Fluoride Is an Industrial Byproduct of Phosphate Fertilizer Manufacturing. A Federal Court Just Ordered the EPA to Regulate It Accordingly.
Hydrofluorosilicic acid, the specific compound added to drinking water in most US municipalities for fluoridation, is recovered from smokestack scrubbers at phosphate mining and fertilizer manufacturing facilities. Before water utilities began purchasing it, this substance was classified as a regulated industrial hazardous waste requiring expensive disposal. Water fluoridation converted that disposal problem into a revenue stream. That is where the fluoride in your tap water comes from.
In September 2024, US District Judge Edward Chen in San Francisco ordered the Environmental Protection Agency to take regulatory action on fluoride after a federal bench trial in which he reviewed 72 human studies and found that fluoride poses an unreasonable risk of neurotoxic harm to children at concentrations used in US water systems. The EPA had contested the finding throughout the trial. The court ordered it to act anyway.
What the 2024 Federal Court Ruling Found
The case was Food and Water Watch et al. v. Environmental Protection Agency, filed in 2017 and decided in the Northern District of California in September 2024. The plaintiffs used Section 21 of the Toxic Substances Control Act to petition the EPA to regulate fluoride as a neurotoxic substance. The EPA denied the petition. The plaintiffs sued. Judge Chen heard the evidence.
The trial centered on the National Toxicology Program's 2024 systematic evidence review, which the federal agency completed after years of study. The NTP reviewed 72 human epidemiological studies on fluoride exposure and neurodevelopmental outcomes. Its conclusion: moderate confidence that fluoride at or above 1.5 mg/L is associated with lower IQ scores in children. The WHO's guideline level is 1.5 mg/L. The US adds fluoride at 0.7 mg/L.
The NTP is housed within the National Institute of Environmental Health Sciences, part of HHS. It is a federal scientific program, not an advocacy organization. An independent expert panel reviewed its methods and conclusions and agreed with the moderate confidence finding.
Judge Chen found that the NTP evidence, alongside supporting prospective cohort studies, established an unreasonable risk to children under TSCA's risk evaluation standard. He ordered the EPA to issue a rule addressing fluoride's neurotoxic risk. The EPA had spent years contesting the petition. It was ordered to regulate.
(Evidence level: 5 for the court order and NTP review as documented federal records. Evidence level: 4 for the association between fluoride and lower IQ in children at or above 1.5 mg/L, based on the NTP's structured systematic review.)
Where Fluoride Comes From Before It Reaches Your Tap
Phosphate mining extracts calcium phosphate rock for fertilizer production. The industrial process releases hydrogen fluoride and silicon tetrafluoride gases. Facilities capture these gases in wet scrubbers, which produce hydrofluorosilicic acid as the capture product. Without a buyer for this acid, it must be treated and disposed of under hazardous waste regulations.
Water fluoridation created the buyer. Water utilities purchase hydrofluorosilicic acid, dilute it to 0.7 mg/L, and add it to municipal water supplies. What enters the process as a scrubber byproduct from a fertilizer plant exits the process in drinking water consumed by American households, including infants fed formula prepared with tap water.
This supply chain is not disputed. It is documented in EPA and water utility records, as well as in the basic industrial chemistry of phosphate processing. The substance is not pharmaceutical-grade fluoride synthesized specifically for water treatment. It is an industrial byproduct captured from a fertilizer manufacturing emission stream, sold to municipalities, and added to the public water supply.
(Evidence level: 5. The industrial origin of hydrofluorosilicic acid is a regulatory and chemical fact, documented in EPA records and water utility procurement documents.)
The National Toxicology Program Review: What 72 Studies Show
The NTP's 2024 systematic review used a structured framework to assess the quality and consistency of 72 human studies on fluoride and neurodevelopment. It evaluated study design, exposure assessment methods, outcome measurement, and potential confounders across the full evidence base before assigning a confidence level.
The review is not the first systematic analysis to find this association. Philippe Grandjean at Harvard School of Public Health and Anna Choi led a 2012 meta-analysis of 27 human studies in Environmental Health Perspectives that found a consistent negative association between high fluoride exposure and child IQ across all reviewed studies. Grandjean subsequently described fluoride as a developmental neurotoxin in peer-reviewed publications and advocated for precautionary action at levels lower than those studied in most research.
