Isophorone 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

Isophorone (3,5,5-trimethyl-2-cyclohexen-1-one) (CAS 78-59-1) is an industrial chemical used as a solvent or co-solvent for finishes, lacquers, resins, pesticides, fats, oils and gums (USEPA 1980o). Bio-oxidation of isophorone in domestic wastewater reached 42% after 20 days; in synthetic salt water, 90% was oxidised during the same time (USEPA 1980o). Little or no information is available concerning the fate of isophorone under environmental conditions. It is soluble in water to 12,000 mg/L (12 g/L) at 25°C and has a low log Kow of 1.7.

Aquatic toxicology

Isophorone is of low toxicity to aquatic life, although it approaches moderate toxicity for marine invertebrates (USEPA 1980o).

Freshwater fish: two species, 96-hour LC50 of 145 to 275 mg/L (i.e. x 1000 µg/L).

Freshwater crustacean: one species, 48-hour LC50 of 120 mg/L.

Marine fish: one species, 96-hour LC50 of 140 mg/L.

Marine crustacean: one species, 96-hour LC50 of 12.9 mg/L.

Marine diatom: one species, 96-hour EC50 (mortality) of 110 mg/L.

Guideline

A freshwater low reliability trigger value of 120 µg/L was derived for isophorone using an assessment factor (AF) of 1000.
A marine low reliability trigger value of 130 µg/L was derived for isophorone using an AF of 100. These figures should only be used as indicative interim working levels.

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.

USEPA 1980o. Ambient water quality criteria for isophorone. Criteria and Standards Division, US Environmental Protection Agency, Washington DC. EPA-Pb 296798