(NewsNation) — Researchers highlighted concerns that fluoride exposure from multiple sources, including water, foods and dental products, potentially impacts child neurodevelopment and IQ scores in a new study published in JAMA Pediatrics.
The new research, led by scientists at the National Institute of Environmental Health Sciences, analyzed 74 studies that measured fluoride in drinking water and urine samples from 10 countries, including Canada, China, Denmark, India, Iran, Mexico, Pakistan, New Zealand, Spain and Taiwan.
For every 1mg/L increase in urinary fluoride, children’s IQ dropped by 1.63 points, according to the study.
The World Health Organization set the safe fluoride limit at 1.5 mg/L, while the U.S. recommends 0.7 mg/L in drinking water.
Meanwhile, a U.S. government report found that fluoride levels in drinking water twice the recommended limit are linked to lower IQ in children.
Based on studies from Canada, China, India, Iran, Pakistan, and Mexico, the National Toxicology Program concluded with “moderate confidence” that high fluoride exposure is associated with decreased IQ.
The report didn’t specify how many IQ points might be lost at different levels of fluoride exposure. However, some of the studies reviewed in the report suggested IQ was 2 to 5 points lower in children who’d had higher exposures.
The U.S. Centers for Disease Control and Prevention (CDC) recommends 0.7mg/L fluoride. Around 1.9 million Americans have water with fluoride levels of about 1.5mg/L.
Fluoride strengthens teeth and reduces cavities by replacing minerals lost during normal wear and tear, according to the CDC. The addition of low levels of fluoride to drinking water has long been considered one of the greatest public health achievements of the last century.
The report calls for more research on lower fluoride levels and their effects on adults.
The Associated Press contributed to this report.