The prospective cohort study most directly relevant to US exposure levels was published in JAMA Pediatrics in 2019 by Bruce Lanphear at Simon Fraser University, with Grandjean as co-author. The study followed 299 mother-child pairs in Canadian cities where water fluoridation levels were comparable to those in the US. Researchers measured maternal urinary fluoride during pregnancy and tracked child IQ from ages 3 to 4. Higher maternal fluoride exposure was associated with lower IQ in male offspring. The magnitude of the effect was comparable to that documented in epidemiological studies for low-level lead exposure.
The Lanphear and Grandjean study was conducted in a high-income country with fluoridation levels comparable to the US. It measured actual biomarker exposure rather than relying on assumed intake from water concentration data alone. It was part of the evidence reviewed in the 2024 trial.
(Evidence level: 4. Multiple independent studies with consistent findings. The NTP's structured review provides the most rigorous synthesis of evidence. The association at US-specific levels carries more uncertainty than at 1.5 mg/L and above.)
The Dose Question: Is 0.7 mg/L the Problem?
The most contested question in the fluoride literature is whether 0.7 mg/L, the US addition level, produces the neurotoxic effects documented at higher concentrations.
The NTP found moderate confidence for effects at or above 1.5 mg/L. The review was more cautious about effects at lower levels, where the evidence was less consistent. This distinction is real and scientifically important. The 1.5 mg/L threshold cannot be cleanly extrapolated to 0.7 mg/L without acknowledging that extrapolation involves uncertainty.
Several factors complicate a straightforward reassurance based on that threshold.
Total fluoride exposure for American children is not only from added water fluoride. Children receive fluoride from multiple sources: fluoridated tap water consumed directly, tap water used to prepare food and beverages, fluoridated toothpaste (which children swallow at higher rates than adults), fluoride gel dental treatments, fluoride mouthwash, some commercially bottled waters, foods and beverages processed using fluoridated municipal water, and pesticide residues on certain crops. Daily fluoride intake for American children in fluoridating communities frequently exceeds what 0.7 mg/L of water fluoride alone would deliver.
The Lanphear and Grandjean 2019 JAMA Pediatrics study was conducted at levels comparable to the US. It found effects at those levels. Judge Chen cited it in his 2024 ruling. It is part of the published evidence base, not a study from a region with extreme industrial fluoride contamination, and it can be dismissed as not applicable to the US.
(Evidence level: 3 for neurotoxic effects specifically at the US water addition level of 0.7 mg/L combined with other fluoride sources. The direction of the association is consistent with higher-level findings. The magnitude and certainty at this specific exposure level remain areas of active research.)
What Most of Western Europe Does Instead
France, Germany, Sweden, the Netherlands, Denmark, Finland, Norway, Austria, and Belgium do not add fluoride to municipal drinking water. Neither does Japan. These countries are among the wealthiest and most medically sophisticated nations in the world. Their public health authorities concluded that the dental benefit of fluoride is achievable through fluoridated toothpaste without systemic ingestion through water.
WHO comparative data on DMFT scores, decayed, missing, and filled teeth, shows that non-fluoridating European countries have dental health outcomes comparable to or better than the US. Their children do not have dramatically worse teeth because they do not drink fluoridated water. Their dental programs emphasize fluoride toothpaste, dental hygiene education, and sugar reduction rather than water fluoridation.
The claim that water fluoridation is necessary for population dental health is not supported by the dental outcomes of countries that have chosen not to practice it. This does not prove that water fluoridation has no dental benefit. It does establish that the benefit is not so large that countries without it suffer visibly worse outcomes than those with it.
(Evidence level: 4. WHO comparative dental health data is published and publicly available. The interpretation is stated in the policy of European public health authorities.)
The Thyroid Connection
Fluoride is a halogen, in the same chemical family as iodine. Halogens compete for the same uptake pathways in the thyroid gland. Fluoride can compete with iodine for binding to thyroid receptors and interfere with thyroid hormone synthesis when present at sufficient levels relative to iodine availability.
The clinical significance of this competition at US water fluoridation levels is contested. What is not contested is the underlying biochemistry: the competition exists, the mechanism is documented, and its relevance depends on an individual's iodine status.
