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Although the 2014 report, Health effects of water fluoridation: a review of the scientific evidence, found that water fluoridation did not adversely affect brain development, it recommended that a similar review should be repeated if a large well-designed study was published that appeared likely to have shifted the balance of health benefit vs health risk.1 Three such large well-designed prospective studies on fluoride and IQ published since 2014,2–4 found through PubMed searching and involving 65, 299 and 601 mother-child pairs, respectively, concluded that fluoride, at the levels found with water fluoridation, 0.7–1.0mg/L,1 does adversely affect brain development. These studies were better designed than two earlier prospective studies from New Zealand which were ecological studies of groups rather than using individual data from mother-child pairs.5,6

In the recent studies,2–4 substantial IQ losses were associated with higher urinary and water fluoride concentrations. In the study by Bashash et al, an increase in the maternal urinary fluoride by 0:5mg/L (approximately equalling the difference between fluoridated and non-fluoridated regions) predicted a decrease in the IQ of the offspring at ages 6 –12 years of 2.50 IQ points.2 In the study by Green et al, an increase in the water fluoride concentration of 1mg/L was associated with a decrease in the 8.8 IQ points in the children who have been formula fed in the first six months of life, while no such difference was seen among the exclusively breast-fed children.4 These IQ impairments are consistent with the difference of almost 7 IQ points between the exposed groups and controls found in a 2012 meta-analysis7 and with a statistically significant loss of 8.6 IQ points for each increase by 1mg/L in the fluoride concentration in water found in a large cross-sectional study from 2018.8 In other recent studies from 2020, Wang et al,9 in a study of 572 children, found a lower loss of 1.6 IQ points for each increase by 1mg/L in the fluoride concentration in water while Till et al,10 in a study of 398 mother-child dyads, found that an increase of 0.5mg/L in water fluoride corresponded to a 9.3 and 6.2 IQ points decrement in performance IQ among formula-fed and breast-fed children, respectively, which remained significant after controlling for fetal fluoride exposure. A 0.5mg increase in fluoride intake from infant formula corresponded to an 8.8 IQ points decrement in performance IQ and this association remained significant after controlling for fetal fluoride.10

Although these recent studies2–4 showed a dose-dependent fluoride neurotoxicity that appeared to be statistically significant at water concentrations of or below 1mg/L, they did not identify a likely threshold. Bench mark dose (BMD) calculations may be used to develop non-cancer health-based limits for dietary intakes, such as drinking water, and Hirzy et al11 used this approach to generate benchmark results from a study by Xiang et al12 of more than 500 children in China. The lower confidence limit for the benchmark dose (BMDL) of 1 IQ point was calculated to be a daily intake level of 0.27mg/day.11 Using the average water intake of 1.24 L/day in non-pregnant women, this BMDL corresponds to a water concentration of 0.22 mg/L.

Grandjean13 used the regression coefficients and their standard deviations in the studies by Bashash et al3 and Green et al4 to estimate tentative BMD values and found a BMDL of about 0.2mg/L or below, a level that is similar to the result calculated by Hirzy et al11 and clearly below the exposure levels in communities with drinking water fluoridation.

In my opinion, there now little doubt that developmental neurotoxicity, with permanent adverse effects, is a serious risk associated with elevated fluoride exposure during early development.  In conclusion, these three recent studies should be quality reviewed to determine whether or not, in the context of the existing evidence, they shift the balance of health benefit vs health risk for water fluoridation.

Summary

Abstract

Aim

Method

Results

Conclusion

Author Information

Bruce Spittle, Editor-in-Chief, Fluoride, Quarterly Journal of the International Society for Fluoride Research Inc, Dunedin.

Acknowledgements

Correspondence

Dr Bruce Spittle, 727 Brighton Road, Ocean View, Dunedin 9035.

Correspondence Email

spittle727@gmail.com

Competing Interests

Nil.

