Propanil
(endorsed 2011)
Guideline
Based on human health concerns, propanil in drinking water should not exceed 0.7 mg/L.
Related chemicals
Propanil (CAS 709-98-8) belongs to the anilide class of chemicals. Another chemical in this class is pentanochlor (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, propanil would not be a health concern unless the concentration exceeded 0.7 mg/L. Minor excursions above this level would need to occur over a significant period to be of 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: Propanil is a herbicide for the post-emergent control of barnyard grass in rice.
There are registered products that contain propanil in Australia. The products are intended for professional use and are available as concentrated solutions to be applied in diluted form using boom, aerial and knapsack spray 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 propanil and its metabolites is residues in food. Residue levels in food produced according to good agricultural practice are generally low.
Agricultural use of propanil on rice fields may lead to contamination of source waters through entry into groundwater and processes such as run-off and spray drift.
Typical values in Australian drinking water
Propanil has been tested but not detected in the Ord River Irrigation Area, Western Australia (Oliver and Kookana 2005). It was detected in one of 53 finished drinking water samples collected at different sites in the USA at 0.7 µg/L (Li et al. 2006). Propanil has been detected in the drainage channels of the main rice cultivating countries in Europe. The highest concentration reported was 16.82 µg/L (Kuster et al. 2008).
Treatment of drinking water
Propanil can be removed from drinking water by granular activated carbon (Ayranci and Hoda 2004) and reverse osmosis treatment.
Measurement
Propanil can be measured in water by online solid-phase extraction (SPE) liquid chromatography mass spectrometry (LC-MS) or direct injection on a triple quadrapole LC-MS instrument in multiple reaction monitoring mode. The method can achieve a limit of quantitation (LOQ) of 1 µg/L. SPE followed by high performance liquid chromatography using photochemically-induced fluorescence detection can achieve a LOQ in the range of 0.07 to 0.7 µg/L (de la Pena et al. 2003). Li et al. (2006) reported a propanil LOQ in drinking water of 0.02 µg/L using liquid chromatography–electrospray ionization–mass spectrometry.
Propanil can also be detected at very low concentrations in water. A fully automated method using on-line solid-phase extraction–liquid chromatography–electrospray-tandem mass spectrometry can achieve a LOQ of 0.5 ng/L (Kampioti et al. 2005). A solid-phase microextraction-gas chromatography-mass spectrometry method can achieve a LOQ of 2 ng/L (Natangelo et al. 1999) and on-line solid-phase extraction-liquid chromatography–electrospray–tandem mass spectrometry can achieve a LOQ of 0.4 ng/L (Kuster et al. 2008). Moreover, a method without any sample pre-treatment and without pre-concentration using a fully automated immunoassay for detection of propanil in aqueous samples can achieve a LOQ of 0.6 ng/L (Tschmelak et al. 2004).
History of the health values
The current acceptable daily intake (ADI) for propanil is 0.2 mg per kg of bodyweight (mg/kg bw), based on a no-observed-effect level (NOEL) of 20 mg/kg bw/day from a 2-year oral study in rats. The NOEL is based on decreased bodyweight gain, mild anaemia and organ weight changes. The ADI incorporates a safety factor of 100, and was established in 1981.
The previous health value was 0.5 mg/L (NHMRC and NRMMC 2004).
Health considerations
Metabolism: Propanil is readily and extensively absorbed via the gastrointestinal tract. It is metabolised and eliminated within 48 hours. The major metabolites are 3,4-dichloroaniline (DCA) and 3,3µ,4,4µ-tetrachloroazobenzene (TCAB) (WHO 2004). These metabolites in addition to tetrachloroazoxybenzene (TCAOB) have been reported as impurities of toxicological concern in propanil. The Australian Pesticides and Veterinary Medicines Authority have set impurity limits of 20 mg/kg for TCAB and 2 mg/kg for TCAOB in propanil active constituent.
Acute effects: Propanil has low oral and dermal acute toxicity. It is not a skin sensitiser.
Short-term effects: A short-term dietary study in rats reported an increase in number of abnormal red blood cells at doses of 25 mg/kg bw/day. At higher dose levels, effects reported included haemolytic anaemia, decreased bodyweight gain and increased mortality. In a 4-week dietary study in dogs, decreased bodyweight gain and food consumption was reported at 375 mg/kg bw/day.
