Aldicarb
(endorsed 2011)
Guideline
Based on human health concerns, aldicarb in drinking water should not exceed 0.004 mg/L.
Related chemicals
Aldicarb (CAS 116-06-3) belongs to the carbamate class of chemicals. There are many other pesticides in this class, including asulam, carbaryl, methomyl and pirimicarb (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, aldicarb would not be a health concern unless the concentration exceeded 0.004 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: Aldicarb is an insecticide used in agriculture for the control of insects and nematodes in the soil. Aldicarb is taken up by plants, where it is metabolised into toxicologically active metabolites.
There is at least one registered product that contains aldicarb in Australia. Aldicarb products are intended for professional use and are available as a concentrated granular formulation to be incorporated by tractor equipment directly into the soil of citrus, cotton, and cane crops. Data on currently registered products are available from the Australian Pesticides and Veterinary Medicines Authority.
Exposure sources: The main source of public exposure to aldicarb and its metabolites is residues in food. Residue levels in food produced according to good agricultural practice are generally low.
Agricultural use of aldicarb may potentially lead to contamination of source waters through processes such as leaching into groundwater.
Typical values in Australian drinking water
There are few data on concentrations of aldicarb in Australian drinking waters. In Canada, aldicarb was reported in 111 of 1017 samples in surveys of private and municipal drinking-water supplies (detection limits 0.00001–0.003 mg/L [0.01–3.0 μg/L]); the maximum concentration was 0.028 mg/L (28 μg/L) (WHO 2003)
Treatment of drinking water
Aldicarb removal in municipal water treatment has been investigated (Kruithof 1994). For the removal of pesticides, operational techniques such as air-stripping, GAC-filtration and ozonation are available and of these, GAC-filtration is considered moderately effective, although is very susceptible to competitive adsorption by natural organic matter.
Reverse osmosis and nanofiltration have been tested for effectiveness at removing Aldicarb degredates from environmental water samples and has been shown to be effective in some applications (Baier et al. 1987, Kiso et al, 2002).
The effectiveness of ultraviolet irradiation and peroxide, ozonation and chlorination for the removal of aldicarb from drinking water has been identified in laboratory studies (Mason et al. 1990, Huston and Pignatello 1999).
Measurement
Aldicarb and its sulfoxide and sulfone oxidation products can be determined simultaneously by capillary gas chromatography with a nitrogen-phosphorus detector (Health Canada 1995, WHO 2003). The detection limit is 1 μg/L for all three compounds.
High-performance liquid chromatography (HPLC) is often the method of choice and is the basis of United States Environmental Protection Agency (USEPA) Method 531 for carbamate pesticides. Aldicarb, its sulfoxide and its sulfone are separated by reversed-phase HPLC, and the analytes are then hydrolysed to methylamine followed by post-column derivatisation with ortho-phthalaldehyde and fluorescence detection. The detection limits are 0.0013, 0.0008 and 0.0005 mg/L (1.3, 0.8 and 0.5 μg/L) for aldicarb, the sulfoxide and the sulfone, respectively (Health Canada 1995, WHO 2003).
History of the health values
The current acceptable daily intake (ADI) for aldicarb is 0.001 mg per kg of bodyweight (mg/kg bw), based on a no-observed-effect level (NOEL) of 0.01 mg/kg bw/day from an acute dietary study in human volunteers. The NOEL is based on cholinesterase inhibition in plasma and erythrocytes at 0.025 mg/kg bw. The ADI incorporates a safety factor of 10 and it was established in 1999.
The previous health value was 0.002 mg/L (NHMRC and NRMMC, 2004).
Health considerations
Metabolism: Aldicarb is readily absorbed from the gastrointestinal tract and widely distributed in the body. It is rapidly excreted, mainly via the urine. The primary metabolites are the sulfoxide and the sulfone.
Acute effects: Aldicarb has a high acute oral and dermal toxicity. Aldicarb is a skin sensitiser in guinea pigs. Significant plasma and erythrocyte cholinesterase inhibition was seen at doses of 0.025 mg/kg bw and above in a single dose study in human volunteers using drinking water as the dosing vehicle. Clinical symptoms of toxicity typical of cholinesterase inhibition, including tremors, prostration, coma, piloerection, ataxia, and salivation, were seen at the highest dose tested (0.06 mg/kg bw/day) in this study. The NOEL was 0.01 mg/kg bw/day and this is the basis for the ADI.
