Substance fact sheet
The National Pollutant Inventory (NPI) provides information on the types and amounts of pollutants being emitted in the Australian community.
This page provides facts about benzene hexachloro- (HCB). It describes how you might be exposed to this substance, how exposure might effect you and the environment, common uses, comparative data about benzene hexachloro- (HCB) and its physical and chemical properties.
For more information about some of the terms used in this page, see the NPI glossary.
The National Pollutant Inventory (NPI) holds data for all sources of benzene hexachloro- (HCB) emissions in Australia.
Worksafe Australia describes HCB as toxic, with a concentration cut-off level of 0.1 % weight/weight.
he heath effects caused by breathing hexachlorobenzene or by getting it on your skin are not known. Porphyria- induced skin disorders have been reported in humans following ingestion of bread prepared from grain containing hexachlorobenzene. There is evidence that hexachlorobenzene is toxic to young children; offspring nursing from hexachlorobenzene exposed mothers are exposed through the milk. Hexachlorobenzene has been found to decrease the survival rates of young children. Therefore, nursing infants of humans may be particularly susceptible due to the transfer of hexachlorobenzene through maternal milk. This has been confirmed by doing experiments in animals. Other animal studies show that eating hexachlorobenzene on a long-term basis can harm the liver, immune system, kidneys, and blood and produce eruptions and pigmentations of the skin. Studies in animals also suggest that eating enough hexachlorobenzene on a long-term basis can lead to cancer of the liver and thyroid. Hexachlorobenzene is generally regarded as a probable carcinogen.
Hexachlorobenzene can enter your body when you eat hexachlorobenzene-contaminated food, breathe hexachlorobenzene particles in the air, and/or when your skin comes in contact with it. Following intake, hexachlorobenzene rapidly spreads to many tissues in the body, especially to fat, probably within a few hours. Most of the hexachlorobenzene leaves your body in the faeces, and smaller amounts are found in the urine. Hexachlorobenzene will remain in your body, especially in fat, for years. A large portion of hexachlorobenzene in fat can be transferred in human milk.
You may be exposed to hexachlorobenzene if you live near an industrial site where hexachlorobenzene is used or produced as a by-product, or a waste dump where it has been discarded. At these sites hexachlorobenzene may be carried in the air on dust particles. If you work in an industry that produces the chemical unintentionally as a by-product or uses hexachlorobenzene, you may also be exposed to hexachlorobenzene particles or dust particles that carry hexachlorobenzene and possibly get it on your skin.
Exposure to hexachlorobenzene can occur through eating and drinking foods and liquids, such as milk, other dairy products, meat, and poultry. When this substance is eaten in combination with fat or oil, more of it is taken up by the body than when consumed in drinking water.
Exposure to hexachlorobenzene can also occur through contact with hexachlorobenzene-contaminated soil, dust particles, or industrial releases into the environment.
Because of its low water solubility, hexachlorobenzene is usually not present in drinking water.
See Sources for more information.
No national guidelines.
Acute toxic effects may include the death of animals, birds, or fish, and death or low growth rate in plants. Acute effects are seen two to four days after animals or plants come in contact with a toxic chemical substance.
Chronic toxic effects may include shortened lifespan, reproductive problems, lower fertility, and changes in appearance or behaviour.
Hexachlorobenzene can remain in the environment for a long time, half-life up to 7.5 years. It is only very slightly soluble in water, so most of it will remain in particles on the bottom of lakes and rivers. Hexachlorobenzene adsorbs strongly to soil. High levels can build up in fish, marine mammals, birds, lichens, and animals that eat lichens or fish. It can also build up in wheat, grasses, some vegetables, and other plants.
It has been estimated that about 50% of hexachlorobenzene will eventually end up in terrestrial soil; about 46.75% will end up in aquatic sediments; about 3% will end up in air; and about 0.25% will end up in water.
Hexachlorobenzene has been detected in environmental samples from around the world, and is recognised as a global pollutant.
Breakdown in soil and groundwater: HCB is a highly persistent compound, with reported field half-lives in the soil environment up to 7.5 years. Evaporation is rapid while it is on soil surfaces, but considerably less so when it is mixed into the soil. HCB is moderately to strongly bound by most soils. Data from testing on hydro-soils indicate that it may be degraded both aerobically and anaerobically. It has low water solubility, and thus is likely to show low mobility in the soil environment. Due to its lengthy persistence, however, even low mobility may result in appreciable travel; therefore, HCB may pose some risk of groundwater contamination. Hexachlorobenzene has been found in well water at low concentrations, up to 5.6 ppb and only in a very small percentage of all of the wells tested.
