Esfenvalerate

(endorsed 2011)

Guideline

Based on human health concerns, esfenvalerate in drinking water should not exceed 0.03 mg/L.

Related chemicals

Esfenvalerate (CAS 66230-04-4) belongs to the pyrethroid class of chemicals. This is a large chemical group and includes fenvalerate, cyfluthrin, permethrin and flucythrinate.

There are four optical isomers of esfenvalerate and fenvalerate (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, esfenvalerate would not be a health concern unless the concentration exceeded 0.03 mg/L. Minor excursions above this level would need to occur over a relatively long period to be a health concern, as the health-based guideline is based on medium-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: Esfenvalerate is an insecticide for the control of ants, cockroaches, fleas, spiders and other insect pests in domestic and industrial areas, and in field and pasture crops.

There are registered products that contain esfenvalerate in Australia. These products are intended for professional and domestic use. These products are available for use in domestic and industrial areas as hand and ground sprays; or for use on crops using ground and aerial sprays. Data on currently registered products are available from the Australian Pesticides and Veterinary Medicines Authority.

Exposure sources: The main sources of public exposure to esfenvalerate are the use of domestic products, and residues in food. Esfenvalerate residues are grouped with those of fenvalerate in the maximum residue limit definition. Residue levels in food produced according to good agricultural practice are generally low.

Agricultural use of esfenvalerate 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

Esfenvalerate has been monitored but not detected in Australian drinking water supplies (Muschal 2001). In the Goulburn Murray irrigation area esfenvalerate was detected on one occasion at 65 μg/L in 2005 (Victoria Department of Primary Industries 2006).

Treatment of drinking water

No specific data on the treatment of esfenvalerate in drinking water have been identified.

Measurement

Esfenvalerate can be measured by liquid/liquid extraction followed by gas chromatography coupled with an electron capture detector. The method can achieve a limit of detection (LOD) of 0.05 μg/L. High-performance liquid chromatography or gas-liquid chromatography with either electron capture detection or electrolytic conductivity detection has been reported for the quantitation of esfenvalerate (Hengel et al. 1997). Solid-phase extraction followed by enzyme linked immunosorbert assay can achieve a LOD of 0.1 μg/L for esfenvalerate in water samples (Shan et al. 1999).

Trace levels of esfenvalerate in water can be measured by stir-bar-sorptive extraction followed by liquid desorption and large-volume injection capillary gas chromatography with mass spectrometric detection. This method can achieve a LOD of 2.5 ng/L (Serodio and Nogueira 2005). Gas chromatography/electron capture detector and gas chromatography / nitrogen-phosphorous detector methods can achieve a LOD of esfenvalerate below 2 ng/L (Wang et al. 2009).

History of the health values

The current acceptable daily intake (ADI) for esfenvalerate is 0.008 mg per kg of bodyweight (mg/kg bw), based on a no-observed-effect level (NOEL) of 7.5 mg/kg bw/day from a medium-term (13-week) dietary study in rats. The NOEL is based on clinical toxicity including abnormal behaviour and parotid salivary gland cell hypertrophy at 35 mg/kg bw/day. The ADI incorporates a safety factor of 1000 and was established in 1993.

A health value has not been previously established by NHMRC.

Health considerations

Metabolism: Esfenvalerate is readily and extensively absorbed via the gastrointestinal tract in rats. It is extensively metabolised, and is readily excreted in the urine, almost completely within 48 hours.

Acute effects: Esfenvalerate has moderate acute oral and dermal toxicity in rats. It is not a skin sensitiser.

Short-term effects: In a 4-week study in mice, there were signs of neurotoxicity in the form of tremors and excessive salivation at 35 mg/kg bw/day, and convulsions and gait abnormalities at 105 mg/kg bw/day.

In a 90-day feeding study in mice, there was decreased bodyweight gain and haematological changes at 30 mg/kg bw/day, and tremors and convulsions at 100 mg/kg bw/day. In a 13-week feeding study in rats, tremors, unsteady movements and convulsions were observed at 15 mg/kg bw/day. Cellular hypertrophy was observed in the parotid salivary glands and in the pituitary glands at 25 mg/kg bw/day. The lowest NOEL was 7.5 mg/kg bw/day in the rat study. This NOEL is the basis for the current ADI.

Long-term effects: Long-term toxicity studies have not been conducted in rodents with esfenvalerate, and were considered unnecessary given the available data on the closely-related fenvalerate (see the fenvalerate fact sheet).

Carcinogenicity: Esfenvalerate is not considered to be carcinogenic, based on the results of long-term toxicity studies in rodents with fenvalerate.

Genotoxicity: Esfenvalerate is not considered to be genotoxic, based on in vitro and in vivo short-term studies.

Reproductive and developmental effects: Reproductive and developmental toxicity studies with esfenvalerate have not been conducted. There are no reproductive or developmental concerns based on studies with fenvalerate.

Neurotoxicity: Esfenvalerate did not cause delayed neurotoxicity in special oral dosing studies in rats.

Poisons Schedule: Esfenvalerate 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 concentration. Current versions of the Poisons Standard should be consulted for further information.

Derivation of the health-based guideline

The health-based guideline of 0.03 mg/L for esfenvalerate was determined as follows:

$$\text{ 0.03 mg/L } = \dfrac{\text{ 7.5 mg/kg bodyweight/day x 70 kg x 0.1 }}{\text{ 2 L/day x 1000 }}$$

where:

• 7.5 mg/kg bw/day is the NOEL based on a medium-term (13-week) 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.

• 1000 is the safety factor applied to the NOEL derived from animal studies. This safety factor incorporates factors of 10 for interspecies extrapolation, 10 for intraspecies variation, and an additional 10 for the lack of long-term studies.

Note: This calculated health-based guideline exceeds the normal aqueous solubility of esfenvalerate.

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.

Hengel MJ, Mourer CR, Shibamoto T (1997). New method for analysis of pyrethroid insecticides: esfenvalerate, cis-permethrin, and trans-permethrin, in surface waters using solid-phase extraction and gas chromatography. Bulletin of Environmental Contamination and Toxicology, 59(2):171-8.

Muschal M (2001). Central & North West Regions’ water quality program. 1999-2000 Report on pesticides monitoring, NSW Department of Land and Water Conservation, Parramatta.

Serodio P, Nogueira JM (2005). Development of a stir-bar-sorptive extraction-liquid desorption-large-volume injection capillary gas chromatographic-mass spectrometric method for pyrethroid pesticides in water samples. Analytical and Bioanalytical Chemistry, 382(4):1141-51.

Shan G, Stoutamire DW, Wengatz I, Gee SJ, Hammock BD (1999). Development of an immunoassay for the pyrethroid insecticide esfenvalerate. Journal of Agricultural and Food Chemistry, 47(5):2145-55.

Tomlin CD (ed) (2006). The Pesticide Manual: a world compendium, 14th Edition, British Crop Production Council, UK.

Victoria Department of Primary Industries (2006). Pesticide Monitoring in Goulburn-Murray Waters Irrigation Supply Channels Covering the Six Irrigation Areas [2004 -2006 Irrigation Season Study Report]. Victorian Government, Werribee.

Wang D, Weston DP, Lydy MJ (2009). Method development for the analysis of organophosphate and pyrethroid insecticides at low parts per trillion levels in water. Talanta, 78(4-5):1345-51.