Water Quality Standards

Summary information extracted from: Guidelines for drinking-water quality, 2nd ed. Vol. 1. Recommendations. - Geneva, World Health Organization, 1993. pp. 68-69.

Releases of monochlorobenzene (MCB) to the environment are thought to be mainly due to volatilization losses associated with its use as a solvent in pesticide formulations, as a degreasing agent, and from other industrial applications. The major source of human exposure is probably air.

MCB is of low acute toxicity. Oral exposure to high doses of MCB affects mainly the liver, kidneys, and haematopoietic system. There is limited evidence of carcinogenicity in male rats, with high doses increasing the occurrence of neoplastic nodules in the liver. The majority of evidence suggests that MCB is not mutagenic; although it binds to DNA in vivo, the level of binding is low.

A TDI of 85.7 µg/kg of body weight was calculated by applying an uncertainty factor of 500 (100 for inter- and intraspecies variation and 5 for the limited evidence of carcinogenicity) to a NOAEL of 60 mg/kg of body weight for neoplastic nodules identified in a 2-year rat study with 5 days per week dosing by gavage. This gives a guideline value of 300 µg/litre (rounded figure) based on an allocation of 10% of the TDI to drinking-water. However, this value far exceeds its lowest reported taste and odour threshold for MCB in water (see Acceptability aspects).