Chlorobenzenes in freshwater and marine water

​​​Toxicant default guideline values for protecting aquatic ecosystems

October 2000

Extracted from Section 8.3.7 ‘Detailed descriptions of chemicals’ of the ANZECC & ARMCANZ (2000) guidelines.

The default guideline values (previously known as ‘trigger values’) and associated information in this technical brief should be used in accordance with the detailed guidance provided in the Australian and New Zealand Guidelines for Fresh and Marine Water Quality.

Description of chemical

Chlorinated benzenes are used as industrial solvents for waxes, gums, resins, rubbers, oil, asphalt and general degreasing (CCREM 1987, Merck Index 1983), as chemical intermediates for nitrochlorobenzenes, chlorophenols, chloroanilines, pesticides, herbicides and fungicides, and as insecticides for termites and borers. 1,4-Dichlorobenzene is used mainly as an air deodorant and insecticide (HSDB 1996). Hexachlorobenzene is used for organic synthesis, for synthetic rubber and as a rubber additive, as a plasticiser for PVC, an intermediate in dye manufacture, in manufacture of electrodes, and previously as a fungicide, particularly for wheat seed treatment against bunt (HSDB 1996). Its use for seed treatment is banned in Australia (ANZEC 1991). Chlorination of effluents containing traces of aromatic chemicals can result in formation of chlorobenzenes (CCREM 1987).

Hexachlorobenzene has been widespread as an environmental contaminant and was detected at varying concentrations in Sydney’s ocean sewage outfalls (Thompson et al. 1992). Levels up to 14 µg/L were measured in effluents in the Canadian Atlantic coast (Environment Canada 1979).

Fate in the aquatic environment

The properties, fate and transport, and toxicity of chlorinated benzenes are related to their degree of chlorination and molecular weight.

Water solubilities and volatility (and hence air-water partition coefficient; Henry’s law constants) decrease with increasing molecular weight and chlorine substitution and octanol-water partition coefficients increase. Chlorinated benzenes tend to be resistant to abiotic and biotic degradation and persist in the environment. The main pathways for removal of chlorinated benzenes from water bodies are volatilisation (and photooxidation), sorption to suspended matter or sediments and bioaccumulation (USEPA 1979a). Log Koc values of between 4.8 and 5.0 for 1,4-dichlorobenzene indicate that it is readily adsorbed to sediment (Oliver & Nicol 1982).

Evaporation, from water is most significant for the lower molecular weight compounds. The half-life for evaporation of chlorobenzene, dichlorobenzenes and 1,2,4-TCB was around 4.5 hours with moderate wind speed (HSDB 1996). Loss of hexachlorobenzene (HCB) at 50 µg/L from an experimental pond occurred with a half-life of 1–3 days (CCREM 1987) but this may be due to adsorption to sediments. The current analytical PQL for dichlorobenzenes and 1,2,4-TCB is 1 µg/L (NSW EPA 2000).

Chlorobenzenes biodegrade under aerobic conditions but not under anaerobic conditions (HSDB 1996), and this occurred more rapidly at warmer temperatures and in freshwater, compared to marine water (Kanno & Nojima 1979).

The high octanol-water partition coefficients for chlorobenzenes indicate that they are likely to bioaccumulate in aquatic organisms and this is reflected by a general increase in measured bioconcentration factors with increasing chlorine substitution and molecular weight (Oliver & Niimi 1983).

It is difficult to assess the relative uptake directly from water compared to food but dietary sources contributed around 6% to the total accumulated residues of 1,2,4-TCB in bluegills Lepomis macrochirus (Macek et al. 1977) and around 17% for HCB (Laseter et al. 1976). In contrast, Niimi and Cho (1980) considered that dietary sources of HCB could be greater than uptake from water in natural waters where HCB concentrations are low.

Jarvinen and Ankley (1999) report data on tissue residues and effects for most chlorobenzenes for both freshwater and marine species. It is not possible to summarise the data here but readers are referred to that publication for more information.

