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 Monoaromatics


1,2,4-Trichlorobenzene (1,2,4-TCB CAS# 120-82-1) has a vapor pressure of 0.46 mm Hg at 25oC (HSDB) and is a Class IIIB combustible liquid (NIOSH 2005). The log Koc of 1,2,4-TCB is 3.1, the log Kow is 4.02, and the Henry's constant is 1.42 e-3 atm-m3/mol at 25oC. The solubility of 1,2,4-TCB is about 31.3 mg/L at 25oC (HSDB) and its specific gravity is about 1.46 (20oC). More extensive data are available through the TOXNET gateway.

The calculated Koc value for this compound in soil indicates that 1,2,4-TCB is likely to have a low mobility in soil and sediment. It is expected to sorb to suspended sediments (HSDB).

Based on a Henry's law constant of 1.42 e-3 atm-m3/mol at 25oC, 1,2,4-TCB is expected to volatilize rapidly from water surfaces. Modeling information in the record for this chemical in the Hazardous Substances Data Bank (HSDB) suggests that the half life of 1,2,4-TCB in a model river is about 5 hours, and about 135 hours in a model lake.

Because of the relatively high Kow of 1,2,4-TCB, bioaccumulation is expected, with high bioaccumulation in aquatic organisms (HSDB). Biomagnification, however, is not expected (CSTEE 2001). Microbial degradation of the compound can occur under either anaerobic (Fung et al. 2009) or aerobic conditions (Lawrence 2006).

When released to the atmosphere, hydroxyl radicals are expected to degrade 1,2,4-TCB with a half life of about 30 days. Direct photolysis is not expected to occur (HSDB).


NIOSH Pocket Guide to Chemical Hazards.
National Institute of Occupational Safety and Health, NIOSH Publication Number 2005-149, 2005

1,2,4-Trichlorobenzene, CASRN: 120-82-1
Hazardous Substances Data Bank (HSDB)
TOXNET, National Library of Medicine Web site.

Description, Properties, and Degradation of Selected Volatile Organic Compounds Detected in Ground Water: A Review of Selected LiteratureAdobe PDF Logo
Lawrence, S.J.
U.S. Geological Survey Open-File Report 2006-1338, 65 pp, 2006

Opinion on the Results of the Risk Assessment of 1,2,4-Trichlorobenzene, CAS No. 120-82-1, EINECS No. 204-428-0Adobe PDF Logo
Scientific Committee on Toxicity, Ecotoxicity and the Environment (CSTEE), 6 pp, 2001

Reductive Dehalogenation of Dichlorobenzenes and Monochlorobenzene to Benzene in Microcosms
Fung, J., B.P. Weisenstein, E.E. Mack, J.E. Vidumsky, T.A. Ei, and S.H. Zinder.
Environmental Science & Technology 43(7):2302-230(2009)

This article has a discussion that includes trichlorobenzenes. View abstract

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 1,2,4-TCB, in Appendix A.

TrichlorobenzenesAdobe PDF Logo
OSPAR Commission, ISBN: 1-904426-10-7, Publication 2005/170, 40 pp, 2005