By Hans Peterson, Saskatchewan Research Council, Saskatoon
Exposure to aluminum can come from food, air, and water. Although we are all exposed to it to some degree, aluminum is not a necessary substance for humans and too much of it may be harmful to your health.
Most of our daily aluminum intake is from food and water. The air we breathe, on the other hand, represents a relatively small portion of that daily intake. Aluminum in water is in a form that is more readily absorbed by the body, and very high aluminum levels in water can be of concern. Aluminum is used in water treatment to remove disease-causing microorganisms and other drinking water impurities that can affect your health.
When properly treated, the amount of residual aluminum left in the water should be similar to or lower than the non-treated water. Aluminum can be removed to extremely low levels by point-of-use treatment devices, such as distillation and reverse osmosis.
Aluminum makes up around 8% of the Earth's surface, making it the third most common element. It is often used in cooking utensils, containers, appliances and building materials, as well as in the production of glass, paints, rubber and ceramics. Aluminum is used in several forms, such as aluminum hydroxide (in antacids), aluminum chlorohydrate (in deodorants), and the most common form, aluminum sulphate (in treating drinking water).
Microorganisms present in drinking water include viruses, bacteria (e.g., E. coli), and protozoa (e.g., Cryptosporidium and the beaver fever causing organism, Giardia). At low levels, these organisms can cause sickness and disease (incl. severe diarrhea) and are generally very difficult to remove from water. The parasites Giardia and Cryptosporidium are very resistant to most types of disinfection, including chlorination. Water treatment with aluminum sulphate is, however, effective at removing these parasites when used in a chemical treatment process called coagulation.
Coagulation is a process in which small particles (0.001 to 10 m) bunch together to form large particles (>10 m), which can then be removed by settling or filtration.
In natural water, most particles (including microorganisms) have a negative electric charge and, rather than clump together to form larger particles, the particles repel each other.
To get the particles in solution to form larger clumps, this negative charge must be neutralized. This can be done by adding positive ions, such as aluminum or ferric ions, which react with the negative particles and form clusters of particles called microflocs. The microfloc then grows and will either settle out or can be filtered out of the water by a treatment system such as sand filtration.
Aluminum sulphate is the most common chemical used for the coagulation of particles. During coagulation, several other undesirable impurities in water are also removed, including naturally occurring organic matter, which reacts with chlorine to form disinfection by-products that may be carcinogenic. Coagulation is an essential step in effective water treatment and, when carried out properly, the residual amount of aluminum in the finished drinking water is small. Other coagulants, such as ferric chloride, are more hazardous to work with. Some coagulation chemicals are organic polymers blended with aluminum- or iron-based products—these are more costly and are generally used only under special circumstances.
More than 90% of our daily intake of aluminum comes from food, but this aluminum appears to be bound to other substances in the food and cannot be absorbed by the blood stream. In contrast, aluminum in water can be absorbed by humans because after water treatment, the aluminum is largely in an unbound form. Even so, the amount of aluminum absorbed from drinking water is usually very small.
At low levels, aluminum in food, air, and water is not likely harmful to your health. However, at high concentrations there is evidence linking aluminum to effects on the nervous system, with possible connections to several diseases, such as Parkinson's, Alzheimer's, and Lou Gehrig's disease. Patients suffering from these diseases tend to have high levels of aluminum in some areas of their brains. It is not known if aluminum is causing these diseases or if the aluminum starts accumulating in people that already have the diseases. There is also some concern that aluminum may cause skeletal problems. There is no evidence to suggest that aluminum affects reproduction, or that it causes cancer.
There are currently no Canadian guidelines with regard to aluminum, but guidelines are being developed by Health Canada in co-operation with the provinces. Recommendations for aluminum levels in drinking water have been made by several organizations and agencies, such as the American Water Works Association [AWWA] and the U.S. Environmental Protection Agency [USEPA]. The AWWA recommends that concentrations of aluminum in drinking water should not exceed 0.05 parts per million (0.05 ppm or mg/L) and the USEPA recommends that the level not exceed 0.2 ppm. Future health guidelines will likely centre on the amount of free aluminum rather than total aluminum, which includes aluminum that is likely not taken up by the human body.
Prairie water often contains aluminum levels above these recommendations, but most of the aluminum in this water is in bound form. Through water treatment, total levels of aluminum can be substantially reduced. For example, in the City of Edmonton, which treats water with a total aluminum content of 1 mg/L, levels are reduced by 70% to 0.3 mg/L in the water which reaches the consumer.
Some point-of-use water treatment devices, such as distillation and reverse osmosis, are effective in removing aluminum from water. The cost of these devices is approximately $300 to $500, and they produce 10 to 50 L of water per day.
Information in support of this article was obtained from several sources including Health Canada, Ottawa and Agency for Toxic Substances and Disease Registry, Atlanta, Georgia.
To contact the author, write to:
Saskatchewan Research Council,
15 Innovation Blvd., Saskatoon,
SK S7N 2X8, Canada.
Reprinted from Prairie Water News (Volume 7, Number 1)
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