FL: Fluoride and the Brain (2010)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

To examine the claim that fluoridating potable water is linked to increased levels of lead in the blood.

Inclusion Criteria:

Not specified.

Exclusion Criteria:

Not specified.

Description of Study Protocol:
  • Recruitment: Not specified
  • Design: Academic review
  • Blinding used: Not applicable
  • Intervention: Chemistry principles applied to previous research
  • Statistical analysis: Not specified.
Data Collection Summary:

Water Fluoridation Chemicals Used by US Public Water Suppliers in 1992
(Population percentage does not include water naturally high in fluoride)

Chemical Hexafluorosilic Acid Sodium Hexafluorosilicate Sodium Fluoride
Population 80,019,175
62.6%
36,084,896
28.2%
11,701,979
9.2%
Utilities Using 5,876 1,635 2,491

Literature Review was conducted to answer the following questions:

  1. What is the residual concentration of hexafluorosilicate ion after the hydrolysis reaction takes place?
  2. How fast does reaction occur?
  3. Do fluoridation additives affect the pH of the finished water at the plant or at the tap? If there is a pH change, does it matter? Can Hydrogen ion from hydrolysis of residual hexafluorosilicate ion promote the solubilization of lead from the distribution system, thereby increasing the lead concentration at the tap?
  4. Can flouride or residual hexafluorosilicate ion complex with lead and make it more bioavailable? In other worlds, do fluoro-species complex with lead, promoting permeation of the gastric mucosa and absorption into the bloodstream?
  5. Can residual hexafluorosilicate ion lower gastric pH and therfore convert particulate lead or lead compounds to bioavailable aqueous lead ion?
  6. How do the lead drinking water regulations and sampling schemes relate to human health effects?
  7. How is human lead exposure measured? What are the weaknesses in its quantitation?
  8. What quality controls exist for drinking water additives? Can the additives themselves be responsible for contaminants in the water supply? Specifically, can they be a source of lead exposure?
  9. What are the routes and nature of human lead exposure? What sorts of factors are linked to human lead exposure?
  10. When all of the chemical and physical phenomena are considered together, what is the magnitude of the effect? That is, what species represent the greatest fractions of total lead and fluoride concentrations under potable water conditions?
Description of Actual Data Sample:

68 references are cited, which include academic-type books, government literature and primary research articles.

Summary of Results:

In response to the questions posed, the following result answers were provided:

  1. Based on chemistry principals, there is essentially no hexafluorosilicate remaining in drinking water at equilibrium.
  2. The reaction occurs very quickly. 
  3. pH is affected by many components much more readily than by fluoridation. The small change in pH possibly related to fluoridation is not significant enough to solubize lead in the way that carbonate could.
  4. There is no sound chemical explanation linking plumbous reactions (lead) to those of hexafluorosilicate, hexafluorsilic acid or flouride.
  5. Even if hexafluorosilicate were remaining (which it would not, per Question One), it would be buffered or blocked by other components of digestion, thereby not affecting lead availability.
  6. The data reviewed did not allow for verifiable comparisons between water exposure and human health (blood levels).
  7. Human lead exposure is measured by blood levels. The source of lead exposure is difficult to measure if not directly related to the individual and the potential exposure routes including paint, environment, food, etc.
  8. The National Sanitation Foundation sets forth the Maximum Allowable Level to be less than 10% of the Maximum Contaminant Level. Water additives could be a source of contaminant only if stored or handled improperly. Although highly unlikely, this could be discovered through normal testing of water sources.
  9. Human lead exposure is primarily through dust, airborne particulates, soil, paint, ceramic glazes and drinking water. The concern of drinking water is that the lead may be more bioavailable in the aqueous form.
  10. Fluoride and fluorosilicate do not affect the distribution of lead species under potable water conditions.
Author Conclusion:

There is no evidence that fluoridating water (when done properly under existing regulations to maintain total water quality) has untoward impact on human health via lead levels.

Funding Source:
Government: United States Environmental Protection Agency
Reviewer Comments:

This academic style review of data, done by EPA employees as part of their job, supports the actions thus far by the EPA. It seems unlikely that it would admit to supporting a potentially harmful practice, therefore potential for bias is significant.

Quality Criteria Checklist: Review Articles
Relevance Questions
  1. Will the answer if true, have a direct bearing on the health of patients? Yes
  2. Is the outcome or topic something that patients/clients/population groups would care about? Yes
  3. Is the problem addressed in the review one that is relevant to dietetics practice? Yes
  4. Will the information, if true, require a change in practice? Yes
 
Validity Questions
  1. Was the question for the review clearly focused and appropriate? Yes
  2. Was the search strategy used to locate relevant studies comprehensive? Were the databases searched and the search termsused described? No
  3. Were explicit methods used to select studies to include in the review? Were inclusion/exclusion criteria specified andappropriate? Wereselectionmethods unbiased? No
  4. Was there an appraisal of the quality and validity of studies included in the review? Were appraisal methodsspecified,appropriate, andreproducible? No
  5. Were specific treatments/interventions/exposures described? Were treatments similar enough to be combined? No
  6. Was the outcome of interest clearly indicated? Were other potential harms and benefits considered? No
  7. Were processes for data abstraction, synthesis, and analysis described? Were they applied consistently acrossstudies and groups? Was thereappropriate use of qualitative and/or quantitative synthesis? Was variation in findings among studies analyzed? Were heterogeneity issued considered? If data from studies were aggregated for meta-analysis, was the procedure described? Yes
  8. Are the results clearly presented in narrative and/or quantitative terms? If summary statistics are used, are levels ofsignificance and/or confidence intervals included? No
  9. Are conclusions supported by results with biases and limitations taken into consideration? Are limitations ofthe review identified anddiscussed? No
  10. Was bias due to the review's funding or sponsorship unlikely? No