Fluometuron
(endorsed 2011)
Guideline
Based on human health concerns, fluometuron in drinking water should not exceed 0.07 mg/L.
Related chemicals
Fluometuron (CAS 2164-17-2) belongs to the phenylurea class of chemicals. Other pesticides in this class include linuron and diuron (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, fluometuron would not be a health concern unless the concentration exceeded 0.07 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: Fluometuron is a herbicide for the control of broad-leaf weeds and grasses in cotton, cereal, citrus and sugar cane crops.
There are currently products registered in Australia that contain fluometuron. Fluometuron products are intended for professional use. They are water-soluble granules, wettable powders, or liquid formulations intended to be diluted and applied by ground spray or aerial spray directly onto soil for pre-emergent treatment, and by hand spray directly at weeds for post-emergent treatment. Data on currently registered products are available from the Australian Pesticides and Veterinary Medicines Authority.
Exposure sources: The main source of public exposure to fluometuron and its metabolites is residues in food. Residue levels in food produced according to good agricultural practice are generally low.
Agricultural use of fluometuron 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 fluometuron occurrence in Australian drinking water supplies were found. In the USA, fluometuron was the most detected pesticide in surface water of the Mississippi river (mean = 2.1 µg/L, median = 0.40 µg/L, maximum = 50 µg/L) (Thurman et al. 1998).
Treatment of drinking water
No specific data on the treatment of fluometuron in drinking water have been identified.
Measurement
Fluometuron in drinking water can be analysed by solid phase extraction followed by high performance liquid chromatography (HPLC) with diode array detector or post-column photolysis and derivatisation detection. Typical limits of reporting (LOR) with DAD range from ranged from 4 to 40 ng/L (Ruberu et al. 2000). HPLC method and measurement with ultraviolet detector can achieve a LOR of 11 µg/L. Photo-induced chemiluminescence has been used for the determination of fluometuron in a quick and continuous procedure (Sa et al. 2007). Fluometuron can also be analysed by direct injection onto a liquid chromatography mass spectrometer (LC-MS) instrument in multiple reaction monitoring mode, with a LOR of 10 µg/L.
In addition to the standard approach of gas chromatography with mass spectrometry (GC-MS) or LC-MS for the evaluation of fluometuron in water, the enzyme-linked immunosorbent assay (ELISA) can be. ELISA is portable and there is a good correlation between the test and GC-MS (Thurman et al. 1998).
History of the health values
The current acceptable daily intake (ADI) for fluometuron 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 long-term study. The NOEL is based on a 2-year dietary study in mice in which conjunctivitis and decreased bodyweight gain were observed. The ADI incorporates a safety factor of 100 and was established in 1989.
The previous ADI of 0.01 mg/kg bw/day was based on a NOEL of 1 mg/kg bw/day from a reproductive toxicity study in rats for decreased body weight gain and haematological disturbances.
The previous health value was 0.05 mg/L (NHMRC and NRMMC 2004).
Health considerations
Metabolism: Fluometuron is rapidly absorbed from the gastrointestinal tract (65-80%) and extensively metabolised. Excretion is rapid, being almost complete by 72 hours, and is mainly through urine.
Acute effects: Fluometuron has low acute oral and dermal toxicity. It was not a skin sensitiser in guinea-pig tests.
Short-term effects: In a 21-day dermal study in rabbits, no toxicity was observed at 1000 mg/kg bw/day.
In 90-day dietary studies in rats, mice, and dogs, red blood cell haemolysis and increased spleen weights were reported at 12.5 mg/kg bw/day, and decreased bodyweight gain and congested liver, spleen, and kidney at higher dose levels.
Long-term effects: In long-term dietary studies in rats, mice and dogs, anaemia, increased spleen size, and haemosiderin deposition in spleen and liver were reported at doses of 63 mg/kg bw/day. Decreased food consumption and bodyweight gain were seen at doses of 100 mg/kg bw/day. The lowest overall NOEL was 2 mg/kg bw/day in the mouse study, and this is the basis for the current ADI.
Carcinogenicity: Based on long-term dietary studies in mice and rats, there is no evidence of carcinogenicity for fluometuron.
Genotoxicity: Fluometuron 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 developmental studies in rats and rabbits did not produce any evidence of reproductive effects, delayed development or teratogenicity.
Poisons Schedule: Fluometuron 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 0.07 mg/L for fluometuron was determined as follows:
where:
2.0 mg/kg bw/day is the NOEL based on a long-term (2-year) dietary study in mice.
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.
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.
Ruberu SR, WM Draper, Perera SK (2000). Multiresidue HPLC methods for phenyl urea herbicides in water. Journal of Agricultural and Food Chemistry, 48(9):4109-4115.
Sa F, Lopez Malo D, Martinez Calatayud J (2007). Determination of the herbicide fluometuron by photo-induced chemiluminescence in a continuous-flow multicommutation assembly. Analytical Letters, 40(13-15):2872-2885.
Thurman EM, Zimmerman LR, Scribner EA, Coupe RH (1998). Occurrence of cotton pesticides in surface water of the mississippi embayment. US Department of the Interior, US Geological Survey.
Tomlin CD (ed) (2006). The Pesticide Manual: a world compendium, 14th Edition, British Crop Production Council, UK.
Last updated
