Spirotetramat
(endorsed 2011)
Guideline
Based on human health concerns, spirotetramat in drinking water should not exceed 0.2 mg/L.
Related chemicals
Spirotetramat (CAS 203313-25-1) belongs to the tetramic acid/cyclic ketoenol class of chemicals. There are no other pesticides in this class (Tomlin 2009).
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, spirotetramat would not be a health concern unless the concentration exceeded 0.2 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: Spirotetramat is an insecticide for the control of aphids, whiteflies and mealybugs in citrus, grapes, pome fruit, stone fruit, tree nuts, hops, vegetables and potatoes.
While spirotetramat is approved as an active ingredient, there are currently no registered products containing spirotetramat in Australia. Spirotetramat is intended for professional use only, to be applied by spray, using open or enclosed cab tractor-mounted or drawn sprayer fitted with hydraulic nozzles.
Exposure sources: If there were registered products, the main source of public exposure to spirotetramat would be residues in food. Residue levels in food produced according to good agricultural practice are generally low.
Future agricultural use of spirotetramat 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
Monitoring studies for spirotetramat in raw and tap water are limited and few data appear to be available (USEPA 2008), Babczinski and Hellpointner 2008).
Treatment of drinking water
There is insufficient information on the treatment of spirotetramat in drinking water, but it is expected that advanced treatment methodologies such as ozonation and advanced oxidation would be effective.
Measurement
Spirotetramat in drinking water can be measured by high performance liquid chromatography (HPLC) with tandem mass spectrometry or HPLC with ultraviolet irradiation. The analytical method 00836 developed by Bayer CropScience has been validated (USEPA 2008).
History of the health values
The current acceptable daily intake (ADI) for spirotetramat is 0.05 mg per kg of bodyweight (mg/kg bw), based on a no-observed-effect level (NOEL) of 5 mg/kg bw/day from a one-year study in dogs. This NOEL is based on decreased thyroid hormone triiodothyronine and thyroxine levels and thymus involution. The ADI incorporates a safety factor of 100, and was established in 2008.
The acute reference dose (ARfD) of 1 mg/kg bw/day for spirotetramat was established in 2008, based on a NOEL of 100 mg/kg bw/day from an acute neurotoxicity study in rats. The ARfD incorporates a safety factor of 100.
A health value has not been previously established by NHMRC.
Health considerations
Metabolism: Spirotetramat is rapidly absorbed from the gastrointestinal tract. There is no evidence of bioaccumulation. Spirotetramat is completely metabolised in the rat and the majority is excreted via the urine and faeces within 24 hours. The primary metabolites are enols (66-100% of all metabolites) and ketohydroxy forms of spirotetramat.
Acute effects: Spirotetramat has low acute oral and dermal toxicity in animal studies. It exhibits skin sensitisation potential in animals and humans.
Short-term effects: Short-term dietary studies in dogs and rats reported effects on the thyroid and thymus gland in dogs and on the testes, lung and kidney in rats at dose levels above 5 mg/kg bw/day.
Long-term effects: Long-term dietary studies in rats and mice reported that the target organs in rats were the kidney in both sexes and the liver in females at dose levels of 169 mg/kg bw/day and above. There were no adverse effects reported in mice up to the highest dose tested. A one-year dietary study in dogs reported the thymus and thyroid as target organs of toxicity at dose levels of 20 mg/kg bw/day and above. The NOEL of 5 mg/kg bw/day in dogs is the basis for the ADI.
Carcinogenicity: Spirotetramat did not demonstrate any evidence of carcinogenicity in rats or mice.
Genotoxicity: Spirotetramat is not considered genotoxic, based on in vitro and in vivo short-term studies.
Reproductive and developmental effects: Reproduction studies in rats reported the presence of abnormal sperm cells, decreased sperm motility and decreased reproductive performance at 70 mg/kg bw/day. In developmental toxicity studies in rats and rabbits, there was an increased incidence of skeletal variations and malformations at the maternally toxic dose of 1000 mg/kg bw/day. Both reproductive and developmental effects occurred at dose levels well in excess of the likely level of human exposure.
Poisons Schedule: Spirotetramat 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 0.2 mg/L for spirotetramat was determined as follows:
where:
5.0 mg/kg bw/day is the NOEL based on a long-term (1-year) dietary 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 estimated maximum amount of water consumed by an adult.
100 is the safety factor applied to the NOEL derived from animal studies. The safety factor of 100 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.
Babczinski P, Hellpointner E (2008). Environmental fate of spirotetramat (Movento®). Bayer CropScience Journal, 61:181-202.
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.
Tomlin CD (ed) (2009). The Pesticide Manual: a world compendium, 15th Edition, British Crop Production Council, UK.
USEPA (United States Environmental Protection Agency) (2008). Pesticide Fact Sheet: Spirotetramat. USEPA, Office of Prevention, Pesticides and Toxic Substances
Last updated