One of the hotly debated topics in water quality is the addition of fluoride into drinking water. Fluoride is any binary compound of fluorine combined with another element. Chlorine is naturally found as a trace element in nearly all soils. Because fluoride is believed to help reduce tooth decay, it is widely used in municipal water supplies at a rate of about 1 mg/L of a fluoride salt.
As a contaminant, Fluoride is designated as Fluoride (F). It is designated in drinking water as Fluoride, F-. In the United States there are guidelines to indicate safe levels of fluoride within water. The Maximum Contaminant Level, known as MCL, is the highest level that a contaminant is allowed to be in drinking water. Fluorides MCL is 4.0 mg/L or parts per million. The MCL is an enforceable standard set by the federal government.
The National Secondary Drinking Water Regulations, known as NSDWRs, or secondary standards, are guidelines but are not enforceable standards, which are levels at which cosmetic effects may be observed such as skin discoloration or tooth discoloration; or at which aesthetic effects like odor, color or taste are observed in the drinking water. The secondary standard for fluoride is set at 2 mg/L or ppm. Although the secondary standards are recommended by the EPA, it does not require compliance by federal laws, but states can decide whether they will enforce these standards.
The World Health Organization (WHO) also has set a guideline for fluoride contaminant levels to be 1.5 mg/L.
According to the Water Quality Association (WQA), sources of fluoride contamination are from natural deposits, and potentially poorly monitored or malfunctioning feeding equipment causing a spike in the fluoride level within a municipally treated drinking water.
The effects of fluoride contamination can be significant. For example, long-term contamination of greater than 4 mg/L can lead to skeletal fluorosis which is a serious bone disorder causing extreme density and hardness as well as significant fragility of the bones, resembling osteoporosis.
Less serious but potentially aesthetic effects include discoloration of teeth in children less than nine years old from long-term consumption of greater than 2 mg/L, referred to as mottling. Other effects can be disfiguration or pitting of teeth in children.
There are several treatment methods that can help reduce the level of fluoride in the water that is delivered to the home. Treatment types can be either point of entry (POE) or point of use (POU). They include reverse osmosis, distillation, activated alumina absorption media, or strong base anion exchange (Cl- form). According to the WQA fluoride fact sheet, rejection rates of 80 to 90% are achievable with reverse osmosis using a cellulose acetate/cellulose triacetate (CA/CTA) membrane when the pH is in the 4 to 8.5 range, or up to 95% using thin-film composite membranes (TFC) in the 3 to 11 pH range. The WQA fact sheet also indicates electro dialysis, deionization, and distillation to also be effective treatment processes. High quality alkaline water ionizers are an excellent POU water purification system for homeowners.
Due to the common practice of fluorination in municipal water supplies, and the significant risks associated with long-term fluoride contamination, families should seriously consider a robust POE or POU fluoride reduction method for their drinking water.