Trichlorobenzenes (TCBs)

The substance
Trichlorobenzenes are a mixture of the isomers 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene and 1,3,5-trichlorobenzene. Trichlorobenzenes are colourless liquids or crystalline solids, with an aromatic odour. They are sparingly soluble in water but miscible in organic solvents. They are non-flammable and decompose when heated to produce toxic gases. Boiling point is above 200 0C. Trichlorobenzenes are synthetic chemicals that do not occur in nature.

Trichlorobenzenes are only used as chemical intermediates, specifically for the production of herbicides, pigments and dyes. The use as solvents, as dielectric fluids, as component in synthetic oils, lubricants and heat transfer fluids, in degreasing agents, cleaning agents for septic tanks and in abrasive formulations has been phased out in Europe.

Major emissions
Trichlorobenzenes are released from the production of trichlorobenzenes and may be released by accidental discharges from any of the productions listed above.

Impacts on human health and environment
Excessive exposure to trichlorobenzene isomers may affect the adrenal gland, digestive system, eye, kidney, liver, lung, nose, skin, throat and thyroid gland. Trichlorobenzenes are toxic to aquatic life and discharges to water would be expected to have significant impacts for local aquatic wildlife. Degradation in surface waters, soils and sediments also takes place very slowly. There is some evidence that they may bioaccumulate through the food chain. Trichlorobenzenes tend to bind to soil and sediment particles and as a result tend not to leach into groundwater. Trichlorobenzenes are subject to a review for identification as possible priority hazardous substance under the Water Framework Directive. 1,2,4-trichlorobenzene (CAS No.120-82-1) is a priority substance (EC.2268/95. OJ L231, 28.9.95, p.18.) under Regulation 793/93. The Risk Assessment Report has been completed and can be downloaded from

Emission to air reporting threshold: 10 kg/year

Data source: European Pollutant Emission Register