Aquatic toxicology

Short-term data (usually acute) used for guideline derivation are outlined in Tables 8.3.18 and 8.3.19 of the ANZECC & ARMCANZ (2000) guidelines chronic NOEC data are summarised below. CCME (1999) cite chronic toxicity figures for trout and amphibians from Birge et al. (1979a) and Black et al. (1982) of between 11 and 50 µg/L for chlorobenzene and 7–150 µg/L for 1,2-DCB. These, however, were effect levels between 6 and 10%, which is not considered statistically significant, given the experimental design and the lack of development of concepts of statistical power at that time. Some of these are more than two orders of magnitude lower than the next chronic figures. Furthermore, the UK reviews (e.g. Crookes & Howe 1996) cautioned against the use of the figures in these studies, and they did not appear to be used by USEPA (1986). Canada did not derive a guideline figure for HCB due to its low water solubility, high persistence, bioaccumulation potential and partitioning behaviour. Instead the use of sediment, tissue and soil-based guidelines was recommended (R Kent, pers. comm. 2000). Quantitative structure activity relationship (QSAR) data were used for calculation of low reliability trigger values for the chlorobenzenes (Tables 8.3.18 and 8.3.19 of the ANZECC & ARMCANZ 2000 guidelines).


Water solubility: 491 mg/L (CCREM 1987); Log Kow 2.84 (Oliver & Niimi 1983).

Freshwater fish: two species, 7-30-d NOEC (reproduction & mortality), 2900-8500 µg/L.

Freshwater crustaceans: two species, 9-16-d NOEC (growth, reproduction, mortality), 320-11,000 µg/L.

Marine crustaceans: Crab Portunus pelagicus, 40-d EC50 (growth) of 573 µg/L, LC10 (growth) 253 µg/L (Australian data: Mortimer & Connell 1995).

Marine algae: one species, 5-d NOEC (biomass), 19,000-100,000 µg/L.

1,2 Dichlorobenzene

Water solubility: 134 mg/L (CCREM 1987); Log Kow 3.4 (Oliver & Niimi 1983).

Freshwater fish: Pimephales promelas 28-d LOEC (not used) for growth & survival 2000 µg/L; Oncorhynchus mykiss 6-d LC50 1540 µg/L.

Freshwater crustacean: Daphnia magna, 14-21 d NOEC (reproduction) of 185-630 µg/L.

Marine fish: one species, 10-d growth and reproduction, 5000 µg/L.

1,3 Dichlorobenzene

Log Kow 3.53 (Oliver & Niimi 1983).

Freshwater fish: two species LOEC growth (not used) to 32 d, 1500-1510 µg/L.

Freshwater crustacean: D. magna 16-21-d NOEC (growth, reproduction), 300-690 µg/L.

Freshwater fish: P. promelas, 32-d NOEC (growth and mortality) of 1000-2400 µg/L.

1,4 Dichlorobenzene

Water solubility: 83 mg/L (CCREM 1987); Log Kow 3.4 (Oliver & Niimi 1983).

Freshwater fish: P. promelas, 27-32-d NOEC (growth, reproduction, mortality), 320-570 µg/L giving an acute-to-chronic ratio (ACR) of 7.4 Brachydanio rerio, 6-28-d NOEC (growth, reproduction, mortality), 650-2100 µg/L.

Freshwater crustacean: D. magna, 8-21 d NOEC (reproduction), 220-400 µg/L.

Freshwater algae: one species, 4-d NOEC growth of 570 µg/L.

Marine crab: Portunus pelagicus, 40-d NOEC (growth), 31 µg/L, giving an ACR of 23.8. The 10% effect level was 65 µg/L and the EC50 was 201 µg/L (Australian data; Mortimer & Connell 1995).


Water solubility: 12 mg/L (CCREM 1987); Log Kow 4.14 (Oliver & Niimi 1983).

Freshwater fish: Brachydanio rerio, 7–28-d NOEC, 250–710 µg/L.

Freshwater crustacean: D. magna 14–21-d NOEC, reproduction, 30–40 µg/L.

Freshwater alga: one species 96-h EC50 (growth) of 900 µg/L.

Marine crab: Portunus pelagicus; 40-d NOEC (growth), 25-50 µg/L, giving an ACR of 24. The EC50 (growth) was 180 µg/L (Australian data; Mortimer & Connell 1995).


Water solubility: 30 mg/L (CCREM 1987); Log Kow 4.02 (Oliver & Niimi 1983).