1. Eason C, Elwood JM, Seymour G, et al. Health effects of water fluoridation: a review of the scientific evidence. Auckland and Wellington; Office of the Prime Minister’s Chief Science Advisor and Royal Society of New Zealand; 2014.

2. Valdez Jiménez L, López Guzmán OD, Cervantes Flores M, et al. In utero exposure to fluoride and cognitive development delay in infants. Neurotoxicology. 2017; 59:65–70.

3. Bashash M, Thomas D, Hu H, et al. Prenatal fluoride exposure and cognitive outcomes in children at 4 and 6–12 years of age in Mexico. Environ Health Perspect. 2017; 125(9):097017.

4. Green R, Lanphear B, Hornung R, et al. Association between maternal fluoride exposure during pregnancy and IQ scores in offspring in Canada. JAMA Pediatr. 2019; 173(10):940–8.

5. Shannon FT, Fergusson DM, Horwood LJ. Exposure to fluoridated public water supplies and child health and behaviour. N Z Med J. 1986; 99(802):371–3.

6. Broadbent JM, Thomson WM, Ramrakha S, et al. Community water fluoridation and intelligence: prospective study in New Zealand. Am J Public Health. 2015; 105:72–6.

7. Choi AL, Sun GF, Zhang Y, Grandjean P. Developmental fluoride neurotoxicity: a systematic review and meta-analysis. Environ Health Perspect. 2012; 120(10):1362–8.

8. Yu X, Chen J, Li Y, et al. Threshold effects of moderately excessive fluoride exposure on children’s health: a potential association between dental fluorosis and loss of excellent intelligence. Environ Int. 2018; 118:116–24.

9. Wang M, Liu L, Li H, et al. Thyroid function, intelligence and low-moderate fluoride exposure among Chinese school-age children. Environ Int. 2020; 134:105229.

10. Till C, Green R, Flora D, et al. Fluoride exposure from infant formula and child IQ in a Canadian birth cohort. Environ Int. 2020; 134:105315.

11. Hirzy JW, Connett P, Xiang QY, et al. Developmental neurotoxicity of fluoride: a quantitative risk analysis towards establishing a safe daily dose of fluoride for children. Fluoride. 2016; 49(4 Pt 1):379–400.

12. Xiang Q, Liang Y, Chen L, et al. Effect of fluoride in drinking water on children’s intelligence. Fluoride. 2003; 36:84–94. Erratum in Fluoride. 2004; 37(4):320.

13. Grandjean P. Developmental fluoride neurotoxicity: an updated review. Environ Health. 2019; 18(1):110.

Contact diana@nzma.org.nz
for the PDF of this article

View Article PDF

Although the 2014 report, Health effects of water fluoridation: a review of the scientific evidence, found that water fluoridation did not adversely affect brain development, it recommended that a similar review should be repeated if a large well-designed study was published that appeared likely to have shifted the balance of health benefit vs health risk.1 Three such large well-designed prospective studies on fluoride and IQ published since 2014,2–4 found through PubMed searching and involving 65, 299 and 601 mother-child pairs, respectively, concluded that fluoride, at the levels found with water fluoridation, 0.7–1.0mg/L,1 does adversely affect brain development. These studies were better designed than two earlier prospective studies from New Zealand which were ecological studies of groups rather than using individual data from mother-child pairs.5,6

