Fluoride and children's IQ: the studies, the courts and the institutions (1945 to 2026)

As of 2026-10-03. Times are UTC; every event here is known to the day, month or year only. Publication dates are online or issue dates as given in the cited record. Events marked "single" rest on one source. Panel B enlarges August 2024 to October 2026, when the US institutional position split. Policy events are adoption, not evidence.

Shape = kind of source: machine-recorded data a primary document an official statement a person's account a scholar's account a news report Style = status: 2+ sources agree one source sources differ our inference / time not reported the same event at another source's time Every dot is a link to its main source; the table lists all sources.

Panel A: 1945 to July 2024 (one tick per ten years)

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1945 1955 1965 1975 1985 1995 2005 2015 Time, UTC Fluoridation and its opponents Studies and reviews Courts and laws Agencies and cities 1. 25 Jan 1945: Grand Rapids becomes the first city to fluoridate its water (single, document). The exact day is from one history source; NIDCR gives only the year [read].1 5. 2006: National Research Council says the 4 mg/L limit should be lowered (reported, analysis). Severe enamel fluorosis in about 10% of children at or near 4 mg/L [read].5 8. 20 Jul 2012: Choi et al. meta-analysis (27 studies, China and Iran) (reported, analysis). Labelled 'the Harvard study' after the school's 25 Jul press release; the authors say it cannot set a US limit [read].8 9. Jan 2015: Dunedin cohort finds no IQ difference by fluoridation (reported, analysis). 992 children; exposure by residence [read].9 11. 18 Jun 2015: Cochrane review: 35% fewer decayed baby teeth, mostly pre-1975 studies (reported, analysis). Over 97% of studies at high risk of bias [abstract].11 13. 19 Sep 2017: Mexico City pregnancy cohort links maternal fluoride to lower child IQ (reported, analysis). Exposure from fluoridated salt [read].13 14. 19 Aug 2019: Canadian MIREC study: lower IQ in boys with higher maternal fluoride (reported, analysis). Girls no significant change [read].14 15. 5 Mar 2020: National Academies: NTP draft's conclusion not adequately supported (reported, analysis). 'That finding does not mean that the conclusion is incorrect' [read].15 16. 13 Jan 2021: Swedish register study: no effect on cognitive ability (reported, analysis). 81,776 conscripts [read, third-party copy].16 17. Feb 2021: National Academies: no conclusions possible for low exposures (reported, analysis). Meta-analysis 'substantially increases the support' for the main conclusion [read].17 18. 26 Jul 2021: Calgary vs Edmonton: more baby-tooth decay after Calgary stopped (reported, analysis). 64.8% vs 55.1% in 2018/19 [read].18 20. 5 Oct 2023: Danish pregnancy cohort finds no association with IQ (reported, analysis). 837 children [read].20 12. 2017: Food & Water Watch sues EPA under the toxics law (TSCA) (reported, official). Year taken from the case number 3:17-cv-02162 [read].12 2. 1962: US Public Health Service sets 0.7-1.2 mg/L, by temperature (reported, official). As described in the 2015 recommendation that replaced it [read].2 3. 1986: EPA sets the legal maximum at 4 mg/L (secondary standard 2 mg/L) (reported, official). Still 4.0 mg/L in the eCFR as of 1 Sep 2026 [read].3 4. 22 Oct 1999: CDC lists fluoridation among ten great public health achievements (reported, official). Says opponents had claimed links to 'low intelligence' and that no credible evidence supports them [read].4 6. 16 May 2011: EU scientific committee finds not enough evidence of IQ harm at EU levels (reported, official). SCHER opinion [read].6 7. 19 May 2011: Calgary council stops fluoridation (reported, official). Edmonton continues; the two cities become a natural comparison [read].7 10. 1 May 2015: US recommended level lowered to 0.7 mg/L (reported, official). To balance cavity protection against dental fluorosis [read].10 19. 15 Nov 2021: Calgary council directs fluoride's return after a plebiscite (reported, official). 62% in favour [read].19

Panel B: August 2024 to October 2026 (one tick per two months)

