Is Fluoride safe in drinking water?

Prolonged consumption of drinking water with high fluoride levels can lead to skeletal fluorosis, a bone disease characterized by joint pain, stiffness, and an increased risk of fractures.

Why here

Fluoride accumulates in bone tissue over many years when ingested through drinking water, replacing calcium and making bones dense yet brittle.

What would have to be true

Skeletal fluorosis typically develops after consuming 10 to 20 milligrams of fluoride daily for 10 to 20 years, often from drinking water with naturally high fluoride levels, typically above 4 parts per million (mg/L). The World Health Organization (WHO) recommends fluoride levels below 1.5 mg/L, while the U.S. EPA sets a primary maximum contaminant level (MCL) of 4.0 mg/L to prevent this condition.

The other side

The risks of skeletal fluorosis are associated with excessive fluoride intake, not the controlled levels used in community water systems, which are typically around 0.7 mg/L.

Excessive fluoride intake during the first eight years of life can cause dental fluorosis, a cosmetic condition that manifests as white lines or streaks on developing teeth.

Why here

Ingestion of fluoride through drinking water during the critical period of tooth formation in childhood affects the mineralization of tooth enamel.

What would have to be true

Dental fluorosis occurs in children when fluoride levels in drinking water exceed 2.0 mg/L. The U.S. Public Health Service (USPHS) recommends an optimal fluoride concentration of 0.7 mg/L for cavity prevention while minimizing dental fluorosis.

The other side

In most cases, dental fluorosis is mild and primarily a cosmetic concern that does not impact the health or function of the teeth.

A federal court has found that the optimal level of drinking water fluoridation (0.7 mg/L) poses an unreasonable risk of reduced IQ in children and has ordered the U.S. Environmental Protection Agency (EPA) to initiate rulemaking under the Toxic Substances Control Act (TSCA).

Why here

Ingestion of fluoride through drinking water during early childhood development is suggested to impact neurocognitive function.

What would have to be true

Drinking water fluoridated at 0.7 mg/L.

The other side

The EPA's established maximum contaminant level (MCL) for fluoride is 4.0 mg/L, a standard designed to prevent known or anticipated adverse health effects. The Centers for Disease Control and Prevention (CDC) and U.S. Department of Health and Human Services (HHS) recommend 0.7 mg/L as the optimal level for dental benefits with minimal side effects, and EPA previously stated this level provides the best balance of benefit to potential harm.

Some studies and reviews suggest fluoride may act as an endocrine disruptor, potentially affecting thyroid function (e.g., increasing TSH and decreasing T3/T4 levels) and sex hormone levels, especially at higher exposure levels or in individuals with iodine deficiency.

Why here

Systemic absorption of fluoride from drinking water can interfere with endocrine gland function.

What would have to be true

Chronic exposure to fluoride in drinking water, particularly at higher levels (e.g., above 1.5 mg/L) or in populations with iodine deficiency.

The other side

Other studies and reviews, including by the Agency for Toxic Substances and Disease Registry (ATSDR) and European Food Safety Authority (EFSA), have concluded that fluoride is not considered an endocrine disruptor or that the evidence of effects on thyroid function at concentrations below 1.5 mg/L is inconclusive and less robust, with some in-vitro studies showing no effects on endocrine disruption targets at relevant concentrations.

Higher levels of fluoride exposure, particularly from drinking water containing more than 1.5 mg/L, are associated with lower IQ scores in children, with some scientific bodies concluding moderate or reasonable confidence in this association.

Why here

Systemic fluoride uptake during early brain development is suspected of causing adverse neurodevelopmental effects.

What would have to be true

Drinking water with fluoride levels greater than 1.5 mg/L. Some studies suggest effects below 1.5 mg/L, but with more uncertainty.

The other side

The National Toxicology Program (NTP) review was designed to evaluate total fluoride exposure from all sources and found insufficient data to determine if the low fluoride level of 0.7 mg/L currently recommended for U.S. community water supplies has a negative effect on children's IQ. Some studies also state that the causal relationship between fluoride exposure and neurotoxicity remains unclear.