Bromacil 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
Bromacil (CAS 314-40-9) is a pyrimidinedione herbicide developed by DuPont that inhibits photosynthesis, and which is mainly absorbed through the roots. Its IUPAC name is 5-bromo-6-methyl-3-(1-methylpropyl)-2,4(1H,3H)-pyrimidinedione, molecular formula is C9H13BrN2O2, and molecular weight is 261.1. Bromacil is soluble in water between 800 and 1300 mg/L, depending on pH and is more soluble in alkaline pH (Tomlin 1994). Its pKa is 9.27.
Uses and fate
Bromacil is used for total weed and brush control in non-crop land (Tomlin 1994) and is often used in conjunction with other herbicides. In Australia, bromacil is registered for use in around 20 location types (including industrial areas, rights-of-way, citrus orchards and pineapple plantations) against over 70 weeds, including grasses, burrs, herbs and shrubs (NRA 1997a). It is degraded in soil under aerobic and wet conditions but is stable in water (Tomlin 1994).
Freshwater fish: one species, 96-h LC50, 182-186 mg/L (i.e. x 1000 µg/L).
No other data were available.
A freshwater low reliability trigger value of 180 µg/L was calculated for bromacil using an AF of 1000. In the absence of marine data, this was adopted as a marine low reliability trigger value. These figures should only be used as indicative interim working levels.
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.
NRA 1997a. Database extraction of selected pesticides: Registered uses in Australia, National Registration Authority, July 1997, Canberra.
Tomlin C 1994. The pesticide manual: A world compendium. 10th edn, British Crop Protection Council & Royal Society of Chemistry, Bath, UK.