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01 Aug 00:00 01 Oct 00:00 01 Dec 00:00 31 Jan 00:00 02 Apr 00:00 02 Jun 00:00 02 Aug 00:00 02 Oct 00:00 02 Dec 00:00 01 Feb 00:00 03 Apr 00:00 03 Jun 00:00 03 Aug 00:00 03 Oct 00:00 Time, UTC Studies and reviews Courts and laws Agencies and cities Statements and opinion 21. Aug 2024: NTP monograph: moderate confidence of lower IQ above 1.5 mg/L (reported, document). Says its findings do not address whether the sole exposure to fluoride added to drinking water has a measurable effect; may also be relevant in fluoridated US areas depending on other sources (p. 84) [read].21 23. 4 Oct 2024: Cochrane update: modern dental benefit small and uncertain (reported, analysis). About a quarter of a tooth; interval includes no benefit [abstract].23 25. 18 Dec 2024: Australian cohort: no IQ difference by early fluoridated water (reported, analysis). 357 young adults [read].25 26. 6 Jan 2025: NTP meta-analysis: water studies below 1.5 mg/L show no association (reported, analysis). Urine studies below 1.5 mg/L show a small inverse one [read].26 34. 19 Nov 2025: US cohort of 57,960: fluoridated adolescents scored slightly higher (reported, analysis). High School and Beyond [read].34 36. 13 Apr 2026: Wisconsin cohort (10,317): no negative association (reported, analysis). [read]36 40. 14 Aug 2026: US ECHO analysis reports a change point near 0.675 mg/L (single, analysis). Abstract only; filed as proposed [abstract].40 22. 24 Sep 2024: court finds 'unreasonable risk' under TSCA at 0.7 mg/L (reported, official). Does not conclude harm with certainty; orders EPA rulemaking, not an end to fluoridation [read].22 27. 27 Mar 2025: Utah bans fluoridation (in force 7 May 2025) (reported, official). H.B. 81 [read].27 30. 20 May 2025: Florida bans additives that are not 'water quality additives' (in force 1 Jul) (reported, official). The law does not use the word fluoride [read].30 37. 21 May 2026: Ninth Circuit vacates the 2024 ruling on procedural grounds (reported, official). Remanded; no ruling on the science [read].37 28. 7 Apr 2025: EPA announces review; Kennedy says he will tell CDC to stop recommending fluoridation (reported, official). EPA: 'Without prejudging any outcomes' [read]; Kennedy's intent reported by AP [read].28 29. 13 May 2025: FDA begins action on children's fluoride drops and tablets (reported, official). Not about water [read].29 31. 30 Jun 2025: Calgary resumes fluoridation at 0.7 mg/L (reported, official). After 14 years without [read].31 32. 22 Jul 2025: EU food safety agency: brain effects above 1.5 mg/L (reported, official). Below 1.5 mg/L not consistent enough to conclude [summary read].32 33. 31 Oct 2025: FDA restricts fluoride drops for under-3s; calls US IQ evidence 'equivocal' (reported, official). Notices to 4 companies [read].33 35. 28 Jan 2026: EPA publishes its assessment plan; no health conclusions (reported, official). Review under the Safe Drinking Water Act [read].35 39. 3 Aug 2026: EPA releases its assessment protocol; draft not yet out (reported, official). Covers neurodevelopment and dental fluorosis [read].39 24. 2 Nov 2024: Kennedy posts that fluoride is 'an industrial waste' linked to IQ loss (reported, witness). Platform record read; reported by NBC News the same day.24 38. 11 Jun 2026: survey: 43% of US adults favor fluoridation, 26% oppose (reported, data). Fielded 14-28 Apr 2026 [read].38

Events (numbers match the diagram)

