1972 August: Murrabit Drain 3. Pesticide detected: Amitrole at 72,000 ug/L

Murrabit Drain 3

State Rivers and Water Supply Commission 1972 August (document).

Contamination limits

At a meeting of the Victorian Interdepartmental Committee on Pesticides on 24th September, 1962, approval was given for the Commission to use amitrole provided the level in domestic drinking water did not exceed 0.3ppm. The only exception was in Gippsland where contamination of drinking water was not permitted as it is a goitre area.

After completion of experiments on the toxicity of amitrole to crops and pastures, the Commission in June, 1963, adopted a maximum contamination level of amitrole in streams of 0.002 ppm. This level was 1/500 th of the concentration which in one irrigation, damaged the most sensitive crop tested.

On the basis of experience the Commission has had with amitrole over the the past ten years, it is considered that the maximum concentration of amitrole in streams could be safely determined at 0.01ppm or higher if necessary. This concentration is slightly higher than the sensitivity of the amitrole analytical method but considerably below the level of 0.3 ppm originally approved.

Although water containing amitrole residues may be pumped from drains for irrigation, this is closely controlled under license to the Commission. Also drainage water is always diluted in streams before use for domestic purposes. Establishment of a separate limit for drainage effluent is therefore unnecessary.

Drain 3 Murrabit

Lot D X Drain 3, Murrabit Amitrole 0.5 parts per million (500 ug/L)
Lot D Y Drain 3, Murrabit Amitrole 72 parts per million (72,000 ug/L)
Lot D Z Drain 3, Murrabit Amitrole 7.2 parts per billion (7,200 ug/L)

State Rivers and Water Supply Commission

Memo 31 August 1983

On 29 July I drew your attention to the expected withdrawal from sale of the herbicide amitrole by a major supplier. It was understood that the basis for the withdrawal was the alleged carcinogenic (cancer producing) nature of amitrole. A confirmatory letter from ICI Australia was tabled at a meeting of the Agricultural and Domestic Chemicals Review Committee (ADCRC) on 26 August.

You will be aware that amitrole has been used extensively by the Commission for about twenty years, mainly to control the growth of water couchgrass in drains. The withdrawal of amitrole from sale would necessitate the use of an alternative herbicide, At present, glyphosate is the only satisfactory alternative, the additional cost being about $40,000 annually.

The main decision arising from discussion at the meeting was that the Premier be notified of the cation taken by ICI, and that ADCRC considers that State Departments and instrumentalities should cease using amitrole.

However, at a meeting of several members of ADCRC on 30 August, convened when further information had been obtained, it was agreed that no recommendation should be made at present to terminate the use of amitrole. Instead, the Premier would be advised that ADCRC was taking immediate steps to consult ICI on the company’s action, and to obtain a review by the National Health and Medical research Council in toxicological data on amitrole.

It is evident that, for the time being at least, the Commission should plan to continue using amitrole for control of water couchgrass in drains in the usual way. Nevertheless contingency plans should be made so that a change from amitrole to glyphosate can be made as smoothly as possible if such as change becomes necessary.