New Delhi: A new study has found a significant association between fluoride exposure and Intelligence Quotient (IQ) levels in children, based on the analysis of data from 10 countries, including India. The higher a child’s fluoride exposure, the lower their IQ is likely to be in contrast to if they were not exposed.
The multi-country report—titled ‘Fluoride Exposure and Children’s IQ Scores: A Systematic Review and Meta-Analysis’ and published in the medical journal JAMA Pediatrics this week—said that for every 1 mg/litre increase of fluoride in kids’ urine, there is a decrease of 1.63 IQ points.
The countries from where studies were analysed included China, Canada, Denmark, Iran, Mexico, New Zealand, Pakistan, Spain, and Taiwan, apart from India.
From India, 12 studies were included in the analysis—the second highest after China from where 45 studies were analysed for the report.
The researchers, associated with the National Institute of Environmental Health Sciences under the US National Institute of Health, found that water and water-based beverages are the main sources of systemic fluoride intake. However, an individual’s total exposure also reflects contributions from other sources, such as food, dental products, industrial emissions, and pharmaceuticals.
Fluoride from natural sources occurs in groundwater and community water systems and in the US and some other countries, but not India, fluoride is added to public drinking water systems or salt for the prevention of tooth decay.
The analysis underlines that although the estimated decreases in IQ may seem small, research on other neurotoxicants has shown that subtle shifts in IQ at the population level can affect people who fall within the high and low ranges of the population’s IQ distribution.
For context, a 5-point decrease in a population’s IQ would nearly double the number of people classified as intellectually disabled.
The researchers said that the latest evidence “may inform future comprehensive public health risk-benefit assessments of fluoride exposures”.
Growing evidence of fluoride’s neurotoxic effects
According to the World Health Organization, the safe limit of fluoride consumption is 1.5 parts per million (ppm), or milligram (mg) per litre. However, in 2022, the Indian government conceded that fluoride beyond the permissible limit had been detected in 370 districts across 23 states.
An important study carried out by researchers from India, Sweden and Iran in 2019 underlined that the pooled concentration of fluoride in groundwater in India was found to be around 2.37 mg/L and that fluoride concentration in rural parts of the country was 1.85 times higher than in urban areas.
The trace element fluoride has been considered important for the prevention and management of dental caries, considered a global health issue, especially in paediatric populations, said a public health dentist associated with the Maulana Azad Institute of Dental Sciences in Delhi, who wished to not be named.
In nature, this mineral can be found in different amounts in water, plants, and food. In India, rock salt is considered a main source of fluoride, the public health dentist said.
But, in addition to the beneficial effects of fluoride on dental caries, there has long been evidence of adverse health effects deriving from the chronic overexposure to this element—such as dental and skeletal fluorosis. The symptoms of fluorosis may vary from mild discolouration in permanent teeth to permanent damage in the body and the skeleton—mainly in kids. India is considered an endemic country for fluorosis.
Of late, evidence has also been gathering of possible neurotoxic effects—changes in the nervous system due to a toxic substance—of excess fluoride exposure in children, mainly due to the capacity of fluoride to accumulate in brain regions responsible for memory and learning, affecting them through oxidative stress.
Oxidative stress is an imbalance of free radicals (highly reactive, unstable oxygen molecules) and antioxidants in the body, which can lead to cell and tissue damage, and may play a role in the development of chronic inflammation and various diseases.
(Edited by Sanya Mathur)
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