#When (UTC)WhatStatusSources
125 Jan 1945 (date only)25 Jan 1945: Grand Rapids becomes the first city to fluoridate its water
The exact day is from one history source; NIDCR gives only the year [read].		single documentsrc-hicks-2011
21962 (year only)1962: US Public Health Service sets 0.7-1.2 mg/L, by temperature
As described in the 2015 recommendation that replaced it [read].		reported officialsrc-phs-2015
31986 (year only)1986: EPA sets the legal maximum at 4 mg/L (secondary standard 2 mg/L)
Still 4.0 mg/L in the eCFR as of 1 Sep 2026 [read].		reported officialsrc-nrc-2006, src-ecfr-fluoride-mcl
422 Oct 1999 (date only)22 Oct 1999: CDC lists fluoridation among ten great public health achievements
Says opponents had claimed links to 'low intelligence' and that no credible evidence supports them [read].		reported officialsrc-cdc-mmwr-1999
52006 (year only)2006: National Research Council says the 4 mg/L limit should be lowered
Severe enamel fluorosis in about 10% of children at or near 4 mg/L [read].		reported analysissrc-nrc-2006
616 May 2011 (date only)16 May 2011: EU scientific committee finds not enough evidence of IQ harm at EU levels
SCHER opinion [read].		reported officialsrc-scher-2011
719 May 2011 (date only)19 May 2011: Calgary council stops fluoridation
Edmonton continues; the two cities become a natural comparison [read].		reported officialsrc-calgary
820 Jul 2012 (date only)20 Jul 2012: Choi et al. meta-analysis (27 studies, China and Iran)
Labelled 'the Harvard study' after the school's 25 Jul press release; the authors say it cannot set a US limit [read].		reported analysissrc-choi-2012
9Jan 2015 (month only)Jan 2015: Dunedin cohort finds no IQ difference by fluoridation
992 children; exposure by residence [read].		reported analysissrc-broadbent-2015
1001 May 2015 (date only)1 May 2015: US recommended level lowered to 0.7 mg/L
To balance cavity protection against dental fluorosis [read].		reported officialsrc-phs-2015
1118 Jun 2015 (date only)18 Jun 2015: Cochrane review: 35% fewer decayed baby teeth, mostly pre-1975 studies
Over 97% of studies at high risk of bias [abstract].		reported analysissrc-cochrane-2015
122017 (year only)2017: Food & Water Watch sues EPA under the toxics law (TSCA)
Year taken from the case number 3:17-cv-02162 [read].		reported officialsrc-fww-v-epa-2024
1319 Sep 2017 (date only)19 Sep 2017: Mexico City pregnancy cohort links maternal fluoride to lower child IQ
Exposure from fluoridated salt [read].		reported analysissrc-bashash-2017
1419 Aug 2019 (date only)19 Aug 2019: Canadian MIREC study: lower IQ in boys with higher maternal fluoride
Girls no significant change [read].		reported analysissrc-green-2019
1505 Mar 2020 (date only)5 Mar 2020: National Academies: NTP draft's conclusion not adequately supported
'That finding does not mean that the conclusion is incorrect' [read].		reported analysissrc-nasem-2020
1613 Jan 2021 (date only)13 Jan 2021: Swedish register study: no effect on cognitive ability
81,776 conscripts [read, third-party copy].		reported analysissrc-aggeborn-ohman-2021
17Feb 2021 (month only)Feb 2021: National Academies: no conclusions possible for low exposures
Meta-analysis 'substantially increases the support' for the main conclusion [read].		reported analysissrc-nasem-2021
1826 Jul 2021 (date only)26 Jul 2021: Calgary vs Edmonton: more baby-tooth decay after Calgary stopped
64.8% vs 55.1% in 2018/19 [read].		reported analysissrc-mclaren-2022
1915 Nov 2021 (date only)15 Nov 2021: Calgary council directs fluoride's return after a plebiscite
62% in favour [read].		reported officialsrc-calgary
2005 Oct 2023 (date only)5 Oct 2023: Danish pregnancy cohort finds no association with IQ
837 children [read].		reported analysissrc-grandjean-2024-odense
21Aug 2024 (month only)Aug 2024: NTP monograph: moderate confidence of lower IQ above 1.5 mg/L
