Brain autopsy of pollution victim rekindles contaminant fears.
Fears of a link between aluminium and Alzheimer's disease have been reignited by the case of a British woman who died of the illness 16 years after an industrial accident polluted her local drinking water.
An autopsy on Carole Cross's brain showed that she was suffering from a rare form of early-onset Alzheimer's when she died in May 2004, and also revealed the presence of high levels of aluminium in her tissues. The researchers who investigated her brain cannot say whether the aluminium was the cause, but point out that the woman had no family history of dementia.
The polluting incident occurred in 1988 when a truck driver mistakenly emptied some 20 tonnes of aluminium sulphate — used in the early stages of wastewater treatment — into a tank containing drinking water destined for the village of Camelford in Cornwall, UK. An estimated 20,000 people may have been exposed to high levels of the chemical for several weeks.
Concerned residents are waiting to see whether more people will be similarly affected. Anecdotal reports state that several other villagers are suffering from dementia.
Something in the water
Although only a single case, the discovery has reopened the possibility that aluminium could be linked to Alzheimer's disease, say Christopher Exley, a chemist at Keele University, UK and Margaret Esiri, a University of Oxford neurologist, who publish details of their investigation on Cross in the Journal of Neurology, Neurosurgery and Psychiatry1.
Aluminium is firmly linked to some temporary forms of dementia, Esiri says. Kidney dialysis patients living in areas where water is high in aluminium, for example, sometimes experience 'dialysis dementia', as a result of the large quantities of contaminated water passing through their bodies.
“Once aluminium binds to proteins, it sticks for good. It's like trying to use superglue to mend a Swiss watch.”
Mount Sinai School of Medicine, New York
But the link between aluminium and Alzheimer's has been more controversial, says Daniel Perl, a neuropathologist at Mount Sinai School of Medicine in New York, who has written a commentary on the Camelford case2.
Aluminium is often found in the twists of deformed protein, called 'neurofibrillary tangles', that characterize the disease. But there is no strong evidence that it is involved in the disease's onset, Perl cautions. "I realize that's quite a conservative answer," he says. "But show me a couple more cases like this and I might have to change it."
Perl points out that, of the 20 most common elements on Earth, aluminium is the only one not involved in any essential biological process. That's because of its feisty chemistry, he explains. When in solution, aluminium ions are small and highly charged, making them very reactive. "Once aluminium binds to proteins, it sticks for good," he says. "It's like trying to use superglue to mend a Swiss watch."
What makes Cross's case interesting is that she had succumbed to a very rare form of Alzheimer's, but had a genetic predisposition, through a gene called APOE, to developing a more common form of the disease later in life, says Esiri. This raises the possibility that her aluminium exposure may have accelerated the onset of disease. Previous studies of transgenic mice expressing a similar gene have shown that feeding them aluminium in drinking water can cause similar symptoms at a young age.
Cross's protein tangles were found in the blood vessels rather than in the brain tissue itself. This is consistent with the idea that the cause of the disease could have originated in the gut, reaching the brain through the bloodstream, Esiri explains.
Combined with the unusually young age at which she died (aged 58), this puts her in a category shared by only a handful of known cases worldwide, Esiri says.
The discovery may also rekindle fears over drinking and cooking using aluminium pots and pans, although Perl says that most aluminium is found in an insoluble form and therefore not dangerous. The only way to ingest aluminium would be by cooking acidic foods such as rhubarb or tomato, which would react with the metal.
The news is worrying for Camelford's residents, says Exley, who carried out the chemical analysis to spot the aluminium in the autopsy samples. "There are still 20,000 people thinking about whether they're susceptible to this chronic disease," he says. "We can't do anything to help them."
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