Profenofos
(endorsed 2011)
Guideline
Based on human health concerns, profenofos in drinking water should not exceed 0.0003 mg/L.
Related chemicals
Profenofos (CAS 41198-08-7) belongs to the organophosphate class of chemicals. There are many other pesticides in this class, which includes temephos, fenthion, and methidathion (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, profenofos would not be a health concern unless the concentration exceeded 0.0003 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
Users: Profenofos is used as an insecticide and acaricide (miticide) for the control of certain insects on cotton crops.
There are registered products containing profenofos in Australia. The products are intended for professional use and are applied as concentrated or diluted solutions by either ground boom spray or aerial application methods. Data on currently registered products are available from the Australian Pesticides and Veterinary Medicines Authority.
Exposure sources: The main source of public exposure to profenfos is residues in food. Residue levels in food produced according to good agricultural practice are generally low.
Agricultural use of chemical 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 reports of profenfos in Australian drinking waters have been identified.
Treatment of drinking water
There is insufficient information on the treatment of profenfos in drinking water, but it is expected that advanced treatment methodologies such as ozonation and advanced oxidation would be effective.
Measurement
Profenofos can be measured in drinking waters by gas chromatography–mass spectrometry, with a practical limit of detection of 0.1 µg/L (QHFSS 2008 pers comm).
History of the health values
The current acceptable daily intake (ADI) for profenofos is 0.0001 mg per kg of bodyweight (mg/kg bw), based on a no-observed-effect level (NOEL) of 0.0072 mg/kg bw/day from a 6-month dog study. The NOEL is based on inhibition of plasma cholinesterase. The ADI incorporates a safety factor of 100, and was established in 1982.
The previous health value was 0.0003 mg/L (NHMRC and NRMMC 2004).
Health considerations
Metabolism: Profenofos is rapidly absorbed in the gastro-intestinal tract and is completely metabolised to four metabolites, which are excreted mainly in urine.
Acute effects: Profenofos has a moderate oral and low dermal toxicity. Profenofos is a skin sensitiser. Clinical symptoms of toxicity were typical of cholinesterase inhibition and included tremors, prostration, coma, piloerection, ataxia, and salivation.
Short-term effects: Medium-term toxicity studies in rats (3 months) and dogs (6 months) reported decreased plasma, red blood cell and brain cholinesterase, with plasma cholinesterase the most sensitive, at dose levels above 0.3 mg/kg bw/day and 0.007 mg/kg bw/day, respectively.
Long-term effects: Long-term studies in mice and rats reported decreased cholinesterase as the most sensitive toxicity endpoint. Decreased plasma cholinesterase was noted at dose levels above 0.015 mg/kg bw/day in the rat.
Carcinogenicity: Based on long-term studies in mice and rats, there is no evidence of carcinogenicity for profenofos.
Genotoxicity: There is equivocal evidence of genotoxicity from in vitro and in vivo short-term studies.
Reproductive and developmental effects: In a reproduction study in rats and developmental studies in rats and rabbits, there was no evidence of effects on reproductive parameters or foetal development.
Poisons Schedule: Profenofos 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 value of 0.0003 mg/L for profenofos was determined as follows:
where:
0.0072 mg/kg bw/day is the NOEL based on a medium-term (6-month) study in dogs.
70 kg is taken as the average weight of an adult
0.1 is a proportionality factor based on the conservative 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 a safety factor applied to the NOEL from a study conducted in dogs. The 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.
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.
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.
QHFSS (Queensland Health Forensic and Scientific Services) (2008). Personal communication.
Tomlin CD (ed) (2006). The Pesticide Manual: a world compendium, 14th Edition, British Crop Production Council, UK.
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