I am a pediatrician who emigrated from Hong Kong more than 20 years ago.
When I started seeing kids here, I was immediately struck by the cavity problem. I looked into the data and found that we have a higher rate of dental caries than Pittsburgh or the nation as a whole.
When I was invited to be a member of the local water fluoridation committee, I used my academic skill and resources to dig deep into all the data available to the public. I reviewed all the original articles in English about water fluoridation from 2010 to 2013. I found that water fluoridation is safe and effective. There is no controversy among the scientific and medical community. There may be individual doctors or scientists with different opinions, but scientific and medical organizations have reviewed the data and endorse water fluoridation.
Assertions have been made that European countries, such as Denmark, Norway, Finland and Sweden, have very low dental caries rates despite no water or salt fluoridation. The picture is very different when you look at Eastern Europe or Asia. The named countries are known for their high gross domestic product per capita, socialism and social equality. They provide free dental care for all children under 18 and subsidized adult care. We do not have these benefits in the U.S. and are unlikely to have them in the future.
In Asia, the rate of cavities in Korea, Japan and Malaysia are much higher than in the U.S. The exceptions are Hong Kong and Singapore. Both are previous British colonies and have the water supply 100 percent fluoridated. Let us look at the situation in Hong Kong and Macau. Hong Kong was a British colony in the past while Macau belonged to Portugal. They are located on the opposite side of the Pearl River. They have the same ethnic origin, language, diet and culture. Hong Kong has had the water fluoridated since 1962 while Macau never has. As expected, the rate of caries was way higher in Macau.
Recently a review article published in Lancet by a Harvard professor suggested that fluoride could be a neurotoxin. To support his argument, he quoted only one article of meta-analysis published in 2012 by a Harvard research scientist titled “Developmental fluoride neurotoxicity: a systematic review and meta-analysis.” Meta-analysis means grouping many studies together and analyzing the data. It included 27 studies — 25 from China and two from Iran. All compared IQ from very high natural occurring fluoride (around 3 to 11 parts per million) areas to that of a low fluoride area. Many of the low fluoride areas actually have fluoride levels around 0.4 to 0.7 ppm, which are usually considered optimal fluoridation levels.
Even if the data were valid, fluoride is safe at 0.7 ppm, the level of water fluoridation. My concern is that most of the studies were published in Chinese. Usually if a Chinese scientist has a good study, he or she would submit to a prestigious international journal first. If rejected, he or she would try less prestigious one. Only as the last resort would one submit to a Chinese-language journal. Most, if not all, of the studies published in Chinese are very poor in quality.
There are areas in U.S., United Kingdom, and Europe with very high levels of natural fluoride. Why don’t we see studies on IQ here? The Program for International Student Assessment of the Organization for Economic Co-operation and Development had done an evaluation of high school students in many countries all over the world. They studied thousands of children in each center. They found that the IQ equivalent score of Hong Kong is about five points higher than that of Macau. Does that mean the fluoride in the water improves the IQ? Actually, it is quite plausible. There are many studies showing that dental caries have a very significant detrimental effect on learning. It would not be a surprise that a higher rate of dental caries could be associated with the lower IQ in Macau.
Another common concern is the possibility of the link of water fluoridation and osteosarcoma, a type of bone cancer. Several animal studies have been conducted but only one found that fluoride exposure may increase osteosarcoma formation in rats. In 2000, a Harvard Ph.D. student studied the link of water fluoridation and osteosarcoma. It involved 103 patients. She found that for patients with osteosarcoma, males had a statistically higher exposure to fluoride at the age of 7. Females did not have a higher exposure, nor did those of any other age. Since then, there were five more studies published. One was a case control study with 142 patients with osteosarcoma comparing them with other bone tumors in bone fluoride content. Another four studies were ecology studies through the cancer registry in U.S., United Kingdom, New Zealand and Ireland respectively. All five studies did not show any association.
The one study in the U.K. involved 2,566 patients with osteosarcoma from 1980 to 2005. The sample size was so large that the 90 percent confident interval for relative risk was very narrow at 0.77 to 1.12. That means it would pick up the association 90 percent of the time if the prevalence is just 12 percent more. That is a lot of technical jargon. All I want to say is that the chance of a real link between fluoride and osteosarcoma is very, very small.
Another common complaint is that there are no double-blind randomized control trials in the evaluation of the effectiveness of water fluoridation in preventing dental caries. It is technically impossible to have such a study done. The people who assess the DMFT score (a measure of dental caries) would definitely know whether the water is fluoridated. But there is another way to assess the severity of the dental caries problem — the money used in dental procedures.
Recently there was a study in New York state comparing the number of restorative, endodontic and extraction procedures per recipient between fluoridated counties and non-fluoridated counties. It found that it was 33.4 percent more in the non-fluoridated counties while there is no difference for the non-dental related procedures. It translates into $23.63 saving per Medicaid recipient. It did not take into account of the economic savings in the private sector, nor the time lost for the parents from work, the child in school and the psychological and physical suffering. Similar results were found earlier in Louisiana and Texas. Just last month, a study in the U.K. using extraction rates as the marker also found that it was much higher in the non-fluoridated area.
Water fluoridation has been shown to be associated with higher incidence of fluorosis. Forty-one percent of 12-year-old kids in the U.S. have dental fluorosis. Yes, 41 percent! I was surprised when I first noticed the number. Since then, I pay more attention to the white spots on the teeth of my patients. I found that actually it was quite common. They are so tiny and not obvious that you would miss them easily.
Fluorosis happens in Meadville even though there is no water fluoridation. There is fluoride in toothpaste and many commercial beverages. However, I do not see it as a problem. I would say it is a plus. There are fewer cavities! Do you know anyone who lives in Erie or Pittsburgh? Ask them if they have heard about fluorosis from their dentist. Do their kids have fluorosis? Most would not even know that there was any controversy.
I have looked into nearly all the aspects — incidences of mechanical failure in the water plants, effect for patients with chronic kidney disease, the infant formula issue, lead and arsenic contamination, impact of health inequality, hip fractures, kidney stones, hypothyroidism, bladder cancer, other cancers, birth defects, osteosarcoma in pets, environmental effects and more. I have no tie to big industry or government. I have studied the data myself independently. If anyone has any questions, please email me at email@example.com and let us discuss the issues in detail. A more expanded version of this column is posted at meadvillesmiles.com.
Dr. Raymond Leung is in medical practice at Meadville Pediatrics on Liberty Street.
Dr. Raymond Leung of Meadville welcomes questions and comments from readers interested in learning more about fluoride. You may reach him at firstname.lastname@example.org.