Short-term effects: Fourteen-day dietary studies in dogs reported reduced bodyweight and clinical signs of cholinesterase inhibition. Cholinesterase inhibition was observed at 0.02 mg/kg bw/day. In 3-month dietary studies in rats and dogs, effects included decreased body weight gain and food consumption in rats, and cholinesterase inhibition was reported at doses of 0.07 mg/kg bw/day and above.
Long-term effects: In medium-term (13-week) dietary studies in rats and dogs, effects were typical of cholinesterase inhibitors and included decreased cholinesterase activity in plasma (dogs and rats), erythrocytes and brain (rats only), at doses of 0.05 mg/kg bw/day and above (rats). Mortality was seen at doses of 0.1 mg/kg bw/day and above (rats). No other effects were seen (in both rats and dogs). The lowest overall NOEL was 0.02 mg/kg bw/day (rats).
In long-term dietary studies in rats and dogs, effects were typical of cholinesterase inhibitors and included plasma and erythrocyte cholinesterase inhibition at the lowest dose tested, 0.024 mg/kg bw/day (dogs), and above. Neuromuscular disturbances, hair loss, decreased bodyweight gain and associated decreases in food consumption, were seen at the highest dose tested in rats, 1.87 mg/kg bw/day. The NOEL in rats was 0.05 mg/kg bw/day. A NOEL was not found in the long-term dietary study in dogs.
Carcinogenicity: Based on long-term studies in rats, there is no evidence of carcinogenicity for aldicarb.
Genotoxicity: Aldicarb and its metabolites are not considered to be genotoxic, based on in vitro and in vivo short-term studies.
Reproductive and developmental effects: A reproduction study in rats, and developmental studies in rats and rabbits did not produce any evidence of effects on reproductive parameters or on foetal development.
Neurotoxicity: Reduced grip strength, inactivity, and delayed sensorimotor responses of offspring were seen in oral dosing studies in pregnant female rats given 0.3 mg/kg bw/day from gestation day 6 to lactation day 10 (23-26 days). The NOEL for effects on the developing nervous system was 0.1 mg/kg bw/day.
Poisons Schedule: Aldicarb 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 value of 0.004 mg/L for aldicarb was determined as follows:
where:
0.01 mg/kg bw/day is the NOEL based on an acute human study.
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 amount maximum of water consumed by an adult.
10 is the safety factor applied to the NOEL derived from human studies to account 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.
Baier JH, Lykins BW, Fronk CA, Kramer SJ (1987). Using reverse osmosis to remove agricultural chemicals from groundwater. Journal of the American Water Works Association, 79(8):55-60.
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.
Health Canada (1995). Guidelines for Canadian Drinking Water Quality – Technical Documents: Aldicarb.
Huston PL, Pignatello JJ (1999). Degradation of selected pesticide active ingredients and commercial formulations in water by the photo-assisted Fenton reaction. Water Research, 33:(5):1238-1246.
Kiso Y, Mizuno A, Othman RA, Jung Y, Kumano A, Ariji A (2002). Rejection properties of pesticides with a hollow fiber NF [nanofiltration] membrane (HNF-1). Desalination, 143(2):147-157.
Kruithof JC, Hopman R, Meijers RT, Hofman J (1994). Presence and removal of pesticides in Dutch drinking water practice. Water Supply, 12(1-2): SS11-10-SS11-14.
Mason Y, Choshen E, Rav-Acha C (1990). Carbamate insecticides: removal from water by chlorination and ozonation. Water Research, 24(1):11-21.
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.
Tomlin CD (ed) (2006). The Pesticide Manual: a world compendium, 14th Edition, British Crop Production Council, UK.
WHO (2003) Background documents for the development of WHO Drinking Guidelines for Drinking-water Quality. Aldicarb in drinking water. WHO/SDE/WSH/03.04/72.
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