Haloacetonitriles

dichloroacetonitrile; trichloroacetonitrile; dibromoacetonitrile bromochloroacetonitrile (endorsed 2011)

Guideline

Data are inadequate to set guideline values for haloacetonitriles in drinking water

General description

Haloacetonitriles are formed from organic precursors during chlorination or chloramination of drinking water. Concentrations of dihaloacetonitriles reported overseas range up to 0.04 mg/L but are typically less than 0.003 mg/L. Concentrations of trichloroacetonitrile are less than 0.001 mg/L.

Trichloroacetonitrile has been used as an insecticide. No data are available on uses for the other haloacetonitriles.

Typical values in Australian drinking water

No data are available on concentrations of haloacetonitriles in Australian drinking waters.

Limiting formation in drinking water

The presence of haloacetonitriles in drinking water can be minimised by removing naturally occurring organic matter from the source water, reducing the amount of chlorine added, or using alternative disinfectants

Measurement

A solvent extraction procedure is suitable for the analysis of haloacetonitriles (USEPA Method 551.1 1995). A salting agent is added to the sample and the haloacetonitriles extracted using methyl tert-butyl ether or pentane. The extracts are then analysed using gas chromatography with an electron capture detector. Limits of determination are less than 0.0001 mg/L.

Health considerations

Haloacetonitriles are rapidly absorbed from the gastrointestinal tract and metabolised to single carbon compounds, including cyanide. Insufficient data are available to indicate whether haloacetonitriles can accumulate in specific organs.

No data are available on the health effects of haloacetonitriles in humans.

Dichloroacetonitrile and dibromoacetonitrile caused decreased body weights in 90-day feeding studies with rats, but specific target organs were not identified. Dibromoacetonitrile and bromochloroacetonitrile caused an increase in the incidence of squamous cell carcinomas when applied to the skin of mice in the presence of agents that promote tumour growth. No significant increase was observed for dichloroacetonitrile or trichloroacetonitrile.

Dichloroacetonitrile and bromochloroacetonitrile were direct-acting mutagens in tests on bacteria, whereas tests with dibromoacetonitrile and trichloroacetonitrile were negative. All four compounds induced DNA damage (sister chromatid exchange and DNA strand breaks) in mammalian cells.

Studies with rats indicate that dichloroacetonitrile and trichloroacetonitrile can cause foetal deformities. A short-term reproductive and developmental toxicity study of dibromoacetonitrile in male and female rats found no evidence of reproductive toxicity at dose levels up to 150 mg/L.

A two-year study of dibromoacetonitrile in drinking water conducted recently by the US National Toxicology Program (2008) is reported to have shown clear evidence of carcinogenicity in male rats, and some evidence of carcinogenic activity in female rats, as well as clear evidence of carcinogenic activity in male and female mice, however the final report from this study is not yet available.

The NHMRC Standing Committee on Toxicity reviewed the available data for haloacetonitriles in 1991, and concluded that data were insufficient to set no-effect levels for these compounds. This finding was supported by a review by the NHMRC Water Quality Advisory Committee in 2009, but will be reassessed when the National Toxicology Program report on dibromoacetonitrile becomes available.

Derivation of guideline

The World Health Organization (WHO 2004) has set a provisional guideline value for dichloroacetonitrile (0.02 mg/L) based on a 90-day study which found increased liver weight in male and female rats. This calculation involved a high uncertainty value. The WHO guideline value for dibromoacetonitrile (0.07 mg/L) is derived from the no-observed-adverse-effects level in a 13-week study of increased body weight in male rats.

These data were not considered to be sufficient to set an Australian guideline value for dichloroacetonitrile. It was also considered not appropriate to set a guideline for dibromoacetonitrile in view of the pending National Toxicology Report report on carcinogenicity for this compound.

References

National Toxicology Program (2008) TR-544 Toxicology and carcinogenesis studies of dibromoacetonitrile (CAS No. 3252-43-5) in F344/N Rats and B6C3F1 mice (Drinking water studies) Draft abstract.

USEPA Method 551.1 (1995). Determination of chlorination disinfection by-products and chlorinated solvents in drinking water by liquid-liquid extraction and gas chromatography with electron capture detection. United States Environmental Protection Agency, Environmental Monitoring and Support Laboratory (EMSL), Cincinnati, Ohio.

WHO (World Health Organization) (2004). Guidelines for Drinking-water Quality. 3rd Edition, WHO, Geneva, Switzerland.