The practice of water fluoridation has been controversial from day one. It was first introduced in the U.S. in the 1940s, when Grand Rapids, Mich. added fluoride to its public water supply in the wake of wide evidence that fluoride helps strengthen teeth and supports oral health. Many of us use toothpaste with fluoride in it for this purpose, and organizations like the American Dental Association and the International Dental Federation believe that drinking water with added fluoride can help our teeth in much the same way that toothpaste does. After the World Health Organization's 1969 endorsement, countries throughout the world began fluoridating their drinking water.
However, in the 1970s through the1990s, some European countries reversed their stance. Countries like Germany, Sweden, the Netherlands and Finland discontinued fluoridation, while France never even started. The exact reasons for the policy change depend on who you ask. Some sources say it's because the proclaimed benefits weren't panning out or because the logistics just weren't practical for certain areas. Others claim it's because, technically, fluoride can be poisonous.
Poisonous? Yes -- but then, lots of the things we ingest are potentially poisonous, like alcoholic beverages, the mercury in fish and the magnesium in antacids. It would be very hard to consume enough antacid medicine to die from magnesium poisoning, though.
At what dosage level does fluoride become harmful? How much is in the U.S. water supply? Next, we'll learn what can happen if we ingest too much of it.
Most of us know fluoride as the stuff that's in our toothpaste. Fluoride is a molecule containing the element fluorine (F) -- and you get it when you combine fluoride with another element. The fluoride added to water is usually either hexafluorosilicic acid (H2SiF6) or sodium hexafluorosilicate (Na2SiF26). But fluoride occurs naturally in all sorts of places, including some tea leaves, seaweed, soil and rocks. It's put in toothpaste and mouthwash to prevent tooth decay, but it's also added to rat poison and insecticides to kill stuff.
Most fluoride toxicity cases occur when someone ingests such poisons or insecticides. It's one of the reasons people child-proof their homes. When someone (typically a child) swallows fluoride, it hits the stomach and forms hydrofluoric acid, which can irritate and corrode the stomach lining. Once the gastrointestinal (GI) tract absorbs the fluoride, it causes, at the very least, bad stomachaches and diarrhea. It can cause serious GI problems and sometimes even seizures at doses of above 3 mg/kg. At doses of 5 to 10 grams for an adult, or 500 mg for a child, fluoride poisoning can damage major organs and cause death.
But that's not the kind of fluoride poisoning people are talking about when they discuss fluoridating water. They're talking about a less immediate form of fluoride toxicity that can result from drinking over-fluoridated water over a significant period of time -- like years. In this type of fluoride poisoning, the most commonly reported effects are dental and skeletal fluorosis -- conditions that weaken the teeth and bones, ironically.
The thing is, our drinking water already has fluoride in it, even without adding a thing. In drinking water, you'll find naturally occurring fluoride in amounts ranging from 0.05 parts per million (ppm, or mg/L) and 14 ppm [source: Bender]. The EPA set the highest safe amount at 4 ppm, so that upper-level 14 ppm is considered dangerous. The reason some states and countries add fluoride is because the low end of natural occurrence -- that 0.05 ppm -- is considered to be too low to help strengthen teeth. About 60 percent of U.S. cities fluoridate public drinking water to achieve levels of about 1 ppm. According to the American Dental Association, the optimal dose varies from 0.7 ppm to 1.2 ppm [source: ADA]. The U.S. National Academy of Sciences even recommends a daily intake of 1.5 mg to 4 mg a day [source: Drugs.com] to support healthy teeth and bones.
So if the right amount of fluoride has such appealing health benefits, and we can control the amount of fluoride in drinking water, why has most of Europe rejected water fluoridation? In the next section, we'll see what the big debate is all about.
The Fluoridation Debate
The most common argument against fluoridation is pretty simple: In excessive doses, fluoride causes health problems -- so why risk it? Fluoride can cause discoloration or corrosion of teeth (dental fluorosis) and it can possibly weaken bones (skeletal fluorosis). In the 1990s, the U.S. Public Health Service noted an increase in dental fluorosis in fluoridated areas since the 1940s, when water fluoridation began. But the evidence is considered inconclusive because lots of products (like toothpaste, mouthwash and dietary supplements) now contain fluoride that didn't 60 years ago. So it's hard to know where the fluoride overdose is coming from -- the water or the toothpaste.
