Di-n-butyl phthalate in freshwater and marine water
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
Di-n-butyl phthalate (CAS 84-74-2) is a phthalate ester.
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 Kow 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).
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, 480 to 1600 µg/L.
Freshwater crustacean: Daphnia magna, 48-hour EC50, 2940 to 5200 µg/L; chronic no observed effect concentration (NOEC) (16-day mortality) of 560 µg/L.
Freshwater insect: Paratanytarsus sp, 96-hour LC50, 6290 µg/L.
Freshwater algae: Selenastrum capricornutum, 96-hour EC50 (mortality), 400 µg/L.
Marine crustacean: Mysidiopsis bahia, 96-hour LC50, 500 µg/L.
A freshwater moderate reliability trigger value of 35 µg/L was derived using the statistical distribution method at 95% protection. The 99% protection level figure is 25 µg/L. Bioaccumulation may need to be specifically considered at the site and if there are no data to calculate a site-specific figure to account for bioaccumulation, the 99% figure is recommended as a precaution. The 99% figure (25 µg/L) was adopted as a low reliability marine trigger value, for use only as an indicative interim working level.
Change the trigger values in Table 3.4.1 of the ANZECC & ARMCANZ (2000) guidelines to 10; 26 (no change for 95%); 40 and 65 for the 99; 95; 90 and 85% levels of protection, respectively.
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.