Bromacil
(endorsed 2011)
Guideline
Based on human health concerns, bromacil in drinking water should not exceed 0.4 mg/L.
Related chemicals
Bromacil (CAS 314-40-9) belongs to the urea group of chemicals. There are no other pesticides in this group of chemicals (Tomlin 2006).
Human risk statement
With good water quality management practices, the exposure of the general population is expected to be well below levels that may cause health concerns.
If present in drinking water as a result of a spillage or through misuse, bromacil would not be a health concern unless the concentration exceeded 0.4 mg/L. Excursions above this level would need to occur over a significant period to be a health concern, as the health-based guideline is based on long-term effects.
With good water quality management practices, pesticides should not be detected in source waters used for drinking water supplies. Persistent detection of pesticides may indicate inappropriate use or accidental spillage, and investigation is required in line with established procedures in the risk management plan for the particular water source.
General description
Uses: Bromacil is a herbicide for the control of weeds and grasses in fruit orchards and plantations, commercial and industrial areas, rights of way and around agricultural buildings.
There are currently products registered in Australia that contain bromacil or its sodium salts. Bromacil products are intended for professional use. The products are available as powdered or granulated formulations and applied in diluted form using ground or hand-held sprays. Data on currently registered products are available from the Australian Pesticides and Veterinary Medicines Authority.
Exposure sources: The main sources of public exposure to bromacil and its metabolites are residues in food. Residue levels in food produced according to good agricultural practice are generally low.
Agricultural use of bromacil may potentially lead to contamination of source waters through processes such as run-off, spray drift or entry into groundwater.
Typical values in Australian drinking water
No reports of bromacil in Australian drinking waters have been identified.
Treatment of drinking water
Advanced oxidation using ultraviolet irradiation and peroxide has been demonstrated to achieve a moderate level of bromacil removal (Kruithof et al. 2002).
Measurement
Bromacil can be measured in drinking waters by solid phase extraction followed by liquid chromatography–mass spectrometry.
History of the health values
The current acceptable daily intake (ADI) for bromacil is 0.1 mg per kg of bodyweight (mg/kg bw), based on a no-observed-effect level (NOEL) of 10 mg/kg bw/day from a long-term (2-year dietary) study. The NOEL is based on decreased bodyweight and increased relative thyroid weight in rats. The ADI incorporates a safety factor of 100 and was established in 1988.
The previous health value was 0.3 mg/L (NHMRC and NRMMC 2004).
Health considerations
Metabolism: Following gastrointestinal absorption, bromacil is excreted via the urine in rats and humans mainly as the metabolite 5-bromo-3-sec-butyl-6-hydroxymethyluracil. Urine samples from the formulation workers indicated that both bromacil and the major metabolite occur in a hydrolysed form. Five other metabolites have been identified.
Acute effects: Bromacil has low acute oral and dermal toxicity. Bromacil is a skin sensitiser in a guinea-pig test.
Short-term effects: In repeat-dose (90-day) dietary studies in rats, the target organs of toxicity were the liver, kidney and thyroid. At dose levels above 2.5 mg/kg bw/day, food consumption and relative organ weights were decreased. Toxic effects were seen in the liver and thyroid at the higher dose levels.
Long-term effects: In an 18-month dietary study, mice were fed at doses up to 714 mg/kg bw/day of bromacil. The reported effects were in the liver and testicle at high doses.
Two-year studies were conducted in rats and dogs. In rats, the reported effects were decreased bodyweight and increased relative thyroid weight at doses above 10 mg/kg bw/day. There were no effects reported in dogs up to the dose level of 30 mg/kg/day. The NOEL of 10 mg/kg/day found in the rat study was used to establish an ADI of 0.1 mg/kg bw/day for bromacil.
Carcinogenicity: Based on long-term studies in mice and rats, there is no evidence of carcinogenicity for bromacil.
Genotoxicity: Bromacil is not considered to be genotoxic, based on in vitro and in vivo short-term studies.
Reproductive and developmental effects: Three-generation reproduction and developmental studies in rats and rabbits showed no adverse effects on reproduction in either species. Evidence of delayed development occurred in rats and rabbits but only at maternally toxic doses which were at levels well in excess of the likely level of human exposure.
Poisons Schedule: Bromacil is considered not to require control by scheduling due to its low toxicity and is therefore included in Appendix B of the Standard for the Uniform Scheduling of Medicines and Poisons No.1, 2010 (the Poisons Standard)(DoHA 2010). Current versions of the Poisons Standard should be consulted for further information.
Derivation of the health-based guideline
The health-based guideline of 0.4 mg/L for bromacil was determined as follows:
where:
10 mg/kg bw/day is the NOEL based on a long-term (2-year) study in rats.
70 kg is taken as the average weight of an adult.
0.1 is a proportionality factor based on the assumption that 10% of the ADI will arise from the consumption of drinking water.
2 L/day is the estimated maximum amount of water consumed by an adult.
100 is the safety factor applied to the NOEL derived from animal studies. This safety factor incorporates a factor of 10 for interspecies extrapolation and 10 for intraspecies variation.
References
NOTE: The toxicological information used in developing this fact sheet is from reports and data held by the Department of Health, Office of Chemical Safety.
DoHA (2010) The Poisons Standard; Schedule 1-Standard for the Uniform Scheduling of Medicines and Poisons, Department of Health and Ageing, Commonwealth of Australia, Canberra.
Kruithof J, Kamp P, Belosevic M (2002). UV/H2O2 treatment: the ultimate solution for pesticide control and disinfection. Water Science Technology: Water Supply, 2(1): pp 113-122
NHMRC (National Health and Medical Research Council), NRMMC (Natural Resources Management Ministerial Council) (2004). Australian Drinking Water Guidelines. National Water Quality Management Strategy, Paper 6. NHMRC and NRMMC.
Tomlin CD (ed) (2006). The Pesticide Manual: a world compendium, 14th Edition, British Crop Production Council, UK.
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