Dieldrin 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

Most organochlorine pesticides have been phased out of use in recent years, mainly because of their residual properties and potential for bioaccumulation. The guideline trigger values stated are for toxicity only and need to be adjusted for bioaccumulation where appropriate. Where the statistical distribution method was used, figures quoted are the 95% protection levels, usually applicable to slightly to moderately disturbed systems although 99% protection figures are recommended for chemicals that bioaccumulate.

Dieldrin (CAS 60-57-1) is a persistent cyclodiene insecticide related to aldrin and is a metabolite of aldrin by hydroxylation. Its chemical name is 1,2,3,4,10,10-hexachloro-exo-6,7-epoxy-1,4,4a,5,6,7,8,8a-octahydro-1,4-endo-exo-5,8-dimethanonaphthalene. Its formula is C₁₂H₈Cl₆O and molecular weight is 380.9. It is soluble in water only to 186 µg/L at 25°C.

Uses and environmental fate

Dieldrin has had some agricultural uses in Australia and New Zealand, particularly on fruit, pastures, sugar cane and bananas. In 1987 its use was restricted to sub-floor use against termites and ceased use in 1994.

Dieldrin rapidly accumulates in invertebrates at concentrations down to 50 ng/L. Bioconcentration factors (BFs) were commonly > 1000.

Aquatic toxicology

Dieldrin had high to very high toxicity to all species tested.

Freshwater fish: 9 spp, 48 to 96-hour LC50, 1 to 79 µg/L. Two figures for Poecilia reticulata were 300 to 340 µg/L.

Freshwater crustaceans: 5 spp, 48 to 96-hour LC50 or EC50 (immobilisation), 5 (Asellus) to 740 (Orconectes) µg/L. Two species of cladocerans had figures between 190 to 250 µg/L.

Freshwater insects: 2 spp, 48 to 96-hour LC50, 0.6 to 12.0 µg/L

Marine fish: 2 spp, 48 to 96-hour LC50, 1.7 to 6.5 µg/L.

Marine invertebrates: 5 spp, 48 to 96-hour LC50, 0.4 to 30.0 µg/L. An additional species Artemia salina showed lower toxicity (65 to 100 µg/L).

Australian and New Zealand data

The 96-hour LC50 to the introduced Gambusia holbrooki was 14.3 µg/L.

Guideline

Although no freshwater algal data were available for dieldrin, abundant data were available for three families. This is sufficient to derive a low reliability trigger value of 0.01 µg/L (10 ng/L) using an assssment factor (AF) of 100. This figure is to be used only as an indicative interim working level.

There were insufficient marine data to derive a guideline and it is recommended that the freshwater value of 0.01 µg/L (10 ng/L) be adopted as a low reliability trigger value for interim guidance in marine systems.

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.