Breakdown in water: HCB is of low water solubility, so it would most likely reach surface waters via surface run-off by attachment to soil particles. Once in the aquatic environment, it is likely to be short-lived; HCB underwent very rapid, almost complete (that is, less than 5 days) degradation to pentachlorophenol and related compounds in inoculated hydro-soil samples under both aerobic and anaerobic conditions.
Breakdown in vegetation: Breakdown in vegetation appears rapid, with residue levels in grass at approximately 1% of the initial amount after 15 days, and at approximately 0.01% after 19 months.
Breakdown in air: The dominant chemical loss process for gas phase hexachlorobenzene in the troposphere is by reaction with the hydroxyl (OH) radical. Based on this reaction, the atmospheric half-life is calculated to be about 1.4 years. Air to water exchange to (and from) the oceans, and gas-phase hexachlorobenzene and wet and dry deposition of particle-associated hexachlorobenzene, are important.
Australian Water Quality Guidelines for Fresh and Marine Waters: (ANZECC, 1992):
Maximum of 0.007 micrograms/L (i.e. 0.000000007 g/L)
The Australian NOHSC National Exposure Standards Database link is probably the most useful source of information.
There are currently no commercial uses of hexachlorobenzene in Australia. Hexachlorobenzene has been used as a pesticide but is no longer registered for this use in Australia. It was also used in the production of fireworks, ammunition, rubber, aluminium, and dyes, and in wood preservation. Hexachlorobenzene was widely used as a pesticide to protect the seeds of onions and sorghum, wheat, and other grains against fungus. Its relevance to the NPI is that it is formed as a by-product during the manufacture of chemicals used as solvents (to dissolve other substances), other chlorine-containing compounds, and pesticides. It is also formed as a by-product in the waste streams of chloralkali and wood-preserving plants, and when burning municipal waste.
The aerospace industry, sanitary services, and agricultural chemicals manufacturers. Industries involved in the manufacture of solvents, other chlorine-containing compounds, and pesticides, chloralkali and wood-preserving plants, and municipal waste incinerators.
Agricultural runoff, especially from grain applications-because this substance is persistent in the environment, it may be present for years after its use was banned.
Sub-threshold facilities, smaller incinerators.
None known.
None known.
Banned from use as a pesticide in Australia. No consumer products should intentionally contain hexachlorobenzene. However, it is a global pollutant and may be found as a contaminant in a variety of foods.
Approximately 400 substances were considered for inclusion on the NPI reporting list. A ranking and total hazard score was given based on health and environmental hazards and human and environmental exposure to the substance.
Benzene hexachloro- (HCB) was ranked as 78 out of 400. The total hazard score taking into account both human health and environmental criteria is 4.2.
On a health hazard rating of 0 - 3 benzene hexachloro- (HCB) registers 1.2. A score of 3 represents a very high hazard to health, 2 represents a medium hazard and 1 is harmful to health.
On an environmental rating of 0 - 3 benzene hexachloro- (HCB) registers 3.0. A score of 3 represents a very high hazard to the environment and 0 a negligible hazard.
Factors taken into account to obtain this ranking and these scores include the extent of the material's toxic or poisonous nature and/or its lack of toxicity, and the measure of its ability to remain active in the environment and whether it accumulates in living organisms. It does not take into account exposure to the substance. Environmental exposure is reflected in the NPI rank for this substance (see comparative data below). A substance that scores highly as an environmental hazard is oxides of nitrogen at 3.0 and one of the lower scores is carbon monoxide at 0.8. A substance that scores highly as a health hazard is arsenic at 2.3 and one of the lowest scores is ammonia at 1.0.
| Substance name | Benzene hexachloro- (HCB) |
| CASR number | 118-74-1 |
| Molecular formula | C6Cl6 formula weight 284.78 |
| Synonyms | The currently accepted name for this substance is hexachlorobenzene. Synonyms other than benzene hexachloro- include: perchlorobenzene; HCB; hexa c.b.; anticarie; bunt-cure; bunt-no-more; ceku C.B.; no bunt; pentachlorophenyl chloride; no bunt 40; julian's carbon chloride; no bunt 80; sanocide; smut-go; amatin; co-op hexa; granox nm; snieciotox |
| Physical properties: White needles. Very slightly soluble in water. Slightly soluble in cold alcohol, soluble in benzene, chloroform, ether, carbon disulfide, and boiling alcohol. Melting Point (°C): 230 |
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| Chemical properties: Hexachlorobenzene has a very low chemical and biochemical reactivity, and this is reflected in its long persistence in the environment. Combustible at high temperatures. The substance decomposes on heating, producing toxic fumes. Reacts violently with dimethyl formamide above 65°C. |
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There is more information that may be useful in understanding some of the issues surrounding the NPI.