Scientific Consensus Statement on Environmental Agents Associated with Neurodevelopmental Disorders

In 2007, a Scientific Consensus Statement, developed by the Collaborative on Health and the Environment’s Learning and Developmental Disabilities Initiative (see panel of scientists) was issued, outlining the current understanding of links between environmental factors and developmental disabilities in children.

Fluoride was discussed as a substance of concern.


“The central question, which is still unresolved, is what level of exposure results in harmful health effects to children. Children’s small size means that, pound-for-pound of body weight, they receive a greater dose of fluoride than adults.”

“The primary question remains as to whether exposures to fluoride via multiple routes of exposure, from drinking water, food and dental-care products, may result in a high enough cumulative exposure to contribute to developmental effects.”

“…emerging science suggests we need to further study the dose at which fluoridation may increase risks of neurodevelopment disorders, cancer and skeletal or dental fluorosis, particularly for sensitive individuals.”

“The CDC estimates that up to 33% of children may have dental fluorosis because of the excessive intake of fluoride either through drinking water or through other sources — an estimate which is supported by other studies. This concern has resulted in CDC issued a recommendation to limit fluoride exposure in children under eight years of age and to use fluoride-free water when preparing infant milk formula.”

“In addition, some recent studies suggest that excessive ingestion of fluoride lowers thyroid hormone levels, which is particularly critical for women with subclinical hypothyroidism. Decreased maternal thyroid levels are known to adversely affect fetal neurodevelopment.”

The statement concludes:

“Given the serious consequences of learning and developmental disabilities, a precautionary approach is warranted to protect the most vulnerable of our society.”

Children at heightened risk

“The development of the human brain begins in utero and continues through adolescence, following a precise and delicate step-by-step sequence involving complex neurobiological processes… The long and complex development of the brain and nervous system leaves it susceptible to the adverse effects of chemical exposures.”

“For their body weight, children eat and breathe more than adults, thus a small exposure translates into a big dose.”

“Their organ systems, particularly the nervous system, are forming and are thus more susceptible to the effects of chemicals.”

“Children are often more susceptible than adults to the effects of exposure to environmental agents.”

“Children lacking certain nutrients are more vulnerable to toxicants. For example, iron and/or calcium deficiency affects the absorption and toxicity of heavy metals such as lead and manganese.”

Fluoridating agents increase the body burden of lead. (See lead studies.)

“Even very low doses of some biologically active contaminants can alter gene expression important to learning and developmental function.”

Variations in individual susceptibility

“Due to genetic variation people differ in susceptibility to exposures. Not identifying and studying susceptible subgroups can result in failure to protect those at high risk.”

“As our testing methods have become more sophisticated, the recognition of individual sensitivity and, in particular, the sensitivity of the developing nervous system to the effects of environmental agents has

“Recent biomonitoring studies reveal the range of compounds we are exposed to and that accumulate in our bodies. Experiments with single chemicals can underestimate the effects of these chemicals in mixtures.”

Fluoride is known as a persistent bioaccumulator. About 50% of each ingested amount is retained in the body, particularly in bone.

Where science meets the roadblock of policy

“[Despite 2000 years of knowledge that it affected the brain], lead was added to paint and gasoline, removed only following considerable research that confirmed what was already known.”

Similarly, fluoride’s toxicity has been known since the 1800s. (See science and reviews.) 

“Lead is probably the most studied of environmental contaminants. Its effects on development and learning are undisputed. Recent research indicates there is no safe level of lead exposure for children. Lead exposure impairs overall intelligence and is associated with ADHD, even at minute exposures. Efforts to prevent lead exposure provide an outstanding example of the struggle when science meets policy. The US CDC has not adjusted the blood-lead action level since 1990 despite scientific evidence of behavioural effects well below 10 micrograms per deciliter (μg/dL).”

Fluoridation increases exposure to, and uptake of, lead. (See lead studies.)

We propose that fluoridation is an equally outstanding example of the clash between science and policy.

Low dose effects differ high dose effects

“The very low-dose effects of endocrine disruptors cannot be predicted from high dose studies, which contradicts the standard ‘dose makes the poison’ rule of toxicology.”

Fluoride was classified as an “endocrine disruptor” in 2006 by the U.S. National Research Council. (See NRC Review 2006.)

 Panel members

David Bellinger, PhD, MSc, Harvard Medical School
Lynn Goldman, MD, MPH, Johns Hopkins University, Bloomberg School of Public Health
Philippe Grandjean, MD, Harvard School of Public Health
Martha Herbert, MD, PhD, MAssachusetts General Hospital
Philip Langrigan, MD, MSc, Mount Sinai School of Medicine
Bruce Lamphear, MD, MPH, University of Cincinnati
Barbara McElgunn, RN, Learning Disabilities Association of Canada
John Meyers, PhD, Environmental health Sciences
Isaac Pessah, PhD, University of california, Davis
Ted Schettler,MD, MPH, Science and Environmental Health Network
Bernard Weiss, PhD, University of Rochester School of Medicine and Dentistry

The 57 signatories to this Scientific Consensus Statement comprise scientists, researchers and medical professionals from leading American institutions, including Harvard Medical School, John Hopkins University, and the University of Rochester.

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