A new retrospective study has shown that exposure to aluminium sulphate via the water supply can cause considerable brain damage.

In July 1988, 20 tonnes of the toxin was accidentally emptied into the treated water reservoir that served 20,000 people in Cornwall, UK. Delays in informing the public meant that a considerable number of people suffered symptoms such as gastrointestinal upsets, musculoskeletal pains, malaise and impairment of concentration and memory.

Two years later, 400 people were still suffering from symptoms, which they attributed to the incident.

Doctors argued that many cerebral symptoms were the result of psychological trauma.

But when researchers compared 55 of the affected people to a control group composed of 15 siblings who had not been exposed to the aluminium, they found that while blood concentrations of aluminium were comparable in both groups, the exposed group performed worse on all test parameters including motor skills, memory and concentration, suggesting that the heavy metal lodges in the brain. Tests for anxiety in both groups revealed relatively low levels of anxiety effectively debunking the idea that the symptoms were psychosomatic.

Exposure to aluminium has been shown in other studies to induce cerebral changes similar to those of Alzheimer's disease (BMJ, 1999; 319: 807-11).