Triadimefon
(endorsed 2011)
Guideline
Based on human health concerns, triadimefon in drinking water should not exceed 0.09 mg/L.
Related chemicals
Triadimefon (CAS 43121-43-3) belongs to the triazole class of chemicals. Another pesticide in this class is amitrole (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, triadimefon would not be a health concern unless the concentration exceeded 0.09 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: Triadimefon is a fungicide for the control of powdery mildews, rusts and other fungal diseases in turf and agricultural crops.
There are registered products that contain triadimefon in Australia. The products are intended for professional use and are available as wettable powders or concentrated solutions, to be applied as a diluted or concentrated spray using ground rig or aerial application, or added to fertilizer and applied using truck mounted 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 triadimefon and its metabolites is residues in food. Residue levels in food produced according to good agricultural practice are generally low.
Agricultural use of triadimefon 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 triadimefon in Australian drinking waters have been identified.
Treatment of drinking water
No specific data on the treatment of triadimefon in drinking water have been identified.
Measurement
Triadimefon can be measured in water using high performance liquid chromatography with tandem mass spectrometry (Schermerhorn et al. 2005). The limit of quantitation for this technique is 0.5 ng/L.
History of the health values
The current acceptable daily intake (ADI) for triadimefon is 0.03 mg per kg of bodyweight (mg/kg bw), based on a no-observed-effect level (NOEL) of 2.5 mg/kg bw/day from a long-term rat dietary study. The NOEL is based on haematological effects. The ADI incorporates a safety factor of 100, and was established in 1987.
The previous health value was 0.002 mg/L (NHMRC and NRMMC 2004).
Health considerations
Metabolism: Triadimefon is readily and extensively absorbed via the gastrointestinal tract of mice and rats. It undergoes some metabolism in rats, and 80% is excreted in the urine and faeces in 7 days. Triadimenol was the major metabolite recovered.
Acute effects: Triadimefon has low to moderate acute oral toxicity and low dermal toxicity. It is not a skin sensitiser.
Short-term effects: A 1-month oral study in rats reported increased relative and absolute liver weights with no associated liver pathology at dose levels of 10 mg/kg bw/day and above.
Medium-term studies conducted in rats and dogs reported no toxicological effects up to doses of 100 mg/kg bw/day in rats, and hepatic enzyme induction at doses of 15 mg/kg bw/day and above in dogs. Pathological effects in the liver were not observed.
Long-term effects: Long-term dietary studies conducted in mice, rats and dogs reported liver toxicity and effects on haematological parameters to be the main toxicological effects. In mice, there was an increase in erythrocyte counts, haemoglobin and haematocrit concentrations, liver weights, and hyperplastic liver nodules (indicative of liver toxicity) at 90 mg/kg bw/day. In rats, decreased body weight gain and reduced erythrocyte counts and haemoglobin levels were observed at doses of 25 mg/kg bw/day and above. The NOEL of 2.5 mg/kg bw/day from this study forms the basis for the current ADI.
A 2-year dietary study in dogs reported reduced bodyweight gain and microsomal enzyme induction in the liver at doses of 25 mg/kg bw/day and above, with no pathological changes.
Carcinogenicity: Based on 2-year studies in mice, rats and dogs there is no evidence of carcinogenicity for triadimefon.
Genotoxicity: Only in vitro short-term studies were available, and these show no evidence of genotoxicity. No in vivo studies were conducted.
Reproductive and developmental effects: In 2- and 3-generation reproduction studies in rats, there was evidence of maternotoxicity and effects on reproductive parameters, but only at doses well in excess of the likely level of human exposure. Developmental studies in rats and rabbits did not produce any evidence of effects on foetal development.
Neurotoxicity: Neurological studies conducted in mice and rats reported no adverse effects up to doses of 3 mg/kg bw/day.
Poisons Schedule: Triadimefon is included in Schedule 5 and 6 of the Standard for the Uniform Scheduling of Medicines and Poisons No.1, 2010 (the Poisons Standard)(DoHA 2010), depending on its concentration and use. Current versions of the Poisons Standard should be consulted for further information.
Derivation of the health-based guideline
The health-based guideline of 0.09 mg/L for triadimefon was determined as follows:
where:
2.5 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.
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.
Schermerhorn PG, Golden PE, Krynitsky AJ, Leimkuehler WM (2005). Determination of 22 triazole compounds including parent fungicides and metabolites in apples, peaches, flour, and water by liquid chromatography/tandem mass spectrometry. Journal of AOAC International, 88(5):1491-1502.
Tomlin CD (ed) (2006). The Pesticide Manual: a world compendium, 14th edition, British Crop Production Council, UK.
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