Aluminium - Why a Concern in Drinking Water?

For years, researchers have puzzled over the surprisingly high levels of aluminium that turn up in the shrivelled brains of Alzheimer's disease victims. While some scientists believe that the aluminium deposits are only a side effect of Alzheimer's, a growing number of investigators say that aluminium may play a central role in causing the disease that afflicts mostly elderly people. Aluminium occurs naturally in some waters but is also introduced as aluminium sulphate by some municipal water departments to remove fine particles, color and bacteria. Municipal water departments usually control the water to a slightly alkaline condition, i.e., pH between 7 and 8. In alkaline conditions aluminium precipitates as fine solid particles, which are then filtered out by means of sand filters. However, sand filters become less efficient for particles as small as 4 to 5 microns and therefore fine particles slip through.

The latest evidence of a link emerged when Australian scientists reported that aluminium used to purify 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 aluminium levels in drinking water. The Australian study was important, said the directorate's chief, Dr. Barry Thomas, because it showed that aluminium in drinking water can be absorbed by the body. "As to whether it actually causes memory loss and brain damage," added Thomas, "there is not conclusive evidence. But we fear that it may." Although tiny amounts of aluminium 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 aluminium sulphate, or alum, to remove mineral particles from water in filtration plants, a process that leaves an aluminium residue in the water.

In the past, studies in Canada and other countries have pointed to links between aluminium 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 aluminium from their brains.

In a far-reaching study published in January (1995), William Forbes, a university of Waterloo gerontologist, demonstrated an apparent connection between mental impairment and aluminium in about 100 Ontario communities. In each community, researchers determined the amount of aluminium 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 functions was "almost 10 times higher in areas where the aluminium levels in drinking water were high."