Years of bitter disputes followed, with people who had drunk the water complaining of health problems. There were government inquiries, accusations of a cover-up – and, in 2004, the death of Carole Cross. This 58-year-old Camelford resident died from a rare and aggressive form of Alzheimer’s, and her brain was found to contain unusually high levels of aluminium.

The inquest into the cause of Mrs Cross’s death, delayed twice in the past few years, is set to report this week. Among those who will be watching the outcome with interest is Professor Chris Exley, who was called in nearly eight years ago to examine Mrs Cross’s brain (it contained 23 micrograms of aluminium per gram of brain, compared to normal levels of 0?2mcg).

But Prof Exley, a world-renowned expert on aluminium, hopes the inquest will do more than finally establish the truth about why Mrs Cross died (he is convinced that aluminium from the drinking water played a role in her mental deterioration). He also hopes it will highlight how little we know about the implications for our health of the most prolific metal on the planet.

Aluminium, he argues, is now added to or used in almost everything we eat, drink, inject or absorb. At high levels, it is an established neurotoxin – yet no one knows whether the levels we are ingesting are safe.

“Hundreds of publications demonstrate that aluminium is not safe,” he says. “But the accumulation of aluminium in the body has yet to become the subject of serious investigation and consideration in medicine.”

Exley, who is Professor of Inorganic Chemistry at Keele University, has been researching aluminium for a quarter of a century. His office is piled high with books on the subject, and he has contributed to scores of peer-reviewed papers and publications.

The metal is the most abundant in the Earth’s crust, naturally absorbed from the soil by plants and foodstuffs. But while 50 years ago we may have ingested minute amounts from vegetables (and possibly from some of the pots they were cooked in), today aluminium is found in almost everything.

In the form of salts, it has properties that make it a versatile and useful additive. “Aluminium sulphate is added to our water to improve clarity,” says Prof Exley. “All foods that need raising agents or additives, such as cakes and biscuits, contain aluminium. Children’s sweets contain aluminium-enhanced food colouring. It is in tea, cocoa and malt drinks, in some wines and fizzy drinks and in most processed foods.

“It is in cosmetics, sunscreens and antiperspirants, as well as being used as a buffering agent in medications like aspirin and antacids. It is even used in vaccines. We know aluminium can be toxic, yet there is no legislation to govern how much of it is present in anything, apart from drinking water.”

“When the amount of aluminium consumed exceeds the body’s capacity to excrete it, the excess is then deposited in various tissues, including nerves, brain, bone, liver, heart, spleen and muscle,” he explains. “We call it the ‘silent visitor’ because it creeps into the body and beds down in our bones and brain.”

Prof Exley’s research has covered everything from the potential dangers of aluminium in antiperspirants and sunscreen to the high levels of the metal in vaccines and infant formula. In one study, his team tested 16 of the UK’s leading formula milk brands for children up to the age of one. The results, published in 2010, showed that traces of the metal exceeded the levels legally allowed in water, and in some cases were more than 40 times that found in breast milk.

“Everyone has some aluminium in their bodies, but infants below the age of six months are especially prone to absorbing it and not so good at getting rid of it,” he says.

His research has led him to believe that accumulation of aluminium in the body is a risk factor not only for Alzheimer’s disease but may also be linked to other neurological conditions such as Parkinson’s and multiple sclerosis – and he believes that the Cross inquest will reignite debate about the potential risk of Alzheimer’s in particular.

“Carole Cross died of a type of Alzheimer’s known as congophilic amyloid angiopathy (CAA), an aggressive form of the disease that is extremely rare and practically unheard of for someone her age,” he says. “Her case demonstrates aluminium’s potential to aggravate and possibly accelerate ongoing disease. There is little doubt in my mind that the huge amounts of aluminium in her brain contributed significantly to the early onset of the condition.”

Aluminium is also used in 80 per cent of vaccines as an adjuvant (to increase the vaccine’s effectiveness), which concerns Prof Exley. “Our research is looking at whether aluminium can cause an adverse reaction to a vaccine,” he says. “Most children get about 14 vaccinations before the age of 13, so in susceptible individuals this could constitute an unacceptably high aluminium load.”

Not everyone agrees with Prof Exley’s views. The theory of a link between aluminium in cooking pots and Alzheimer’s has fallen out of favour in some quarters, as evidence for other triggers for the disease has grown. The Alzheimer’s Society says no causal relationship has been proved. “It is more likely to be a harmless secondary association,” says Lynsey Roberts from the society.

And Diane Benford, head of the Chemical Risk Assessment Unit at the Food Standards Agency, is confident that babies are not at risk from formula milk. But she does concede that “some small groups of the UK population may now be consuming more than the safety guideline amount of aluminium. This may particularly affect children who consume food with higher amounts of aluminium such as bread and bakery products, cocoa and cocoa products, and some leafy vegetables.”

She adds that measures to reduce aluminium in foodstuffs are being implemented by the EU. A recommended tolerable intake was recently set by the World Health Organisation (WHO) at 2 milligrams per kg of body weight per week. But Prof Exley says: “If my colleagues around the world are unable to come up with safe tolerable levels of aluminium, then how can the WHO?

“Don’t get me wrong. Aluminium has transformed the way we live. I am simply concerned about its ubiquity – in water, food packaging, vaccines, the drugs we take and even food and drink. We are living in the Aluminium Age and we need to be aware of how much we are ingesting.”

What happened at Camelford?

In July 1988, a relief lorry driver mistakenly added 20 tonnes of aluminium sulphate to drinking water at the Lowermoor treatment works near Camelford, Cornwall. There were hundreds of complaints about foul-tasting water on the night of the incident and South West Water Authority was criticised for not issuing a warning to the public for three weeks. The authority was eventually fined £10,000 and paid out more than £500,000 in damages or compensation.

Short-term health problems reported by residents included urinary complaints, skin problems, stomach cramps, joint pains and diarrhoea. Other complaints included fatigue, loss of memory and premature ageing.

Various government inquiries into the effects of the incident on health have been inconclusive, with one investigation reporting in 2005 that the long-term effects were unknown. A 1999 report in the BMJ concluded that some people had suffered “considerable damage” to their brain function.

The inquest into Mrs Cross’s death has been adjourned twice pending further research into the significance of the high levels of aluminium in her brain. In 2008, coroner Michael Rose said the government had refused to assist research into the hypothesis of a link between the aluminium in her brain and her illness and asked police to look into “allegations of a cover-up”.

The ubiquitous metal

Aluminium in the form of salts is naturally present in food because plants take it up from the soil and water. Unprocessed foods can contain between 0.1mg and20mg of aluminium per kg. Tea, some herbs and leafy vegetables especially can have naturally high levels.

It can migrate to food from cookware and packaging materials such as foil and cartons. One study found that around 20 per cent of aluminium in the diet came from the use of aluminium cookware and foil, according to the Food Standards Agency. Tomatoes, rhubarb, cabbage and many soft fruits should not be cooked in aluminium pans, it says.

Bread and bakery products contain relatively high levels of aluminium salts. Other products with added aluminium include fizzy drinks, children’s sweets, antiperspirants (where they inhibit the sweat glands), some processed cheeses, toothpaste, sunscreen, talcs and cosmetics, some over?the-counter medications and vaccines. It is also found as a contaminant in infant formulas. Soya formulas have been found to contain 10 times more aluminum than milk-based formulas.