But in March 2006, the National Research Council declared that the U.S. EPA is allowing levels of fluoride in drinking water that could damage children's teeth. At water-fluoride levels at or above 4 ppm (or 4 mg/L), there is evidence to suggest that consumption could increase the risk of serious fluorosis [source: Prevention].
The National Academy of Sciences estimates that as of 1992, more than 200,000 people in the U.S. were drinking water with fluoride levels above 4 ppm. The NAS states that levels above 2 ppm can cause cosmetic dental issues like white spots on teeth, a very mild form of dental fluorosis [source: NAS]. This may seem like a cut-and-dry case for discontinuing water fluoridation, but the ADA points out that while these levels surpass the optimal fluoridation level for dental benefits, they're still safe -- 4 ppm is what the EPA has set as the maximum amount of naturally occurring fluoride. Above that level, cities are supposed to remove fluoride before the water is considered safe.
It's proven that ingesting high levels of fluoride can cause health problems, and the EPA has been regulating fluoride as a drinking-water contaminant for decades. But from there, the case gets hazy, since so many experts set forth the case that adding small amounts of fluoride to the public water supply can safely decrease the incidence of dental problems. Organizations like the U.S. Public Health Service, the Centers for Disease Control and Prevention, the National Cancer Institute, the International Dental Federation and the World Health Organization all believe that water fluoridation is a health benefit. In 1999, the CDC actually named water fluoridation on the top 10 list of 20th century health achievements.
The debate about the risks and benefits of fluoride will continue until not only the scientific community but also the general public can agree on the matter. The biggest argument against fluoride is that it damages children's teeth, and there's some evidence to that effect.
Many countries, including the U.S., Canada, Ireland, Australia and New Zealand, still fluoridate drinking water (and about 10 percent of the British population drinks fluoridated water). Germany, France, Belgium and Switzerland do not -- although some of those countries do fluoridate their table salt.
Most organizations and countries agree, however, that infants shouldn't ingest extra fluoride. In November 2006, the American Dental Association recommended against giving fluoride-enhanced products to children less than one year old. Studies have shown that infants who drink fluoridated water are at significant risk for dental fluorosis. For decades, parents have been warned to supervise young children brushing with fluoride toothpaste so they don't swallow a mouthful of the stuff.
Clearly, there are risks associated with fluoride consumption. What people can't seem to agree on is whether fluoridated water carries risks for adults and whether those risks outweigh the possible benefits to oral health.
To learn more about fluoride, look over the links on the next page.
Related HowStuffWorks Articles
More Great Links
- Bender, David A. "Bender's Dictionary of Nutrition and Food Technology (8th Edition)." Woodhead Publishing.
- Fluoride. National Institute of Dental and Craniofacial Research. http://www.nidcr.nih.gov/HealthInformation/DiseasesAndConditions/Fluoride/
- Fluoride in Drinking Water: A Scientific Review of EPA's Standards. The National Academy of Science. http://dels.nas.edu/dels/rpt_briefs/fluoride_brief_final.pdf
- Fluoride Toxicity. eMedicine. http://www.emedicine.com/emerg/topic181.htm
- Gower, Timothy. The Danger in Your Water. Prevention.com. http://www.prevention.com/cda/article/the-danger-in-your-water/319972e50d803110VgnVCM10000013281eac____/health/healthy.lifestyle/wellness
- "National Research Council Issues Report on EPA Standards for Fluoride in Drinking Water." American Dental Association. http://www.ada.org/prof/resources/topics/science_fluoride_water.asp
- New Fluoride Warning for Infants. Mothering Magazine. November 2006. http://www.mothering.com/sections/news_bulletins/november2006.html#fluoride
- Oral Health. Rhode Island Department of Health. http://www.health.ri.gov/disease/primarycare/oralhealth/prevention-fluoridation-map.php
- Prevention Magazine Looks at Water Fluoridation. ADA.org. http://www.ada.org/prof/resources/topics/science_fluoridation_prevention.asp
- Review of Fluoride: Benefits and Risks. Public health Service. http://health.gov/environment/ReviewofFluoride/
- "Sodium Fluoride (Systemic).Drugs.com. http://www.drugs.com/cons/sodium-fluoride.html
- Water Fluoridation: Questions and Answers. Ireland Dental Health Foundation. http://www.dentalhealth.ie/information/index.tmpl?secid=20020822160750&subid=20020828150540
- Ziegelbecker, Rudolf. International Society for Fluoride Research. http://www.fluoride-journal.com/98-31-3/313-171.htm