, Transport, and Fate of Volatile Organic Compounds and Their Mixtures in Aquifers of the United States
Squillace, P.J. and M.J. Moran.
Environmental Science & Technology 41(7):2123-2130(2007)
View abstract