Perchlorate has been used as an oxidant in solid fuel propellants for rockets and missiles since the 1950s. Lesser amounts of perchlorate are used in matches and fireworks. Perchlorate can also form naturally in the environment and can accumulate in nitrate-rich mineral deposits mined for use in fertilizers. Drinking water, milk, and certain plants with high water content (e.g., lettuce) can be the main sources of perchlorate intake for humans. Perchlorate has been used medically to treat hyperthyroidism. Its inhibitory effect on thyroid hormone production has led to concerns that exposure even to low levels of perchlorate in the environment might affect vulnerable groups, such as pregnant women with inadequate iodine intake and infants for whom thyroid hormone levels must be maintained adequately for normal brain development. Perchlorate taken into the body is rapidly eliminated in the urine, within a matter of hours. Measurement of urinary perchlorate is useful to assess recent human exposure.
Participants aged 6 years and older on a 1/3 sample were tested.
This method is a quantitative procedure for the measurement of perchlorate in human urine using ion chromatography coupled with electrospray tandem mass spectrometry. Chromatographic separation is achieved using an IonPac AS16 column with 100 mM sodium hydroxide as the eluant. The eluant from the column is ionized using an electrospray interface to generate and transmit negative ions into the mass spectrometer. Comparison of relative response factors (ratio of native analyte to stable isotope labeled internal standard) with known standard concentrations yields individual analyte concentrations. The method is applicable to the determination of perchlorate in 0.5 mL of urine over the range 0.05 to 100 ng/mL.
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.
The NHANES QA/QC protocols meet the 1988 Clinical Laboratory Improvement Act mandates. Detailed QA/QC instructions are discussed in the NHANES LPM.
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 second examinations on previously examined participants and 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 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 and Westat quarterly. The reports are reviewed for trends or shifts in the data. The laboratories are required to explain any identified areas of concern.
All QC procedures recommended by the manufacturers were followed. Reported results for all assays meet the Division of Laboratory Science’s quality control and quality assurance performance criteria for accuracy and precision (similar to specifications outlined by Westgard (1981).
Specimens were processed, stored and shipped to Division of Laboratory Sciences, National Center for Environmental Health.
The NHANES quality assurance and quality control protocols (QA/QC) meet the 1988 Clinical Laboratory Improvement Act mandates. Detailed QA/QC instructions are discussed in the NHANES Laboratory/Medical Technologists Procedures Manual (LPM). Read the LABDOC file for detailed QA/QC protocols.
Revised Analytical Note For NHANES 2001-2004 Urinary Perchlorate, Nitrate, And Thiocyanate Analysis (Revised February 2011)
Data Advisory
The purpose of this revised note is to inform users that urinary perchlorate, nitrate, and thiocyanate data from NHANES 2001-2002 and 2003-2004 have been adjusted for laboratory methodological changes, and have replaced previous urinary perchlorate, nitrate, and thiocyanate files. In the ongoing pursuit of new technology and method quality improvement, we discovered a slight bias (-4.7%) in the sample volume accuracy of the aliquoting technique used to measure urinary perchlorate, nitrate, and thiocyanate in NHANES 2001-2004. This bias can be diminished by manually pre-rinsing each pipette tip with sample or by using an automated aliquoting system such as a Hamilton MicroLab Star (Hamilton Robotics, Inc. Reno, NV). Due to this slight bias in volume accuracy we adjusted analytical measurements for all NHANES 2001-2004 samples by a factor of 1.049. No further adjustment is needed.
Subsample weights
Measures of urinary perchlorate were measured in a one third subsample of persons 6 years and over. Special sample weights are required to analyze these data properly. Specific sample weights for this subsample are included in this data file and should be used when analyzing these data.
Variance estimation
The analysis of NHANES 2003-2004 laboratory data must be conducted with the key survey design and basic demographic variables. The NHANES 2003-2004 Demographic Data File contains demographic and sample design variables. The recommended procedure for variance estimation requires use of stratum and PSU variables (SDMVSTRA and SDMVPSU, respectively) in the demographic data file.
Links to NHANES
This laboratory data file can be linked to the other NHANES 2003-2004 data files using the unique survey participant identifier SEQN.
Detection Limits
The detections limits for urinary perchlorate measures were constant during this two-year period.
Please refer to the Analytic Guidelines for further details on the use of sample weights and other analytic issues.
| Code or Value | Value Description | Count | Cumulative | Skip to Item |
|---|---|---|---|---|
| 0 to 456851.11941 | Range of Values | 2544 | 2544 | |
| . | Missing | 68 | 2612 |
| Code or Value | Value Description | Count | Cumulative | Skip to Item |
|---|---|---|---|---|
| 0.052 to 290 | Range of Values | 2522 | 2522 | |
| . | Missing | 90 | 2612 |
| Code or Value | Value Description | Count | Cumulative | Skip to Item |
|---|---|---|---|---|
| 7 to 648 | Range of Values | 2530 | 2530 | |
| . | Missing | 82 | 2612 |