In the recent studies,2–4 substantial IQ losses were associated with higher urinary and water fluoride concentrations. In the study by Bashash et al, an increase in the maternal urinary fluoride by 0:5mg/L (approximately equalling the difference between fluoridated and non-fluoridated regions) predicted a decrease in the IQ of the offspring at ages 6 –12 years of 2.50 IQ points.2 In the study by Green et al, an increase in the water fluoride concentration of 1mg/L was associated with a decrease in the 8.8 IQ points in the children who have been formula fed in the first six months of life, while no such difference was seen among the exclusively breast-fed children.4 These IQ impairments are consistent with the difference of almost 7 IQ points between the exposed groups and controls found in a 2012 meta-analysis7 and with a statistically significant loss of 8.6 IQ points for each increase by 1mg/L in the fluoride concentration in water found in a large cross-sectional study from 2018.8 In other recent studies from 2020, Wang et al,9 in a study of 572 children, found a lower loss of 1.6 IQ points for each increase by 1mg/L in the fluoride concentration in water while Till et al,10 in a study of 398 mother-child dyads, found that an increase of 0.5mg/L in water fluoride corresponded to a 9.3 and 6.2 IQ points decrement in performance IQ among formula-fed and breast-fed children, respectively, which remained significant after controlling for fetal fluoride exposure. A 0.5mg increase in fluoride intake from infant formula corresponded to an 8.8 IQ points decrement in performance IQ and this association remained significant after controlling for fetal fluoride.10

Although these recent studies2–4 showed a dose-dependent fluoride neurotoxicity that appeared to be statistically significant at water concentrations of or below 1mg/L, they did not identify a likely threshold. Bench mark dose (BMD) calculations may be used to develop non-cancer health-based limits for dietary intakes, such as drinking water, and Hirzy et al11 used this approach to generate benchmark results from a study by Xiang et al12 of more than 500 children in China. The lower confidence limit for the benchmark dose (BMDL) of 1 IQ point was calculated to be a daily intake level of 0.27mg/day.11 Using the average water intake of 1.24 L/day in non-pregnant women, this BMDL corresponds to a water concentration of 0.22 mg/L.

Grandjean13 used the regression coefficients and their standard deviations in the studies by Bashash et al3 and Green et al4 to estimate tentative BMD values and found a BMDL of about 0.2mg/L or below, a level that is similar to the result calculated by Hirzy et al11 and clearly below the exposure levels in communities with drinking water fluoridation.

In my opinion, there now little doubt that developmental neurotoxicity, with permanent adverse effects, is a serious risk associated with elevated fluoride exposure during early development.  In conclusion, these three recent studies should be quality reviewed to determine whether or not, in the context of the existing evidence, they shift the balance of health benefit vs health risk for water fluoridation.

Summary

Abstract

Aim

Method

Results

Conclusion

Author Information

Bruce Spittle, Editor-in-Chief, Fluoride, Quarterly Journal of the International Society for Fluoride Research Inc, Dunedin.

Acknowledgements

Correspondence

Dr Bruce Spittle, 727 Brighton Road, Ocean View, Dunedin 9035.

Correspondence Email

spittle727@gmail.com

Competing Interests

Nil.

1. Eason C, Elwood JM, Seymour G, et al. Health effects of water fluoridation: a review of the scientific evidence. Auckland and Wellington; Office of the Prime Minister’s Chief Science Advisor and Royal Society of New Zealand; 2014.

2. Valdez Jiménez L, López Guzmán OD, Cervantes Flores M, et al. In utero exposure to fluoride and cognitive development delay in infants. Neurotoxicology. 2017; 59:65–70.

3. Bashash M, Thomas D, Hu H, et al. Prenatal fluoride exposure and cognitive outcomes in children at 4 and 6–12 years of age in Mexico. Environ Health Perspect. 2017; 125(9):097017.

4. Green R, Lanphear B, Hornung R, et al. Association between maternal fluoride exposure during pregnancy and IQ scores in offspring in Canada. JAMA Pediatr. 2019; 173(10):940–8.

5. Shannon FT, Fergusson DM, Horwood LJ. Exposure to fluoridated public water supplies and child health and behaviour. N Z Med J. 1986; 99(802):371–3.

6. Broadbent JM, Thomson WM, Ramrakha S, et al. Community water fluoridation and intelligence: prospective study in New Zealand. Am J Public Health. 2015; 105:72–6.

7. Choi AL, Sun GF, Zhang Y, Grandjean P. Developmental fluoride neurotoxicity: a systematic review and meta-analysis. Environ Health Perspect. 2012; 120(10):1362–8.

