In the vast majority of communities where water fluoridation is present, hydrofluosilicic acid is used as the fluoridation chemical. This chemical is produced as a byproduct of fertilizer and aluminum manufacturing.
The Cominco phosphate mine in Trail, British Columbia Canada is a major supplier of hydrofluosilicic acid for western Canada and the Pacific Northwest. The table below lists the results of a Cominco heavy metal chemical analysis of a solution of hydroflusilicic acid from their phosphate plant.
The data was published in the Alberta Report on February 17, 1992.
There is reason for concern. The National Academy of Sciences has shown that levels of arsenic in drinking water, in amounts LESS than shown above, is known to cause cancer. Chromium in drinking water, is also is linked to cancer.
In addition to fluoride, sodium hydroxide (commonly known as lye) is typically added to the the water supply to provide pH adjustment. The exact quantities vary by each area.