National surveys document declining iodine status in segments of the US population, particularly among people who have shifted from iodized salt to specialty salts that may not be iodized. For individuals with marginal iodine intake, the competitive pressure from fluoride may be more clinically relevant than population averages suggest. Subclinical thyroid disruption can affect energy levels, weight regulation, and cognitive function without producing obvious clinical hypothyroidism on standard testing.
See article #294 on iodine, the thyroid, and halogen competition for the detailed mechanism and the full picture of thyroid health.
(Evidence level: 5 for the biochemical competition between fluoride and iodine. Evidence level: 2 for clinical significance, specifically at US water fluoridation levels in iodine-sufficient individuals. Level 3 for clinical significance in iodine-marginal individuals.)
Follow the Funding
The promotion of water fluoridation in the United States in the 1940s and 1950s involved financial interests that were not neutral about whether fluoride was safe.
The Mellon family funded the Mellon Institute, which produced research supporting fluoride's safety at a time when the evidence base for that conclusion was thin. The Mellon family held a controlling interest in ALCOA, the Aluminum Company of America. ALCOA produced fluoride as a byproduct of aluminum smelting. ALCOA had been ordered to compensate farmers near its facilities for fluoride poisoning of livestock from its industrial emissions. A finding that fluoride was safe in small quantities was beneficial to ALCOA's legal and commercial interests.
Oscar Ewing served as an attorney for ALCOA before being appointed head of the Federal Security Agency by President Truman in 1947. In 1950, Ewing's agency launched the national campaign for municipal water fluoridation. The timeline runs from an ALCOA attorney to a federal health administrator to a national fluoridation advocate in a three-year sequence.
The phosphate fertilizer industry continues to benefit from the fluoridation policy. Hydrofluorosilicic acid disposal costs money. Selling it to water utilities generates revenue. When the 2024 court ruling ordered the EPA to take regulatory action, the American Dental Association and the American Academy of Pediatrics filed comments opposing stricter regulation. Both organizations have decades of public commitment to fluoridation policy and organizational credibility tied to that position.
The NTP's systematic review and the research by Grandjean and Lanphear were conducted without industry funding. The research supporting the continuation of fluoridation has come primarily from researchers and institutions with organizational histories of endorsing it.
What Is Proven, Plausible, and Unknown
Proven (Level 4-5 evidence): Fluoride added to US municipal water is hydrofluorosilicic acid derived from phosphate fertilizer manufacturing (Level 5. Regulatory and chemical documentation). The NTP found moderate confidence that fluoride at or above 1.5 mg/L is associated with lower IQ in children, based on a structured, systematic review of 72 studies (Level 4, Federal scientific agency systematic review). A federal court ordered the EPA to regulate fluoride as a neurotoxin in September 2024 (Level 5. Legal record). Most of Western Europe does not fluoridate water and has comparable dental health outcomes (Level 4. WHO DMFT data). Fluoride competes with iodine for thyroid uptake as a documented biochemical mechanism (Level 5. Established chemistry). Reverse osmosis filters remove fluoride; standard activated carbon filters do not (Level 5. NSF/ANSI 58 certification data).
Plausible: mechanism documented, human evidence at US exposure levels less settled (Level 2-3): Fluoride at US water addition levels, combined with fluoride from toothpaste, dietary sources, and dental treatments, contributes to neurodevelopmental effects in children below the 1.5 mg/L threshold documented in the NTP review (Level 3. Direction consistent, magnitude uncertain). Fluoride at typical US exposure levels impairs thyroid function in individuals with marginal iodine status (Level 2: mechanism established; clinical significance at US levels not confirmed).
Unknown (Level 1-2): The full dose-response curve for neurodevelopmental effects across the range of total combined fluoride exposures typical of American children. The population-level attributable fraction of thyroid disorders associated with fluoride exposure. Whether the 0.7 mg/L addition level, combined with all other fluoride sources, produces measurable population-level IQ effects detectable in large-scale studies designed to find them.
