Letter to the editor regarding critical windows of fluoride neurotoxicity in Canadian children by Farmus, L., and colleagues (2021). Environmental Research, 2021;200;111315. https://doi.org/10.1016/j.envres.2021.111315
Bibliographic record
Abstract
Prenatal exposure to fluoride has been associated with adverse neurodevelopmental outcomes. However, the neuropsychological profile of fluoride's developmental neurotoxicity at low levels and the stability of this relationship across childhood has not been characterized. We investigated the longitudinal and domain specific effect of prenatal fluoride exposure on IQ among children ages 4, 5, and 6–12 years in the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) cohort.We measured the average of maternal urinary fluoride at each trimester of pregnancy adjusted for creatinine (MUFCRE). Children were administered the McCarthy Scales of Children's Abilities at ages 4 (N = 386) and 5 (N = 308), and the Wechsler Abbreviated Scale of Intelligence at age 6–12 (N = 278). We used generalized estimating equation (GEE) models to estimate the population averaged effect of MUFCRE concentration on longitudinal General Cognitive Index (GCI)/Full-Scale IQ (FSIQ), Verbal IQ (VIQ), and Performance IQ (PIQ) scores (N = 348). We tested for possible interactions between MUFCRE and child sex as well as for MUFCRE and time point on children's IQ. All models controlled for relevant available covariates.The mean/median MUFCRE concentration was 0.90/0.83 mg/L (SD = 0.39; IQR, 0.64–1.11 mg/L). A 0.5 mg/L increase in MUFCRE predicted an average 2.12-point decrease in GCI/FSIQ (95% CI: −3.49, −0.75) and 2.63-point decrease in PIQ (95% CI: −3.87, −1.40). MUFCRE was marginally associated with VIQ across time (B = −1.29, 95% CI: −2.60, 0.01). No interactions between MUFCRE and child sex or MUFCRE and time were observed.The negative association between prenatal fluoride exposure and longitudinal IQ was driven by decrements in non-verbal intelligence (i.e. PIQ), suggesting that visual-spatial and perceptual reasoning abilities may be more impacted by prenatal fluoride exposure as compared to verbal abilities.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.020 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.003 | 0.002 |
| Scholarly communication | 0.003 | 0.002 |
| Open science | 0.003 | 0.001 |
| Research integrity | 0.014 | 0.014 |
| Insufficient payload (model declined to judge) | 0.008 | 0.003 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".