Table of Contents

Component Description

Exposure to volatile organic compounds (VOCs) is ubiquitous. Chronic exposure to extremely high levels of some VOCs can lead to cancer and neurocognitive dysfunction. Urinary metabolites of VOCs can be detectable in urine for a longer period of time than the parent VOCs can be detected in blood.

Nearly 200 air toxics have been associated with adverse health effects in occupational studies or laboratory studies, but have not been monitored in general population groups. Information on levels of exposure to these compounds, as measured by their metabolite levels in urine, is essential to determine the need for regulatory mechanisms to reduce the levels of hazardous air pollutants to which the general population is exposed.

Eligible Sample

Examined participants aged 6 years and older from a one-third sample were eligible.

Description of Laboratory Methodology

This method is a quantitative procedure for the measurement of VOC metabolites in human urine using ultra performance liquid chromatography coupled with electrospray tandem mass spectrometry (UPLC-ESI/MSMS) as described by Alwis et al (2012). Chromatographic separation is achieved using an Acquity UPLC® HSS T3 (Part no. 186003540, 1.8 µm x 2.1 mm x 150 mm, Waters Inc.) column with 15 mM ammonium acetate and acetonitrile as the mobile phases. The eluent 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.

Refer to NHANES 2011-2012 Lab Methods for VOC Metabolites for detailed description of the laboratory method used.

Laboratory Method Files

Laboratory Quality Assurance and Monitoring

Urine specimens are processed, stored, and shipped to the Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta GA for analysis.

Detailed instructions on specimen collection and processing are discussed in the NHANES 2011-2012 Laboratory Procedures Manual (LPM). Vials are stored under appropriate frozen (–20°C) conditions until they are shipped to National Center for Environmental Health for testing.

The NHANES QA/QC protocols meet the 1988 Clinical Laboratory Improvement Act mandates. Detailed QA/QC instructions are discussed in the NHANES Laboratory Procedures Manual (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 second examinations on previously examined participants and blind split samples collected on “dry run” sessions.

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 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 CDC/NCEH Tobacco and Volatile Branch quality control and quality assurance performance criteria for accuracy and precision, similar to the Westgard rules (Caudill et al., 2008).

Data Processing and Editing

The data were reviewed. Incomplete data or improbable values were sent to the performing laboratory for confirmation.

Analytic Notes

Refer to the 2011-2012 Laboratory Data Overview for general information on NHANES laboratory data.

Subsample Weights

VOC metabolites in urine were assessed in a subsample of participants aged 6 years and older. Use the special one-third weights included in this data file when analyzing data. 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.

Demographic and Other Related Variables

The analysis of NHANES laboratory data must be conducted with the key survey design and basic demographic variables. The NHANES 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.

This laboratory data file can be linked to the other NHANES data files using the unique survey participant identifier SEQN.

Special Analytic Note: Bias Adjustments Applied to VOC Metabolites in Urine Assay in NHANES 2011–2012 cycle

Adjustments have been applied to the previously published data.

During routine review, several systematic biases were discovered in measurements of certain urinary VOC metabolites in the 2005 – 2006 and 2011 – 2012 NHANES cycles. The systematic nature of these biases permitted retrospective adjustment through a statistical approach based on linear regression modeling where adjusted measurements are predicted from unadjusted measurements using suitable data. The “statistical recalibrations” implemented here have the general form of a univariate linear regression equation (accounting for dilution factors routinely used during measurement):

where exp[·] and ln(·) are the natural exponential and natural logarithm functions, respectively. Natural log-transformation of both the un-adjusted and adjusted measurements moderated adverse influence on model fit from extreme measurements. The estimated regression slope and intercept are m and b, respectively, which are tabulated below for each analyte. The dilution factor was accounted for only once for each analyte that underwent more than one statistical recalibration (e.g., URXMB3). Statistical recalibration for the mass fraction of salt (URXHP2, URXGAM) only required a regression slope (i.e., b=0).

The explanatory power of the linear regressions was excellent (R2≥0.95), and residuals exhibited distributions with good approximation to normality, as well as stable variance over the observed range of measurements. These favorable diagnostics demonstrate the efficacy of statistical recalibration for the retrospective amelioration of systematic bias.

Correction for Variation in Preparation of Neat Native Metabolites Standards

During the 2005–2006 and 2011–2012 NHANES cycles, calibrators were prepared from a multi-analyte stock solution formulated from neat materials in-house. Beginning with the NHANES 2015–2016 cycle, calibrators and the multi-analyte stock solution were prepared externally. A systematic bias between the cycles that used in-house calibration materials and the cycle using externally prepared calibration materials was observed for analytes listed in the table below. Further validation of the externally prepared calibrators suggested that the in-house calibrators were inaccurate due to special requirements for handling and preparing accurate solutions from neat materials, some of which are highly hygroscopic.

