Fluoridation of public water supplies has raised concern of fluorosis, a childhood dental condition brought on by high levels of fluoride. This has also sparked interest in whether common household reverse osmosis purification systems can remove fluoride. Fluorosis in its mildest form shows up as white streaks or specks on a child's teeth. In its most severe form, the stains are black or brown and there is pitting or cracking on the teeth as well. The condition affects children between ages 1 and 4 (those older than 8 are immune) because these are the most critical years in the development of teeth. The degree of tooth damage depends on other factors, too, including the levels of fluoride ingested and individual reactions. The American Dental Association still supports water fluoridation as the top public solution for preventing tooth decay. The ADA also notes that fluorosis is a cosmetic issue and not a serious disease.
Still, many with fluorosis concerns want fluoride removed from their water. Removing fluoride from public drinking water can be performed several ways. Reverse osmosis is the most common method. It can remove particles and compounds smaller than water molecules, including fluoride. The process takes out as much as 90 percent of fluoride in drinking water. The reverse osmosis process starts with water being forced through a filter or membrane in a reversal of the natural process of osmosis. In nature, the less concentrated solution (water free of minerals, for example) will move to dilute solutions with higher concentrations. Tiny holes in the membrane let water move past. However, compounds such as fluoride that are bigger than water molecules become trapped, according to the Water Quality Association. Water from the higher concentration solution moves through the filter to a solution of lower concentration, resulting in water free of particles, minerals and other contaminants.
A typical reverse osmosis filtration system in the home uses one of two types of membranes. A TFC or thin film composite membrane more effectively traps contaminants. A CTA or cellulose triacetate membrane fares better in water containing a lot of chlorine. Though the reverse osmosis process can remove fluoride, the amount depends largely on the membranes (and the size of the microscopic holes that allow water through). It's a good practice to check with the membrane manufacturer to determine the amount of fluoride the membrane can remove.