Mevinphos
(endorsed 2011)
Guideline
Based on human health concerns, mevinphos in drinking water should not exceed 0.005 mg/L.
Related chemicals
Mevinphos (CAS 7786-34-7) belongs to the organophosphate class of chemicals. There are many other pesticides in this class, which includes chlorfenvinphos, chlorpyrifos, dichlorvos and diazinon (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, mevinphos would not be a health concern unless the concentration exceeded 0.005 mg/L. Excursions above this level even for a short period are of concern as the health-based guideline is based on short-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: Mevinphos is an anticholinesterase acaricide (miticide) and insecticide for the control of moths in Brassica crops (cabbages, cauliflowers, broccoli and brussel sprouts).
There is at least one registered product that contains mevinphos in Australia. Mevinphos products are intended for professional use and are available as concentrated solutions to be applied in diluted form, by boom spray. Data on currently registered products are available from the Australian Pesticides and Veterinary Medicines Authority.
Exposure sources: The main source of public exposure to mevinphos and its metabolites is residues in food. Residue levels in food produced according to good agricultural practice are generally low.
Agricultural use of mevinphos 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 published reports on mevinphos occurrence in Australian drinking water supplies were found.
Treatment of drinking water
A reverse osmosis (RO) membrane challenge test was conducted by injecting 1200 µg/L of mevinphos before treatment. RO removed 96% of the initial concentration of mevinphos (1200 µg/L), and the post-membrane carbon filter further removed 95% of the remaining mevinphos, from 40 µg/L to 2.1 µg/L (USEPA 2005). In another challenge test, the concentration of mevinphos remained the same after ultraviolet (UV) light and ozone treatment; however, the activated carbon filter located after the UV and ozone treatment removed 99% of the pesticide (USEPA 2007).
Measurement
Mevinphos is one of the organophosphorus pesticides analysed by the United States Environmental Protection Agency (USEPA) Method 622 (Pressley et al. 2002). The sample is solvent-extracted and the extract is dried with sodium sulfate concentrated and analyzed by gas chromatography using a flame photometric or phosphorus/nitrogen detector. The concentrated can also be analysed by gas chromatography–mass spectrometry in selected ion monitoring mode. The method can achieve a limit of quantitation (LOQ) of 0.05 mg/L. Hollow fiber liquid phase micro-extraction with gas chromatography by flame thermionic detection can achieve a LOQ of 40 ng/L in drinking water (Lambropoulou and Albanis 2005). A solid-phase microextraction method coupled with a flame photometric can achieved a LOQ for mevinphos of 420 µg/L (Su and Huang 1999).
History of the health values
The current acceptable daily intake (ADI) for mevinphos is 0.002 mg per kg of bodyweight (mg/kg bw), based on a no-observed-effect level (NOEL) of 0.016 mg/kg bw/day (1 mg/person/day using a mean bodyweight of 62.5 kg) from a 30-day human volunteer study. The NOEL is based on inhibition of erythrocyte cholinesterase. The ADI incorporates a safety factor of 10 and was established in 1998.
The previous ADI established in 1996 was 0.0008 mg/kg bw based on a NOEL of 0.016 mg/kg bw/day (1 mg/person/day) in a human volunteer study and using a safety factor of 20. An additional factor of 2 was included because of the decrease in slow motor fibre nerve conduction velocity observed in a different human volunteer study at 0.025 mg/kg bw/day.
The acute reference dose (ARfD) of 0.003 mg/kg bw for mevinphos was based on a LOEL of 0.025 mg/kg bw/day from a 28-day human volunteer study. The ARfD incorporates a safety factor of 10 and was established in 2000.
The previous health value was 0.005 mg/L (NHMRC and NRMMC 2004).
Health considerations
Metabolism: Mevinphos is rapidly and extensively absorbed via the gastrointestinal tract and rapidly metabolised and excreted, predominantly as carbon dioxide in expired air (78%), with only 14% in the urine over 24 hours. There were four major metabolites in the urine.
Acute effects: Mevinphos has high acute oral and dermal toxicity. It is not a skin sensitiser.
Short-term effects: In 3-, 12- and 13-week dietary studies in rats at dose levels up to 20 mg/kg bw/day, the principal sign of toxicity at the higher dose levels was death. Four dogs also died in a dietary study at a dose of 15 mg/kg bw/day. In a 30-day five-person human volunteer study, erythrocyte cholinesterase activity was decreased at 1.5 mg/person/day. The NOEL was 0.015 mg/kg bw/day (1 mg/person/day) and this NOEL is the basis for the ADI. In a 28-day eight person volunteer study, plasma and erythrocyte cholinesterase activity was decreased at 0.025 mg/kg bw/day. There was also a decrease in slow fibre motor conduction at this dose level. This LOEL, the only dose tested, is the basis for the ARfD.
Long-term effects: In a 2-year dietary study in rats at dose levels up to 0.6 mg/kg bw/day, there were no treatment-related effects on general health or bodyweight gain. No histopathological changes were observed. In a 2-year dietary study in dogs at doses up to 0.75 mg/kg bw/day, plasma and erythrocyte cholinesterase activity were decreased at 0.075 mg/kg bw/day and above and increased with time. At the two-year period, brain cholinesterase activity was significantly decreased at 0.25 mg/kg/day in females and at 0.75 mg/kg in males and females. All but two high dose male animals survived in good health.
Carcinogenicity: Based on a 2-year study in rats and dogs, there is no evidence of carcinogenicity for mevinphos.
Genotoxicity: Mevinphos 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 did not produce any evidence of effects on reproductive parameters or foetal development.
Poisons Schedule: Mevinphos is included in Schedule 7 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 0.005 mg/L for mevinphos was determined as follows:
where:
0.015 mg/kg bw/day is the NOEL established in a short-term (30-day) study in humans.
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.
10 is the safety factor applied to the NOEL derived from the human study to allow 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.
Lambropoulou DA, Albanis TA (2005). Application of hollow fiber liquid phase microextraction for the determination of insecticides in water. Journal of Chromatography A, 1072(1): 55-61
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.
Pressley T, Longbottom J (2002). Method 622 The Determination of Organophosphorus Pesticides in Municipal and Industrial Wastewater. United States Environmental Protection Agency, Washington D.C.
Su PG, Huang SD (1999). Determination of organophosphorus pesticides in water by solid-phase microextraction. Talanta, 49(2):393-402.
Tomlin CD (ed) (2006). The Pesticide Manual: a world compendium, 14th edition, British Crop Production Council, UK.
USEPA (United States Environmental Protection Agency) (2005). Point of use drinking water treatment system application: Removal of chemical contaminants in drinking water: Reverse osmosis. The Environmental Technology Verification Program, USEPA.
USEPA. (United States Environmental Protection Agency) (2007). Point of use drinking water treatment system application: Removal of chemical contaminants in drinking water: Advanced simultaneous oxidation process. The Environmental Technology Verification Program, USEPA.
Last updated
