Guidelines for drinking-water quality. Volume 1 - BVSDE

it is not a genotoxic carcinogen and that genotoxic metabolites are not formed in relevant
amounts in vivo.
A TDI of 6 µg/kg of body weight was calculated by applying an uncertainty factor of 1000 (100 for
inter- and intraspecies variation and 10 reflecting concern for carcinogenic potential) to a NOAEL
of 6 mg/kg of body weight per day for hepatotoxic effects in a 2-year drinking-water study in rats.
This gives a guideline value of 20 µg/litre (rounded figure), allocating 10% of the TDI to drinkingwater.
It should be noted that widespread exposure from other sources is possible.
1,1-Dichloroethane
1,1-Dichloroethane is used as a chemical intermediate and solvent. There are limited data
showing that it can be present in concentrations of up to 10 µg/litre in drinking-water. However,
because of the widespread use and disposal of this chemical, its occurrence in ground water may
increase.
1,1-Dichloroethane is rapidly metabolized by mammals to acetic acid and a variety of chlorinated
compounds. It is of relatively low acute toxicity, and limited data are available on its toxicity from
short- and long-term studies.
There is limited in vitro evidence of genotoxicity. One carcinogenicity study by gavage in mice
and rats provided no conclusive evidence of carcinogenicity, although there was some evidence
of an increased incidence of haemangiosarcomas in treated animals.
In view of the very limited database on toxicity and carcinogenicity, it was concluded that no
guideline value should be proposed.
1,2-Dichloroethane
1,2-Dichloroethane is used mainly as an intermediate in the production of vinyl chloride and other
chemicals and to a lesser extent as a solvent. It has been found in drinking-water at levels of up
to a few micrograms per litre. It is found in urban air.
IARC has classified 1,2-dichloroethane in Group 2B. It has been shown to produce statistically
significant increases in a number of tumour types in laboratory animals, including the relatively
rare haemangiosarcoma, and the balance of evidence indicates that it is potentially genotoxic.
There are no suitable long-term studies on which to base a TDI.
On the basis of haemangiosarcomas observed in male rats in a 78-week gavage study, and
applying the linearized multistage model, a guideline value for drinking-water of 30 µg/litre,
corresponding to an excess lifetime cancer risk of 10 -5 , was calculated.
1,1,1-Trichloroethane
1,1,1-Trichloroethane has been found in only a small proportion of surface and ground waters,
usually at concentrations of less than 20 µg/litre. In a few instances, much higher concentrations
have been observed. There appears to be increasing exposure to 1,1,1-trichloroethane.
1,1,1-Trichloroethane is rapidly absorbed from the lungs and gastrointestinal tract, but only small
amounts - about 6% in humans and 3% in experimental animals - are metabolized. Exposure to
high concentrations can lead to hepatic steatosis (fatty liver) in both humans and laboratory
animals.
IARC has placed 1,1,1-trichloroethane in Group 3. Available studies of oral administration were
considered inadequate for calculation of a TDI. As there is an increasing need for guidance on
this compound, a 14-week inhalation study in male mice was selected for use in calculating the