Dimethylphthalate in freshwater and marine water

October 2000

Toxicant default guideline values for protecting aquatic ecosystems

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

Dimethylphthalate (CAS 131-11-3) is a phthalate ester.

Phthalate esters

Phthalate esters represent a large family of chemicals widely used as plasticisers, primarily in the production of polyvinyl chloride (PVC) resins (USEPA 1980e). Other applications are found in cosmetics, rubbing alcohol, insect repellent, insecticides and tablet coatings (CCREM 1987). Although phthalate esters are insoluble in pure water, they may be transported in the aquatic environment in solubilised forms by fulvic and humic acids. This solubilisation has been found to be pH-dependent (CCREM 1987). Depending on specific conditions in aquatic ecosystems, bioaccumulation and biodegradation will also be significant (CCREM 1987, Brooke et al. 1991). Log K_ow values vary from 1.5 to 4, indicating some potential for bioaccumulation for the longer chain esters (CCREM 1987). The current analytical practical quantitation limit (PQL) for dimethyl-, diethyl- and dibutylphthalate is 2 µg/L (NSW EPA 2000).

Aquatic toxicology

Phthalate esters are a diverse group of organic compounds and toxicity in aquatic ecosystems varies with the ester tested. The insolubility of some phthalate esters in water makes it difficult to determine the actual concentrations used in toxicological tests (Brooke et al. 1991), and results exceeding water solubility were not considered. Appropriate acute toxicity data for freshwater organisms were available for five esters: butylbenzyl phthalate, diethyl phthalate, dimethyl phthalate, di-n-butyl phthalate and di-2-ethylhexylphthalate (USEPA 1980e). The sensitivity of fish and invertebrates was generally similar, with most values exceeding 1000 µg/L. Concentrations causing chronic toxicity in freshwater animals were as low as 3 µg/L (USEPA 1986).

Freshwater fish: 3 spp, 96-hour LC50 of 39,000 to 121,000 µg/L. Chronic no observed effect concentration (NOEC) (104-day mortality) of 11,000 µg/L.

Freshwater crustaceans: Daphnia magna 48-hour EC50, 45,900 µg/L; 21-day NOEC (mortality) of 9600 µg/L.

Freshwater insects: Paratanytarsus sp. 96-hour LC50, 377,000 µg/L.

Freshwater algae: Selenastrum capricornutum, 96-hour EC50 (mortality) 142,000 µg/L.

Marine fish: Cyprinodon variegatus, 96-hour LC50, 29,000 µg/L.

Marine crustaceans: Mysidiopsis bahia, 96-hour LC50, 68,600 µg/L.

Guidelines

A freshwater moderate reliability trigger value of 3700 µg/L was derived for dimethylphthalate by the statistical distribution method with 95% protection and the default acute-to-chronic ratio (ACR) of 10. This was adopted as a marine low reliability trigger value for indicative guidance only.

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.

Brooke DN, Nielsen IR, Dobson S & Howe PD 1991. Environmental hazard assessment: Di-(2-ethylhexyl) phthalate. TSD 2, UK Department of the Environment, Garston.

CCREM 1987. Canadian water quality guidelines. Canadian Council of Resource and Environment Ministers, Ontario.

NSW EPA 2000. Analytical Chemistry Section, Table of Trigger Values 20 March 2000, LD33/11, Lidcombe, NSW.

USEPA 1980e. Ambient water quality criteria for phthalate esters. Criteria and Standards Division, US Environmental Protection Agency, Washington DC.