Table of Contents

Locator Record

Title: Nitrate, thiocyanate, perchlorate (Surplus Urine) (SSNO3P_B )
Contact Number: 1-866-441-NCHS
Years of Content: 2001 - 2002
First Published: September, 2006
Revised: February, 2013
Access Constraints: None
Use Constraints: None
Geographic Coverage: National
Subject:Perchlorate, nitrate and thiocyanate
Record Source: NHANES 2001 - 2002
Survey Methodology: NHANES 2001 - 2002 is a stratified multistage probability sample of the civilian non-institutionalized population of the U.S.
Medium: NHANES Web site; SAS transport files

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

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
520 to 810000 Range of Values 2818 2818
. Missing 124 2942

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
15 to 39000 Range of Values 2817 2817
. Missing 125 2942

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 2820 2820
. Missing 122 2942

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 2847 2847
. Missing 95 2942

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 2942 2942
. Missing 0 2942