Flamprop-methyl
(endorsed 2011)
Guideline
Based on human health concerns, flamprop-methyl in drinking water should not exceed 0.004 mg/L.
Related chemicals
Flamprop-methyl and its isomer, flamprop-m-methyl (CAS 52756-25-9) belong to the arylaminopropionic acid class of chemicals. There are no other pesticides in this class registered for use in Australia (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, flamprop-methyl would not be a health concern unless the concentration exceeded 0.004 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: Flamprop-methyl is a herbicide for the control of wild-oat weeds in wheat and triticale crops.
There are currently products registered in Australia that contain flamprop-methyl, all as the m-methyl isomer. Flamprop-methyl products are intended for professional use. Products are emuslifiable concentrate and liquid formulations intended to be sprayed in diluted form onto crops by aerial, boom spray, and hand-held spray equipment. Data on currently registered products are available from the Australian Pesticides and Veterinary Medicines Authority.
Exposure sources: The main source of public exposure to flamprop-methyl and its metabolites is residues in food. Residue levels in food produced according to good agricultural practice are generally low.
Agricultural use of flamprop-methyl 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 published reports on flamprop-methyl occurrence in Australian drinking water supplies have been identified.
Treatment of drinking water
No specific data on the treatment of flamprop-methyl in drinking water have been identified.
Measurement
Flamprop-methyl in drinking water can be determined by gas chromatography (GC) or gas-liquid chromatography after abstraction followed by electron capture detection. Determination by GC or GC with mass spectrometry can achieve limits of detection of 0.1 mg/L (Hirahara et al. 2005). Flamprop-methyl can also be analysed by high-performance liquid chromatography with ultraviolet detection.
History of the health values
The current acceptable daily intake (ADI) for flamprop-methyl is 0.001 mg per kg of bodyweight (mg/kg bw), based on a no-observed-effect level (NOEL) of 0.125 mg/kg bw/day from a long-term study. The NOEL is based on liver hypertrophy and increased liver weight in a 2-year dietary study. The ADI incorporates a safety factor of 100. It was established in 1980 and reaffirmed in 1991.
The previous health value was 0.003 mg/L (NHMRC and NRMMC 2004).
Health considerations
Metabolism: In rats, flamprop-methyl is readily absorbed and extensively metabolised, and completely excreted (>95-97%) within 48 hours of dosing. Excretion is mostly via faeces.
Acute effects: Flamprop-methyl and its m-isomer have low oral and dermal acute toxicity. Flamprop-methyl is not a skin sensitiser in guinea-pig tests.
Short-term effects: In a 5-week dietary study in rats, increased liver weight was reported at 2.5 mg/kg bw/day and above, and increased caecum weight at 25 mg/kg bw/day. In a 6-week dietary study in dogs, increased liver weights and associated increases in liver enzymes were seen at 125 mg/kg bw/day. The lowest overall NOEL was 0.25 mg/kg bw/day based on increased liver weights in rats.
In 90-day dietary studies in rats and dogs, liver changes were observed at 50 mg/kg bw/day in rats, and 2.5 mg/kg bw/day in dogs.
Long-term effects: In 2-year dietary studies in rats and dogs, liver hypertrophy and increased liver weight were seen at 12.5 mg/kg bw/day in rats, and at 2.5 mg/kg bw/day in dogs. The lowest overall NOEL in these studies was 0.125 mg/kg bw/day in rats.
Carcinogenicity: Based on a 2-year study in rats, there is no evidence of carcinogenicity for flamprop-methyl.
Genotoxicity: Flamprop-methyl is not considered to be genotoxic, based on in vitro and in vivo short-term studies.
Reproductive and developmental effects: A 3-generation reproduction study in rats and a developmental study in rabbits did not produce any evidence of reproductive effects, delayed development or teratogenicity.
Poisons Schedule: Flamprop-methyl and flamprop-m-methyl are 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 0.004 mg/L for flamprop-methyl was determined as follows:
where:
0.125 mg/kg bw/day is the NOEL based on a long-term (2-year) dietary 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.
Hirahara Y, Kimura M, Inoue T, Uchikawa S, Otani S, Haganuma A, Matsumoto N, Hirata A, Maruyama S, Iizuka T, Ukyo M, Ota M, Hirose H, Suzuki S, Uchida Y (2005). Validation of multiresidue methods for the determination of 186 pesticides in 11 agricultural products using gas chromatography. Journal of Health Science, 51(5):617-27.
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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