National Health and Nutrition Examination Survey

2001-2002 Data Documentation, Codebook, and Frequencies

Perchlorate, Nitrate & Thiocyanate - Urine (Surplus) (SSNO3P_B)

Data File: SSNO3P_B.xpt

First Published: September 2006

Last Revised: April 2022

Note: The NHANES Biospecimen Program processes were reevaluated in 2021 and 2022 to monitor quality control after a procedural error was identified. This error did not pose any risk of participant disclosure. Addressing this error resulted in the removal of some records from various stored biospecimen data files between 1999 and 2018 that did not meet program standards. After a comprehensive review of all stored specimen datasets, this data file was modified to remove records (5-<10% of records) that were initially included in error. No data values were altered. The sample weights and overall estimates were compared between the original and revised files. The sample weights provided with the original data release are appropriate to use with this updated data file; therefore, no new survey weights were created. The overall estimates from these files were examined and are consistent with the previous file. However, not all possible analyses were performed. For any queries related to this dataset please email the Biospecimen Program at serumplasmaurine@cdc.gov.

Component Description

Perchlorate, nitrate and thiocyanate were measured in all available urine samples from one of the environmental 1/3 subsets of study participants ages 6 and older in NHANES 2001 – 2002. Perchlorate, nitrate, and thiocyanate are polyatomic anions.

Eligible Sample

Study participants aged 6+ years from of NHANES 2001 - 2002 with stored urine.

Description of Laboratory Methodology

Urine samples from NHANES 2001-2002 were stored frozen (-70°C) for up to 4 years before analysis. Experiments evaluating storage at -70°C for greater than 2 years indicate no changes in urinary levels of perchlorate, thiocyanate and nitrate. Samples were analyzed for perchlorate, hiocyanate and nitrate using ion chromatography tandem mass spectrometry (Valentin-Blasini et al. 2005). Chromatographic separation is achieved using an IonPac AS16 column with 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 0.05 μg/L of urine over the range 0.005 to 1000 μg/L. The limit of detection for thiocynate was 20 μg/L and for nitrate 700 μg/L . Stable isotope labeled internal standards were employed in the analysis of perchlorate, thiocyanate and nitrate.

Data Processing and Editing

All peak integrations were evaluated by trained employees in a blinded fashion. Subsequently quality control specimens were evaluated by an independent quality control officer. 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)). Quality control results are reported to NCHS along with the SP results.

Laboratory Quality Assurance and Monitoring

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).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).

Analytic Notes

Revised Analytical Note For NHANES 2001-2004 Urinary Perchlorate, Nitrate, And Thiocyanate Analysis

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, thiocyanate, and nitrate 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 2001-2002 laboratory data must be conducted with the key survey design and basic demographic variables. The NHANES 2001-2002 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 2001-2002 data files using the unique survey participant identifier SEQN.

Detection Limits

Urinary perchlorate measures were above the limit of detection (0.05 μg/L) for all samples. The limit of detection for thiocynate was 20 μg/L and for nitrate 700 μg/L . The detection limit divided by the square root of 2 is the value that is provided for results that are below the limit of detection.

Please refer to the Analytic Guidelines for further details on the use of sample weights and other analytic issues.

References

NAS. 2005. Health Implications of Perchlorate Ingestion. Washington. D.C: National Research Council, National Academy Press.
Valentin-Blasini L, Mauldin JP, Maple D, Blount BC. 2005. Analysis of perchlorate in human urine using ion chromatography and electrospray tandem mass spectrometry. Anal Chem 77: 2475-2481.
Westgard JO, Barry PL, Hunt MR, Groth T. 1981. A multi-rule Shewhart chart for quality control in clinical chemistry. Clin Chem 27: 493-501.

Codebook and Frequencies

SEQN - Respondent sequence number

Variable Name:: SEQN
SAS Label:: Respondent sequence number
English Text:: Respondent sequence number.
Target:: Both males and females 6 YEARS - 150 YEARS

SSXNO3 - Nitrate (ug/L)

Variable Name:: SSXNO3
SAS Label:: Nitrate (ug/L)
English Text:: Continuous variable describing urinary concentration of nitrate (NO3) (ug/L). Limit of detection: 700 ug/L.
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative	Skip to Item
495 to 810000	Range of Values	2637	2637
.	Missing	83	2720

SSXSCN - Thiocyanate (ug/L)

Variable Name:: SSXSCN
SAS Label:: Thiocyanate (ug/L)
English Text:: Continuous variable describing urinary concentration of Thiocyanate (SCN) (ug/L). Limit of detection: 20 ug/L.
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative	Skip to Item
14 to 39000	Range of Values	2636	2636
.	Missing	84	2720

SSXUP8 - Urinary Perchlorate (ug/L)

Variable Name:: SSXUP8
SAS Label:: Urinary Perchlorate (ug/L)
English Text:: Urinary Perchlorate (ug/L)
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative	Skip to Item
0.2 to 170	Range of Values	2638	2638
.	Missing	82	2720

URXUCR - Creatinine, urine (mg/dL)

Variable Name:: URXUCR
SAS Label:: Creatinine, urine (mg/dL)
English Text:: Creatinine, urine (mg/dL)
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative	Skip to Item
9 to 774	Range of Values	2659	2659
.	Missing	61	2720

WTUIO2YR - Subsample 2 year Mec Weight

Variable Name:: WTUIO2YR
SAS Label:: Subsample 2 year Mec Weight
English Text:: Subsample 2 year Mec Weight
Target:: Both males and females 6 YEARS - 150 YEARS

Code or Value	Value Description	Count	Cumulative	Skip to Item
0 to 663502.48	Range of Values	2720	2720
.	Missing	0	2720

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