Freshwater fish: O. mykiss, 45-85-d NOEC (growth, mortality), 350-470 µg/L; P. promelas, 32-d NOEC (growth), 210-500 µg/L.

Freshwater crustacean: D. magna 16-28-d NOEC (growth, reproduction and mortality) 100-360 µg/L).

Freshwater algae: Selenastrum capricornutum 4-d NOEC (growth), 190-1400 µg/L.

The geometric mean of ACRs was 5.32.


Log Kow 4.19 (Oliver & Niimi 1983).

No chronic data.


Log Kow 4.64 (Oliver & Niimi 1983).

Freshwater fish: Brachydanio rerio 7-28 d NOEC, 100-310 µg/L; P. promelas, 33-d NOEC (growth, mortality), 250 µg/L.

Freshwater crustacean: D. magna, 16 d (mortality, reproduction), 55-100 µg/L.

Marine crab: P. pelagicus; 40-d EC10 (growth), 36 µg/L. The EC50  growth was 125 µg/L (Australian data; Mortimer & Connell 1995).


Log Kow 4.66 (Oliver & Niimi 1983).

No chronic data.


Water solubility: 0.6 mg/L (CCREM 1987); Log Kow 4.52 (Oliver & Niimi 1983)

Marine fish: 1 sp, 28-d NOEC, 90-300 µg/L (mortality and growth) Cyprinodon variegatus.

Some data points were removed because they were well above the water solubility.


Water solubility: 0.6 mg/L (CCREM 1987); Log Kow 4.94 (Oliver & Niimi 1983).

Freshwater fish: B. rerio, 7-28-d NOEC (growth, mortality, reproduction), P. promelas, 34-110 µg/L; 33-d NOEC 55 µg/L.

Freshwater crustacean: D. magna, 14-21-d NOEC (growth, mortality, reproduction), 10-100 µg/L.

Marine fish: C. variegatus, 28-d NOEC (mortality), 19-120 µg/L.

Marine crab: P. pelagicus; 40-d EC10 (growth), 14 µg/L. The EC50  growth was 40 µg/L (Australian data; Mortimer & Connell 1995).

Some data points were removed because they were well above the water solubility. Data were insufficient for either high or moderate reliability trigger values. The best trigger value was derived from QSAR data using the assessment factor (AF) method.


Water solubility: 0.005 mg/L (CCREM 1987); Log Kow 5.7 (Oliver & Niimi 1983).

Freshwater crustacean: 28-d NOEC (mortality), 1.8 µg/L (Gammarus lacustris).

Freshwater algae: 4-d NOEC (growth), 14 µg/L.

Some data points for HCB were removed because they were well above the water solubility.

Australian and New Zealand - toxicity data

Toxicity data were available on the marine crab P. pelagicus, for 1,4-DCB (96-h LC50, 729 µg/L; 40-d NOEC, growth, 31 µg/L), 1,2,3-TCB (96-h LC50, 561 µg/L; 40-d NOEC, growth, 24-50 µg/L) and 1,2,3,4-TeCB (96-h LC50, 410 µg/L).

Factors that modify toxicity of chlorobenzenes

Chlorobenzenes are not chemically active and will not interact with most water quality parameters. They do, however, strongly adsorb to sediment, suspended matter and organic carbon, which should reduce availability significantly. The high Koc values for 1,4-DCB are indicative of the propensity to adsorb to sediments and this should increase for the more highly chlorinated benzenes.

Bioaccumulation and food uptake need to be considered for the higher chlorinated benzenes. The effect of temperature on their toxicity is unknown.

Guideline values

Most of the trigger values listed in Tables 8.3.18 and 8.3.19 of the ANZECC & ARMCANZ (2000) guidelines were calculated after enhancement of the data with QSAR calculations, where data were lacking. These levels of tri – hexa CBs do not include bioaccumulation effects, which need to be considered further. There are large variations in Kow and bioconcentration factor (BF) values, which may also need closer screening.

Alternative protection levels for low reliability trigger values for chlorobenzenes derived by QSAR data are as follows (µg/L); alternative values for moderate reliability trigger values are in Table 3.4.1 of the ANZECC & ARMCANZ (2000) guidelines*









































* As these are all potential bioac​cumulators (except CB), users are advised to use the 99% protection level if no site-specific data are available on bioaccumulation effects.


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