UP to three safeguard systems failed at the Brisbane water-treatment plant that released drinking water to residents with fluoride levels that were 20 times the legal limit.
The revelation came as the Queensland Government yesterday sent apology letters to the 4000 people in northern Brisbane whose water was dosed with 30 milligrams of fluoride per litre, rather than the 1.5mg/litre maximum, for three hours on May 2.
A member of the Queensland Government’s Fluoridation Committee, toxicology expert Michael Moore, yesterday called for a review of fluoridation engineering to prevent a repeat bungle.
Mike Foster, a spokesman for Queensland government water authority Seqwater, yesterday admitted that up to three safeguard systems at the North Pine treatment plant had malfunctioned, allowing the fluoride overdose to occur.
The plant had been shut down for maintenance between April 27 and 30, but the dosing machinery continued to pour fluoride into the system.
When the plant came back online, a concentrated amount of fluoride flowed into the system and was not detected until another water company tested water in the pipeline, a process that took two weeks.
The Queensland Health Department’s code of practice for water fluoridation warns of the need for back-up systems to prevent accidental overdoses. It specifically warns of the potential to overdose if the water supply is cut off but the fluoride continues to dose, as happened last month.
“All key components should be alarmed to alert the operator of a failure of the system,” it says.
The fluoride overdose marks the second water crisis in six months to hit the Bligh Government, after it was forced to back down late last year on plans to add recycled effluent to southeast Queensland dams. The plan was deferred in the face of community and expert concerns about the safety of recycled water, but treated effluent will be added to dams when their levels fall to 40 per cent.
The overdose comes barely four months after Queensland became the last state or territory to introduce fluoride into drinking water.
Professor Moore, the chairman of Water Policy Research Australia, yesterday called for the safety aspects of fluoridation engineering to be re-examined.
“I’m a very firm believer in the benefits associated with fluoridation and this is the worst thing that could have happened,” he said.
Professor Moore said the overdose was unlikely to have caused toxic effects.
Seqwater yesterday wrote to “sincerely apologise” to all affected residents in the suburbs of Warner and Brendale.
“It should not have happened and we are committed to ensuring it does not happen again,” said the letter, co-signed by Seqwater chief executive Peter Borrows and Queensland Chief Health Officer Jeannette Young.
It says Queensland Health is confident the health hazards are “remote”.
Fluoride overdoses can cause mottled teeth at concentrations above 1.5mg/litre and bone damage known as skeletal fluorosis at levels exceeding 4mg/litre, according to the Australian Drinking Water Guidelines.
“Fluoride is absorbed quickly following ingestion,” the guidelines state. “It is not metabolised, but diffuses passively into all body compartments.”