Long-term effects: Long-term dietary studies with propanil in rats and dogs showed the main toxicological effect to be haemotoxicity. A 2-year dietary study in rats reported decreased bodyweight gain, decreased haemoglobin and haematocrit levels, and increased spleen, liver and testes weights at 80 mg/kg bw/day. In dogs, there was decreased bodyweight gain and decreased haemoglobin levels at 225 mg/kg bw/day and above. The lowest overall NOEL was 20 mg/kg bw/day in the rat study and this is the basis for the current ADI.
Carcinogenicity: Based on 2-year studies in rats and dogs, there is no evidence of carcinogenicity for propanil.
Genotoxicity: The genotoxicity of propanil has not been evaluated in Australia, but studies evaluated by the World Health Organization are reported as negative.
Reproductive and developmental effects: A 3-generation reproduction study in rats did not show any evidence of effects on reproductive parameters or foetal development. No specific developmental toxicity study was available.
Poisons Schedule: Propanil is included in Schedule 5 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 0.7 mg/L for propanil was determined as follows:
where:
20 mg/kg bw/day is the NOEL based on a long-term (2-year) 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.
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.
The World Health Organization has not established a health-based guideline value for propanil. The following reason is given: “Although a health-based value for propanil can be derived, this has not been done, because propanil is readily transformed into metabolites that are more toxic. Therefore, a guideline value for the parent compound is considered inappropriate, and there are inadequate data on the metabolites to allow the derivation of a guideline value for them. Authorities should consider the possible presence in water of more toxic environmental metabolites.” (WHO 2004).
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.
Ayranci E, Hoda N (2004). Adsorption of bentazon and propanil from aqueous solutions at the high area activated carbon-cloth. Chemosphere, 57(8):755-762.
de la Pena AM, Mahedero MC, Bautista-Sanchez A (2003). Monitoring of phenylurea and propanil herbicides in river water by solid-phase-extraction high performance liquid chromatography with photoinduced-fluorimetric detection. Talanta, 60(2-3):279-85.
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.
Kampioti AA, Borba da Cunha AC, Lopez de Alda M, Barcelo D (2005). Fully automated multianalyte determination of different classes of pesticides, at picogram per litre levels in water, by on-line solid-phase extraction-liquid chromatography-electrospray-tandem mass spectrometry. Analytical and Bioanalytical Chemistry, 382(8):1815-25.
Kuster M, Lopez de Alda MJ, Barata C, Raldua D, Barcelo D (2008). Analysis of 17 polar to semi-polar pesticides in the Ebro river delta during the main growing season of rice by automated on-line solid-phase extraction-liquid chromatography-tandem mass spectrometry. Talanta, 75(2):390-401.
Li Y, George JE, McCarty CL, Wendelken SC (2006). Compliance analysis of phenylurea and related compounds in drinking water by liquid chromatography/electrospray ionization/mass spectrometry coupled with solid-phase extraction. Journal of Chromatography A, 1134(1-2):170-6.
Natangelo M, Tavazzi S, Fanelli R, Benfenati E (1999). Analysis of some pesticides in water samples using solid-phase microextraction-gas chromatography with different mass spectrometric techniques. Journal of Chromatography A, 859(2):193-201
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.
Oliver D, Kookana R (2005). Pesticide use in the 6th Creek Sub-catchment, Mt. Lofty Ranges, S.A. and Assessment of Risk of Off-site MOVEMENT using Pesticide Impact Rating Index (PIRI). Adelaide, CSIRO Land and Water Technical Report
Tomlin CD (ed) (2006). The Pesticide Manual: a world compendium, 14th edition, British Crop Production Council, UK.
Tschmelak J, Proll G, Gauglitz G (2004). Ultra-sensitive fully automated immunoassay for detection of propanil in aqueous samples: steps of progress toward sub-nanogram per liter detection. Analytical and Bioanalytical Chemistry, 379(7-8):1004-12.
WHO (World Health Organization) (2004). Guidelines for Drinking-water Quality. 3rd Edition, WHO, Geneva, Switzerland.
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