Toxaphene in freshwater and marine water
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.
Toxaphene (CAS 8001-35-2) is a mixture of over 175 components produced by the chlorination of camphene. Its molecular formula is C10H10C18 and molecular weight is 414. It has low water solubility (around 3 mg/L) and its log Kow is 3.3.
Uses and environmental fate
Toxaphene has been used extensively as a cotton insecticide, often in conjunction with dichlorodiphenyltrichloroethane (DDT), but its use decreased in the 1980s and it is no longer used.
Toxaphene is very persistent in soil (1 to 14 years) (HSDB 1996) and will not hydrolyse, photolyse or biodegrade to a significant extent in water, although evaporation is significant (HSDB 1996). It will adsorb strongly to sediments. Field studies indicate that toxaphene can be rapidly detoxified in shallow lake water (HSDB 1996), largely due to adsorption to sediments, although it still took 1 year to detoxify at 0.6 mg/L.
Toxaphene can bioaccumulate and bioaccumulation factor (BF) values of between 3100 and 33,300 have been reported for fish and 400 to 1200 for shrimp (Reish et al. 1978). The current analytical practical quantitation limit (PQL) for toxaphene in water is 0.5 µg/L (NSW EPA 2000).
Aquatic toxicology
Freshwater fish: 16 species, 48 to 96-hour LC50 0.8 to 56 µg/L. Some outlying figures were reported for some of these species: Gambusia affinis (301 µg/L; compared to ≤49), Ictalurus punctaus (1900 µg/L; compared to ≤16.5) and P. promelas (78 µg/L; compared to ≤18).
Freshwater amphibians: five species, 96-hour LC50, 34 to 195 µg/L.
Freshwater crustaceans: six species, 48 to 96-hour LC50 or EC50 (immobilisation), 1.4 to 35 µg/L.
Freshwater insects: five species, 48 to 96-hour LC50, 1.3 to 40 µg/L. Stoneflies were most sensitive (two species, 1.3 to 7 µg/L). An outlying figure of 180 µg/L was reported for a midge.
Freshwater molluscs: one species, 96-hour LC50, 740 µg/L.
Freshwater algae: one species, 96-hour EC50 (growth), 380 µg/L.
Marine fish: six species, 96-hour LC50, 0.5 to 8.6 µg/L.
Marine crustaceans: five species, 96-hour LC50, 0.054 to 44 µg/L. All except the crab, Rhithopanopeus harrissii, had figures < 9 µg/L.
Marine molluscs: one species 96-hour LC50 16 to 63 µg/L. An outlying figure of 560,000 µg/L for Rangia cuneata was well above water solubility.
Due to the greater sensitivity of marine organisms, it was preferred to derive a low reliability marine trigger value from the data, rather than by adopting the freshwater trigger value.
Australian and New Zealand data
The 96-hour LC50 of toxaphene to the introduced mosquitofish, G. holbrooki, varied from 6.1 to 12.2 µg/L, and to the firetail gudgeon, Hypseleotris gallii, it was 8.1 µg/L, within the range of overseas species.
Factors that modify toxicity
Hardness and pH changes did not alter the toxicity of toxaphene to fish.
Guideline
A freshwater moderate reliability guideline value of 0.2 µg/L was calculated for toxaphene using the statistical distribution method at 95% protection and an acute-to-chronic ratio (ACR) of 9.8. The 99% protection level is 0.1 µg/L and is recommended as the trigger value for slightly to moderately disturbed systems.
These figures do not account for bioaccumulation and the 99% protection level (0.1 µg/L) is recommended for slightly to moderately disturbed systems if there are no data to adjust for bioaccumulation at the specific site.
A marine low reliability trigger value of 0.0006 µg/L was calculated for toxaphene using an assessment factor (AF) of 10 and an ACR of 8.65. This figure should only be used as an indicative interim working level. These figures do not account for bioaccumulation at the specific site.
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.
HSDB (Hazardous Substances Data Bank) 1996. Micromedex Inc. 31 July 1996.
NSW EPA 2000. Analytical Chemistry Section, Table of Trigger Values 20 March 2000, LD33/11, Lidcombe, NSW.
Reish DJ, Kauling TJ, Mearns AJ, Oshida PS, Rossi SS, Wilkes FG & Ray MJ 1978. Marine and estuarine pollution, Journal of the Water Pollution Control Federation 50, 1424-1469.
