Chlorinated methanes in freshwater and marine water

​​Toxicant default guideline values for protecting aquatic ecosystems

October 2000

Description of chemical

Chloromethane (CH3Cl), dichloromethane (CH2Cl2), chloroform (CHCl3) and carbon tetrachloride (CCl4) are volatile solvents which have decreasing volatility and water solubility with increasing chlorine substitution: solubility decreases from 20 g/L at 20°C for dichloromethane to 8.2 g/L for chloroform and 0.8 g/L for carbon tetrachloride. Log K_ow of CCl4 is 2.83.

They are commonly used solvents for adhesives, pesticides, fats, oils, rubbers, alkaloids, waxes, resins and for specialty chemicals and as a cleansing agent such as in dry cleaning. Some are used in paint strippers, for manufacture of fluorocarbon refrigerants and in the past in fire extinguishers. Chloroform has been used as an anaesthetic, and has limited use as a fumigant for foods and seeds and was used in some household products such as toothpaste and cough syrups (HSDB 1996). Chlorinated methanes are formed as by-products of chlorination of water and wastewater (Crookes et al. 1994). World production of chloroform was estimated at 250,000 tonnes in 1990 (Crookes et al. 1994) but its future demand may decrease with the control on ozone-depleting refrigerants.

Environmental fate

Chloroform has a negligible rate of hydrolysis, slow biodegradation and negligible photodegradation (HSDB 1996). The main route of loss of these chloromethanes from water is by evaporation (<3 days) (Crookes et al. 1994). Rates of loss by evaporation and degradation decrease with increasing chlorine substitution. Little would be transported to sediments and they would be generally highly mobile in soils and sediments. They do not have the potential to bioaccumulate in aquatic organisms (Crookes et al. 1994) and are rapidly metabolised.

Aquatic toxicology

Short-term acute toxicity data for guideline derivation for chloromethanes are outlined in Table 8.3.11, along with derived trigger values for 95% protection. The quantitative structure activity relationship (QSAR) estimates were generally lower than the measured acute toxicity values, and these were used for guideline derivation. Experimental chronic data are given below.

Dichloromethane

Freshwater fish: Pimephales promelas, embryo-larval (weight) 28-d MATC 108 mg/L and 8-d mortality 471 mg/L. QSAR data were used for the guideline calculations. Low reliability trigger values for 99%, 95%, 90% and 80% protection were 3, 4, 5 and 7 mg/L respectively, which are all below the experimental figures.

Chloroform

Freshwater amphibian: A figure of 270 µg/L for a 7-d LC50 (4-d post hatch) was reported for Hyala crucifer. These data were much lower than any other reported but, as concerns had been expressed on the reliability of these data (Crookes et al. 1994), they were not included in calculations.

Freshwater invertebrates: Ceriodaphniadubia, 7-d NOEC for mortality was 2.4 mg/L and for reproduction, 200 µg/L (Cowgill & Milazzo 1991). A 21-day NOEC of 6.3 mg/L (measured) was determined for reproductive impairment of Daphnia magna (Kuhn et al. 1989) and for growth after 16 days, the NOEC was 15 mg/L.

Figures after 9 days were between 12 and 20 mg/L.

Freshwater algae: 8-d NOEC (growth), 93–550 mg/L.

Marine diatoms: 5-d NOEC (growth, biomass), 41–216 mg/L.

An ACR of 9.1 could be applied but chronic QSAR figures were used: Trigger values for chloroform at 99%, 95%, 90% and 80% protection were 370 µg/L, 770 µg/L, 1100 and 1900 µg/L respectively. The 99% figure is recommended for slightly to moderately disturbed systems to protect key species from chronic toxicity.

Carbon tetrachloride

No data were available and low reliability trigger values were derived from QSAR estimates using the statistical distribution approach: 99% 150 mg/L, 95% 240 mg/L, 90% 320 mg/L and 80% 460 µg/L.

Only low reliability trigger values could be derived for chloromethanes (Table 8.3.11) and these should only be used as indicative interim working levels.

Australian and New Zealand toxicity data

There are no reports of Australian or New Zealand toxicity data for chlorinated methanes.

Factors that modify toxicity of chloroform

There are no data or factors that modify toxicity of chloroform. Its high volatility should rapidly reduce environmental concentrations.

References

ANZECC & ARMCANZ 2000. Australian and New Zealand Guidelines for Fresh and Marine Water Quality, Australian and New Zealand Environment and Conservation Council and Agriculture and Resource Management Council of Australia and New Zealand, Canberra.

Cowgill UM & Milazzo DP 1991. The sensitivity of Ceriodaphnia dubia and Daphnia magna to several chemicals utilising the three-brood test. Archives of Environmental Contamination and Toxicology 20, 211-217.

Crookes MJ, Willis B, Howe PD & Dobson SD 1994. Environmental hazard assessment: Chloroform. TSD22. Toxic substances Division, Department of Environment, Garston, UK.

HSDB (Hazardous Substances Data Bank) 1996. Micromedex Inc. 31 July 1996.

Kuhn R, Pattard M, Pernak K-D & Winter A 1989. Results of the harmful effects on selected water pollutants (anilines, phenols, aliphatic compounds) to Daphnia magna.Water Research 23, 495-499.