In 2010, a panel of federal scientists representing CDC/Division of Oral Health and National Institute of Dental (DOH) and Craniofacial Research (NIDCR) participated in the development of a new HHS recommendation for optimal fluoride level in drinking water (community water fluoridation), as well as development of guidelines for maximum fluoride levels in naturally fluoridated water. One of the recommendations of the federal panel was to strengthen the surveillance of dental caries and dental fluorosis with emphasis on determining fluoride exposures.
A water sample was collected from all households with survey participants aged birth to 19 years.
Fluoride in Water:
Fluoride concentrations in water samples and appropriate aqueous standards are measured electrometrically using the ion-specific electrode. The limit of detection (LOD) of the electrode is ~1 µmole/L (0.019 mg/L), a concentration far below the concentration typically found in water. The linear portion of the standard curve extends from 0.1 mg/L to 19,000 mg/L at the electrode.
Refer to the Laboratory Method Files section for detailed laboratory procedure manual(s) of the methods used.
Analysis of fluoride in water was added in NHANES 2013-2014 cycle
Fluoride - Water (August 2016)
Water specimens were processed, stored, and shipped to the College of Dental Medicine, Georgia Regents University, Augusta, GA for analysis.
Detailed instructions on specimen collection and processing are discussed in the NHANES Laboratory Procedures Manual (LPM). Vials are stored under appropriate frozen (–70°C) conditions until they are shipped to Georgia Regents University for testing.
The NHANES quality assurance and quality control (QA/QC) protocols meet the 1988 Clinical Laboratory Improvement Amendments mandates. Detailed QA/QC instructions are discussed in the NHANES LPM.
Mobile Examination Centers (MECs)
Laboratory team performance is monitored using several techniques. NCHS and contract consultants use a structured quality assurance evaluation during unscheduled visits to evaluate both the quality of the laboratory work and the quality-control procedures. Each laboratory staff person is observed for equipment operation, specimen collection and preparation; testing procedures and constructive feedback are given to each staff. Formal retraining sessions are conducted annually to ensure that required skill levels were maintained.
Analytical Laboratories
NHANES uses several methods to monitor the quality of the analyses performed by the contract laboratories. In the MEC, these methods include performing blind split samples collected on “dry run” sessions. In addition, contract laboratories randomly perform repeat testing on 2.0% of all specimens.
NCHS developed and distributed a quality control protocol for all the contract laboratories which outlined the Westgard rules (Westgard et al, 1981) used when running NHANES specimens. Progress reports containing any problems encountered during shipping or receipt of specimens, summary statistics for each control pool, QC graphs, instrument calibration, reagents, and any special considerations are submitted to NCHS quarterly. The reports are reviewed for trends or shifts in the data. The laboratories are required to explain any identified areas of concern.
The data were reviewed. Incomplete data or improbable values were sent to the performing laboratory for confirmation.
Refer to the 2013 - 2014 Laboratory Data Overview for general information on NHANES laboratory data.
MEC exam sample weights should be used for analyses.
Demographic and Other Related Variables
The analysis of NHANES 2013 - 2014 laboratory data must be conducted using the appropriate survey design and demographic variables. The NHANES 2013-2014 Demographics File contains demographic data, health indicators, and other related information collected during household interviews as well as the sample weight variables. The Fasting Questionnaire File includes auxiliary information such as fasting status, the time of venipuncture, and the conditions precluding venipuncture. The demographics and fasting questionnaire files may be linked to the laboratory data file using the unique survey participant identifier (i.e., SEQN).
The water and plasma fluoride data may be linked using the unique survey participant identifier (i.e., SEQN).
Water fluoride was measured in duplicate. The variability between test results A and B is pretty low especially since both tests were performed on the same sample. The average of the two results was released.
Detection Limits
The detection limits were constant for this analyte in the data set.
The lower limit of detection (LLOD, in mg/L) for fluoride:
| Analyte | Item ID | LLOD |
| Fluoride, water, averaged | LBDWFL | 0.10 |
Please refer to the NHANES Analytic Guidelines and the on-line NHANES Tutorial for further details on the use of sample weights and other analytic issues.
| Code or Value | Value Description | Count | Cumulative | Skip to Item |
|---|---|---|---|---|
| 0.07 to 7.32 | Range of Values | 4100 | 4100 | |
| . | Missing | 125 | 4225 |
| Code or Value | Value Description | Count | Cumulative | Skip to Item |
|---|---|---|---|---|
| 0 | At or above the detection limit | 3675 | 3675 | |
| 1 | Below lower detection limit | 425 | 4100 | |
| . | Missing | 125 | 4225 |