Water Quality Standards

Summary information extracted from: Guidelines for drinking-water quality, 2nd ed. - Vol. 1. Recommendations. - Geneva, World Health Organization, 1993. p. 70.

Releases of trichlorobenzenes (TCBs) into the environment occur through their manufacture and use as industrial chemicals, chemical intermediates, and solvents. TCBs are found in drinking-water but rarely at levels above 1 µg/litre. General population exposure will primarily result from air and food.

The TCBs are of moderate acute toxicity. After short-term oral exposure, all three isomers show similar toxic effects, predominantly on the liver. Long-term toxicity and carcinogenicity studies via the oral route have not been carried out, but the data available suggest that all three isomers are non-genotoxic.

A TDI of 7.7 µg/kg of body weight was calculated by applying an uncertainty factor of 1000 (100 for inter- and intraspecies variation and 10 for the short duration of the study) to the NOAEL of 7.7 mg/kg of body weight per day for liver toxicity identified in a 13-week rat study. The guideline value would be 20 µg/litre (rounded figure) for each isomer based on an allocation of 10% of the TDI to drinking-water; however, because of the similarity in the toxicity of the TCB isomers, a guideline value of 20 µg/litre is proposed for total TCBs. This value exceeds the lowest reported odour threshold in water (see Acceptability aspects).