South West Water Authority has been accused of "gambling" with the lives of 20,000 people by not telling them about Britain's worst mass poisoning for more than a fortnight.
The water poisoning occurred when a relief lorry driver mistakenly added 20,000 tonnes of aluminium sulphate to the drinking water at the Lowermoor treatment works in 1988.
West Somerset Coroner Michael Rose criticised the South West Water Authority as he gave his verdict on the death of Carole Cross.
Mrs Cross, 59, died in 2004 from a rare disorder usually associated with much older people suffering from Alzheimer's disease.
She was one of 20,000 customers affected by the mass water poisoning in the Camelford area of north Cornwall.
The coroner recorded a lengthy narrative verdict in which he said there was a "very real possibility" that the ingestion of aluminium by Mrs Cross had contributed to her death.
The inquest, which first began in November 2010, heard that a post-mortem examination later found high levels of aluminium in Mrs Cross's brain.
The inquest was told that, for more than two weeks, South West Water Authority, which ran the treatment works, did not tell the public the cause of the poisoning and insisted the water was safe to drink.
Many people reported rashes, diarrhoea, mouth ulcers and other health problems after drinking the water or bathing in it.
The water became so polluted in the first few hours that customers reported hairs sticking to their body like superglue as they got out of the bath.
Customers flooded the switchboard of the water authority but were told it was safe and it has been claimed some were even advised to boil the water, which increased the levels of aluminium still further.
Mrs Cross, who lived on the outskirts of the town and later moved to Dulverton in Somerset, died in Taunton's Musgrove Park Hospital.
She suffered from a rare neurological disease - cerebral amyloid angiopathy.
Her husband, Dr Doug Cross, believes her exposure to high levels of aluminium during the incident caused her death 16 years later.
Professor Chris Exley, a reader in bioinorganic chemistry at Keele University, who has studied the effects of aluminium for 25 years, told the inquest the aluminium found Mrs Cross's brain was a factor in her death.
He told the inquest in 2010 it was "highly likely" the high concentrations of aluminium in Mrs Cross's brain contributed to the early onset of the disease.
He added that he had studied samples of more than 100 brains and "Carole Cross has the record" in terms of amounts of the metal.
His evidence in 2010 and that of Margaret Esiri, emeritus professor of neuropathology at the University of Oxford, prompted an adjournment to allow South West Water Authority time to seek its own expert evidence.
Dr Cross, who now lives in Cumbria, did not attend today's hearing in Taunton, Somerset.
Mr Rose said: "From July 9 for a few days Mrs Cross ingested a quantity of aluminium, precise measurements of which are not possible, because of the failure of the authority to ensure the public were encouraged to give urine and blood samples.
"I also regard the failure of the authority to visit every house after the incident to advise them to thoroughly flush their systems as a serious dereliction of duty.
"At the end of the day, I can say that the incident may either have contributed to or possibly caused Mrs Cross's death, but I do not have sufficient evidence to say so conclusively."
Mr Rose said the delivery driver putting 20 tonnes of aluminium in the wrong tank at the unattended treatment works was "an accident waiting to happen".
"I do not think that relief driver John Stephens should be vilified," the coroner said.
"He struck me as a conscientious man who tried to use his initiative and had acted responsibly.
"It was an accident waiting to happen though, whether or not the procedure in the Fowey district differed greatly from those in the other five districts of the authority, or indeed in other authorities across the country, I do not know.
"Clearly the safety devices to prevent this mistake causing further trouble were not in place."
Mr Rose said that after the incident he was concerned that South West Water Authority did not have an emergency call-out system for water treatment works staff.
However, he said he would not criticise the authority for not stopping the water supply to Camelford, having heard strong evidence of the effect of doing so.
Mr Rose said that two days after the incident senior staff and authority chairman Keith Court were aware that aluminium poisoning was the likely cause.
He said he was "surprised" no one contacted Mr Stephens until July 12 - six days after the incident - to find out where he had put the aluminium sulphate.
"This was a totally unacceptable delay," Mr Rose said.
"At that stage either late on the Friday evening or even on the Saturday, the relevant public health officials should have been told the full facts.
"What I do have problems with was the failure to advise the public health authorities of the real problem and also the fact is that the public were not told for 16 days that aluminium sulphate had been put in the water supply."
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