SCIENCE

Water worries

Studies suggest that aluminum may play a role in Alzheimer's

MARK NICHOLS April 10 1995
SCIENCE

Water worries

Studies suggest that aluminum may play a role in Alzheimer's

MARK NICHOLS April 10 1995

Water worries

SCIENCE

For years, researchers have puzzled over the surprisingly high levels of aluminum that turn up in the shrivelled brains of Alzheimer’s disease victims. While some scientists believe that the aluminum deposits are only a side effect of Alzheimer’s, a growing number of investigators say that aluminum may play a central role in causing the disease that afflicts more than 250,000 mostly elderly Canadians. The latest evidence of a link emerged when Australian scientists reported in a study published last week that aluminum used to purity water accumulated in the brains of laboratory rats. The Australian study focused new interest on the issue at a time when Ottawa’s environmental health directorate is preparing to propose Canada’s first national guidelines for aluminum levels in drinking water.

The Australian study was important, said the directorate’s chief, Dr. Barry Thomas, because it showed that aluminum in drinking water can be absorbed by the body. “As to whether it actually causes memory loss and brain damage,” added Thomas, “there is no conclusive evidence. But we fear that it may.”

Although tiny amounts of aluminum are used in a variety of products, including antacids, antiperspirants and some processed foods, the metal is pervasively present in drinking water. The reason: municipalities in Canada and other countries often use aluminum sulphate, or alum, to remove mineral particles from water in filtration plants—a process that leaves an aluminum residue in the water. In the past, studies in Canada and other countries have pointed to links between aluminum and Alzheimer’s. University of Toronto researchers found in a 1991 study that they could slow the rate of deterioration in Alzheimer’s patients by treating them with a drug that removed some aluminum from their brains.

In a far-reaching study published in Janu-

Studies suggest that aluminum may play a role in Alzheimer's

ary, William Forbes, a University of Waterloo gerontologist, demonstrated an apparent connection between mental impairment and aluminum in about 100 Ontario communities. In each community, researchers determined the amount of aluminum in the water supply and tested the mental state of people starting at the age of 45 and continuing over a period of 35 years. They concluded, said Forbes, that the risk of impaired mental functioning was “almost 10 times higher in areas where the aluminum levels in drinking water were high.”

The problem is that in Canada there are no real controls on the amount of aluminum in water. Ontario guidelines call for a maximum of 100 parts per billion. But many experts say that aluminum levels in Ontario and other provinces sometimes range up to 200 ppb—or even up to and beyond the 300 ppb level that Forbes’s study identified as the danger point. Last week, however, officials in three Canadian cities cited reassuringly low levels of aluminum in 1994: Regina averaged 34 ppb, Toronto had an 80-ppb average, while in St. John’s, Nfld., water from two plants averaged between 50 and less than 100 ppb.

Within the next year or so, Ottawa is expected to propose national guidelines—and many experts say that the limit should be 100 ppb or less. According to the environmental health directorate’s Thomas, Ottawa’s recommendation will depend on the findings of a review of international studies into the health risks that aluminum may pose. But some researchers insist that the answer is clear enough already. “Aluminum,” said Theo Knick, an associate professor of physiology at the University of Toronto who has worked on several studies involving aluminum and health, “is a highly toxic substance in your brain.”

MARK NICHOLS

DAN HAWALESHKA