8. Yu X, Chen J, Li Y, et al. Threshold effects of moderately excessive fluoride exposure on children’s health: a potential association between dental fluorosis and loss of excellent intelligence. Environ Int. 2018; 118:116–24.

9. Wang M, Liu L, Li H, et al. Thyroid function, intelligence and low-moderate fluoride exposure among Chinese school-age children. Environ Int. 2020; 134:105229.

10. Till C, Green R, Flora D, et al. Fluoride exposure from infant formula and child IQ in a Canadian birth cohort. Environ Int. 2020; 134:105315.

11. Hirzy JW, Connett P, Xiang QY, et al. Developmental neurotoxicity of fluoride: a quantitative risk analysis towards establishing a safe daily dose of fluoride for children. Fluoride. 2016; 49(4 Pt 1):379–400.

12. Xiang Q, Liang Y, Chen L, et al. Effect of fluoride in drinking water on children’s intelligence. Fluoride. 2003; 36:84–94. Erratum in Fluoride. 2004; 37(4):320.

13. Grandjean P. Developmental fluoride neurotoxicity: an updated review. Environ Health. 2019; 18(1):110.

Contact diana@nzma.org.nz
for the PDF of this article

View Article PDF

Although the 2014 report, Health effects of water fluoridation: a review of the scientific evidence, found that water fluoridation did not adversely affect brain development, it recommended that a similar review should be repeated if a large well-designed study was published that appeared likely to have shifted the balance of health benefit vs health risk.1 Three such large well-designed prospective studies on fluoride and IQ published since 2014,2–4 found through PubMed searching and involving 65, 299 and 601 mother-child pairs, respectively, concluded that fluoride, at the levels found with water fluoridation, 0.7–1.0mg/L,1 does adversely affect brain development. These studies were better designed than two earlier prospective studies from New Zealand which were ecological studies of groups rather than using individual data from mother-child pairs.5,6

In the recent studies,2–4 substantial IQ losses were associated with higher urinary and water fluoride concentrations. In the study by Bashash et al, an increase in the maternal urinary fluoride by 0:5mg/L (approximately equalling the difference between fluoridated and non-fluoridated regions) predicted a decrease in the IQ of the offspring at ages 6 –12 years of 2.50 IQ points.2 In the study by Green et al, an increase in the water fluoride concentration of 1mg/L was associated with a decrease in the 8.8 IQ points in the children who have been formula fed in the first six months of life, while no such difference was seen among the exclusively breast-fed children.4 These IQ impairments are consistent with the difference of almost 7 IQ points between the exposed groups and controls found in a 2012 meta-analysis7 and with a statistically significant loss of 8.6 IQ points for each increase by 1mg/L in the fluoride concentration in water found in a large cross-sectional study from 2018.8 In other recent studies from 2020, Wang et al,9 in a study of 572 children, found a lower loss of 1.6 IQ points for each increase by 1mg/L in the fluoride concentration in water while Till et al,10 in a study of 398 mother-child dyads, found that an increase of 0.5mg/L in water fluoride corresponded to a 9.3 and 6.2 IQ points decrement in performance IQ among formula-fed and breast-fed children, respectively, which remained significant after controlling for fetal fluoride exposure. A 0.5mg increase in fluoride intake from infant formula corresponded to an 8.8 IQ points decrement in performance IQ and this association remained significant after controlling for fetal fluoride.10

Although these recent studies2–4 showed a dose-dependent fluoride neurotoxicity that appeared to be statistically significant at water concentrations of or below 1mg/L, they did not identify a likely threshold. Bench mark dose (BMD) calculations may be used to develop non-cancer health-based limits for dietary intakes, such as drinking water, and Hirzy et al11 used this approach to generate benchmark results from a study by Xiang et al12 of more than 500 children in China. The lower confidence limit for the benchmark dose (BMDL) of 1 IQ point was calculated to be a daily intake level of 0.27mg/day.11 Using the average water intake of 1.24 L/day in non-pregnant women, this BMDL corresponds to a water concentration of 0.22 mg/L.

