Cyfluthrin, Beta-cyfluthrin

(endorsed 2011)

Guideline

Based on human health concerns, cyfluthrin or beta-cyfluthrin in drinking water should not exceed 0.05 mg/L.

Related chemicals

Cyfluthrin and beta-cyfluthrin (CAS 68359-37-5) are in the pyrethroid class of chemicals. Cyfluthrin is a mixture of 8 isomers, comprising 4 diastereoisomeric pairs. Beta-cyfluthrin contains the two active diastereoisomers. Other pesticides in this class include cypermethrin, alpha-cypermethrin, deltamethrin and permethrin (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, cyfluthrin or beta-cyfluthrin would not be a health concern unless the concentration exceeded 0.05 mg/L. Minor excursions above this level even for a short period are of concern, as the health-based guideline is based on short- to 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: Cyfluthrin and beta-cyfluthrin are broad-spectrum insecticides used for the control of spiders, ants, fleas, flies, silverfish, cockroaches, bedbugs and mosquitoes.

There are registered products containing and registered products containing beta-cyfluthrin in Australia. The majority of those containing cyfluthrinvare household insecticide sprays, of both the knock-down and surface spray varieties. Some products are also used to impregnate mosquito nets. Cyfluthrin is not applied to crops. Products containing beta-cyfluthrin are used on a variety of fruits, vegetables, cereals and pastures. Data on currently registered products are available from the Australian Pesticides and Veterinary Medicines Authority.

Exposure sources: The main sources of public exposure are the use of household insecticide sprays, and residues in food. Residue levels in crops grown according to good agricultural practice are generally low.

Agricultural use may potentially lead to contamination of sources waters through processes such as run-off, spray drift, or entry into groundwater.

Typical values in Australian drinking water

No reports of cyfluthrin or beta-cyfluthrin in Australian drinking waters have been identified.

Treatment of drinking water

No reports of the treatment of cyfluthrin or beta-cyfluthrin in drinking water have been identified.

Measurement

Several methods have been reported for the analysis of cyfluthrin and beta-cyfluthrin in water, including gas chromatography with micro-electron capture detection (limit of detection [LOD] 0.85 ng/L, Casas et al. 2006; LOD 2 ng/L, Mekebri et al. 2008) and gas chromatography with high resolution mass spectrometry (LOD 0.10 ng/L, Woudneh and Oras 2006).

History of the health values

For cyfluthrin, the current acceptable daily intake (ADI) is 0.02 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 2-year dietary study in rats. The NOEL is based on decreased bodyweight gain and a small increase in fluorine content of bones. The ADI incorporates a safety factor of 100 and was established in 1985.

For beta-cyfluthrin, the current ADI is 0.01 mg/kg bw, based on a NOEL of 1.5 mg/kg bw/day from a 13-week dietary study in dogs. The NOEL is based on vomiting, diarrhoea and effects on motor function. The ADI incorporates a safety factor of 100 and was established in 1990.

A health value has not previously been established for cyfluthrin or beta-cyfluthrin.

Health considerations

Metabolism: Absorption of cyfluthrin and beta-cyfluthrin via the gastrointestinal tract is rapid and extensive (86-100%). Metabolism occurs via ester hydrolysis, oxidation of the alcohol moiety, hydroxylation and conjugation. The metabolites are excreted in urine (66%) and faeces (33%).

Acute effects: Cyfluthrin has low to moderate acute oral toxicity and low acute dermal toxicity. It does not cause skin sensitisation. Experience in the use of cyfluthrin has shown that skin irritation and peripheral sensory nerve excitation can result from human exposure, but these effects are reversible.

Beta-cyfluthrin has moderate acute oral toxicity and low dermal toxicity. It is not a skin sensitiser.

Short-term effects: In a 28-day dietary study in rats, cyfluthrin significantly decreased weight gain, elevated serum alanine amino transferase levels, increased absolute and relative liver and adrenal weights, and caused increased mortality at 80 mg/kg bw/day.

Medium-term dietary studies with cyfluthrin were conducted in rats and dogs. In the 3-month rat study, no toxicity was observed up to the highest dose of 25 mg/kg bw/day. A 6-month dog study reported decreased weight gain at 6.2 mg/kg bw/day, and vomiting, diarrhoea, trembling and poor motor co-ordination at 18.5 mg/kg bw/day.

A 28-day dietary study in rats with beta-cyfluthrin reported behavioural changes and increased mortality at 4 mg/kg bw/day and above, and salivation, apathy, changes in gait, respiratory distress and body rolling at 16 mg/kg bw/day.

Medium-term dietary studies were conducted in rats and dogs with beta-cyfluthrin. In a 90-day rat study, head and neck necrosis, uncoordinated gait, poor general condition, reduced bodyweight gain, and decreased cholesterol and triglyceride levels were observed at 50 mg/kg bw/day. A 13-week study in dogs reported toxic effects on motor function, vomiting and diarrhoea at 9 mg/kg bw/day. The NOEL of 1.5 mg/kg bw/day in this dog study is the basis for the current ADI for beta-cyfluthrin.

Long-term effects: Long-term studies with cyfluthrin in mice, rats and dogs produced decreased bodyweight gain at dose levels of 220 mg/kg bw/day, 6 mg/kg bw/day and 24 mg/kg bw/day, respectively. A 2-year rat study reported a small increase in fluoride concentration in bones at 6 mg/kg bw/day. In a 12-month dietary study in dogs, clinical signs of toxicity were observed at a dose of 24 mg/kg bw/day. The NOEL of 2.5 mg/kg bw/day in the rat study is the basis for the current ADI for cyfluthrin.

Carcinogenicity: Based on long-term studies in rodents, there is no evidence of carcinogenicity for cyfluthrin.

Genotoxicity: Cyfluthrin and beta-cyfluthrin are 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 with cyfluthrin showed evidence of reduced fertility and pup survival at dose levels of 6 mg/kg bw/day and above. A developmental toxicity study in rats did not produce any evidence of effects on foetal development.

Neurotoxicity: There was no evidence of delayed neurotoxicity with cyfluthrin in studies in hens.

Poisons Schedule: Cyfluthrin is included in Schedule 5 or 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. Beta-cyfluthrin is included in Schedules 5, 6 and 7 , 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 0.05 mg/L for beta-cyfluthrin was determined as follows:

$$\text{ 0.05 mg/L } = \dfrac{\text{ 1.5 mg/kg bodyweight/day x 70 kg x 0.1 }}{\text{ 2 L/day x 100 }}$$

where:

• 1.5 mg/kg bw/day is a NOEL based on a medium-term (13-week) study in dogs.

• 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 average 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.

Casas V, Llompart M, Garcia-Jares C, Cela R, Dagnac T (2006). Multivariate optimisation of the factors influencing the solid-phase microextraction of pyrethroid pesticides in water. Journal of Chromatography A, 1124:148-156.

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.

Mekebri A, Crane DB, Blondina GJ, Oros DR, Rocca JL (2008). Extraction and analysis methods for the determination of pyrethroid insecticides in surface water, sediments and biological tissues at environmentally relevant concentrations. Bulletin of Environmnetal Contamination and Toxicology, 80:455-460.

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

Woudneh MB, Oros DR (2008). Quantitative determination of pyrethroids, pyrethrins and piperonyl butoxide in surface water by high-resolution gas chromatography/high resolution mass spectrometry. Journal of Agricultural and Food Chemistry, 54(19):6957-6962.