The Risk/Reward Verdict
ATH Verdict: Plausible Concern: Better Safe Than Sorry
The evidence that fluoride at US addition levels poses a neurotoxic risk to children is not conclusive at 0.7 mg/L specifically, but the direction of the evidence is consistent, a federal court has found the overall risk unreasonable, and the NTP, a government scientific agency, found moderate confidence for effects at levels close to what US children receive when total exposure is considered. The alternative is a reverse osmosis filter. The switch costs $200 to $400 for a countertop unit, is a one-time purchase, and eliminates a systemic ingestion exposure with zero loss of benefit. Fluoride toothpaste continues to provide topical dental benefit regardless of whether drinking water is filtered. The downside of caution here is effectively zero.
What To Do Today
Install a reverse osmosis filter for drinking and cooking water. A counter-top or under-sink unit certified to NSF/ANSI 58 removes fluoride at 85 to 95% efficiency. That certification is what to look for on the product label. Whole-house RO is more expensive and rarely necessary for the fluoride concern specifically, since the exposure route that matters most is ingestion through drinking water and food preparation.
Do not confuse filter types. Standard pitcher filters using activated carbon, including all major consumer brands, do not remove fluoride. Gravity-fed countertop ceramic filters do not remove fluoride. Reverse osmosis is the technology that works. Distillation also removes fluoride, but it is impractical for daily use in most households.
For infants drinking formula, formula prepared with fluoridated tap water delivers fluoride at concentrations that may exceed the EPA's reference dose for infants per body weight. Preparing a formula with reverse-osmosis-filtered water is the conservative choice consistent with the precautionary principle and the 2024 court ruling's finding of unreasonable risk.
Fluoride toothpaste is a separate question from water fluoridation. The dental benefit of fluoride comes from topical contact with tooth enamel, which is how toothpaste works. Filtering your drinking water does not remove fluoride from your toothpaste. It removes only the systemic ingestion route.
Look for a reverse osmosis system certified to NSF/ANSI 58 in the ATH Water collection. The ATH standard for water products requires disclosure of which contaminants are removed and at what efficiency, with certification from an accredited testing body.
Go Verify
Read the National Toxicology Program's 2024 systematic review directly. Go to ntp.niehs.nih.gov and search "fluoride systematic review 2024." The full document is publicly available. Read the confidence ratings section and the studies that drove the moderate confidence finding.
Read Judge Chen's ruling in Food and Water Watch v. EPA. Go to courtlistener.com and search the case name. The ruling is public. Read specifically the section on the NTP evidence and the TSCA unreasonable risk standard the court applied.
Search the WHO Global Oral Health Status Report for DMFT data comparing the US to non-fluoridating European countries. The WHO publishes this data publicly. Note where Germany, France, and Sweden rank relative to the US.
Call your water utility and ask: what specific compound do you add for fluoridation, and where does it come from? A direct answer should include hydrofluorosilicic acid and a reference to phosphate processing.
Ask your child's pediatrician: given the 2024 federal court ruling and the NTP systematic review finding moderate confidence of neurotoxic risk, is there a precautionary basis for filtering fluoride from drinking water used to prepare infant formula? If they are unaware of the NTP review or the ruling, that is information.
Sources and Citations
- National Toxicology Program. "Fluoride: Systematic Evidence Map and State of the Science Report." US Department of Health and Human Services. March 2024.
- Food and Water Watch et al. v. Environmental Protection Agency. US District Court, Northern District of California. Case No. 17-cv-02162-EMC. Judge Edward Chen. Ruling issued September 2024.
- Choi AL, Sun G, Zhang Y, Grandjean P. "Developmental Fluoride Neurotoxicity: A Systematic Review and Meta-Analysis." Environmental Health Perspectives. 2012;120(10):1362-1368.
- Green R, Lanphear B, Hornung R, et al. "Association Between Maternal Fluoride Exposure During Pregnancy and IQ Scores in Offspring in Canada." JAMA Pediatrics. 2019;173(10):940-948.
- Grandjean P, Landrigan PJ. "Neurobehavioural effects of developmental toxicity." Lancet Neurology. 2014;13(3):330-338.
- US Centers for Disease Control and Prevention. "Water Fluoridation Statistics." cdc.gov/fluoridation. 2022.
- World Health Organization. "WHO Guidelines for Drinking-Water Quality." Fourth Edition. 2011. Fluoride chapter.