Grandjean13 used the regression coefficients and their standard deviations in the studies by Bashash et al3 and Green et al4 to estimate tentative BMD values and found a BMDL of about 0.2mg/L or below, a level that is similar to the result calculated by Hirzy et al11 and clearly below the exposure levels in communities with drinking water fluoridation.

In my opinion, there now little doubt that developmental neurotoxicity, with permanent adverse effects, is a serious risk associated with elevated fluoride exposure during early development.  In conclusion, these three recent studies should be quality reviewed to determine whether or not, in the context of the existing evidence, they shift the balance of health benefit vs health risk for water fluoridation.

Summary

Abstract

Aim

Method

Results

Conclusion

Author Information

Bruce Spittle, Editor-in-Chief, Fluoride, Quarterly Journal of the International Society for Fluoride Research Inc, Dunedin.

Acknowledgements

Correspondence

Dr Bruce Spittle, 727 Brighton Road, Ocean View, Dunedin 9035.

Correspondence Email

spittle727@gmail.com

Competing Interests

Nil.

1. Eason C, Elwood JM, Seymour G, et al. Health effects of water fluoridation: a review of the scientific evidence. Auckland and Wellington; Office of the Prime Minister’s Chief Science Advisor and Royal Society of New Zealand; 2014.

2. Valdez Jiménez L, López Guzmán OD, Cervantes Flores M, et al. In utero exposure to fluoride and cognitive development delay in infants. Neurotoxicology. 2017; 59:65–70.

3. Bashash M, Thomas D, Hu H, et al. Prenatal fluoride exposure and cognitive outcomes in children at 4 and 6–12 years of age in Mexico. Environ Health Perspect. 2017; 125(9):097017.

4. Green R, Lanphear B, Hornung R, et al. Association between maternal fluoride exposure during pregnancy and IQ scores in offspring in Canada. JAMA Pediatr. 2019; 173(10):940–8.

5. Shannon FT, Fergusson DM, Horwood LJ. Exposure to fluoridated public water supplies and child health and behaviour. N Z Med J. 1986; 99(802):371–3.

6. Broadbent JM, Thomson WM, Ramrakha S, et al. Community water fluoridation and intelligence: prospective study in New Zealand. Am J Public Health. 2015; 105:72–6.

7. Choi AL, Sun GF, Zhang Y, Grandjean P. Developmental fluoride neurotoxicity: a systematic review and meta-analysis. Environ Health Perspect. 2012; 120(10):1362–8.

8. Yu X, Chen J, Li Y, et al. Threshold effects of moderately excessive fluoride exposure on children’s health: a potential association between dental fluorosis and loss of excellent intelligence. Environ Int. 2018; 118:116–24.

9. Wang M, Liu L, Li H, et al. Thyroid function, intelligence and low-moderate fluoride exposure among Chinese school-age children. Environ Int. 2020; 134:105229.

10. Till C, Green R, Flora D, et al. Fluoride exposure from infant formula and child IQ in a Canadian birth cohort. Environ Int. 2020; 134:105315.

11. Hirzy JW, Connett P, Xiang QY, et al. Developmental neurotoxicity of fluoride: a quantitative risk analysis towards establishing a safe daily dose of fluoride for children. Fluoride. 2016; 49(4 Pt 1):379–400.

12. Xiang Q, Liang Y, Chen L, et al. Effect of fluoride in drinking water on children’s intelligence. Fluoride. 2003; 36:84–94. Erratum in Fluoride. 2004; 37(4):320.

13. Grandjean P. Developmental fluoride neurotoxicity: an updated review. Environ Health. 2019; 18(1):110.

Contact diana@nzma.org.nz
for the PDF of this article

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