Ametryn
(endorsed 2011)
Guideline
Based on human health concerns, ametryn in drinking water should not exceed 0.07 mg/L.
Related chemicals
Ametryn (CAS 834-12-8) belongs to the triazine class of chemicals. Other pesticides in this class include atrazine, propazine, symazine and cyanazine (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, ametryn would not be a health concern unless the concentration exceeded 0.07 mg/L. Minor 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: Ametryn is a pre- and post-emergent herbicide for the control of summer grasses and broad-leaf weeds in sugarcane, pineapples and in industrial areas, such as roadsides and railway lines.
There are registered products containing ametryn in Australia. These products are intended for professional use and are formulated as a liquid concentrate or a water dispersible granule, either alone or with other active ingredients. These products are applied using ground boom, aerial and hand-held methods of spraying. Data on currently registered products are available from the Australian Pesticides and Veterinary Medicines Authority.
Exposure sources: The main source of public exposure to ametryn is residues in food. Residue levels in food produced according to good agricultural practice are generally low.
Agricultural use of ametryn may potentially lead to contamination of sources waters through processes such as run-off, spray-drift or entry into groundwater.
Typical values in Australian drinking water
Ametryn has been reported in Australian source waters at concentrations up to 0.3 mg/L in sugar cane growing areas (Mitchell et al, 2004). Similar results have been reported in drinking source waters of a sugar cane growing area of Brazil (Lanchote et al, 2000).
Treatment of drinking water
Ametryn has been shown to be completely removed from water by chlorination when the chlorine dose is adjusted to match chlorine demand (Ormad et al. 2008).
Ozonation and activated carbon adsorption for ametryn removal has also been reported with moderate to low success (Ormad et al. 2008). Conventional coagulation/flocculation has been shown to be unreliable for removal, although complete removal can be obtained if activated carbon adsorption is practiced in conjunction with conventional clarification. Jar testing with different oxidants, adsorbents, coagulants, dose rates and contact times is recommended to optimise removal if ametryn is detected.
Measurement
Ametryn can be measured in drinking waters using solid phase extraction followed by high performance liquid chromatography with ultraviolet detection (Carabias-Martinez et al. 2006). The practical limit of detection for this method is 1 mg/L. Alternatively, ametryn can be monitored by direct aqueous injection liquid chromatography with electrospray ionisation–tandem mass spectrometry, with a reported detection limit of 0.05 mg/L (Huang et al. 2008).
History of the health values
The acceptable daily intake (ADI) for ametryn is 0.02 mg per kg of bodyweight (mg/kg bw), based on a no-observed-effect level (NOEL) of 2 mg/kg bw/day from a reproduction study in rats. The ADI incorporates a safety factor of 100 and was established in 2006.
The previous health value was 0.05 mg/L (NHMRC and NRMMC 2004).
Health considerations
Metabolism: Ametryn is absorbed readily from the gastrointestinal tract and is rapidly excreted (89% in urine and faeces over 7 days). Thirty-five metabolites were identified in the urine and faeces in the rat.
Acute effects: Ametryn has low acute oral and dermal toxicity. It is a skin sensitiser in guinea pigs. Symptoms associated with acute toxicity were dyspnoea, ruffled fur, diarrhoea, sedation, and curved body posture.
Short-term effects: Short-term dietary studies in rats and a 21-day dermal study in rabbits showed transient decreases in body weight and food consumption at dose levels of 1000 mg/kg bw/day.
Long-term effects: Long-term studies were conducted in rats and dogs. A 2-year dietary study in rats reported anaemia and evidence of liver damage at dose levels of 2.2 mg/kg bw/day. A one-year study in dogs reported anaemia and degenerative changes in a number of organs at dose levels above 8 mg/kg bw/day.
Carcinogenicity: Based on long-term studies in mice and rats, there is no evidence of carcinogenicity for ametryn.
Genotoxicity: Ametryn is not considered to be genotoxic, based on in vitro and in vivo short-term studies.
Reproduction and developmental effects: A reproduction study in rats and developmental studies in rats and rabbits did not produce any evidence of effects on reproductive parameters or foetal development. There was a transient decrease in bodyweight gain at 2 mg/kg bw/day, which was the overall NOEL. This is the basis for the ADI.
Poisons Schedule: Ametryn is included in Schedule 5 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 health-based guideline
The health-based guideline of 0.07 mg/L for ametryn was determined as follows:
where:
2 mg/kg bw/day is the NOEL based on a reproduction 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 a 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.
Carabias-Martinez R, Rodriguez-Gonzalo E, Miranda-Cruz E, Dominguez-Alvarez J, Hernandez-Mendez J (2006). Comparison of a non-aqueous capillary electrophoresis method with high performance liquid chromatography for the determination of herbicides and metabolites in water samples. Journal of Chromatography A, 1122(1-2):194-201.
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.
Huang, S. B., Mayer, T. J. and Yokley, R. A. (2008) Direct aqueous injection LC-ESI/MS/MS analysis of water for 11 chloro- and thiomethyltriazines and metolachlor and its ethanesulfonic and oxanilic acid degradates. Journal of Agricultural and Food Chemistry, 56(8): 2595-2602.
Lanchote VL, Bonato PS, Cerdeira AL, Santos NAG, de Carvalho D, Gomes MA (2000). HPLC screening and GC-MS confirmation of triazine herbicides residues in drinking water from sugar cane area in Brazil. Water Air and Soil Pollution, 118(3-4):329-337.
Mitchell, C., Brodie, J. and White, I. (2004) Sediments, nutrients and pesticide residues in event flow conditions in streams of the Mackay Whitsunday Region, Australia. In: Conference for Reef Research Townsville, Australia, pp. 23-36.
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.
Ormad MP, Miguel N, Claver A, Matesanz JM, Ovelleiro JL (2008). Pesticides removal in the process of drinking water production. Chemosphere, 71: 97–106.
Tomlin CD (ed) (2006). The Pesticide Manual: a world compendium, 14th Edition, British Crop Production Council, UK.
Last updated