Says its findings do not address whether the sole exposure to fluoride added to drinking water has a measurable effect; may also be relevant in fluoridated US areas depending on other sources (p. 84) [read].		reported documentsrc-ntp-2024
2224 Sep 2024 (date only)24 Sep 2024: court finds 'unreasonable risk' under TSCA at 0.7 mg/L
Does not conclude harm with certainty; orders EPA rulemaking, not an end to fluoridation [read].		reported officialsrc-fww-v-epa-2024
2304 Oct 2024 (date only)4 Oct 2024: Cochrane update: modern dental benefit small and uncertain
About a quarter of a tooth; interval includes no benefit [abstract].		reported analysissrc-cochrane-2024
2402 Nov 2024 (date only)2 Nov 2024: Kennedy posts that fluoride is 'an industrial waste' linked to IQ loss
Platform record read; reported by NBC News the same day.		reported witnesssrc-rfk-x-2024
2518 Dec 2024 (date only)18 Dec 2024: Australian cohort: no IQ difference by early fluoridated water
357 young adults [read].		reported analysissrc-do-2024
2606 Jan 2025 (date only)6 Jan 2025: NTP meta-analysis: water studies below 1.5 mg/L show no association
Urine studies below 1.5 mg/L show a small inverse one [read].		reported analysissrc-taylor-2025
2727 Mar 2025 (date only)27 Mar 2025: Utah bans fluoridation (in force 7 May 2025)
H.B. 81 [read].		reported officialsrc-utah-hb81
2807 Apr 2025 (date only)7 Apr 2025: EPA announces review; Kennedy says he will tell CDC to stop recommending fluoridation
EPA: 'Without prejudging any outcomes' [read]; Kennedy's intent reported by AP [read].		reported officialsrc-epa-2025-04-07, src-pbs-2025-04-07
2913 May 2025 (date only)13 May 2025: FDA begins action on children's fluoride drops and tablets
Not about water [read].		reported officialsrc-fda-2025-05-13
3020 May 2025 (date only)20 May 2025: Florida bans additives that are not 'water quality additives' (in force 1 Jul)
The law does not use the word fluoride [read].		reported officialsrc-florida-sb700
3130 Jun 2025 (date only)30 Jun 2025: Calgary resumes fluoridation at 0.7 mg/L
After 14 years without [read].		reported officialsrc-calgary
3222 Jul 2025 (date only)22 Jul 2025: EU food safety agency: brain effects above 1.5 mg/L
Below 1.5 mg/L not consistent enough to conclude [summary read].		reported officialsrc-efsa-2025
3331 Oct 2025 (date only)31 Oct 2025: FDA restricts fluoride drops for under-3s; calls US IQ evidence 'equivocal'
Notices to 4 companies [read].		reported officialsrc-fda-2025-10-31
3419 Nov 2025 (date only)19 Nov 2025: US cohort of 57,960: fluoridated adolescents scored slightly higher
High School and Beyond [read].		reported analysissrc-warren-2025
3528 Jan 2026 (date only)28 Jan 2026: EPA publishes its assessment plan; no health conclusions
Review under the Safe Drinking Water Act [read].		reported officialsrc-fr-2026-01657
3613 Apr 2026 (date only)13 Apr 2026: Wisconsin cohort (10,317): no negative association
[read]		reported analysissrc-warren-2026
3721 May 2026 (date only)21 May 2026: Ninth Circuit vacates the 2024 ruling on procedural grounds
Remanded; no ruling on the science [read].		reported officialsrc-ca9-2026
3811 Jun 2026 (date only)11 Jun 2026: survey: 43% of US adults favor fluoridation, 26% oppose
Fielded 14-28 Apr 2026 [read].		reported datasrc-annenberg-2026
3903 Aug 2026 (date only)3 Aug 2026: EPA releases its assessment protocol; draft not yet out
Covers neurodevelopment and dental fluorosis [read].		reported officialsrc-epa-2026-08-protocol
4014 Aug 2026 (date only)14 Aug 2026: US ECHO analysis reports a change point near 0.675 mg/L
Abstract only; filed as proposed [abstract].		single analysissrc-simon-2026

People and bodies involved

Sources

Generated from timeline.yaml by build/tools/render_timeline.py. This page records what is reported and where reports differ. It is not a finding about what happened.