Water Quality Standards

Summary information extracted from: Guidelines for drinking-water quality, 2nd ed. - Vol. 1. Recommendations. - Geneva, World Health Organization, 1993. p. 65.

Toluene is used primarily as a solvent and in blending petrol. Concentrations of a few micrograms per litre have been found in surface water, ground water, and drinking-water. Point emissions can lead to higher concentrations in ground water. The main exposure is via air. Exposure is increased by smoking and in traffic.

Toluene is absorbed completely from the gastrointestinal tract and rapidly distributed in the body with a preference for adipose tissue. Toluene is rapidly metabolized and, following conjugation, excreted predominantly in urine.

With occupational exposure, impairment of the central nervous system and irritation of mucous membranes are observed. The acute oral toxicity is low. Toluene exerts embryotoxic and fetotoxic effects, but there is no clear evidence for teratogenic activity in laboratory animals and humans.

In long-term inhalation studies in rats and mice, there is no evidence for carcinogenicity of toluene. Genotoxicity tests in vitro were negative, whereas in vivo assays showed conflicting results with respect to chromosomal aberrations.

A TDI of 223 µg/kg of body weight was derived using a LOAEL for marginal hepatotoxic effects of 312 mg/kg of body weight per day in a 13-week gavage study in mice (administration 5 days per week) and applying an uncertainty factor of 1000 (10 for inter- and intraspecies variation and 10 for the short duration of the study and use of a LOAEL instead of a NOAEL). This yields a guideline value of 700 µg/litre (rounded figure), allocating 10% of the TDI to drinking-water. It should be noted, however, that this value exceeds the lowest reported odour threshold for toluene in water (see Acceptability aspects).