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Who determines the safe level of pesticides in drinking water?

10 December 2010

The National Health and Medical Research Council (NHMRC) develops and maintains the Australian Drinking Water Guidelines (ADWG). These Guidelines are designed to provide relevant authorities with standards to assess drinking water quality. Guidelines are provided for managing microorganisms, waterborne pathogens and chemicals – including pesticides – together with standards that define safe levels of these substances. The pesticide guidelines inform APVMA registration decisions.

More detail

While pesticides are unlikely to be in drinking water some are occasionally detected. The ADWG recognises this and provides two levels for common pesticides to assist water supply managers take appropriate action.

The first is the Guideline Value. This is based on the level at which the pesticide can be reliably detected using practicable, readily available and validated analytical measures. If a pesticide is detected at or above this level the source should be identified and action taken to prevent further contamination.

The second is the Health Value. This is set by the Office of Chemical Safety and Environmental Health in the Department of Health and Ageing at 10% of the Acceptable Daily Intake (ADI) for each chemical. The ADI is the amount of a substance that can be ingested in food or drinking water on a daily basis over a lifetime without an appreciable health risk. It is based on scientific studies set up to measure the maximum dose of a chemical that does not cause any detectable (usually adverse) effects in a test animal. The ADI is usually calculated by dividing this dose (known as the no observable effect level) by a safety factor (often 100). Detections above the Health Value warrant an immediate managerial response although there may be no immediate health risk.

Both guideline and health values are expressed in terms of milligrams per litre of water. Under the current edition of the Guidelines, for example, the guideline and health values for carbaryl are 0.005 and 0.03 mg/L respectively.

Both the Commonwealth Department of Health and Ageing and the Department of Sustainability, Environment, Water, Population and Communities take these levels into account in providing human health and environmental advice respectively to the APVMA.

The NHMRC is currently revising the ADWG. More pesticides will be listed than in the current version and there is likely to be a downward revision of some guideline values in response to technological advances in chemical detection. Some variation on health values is also expected in response to the continued refinement of toxicity models and periodic revisions of ADI’s for various chemicals by the Australian Department of Health and Ageing.

Further information

See the Australian Drinking Water Guidelines (2004) (external site).

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Last updated on 10 December, 2010