New Study: No Neurotoxic Effect
In recent years, opponents of community water fluoridation (CWF) have pointed to some studies as supporting their concerns that fluoride is a neurotoxin that can lead to lower IQs or cognitive scores among children. Experts have examined those studies and cited significant weaknesses or limitations. Nonetheless, researchers in multiple countries have continued to explore this issue carefully. In each case, they have found no link or a weak link between the levels of fluoride found in fluoridated water and lower IQs.
The latest study, published in February, was conducted by a team of environmental scientists with the support of the National Toxicology Program (NTP) Division of the National Institute of Environmental Health Sciences (NIEHS). These scientists examined rats that consumed water and food with different concentrations of fluoride, including fluoride exposure during prenatal development. At these exposure levels, the researchers wrote that they “observed no exposure-related differences in motor, sensory, or learning and memory performance” for any of the nine different tests they conducted. Furthermore, thyroid hormone levels (TSH) were not altered as a function of 10 or 20 parts per million (ppm) of fluoride.
The only side effect the NIEHS study found—inflammation of the prostate gland—occurred only at a fluoride exposure that created levels in the animals equivalent to more than five times higher than the level humans experience by drinking fluoridating water.
When the NIEHS study was first announced, the leading anti-fluoride group welcomed the news and declared that the results of this study “could end fluoridation” around the world. We hope this group will pay close attention to the NIEHS study findings even though the results disprove their claims.
The NIEHS is not the only study that reinforces the safety of fluoride at the levels used for water fluoridation. In 2015, a New Zealand study examined fluoride and IQ scores for more than 1,000 people who were followed over a 31-year period. Many of them lived in communities with fluoridated water, and others lived in non-fluoridated areas. The New Zealand researchers concluded that their findings “do not support the assertion that ﬂuoride exposure . . . can affect neurologic development or IQ.”
Years earlier, Dr Gary Whitford, a professor at Georgia Health Sciences University, led a fluoride animal study examining chronic ingestion of fluoride at levels up to 230 times the exposure for humans whose main source is fluoridated water. The Whitford study showed that even this level of exposure had no significant effect on learning.