Fenvalerate
(endorsed 2011)
Guideline
Based on human health concerns, fenvalerate in drinking water should not exceed 0.06 mg/L.
Related chemicals
Fenvalerate (CAS 51630-58-1) belongs to the pyrethroid class of chemicals. This is a large chemical group and includes the closely related esfenvalerate (esterified form), cyfluthrin, permethrin, and flucythrinate.
There are four optical isomers of fenvalerate and esfenvalerate (SS, SR, RS, RR). The SS isomer is responsible for the insecticidal activity of these compounds. Fenvalerate contains around 20% as the SS form, while esfenvalerate is highly enriched in this form. Most of the toxicity of fenvalerate is caused by the RS isomer (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, fenvalerate would not be a health concern unless the concentration exceeded 0.06 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: Fenvalerate is an insecticide used for the control of buffalo fly and Culicoides midge on cattle and horses.
There is at least one registered product containing fenvalerate in Australia. Fenvalerate products are intended for professional use, to be diluted and applied by handspray to the backline of cattle and horses.
Exposure sources: The main source of public exposure to fenvalerate and its metabolites is residues in meat. Residue levels in food produced according to good agricultural practice are generally low.
The veterinary use of fenvalerate provides some potential for contamination of drinking water through the washing of equipment near dams, streams or watercourses.
Typical values in Australian drinking water
Esfenvalerate, a sterified form of fenvalerate, has been detected in 2004-2006 in passive samples and spot water samples from the Goulburn Murray Water irrigation supply channels in Victoria. In October 2005 the Torrumbarry Irrigation Area Kerang Town Channel reported an esfenvalerate concentration of 65 µg/L (Rose and Kibria 2006).
Treatment of drinking water
No specific data on the treatment of fenvalerate in drinking water have been identified.
Measurement
After extraction with n-hexane or dichloromethane, fenvalerate can be analysed by gas chromatography equipped with an electron capture detector (ECD) or with a mass selective detector (MSD). A limit of quantitation (LOQ) of 0.05 µg/L using the ECD and 0.1 µg/L using the MSD have been reported (California Department of Food and Agriculture 2000, Xue et al. 2005). Fenvalerate can also be extracted and pre-concentrated by micro liquid–liquid extraction and analysed by gas chromatography–mass spectrometry (GC-MS) with selected ion monitoring, with a reported LOQ in the ng/L concentrations (Fernández-Gutiérrez et al. 1998). A modification of the EPA method 8270: GC-MS electron ionisation, using a narrow range selected ion scan to analyse pyrethroids, can achieve a LOQ of 5 ng/L in water (Heines and Halpin 2006).
History of the health values
The current acceptable daily intake (ADI) for fenvalerate is 0.02 mg per kg of bodyweight (mg/kg bw), based on a no-observed-effect level (NOEL) of 1.7 mg/kg bw/day from a 2-year dietary mouse study. The NOEL is based on micro-nodular inflammation in the liver, lymph nodes, and spleen. The ADI incorporates a safety factor of 100 and was established in 1987.
The previous ADI of 0.04 mg/kg bw was set in 1985 based on a NOEL of 3.5 mg/kg bw/day from a 20-month dietary study in mice. The ADI was updated after submission of an additional long-term study demonstrating a lower overall NOEL.
The previous health value was 0.05 mg/L (NHMRC and NRMMC 2004).
Health considerations
Metabolism: Fenvalerate is readily and extensively absorbed via the gastrointestinal tract in rats. It is extensively metabolised, and is rapidly excreted in the urine, almost completely within 48 hours.
Acute effects: Fenvalerate has moderate acute oral toxicity and low dermal toxicity. It is not a skin sensitiser.
Short-term effects: A 90-day and a 15-month dietary study in rats reported decreased bodyweight gain and decreased haemoglobin levels at 7.5 mg/kg bw/day and above. A 6-month dietary study in dogs reported behavioural effects including tremors and lack of coordination at 6.25 mg/kg bw/day.
Long-term effects: Long-term (2-year) dietary studies in mice and rats reported micro-nodular inflammatory changes in the liver, lymph nodes, and spleen of mice at doses of 9 mg/kg bw/day, and decreased bodyweight gain and decreased haemoglobin levels in rats at higher doses. The lowest overall NOEL was 1.7 mg/kg bw/day in mice. This NOEL is the basis for the current ADI.
Carcinogenicity: Based on 2-year studies in mice and rats, there is no evidence of carcinogenicity for fenvalerate. The micro-nodular changes noted in mouse tissues were considered evidence of localised tissue inflammation rather than cancer.
Genotoxicity: Fenvalerate 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 effects on reproductive parameters or foetal developmental.
Neurotoxicity: Fenvalerate has some potential for neurotoxicity, but only at levels much greater than likely human exposures. A single oral dose of 500 mg/kg bw in rats caused axonal and myelin lesions, with a NOEL of 200 mg/kg bw/day. In a 15-month dietary study in rats, the NOEL was 75 mg/kg bw/day based on sciatic nerve damage at higher doses. Doses up to 1 g/kg bw did not caused delayed neurotoxicity in hens.
Poisons Schedule: Fenvalerate is included in Schedule 6 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 0.06 mg/L for fenvalerate was determined as follows:
where:
1.7 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.
Note: This calculated health-based guideline exceeds the normal aqueous solubility of fenvalerate.
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.
California Department of Food and Agriculture (2000). Method #: EM 52.5 Determination of Permethrin and Esfenvalerate/Fenvalerate in sediment water. Center for Analytical Chemistry, Environmental Monitoring Section, Sacramento, CA.
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.
Fernández-Gutiérrez, A, Martínez-Vidal JL, Arrebola-Liébanas J, Gonzalez-Casado J, Vílchez JL (1998). Determination of endosulfan and some pyrethroids in waters by micro liquid-liquid extraction and GC-MS. Fresenius’ Journal of Analytical Chemistry, 360:568-57.
Heines RL, Halpin PW (2006). Pyrethroid pesticides by modified EPA 8270. Caltest Analytical Laboratory.
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.
Rose G, Kibria G (2006). Pesticide Monitoring in Goulburn-Murray Waters Irrigation Supply Channels Covering the Six Irrigation Areas. [2004 -2006 Irrigation Season Study Report]. Werribee, Victoria, Department of Primary Industries & Goulburn Murray Rural Water Authority.
Tomlin CD (ed) (2006). The Pesticide Manual: a world compendium, 14th edition, British Crop Production Council, UK.
Xue N, X Xu, Jin Z (2005). Screening 31 endocrine-disrupting pesticides in water and surface sediment samples from Beijing Guanting reservoir. Chemosphere, 61(11):1594-606.
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