Analyte Code m used in correction b used in correction
URXAMC 0.99687 0.12843
URXCEM 1.01462 -0.13642
URXDHB 0.99654 0.04687
URXHEM 1.00947 0.30195
URXHPM 0.98949 -0.23802
URXMAD 1.00736 -0.18993
URXTTC 1.03057 -0.0746
URXMB3 0.97491 -0.43202
URX2DC 1.00155 -0.32374

Correction for Mass Fraction of Salt in Neat Compound Standard

During the 2005–2006 and 2011–2012 NHANES cycles, calibrators were prepared from a multi-analyte stock solution formulated from neat materials in-house. Beginning with the NHANES 2015–2016 cycle, calibrators and the multi-analyte stock solution were prepared externally. A systematic bias between the cycles that used in-house calibration materials and the cycle using externally prepared calibration materials was observed for analytes listed in the table below. Further validation confirmed that the large mass fraction of salt in the neat materials was not accounted for during formulation of in-house calibration materials. This discrepancy between the calculated concentration of the calibrators and the actual concentration led to a systematic bias in results for URXHP2 and URXGAM.

Analyte Code m used in correction
URXHP2 0.54711990
URXGAM 0.57755045

 Correction for Stereoisomerism in Urine Samples

UXMB3 occurs in human urine predominantly in the cis isomer, but quantitation in the NHANES 2005–2006 and NHANES 2011–2012 cycles used standards containing the trans isomer. This discrepancy led to a systematic bias in the URXMB3 results. Neat material that is purely cis isomer cannot be readily obtained, but a predictive regression equation can account for these quantitative differences.

Analyte Code m used in correction used in correction
URXMB3 0.97741 -0.18775

Detection limits

The detection limits were constant for the analytes in the data set. Two variables are provided for each of these analytes. The variable named ending in “LC” (ex., URDAAMLC) indicates whether the result was below the limit of detection: the value “0” means that the result was at or above the limit of detection, “1” indicates that the result was below the limit of detection. For analytes with analytic results below the lower limit of detection (ex., URDAAMLC=1), an imputed fill value was placed in the analyte results field. This value is the lower limit of detection divided by the square root of 2 (LLOD/sqrt [2]). The other variable prefixed URX (ex., URXAAM) provides the analytic result for the analyte.

The lower limit of detection (LLOD, in µg/L) for urinary VOC metabolites:

VARIABLE Analyte LLOD
URXAAM Urinary N-Acetyl-S-(2-carbamoylethyl)-L-cysteine 2.20
URXAMC Urinary N-Acetyl-S-(N-methylcarbamoyl)-L-cysteine 6.26
URXATC Urinary 2-Aminothiazoline-4-carboxylic acid 15.0
URXBMA Urinary N-Acetyl-S-(benzyl)-L-cysteine 0.500
URXBPM Urinary N-Acetyl-S-(n-propyl)-L-cysteine 1.20
URXCEM Urinary N-Acetyl-S-(2-carboxyethyl)-L-cysteine 6.96
URXCYM Urinary N-Acetyl-S-(2-cyanoethyl)-L-cysteine 0.500
URX1DC Urinary N-Acetyl-S-(1,2-dichlorovinyl)-L-cysteine 12.6
URX2DC Urinary N-Acetyl-S-(2,2-dichlorovinyl)-L-cysteine 4.70
URXDHB Urinary N-Acetyl-S-(3,4-dihydroxybutyl)-L-cysteine 5.25
URXDPM Urinary N-Acetyl-S-(dimethylphenyl)-L-cysteine 0.500
URXGAM Urinary N-Acetyl-S-(2-carbamoyl-2-hydroxyethyl)-L-cysteine 9.40
URXHEM Urinary N-Acetyl-S-(2-hydroxyethyl)-L-cysteine 0.791
URXHPM Urinary N-Acetyl-S-(3-hydroxypropyl)-L-cysteine 13.0
URXHP2 Urinary N-Acetyl-S-(2-hydroxypropyl)-L-cysteine 5.30
URXPMM Urinary N-Acetyl-S-(3-hydroxypropyl-1-methyl)-L-cysteine 2.00
URXMAD Urinary Mandelic acid 12.0
URX2MH Urinary 2-Methylhippuric acid 5.00
URX34M Urinary 3- and 4-Methylhippuric acid 8.00
URXMB1 Urinary N-Acetyl-S-(1-hydroxymethyl-2-propenyl)-L-cysteine 0.700
URXMB2 Urinary N-Acetyl-S-(2-hydroxy-3-butenyl)-L-cysteine 0.700
URXMB3 Urinary N-Acetyl-S-(4-hydroxy-2-butenyl)-L-cysteine 0.600
URXPHE Urinary N-Acetyl-S-(phenyl-2-hydroxyethyl)-L-cysteine 0.700
URXPHG Urinary Phenylglyoxylic acid 12.0
URXPMA Urinary N-Acetyl-S-(phenyl)-L-cysteine 0.600
URXTCV Urinary N-Acetyl-S-(trichlorovinyl)-L-cysteine 3.00
URXTTC Urinary 2-Thioxothiazolidine-4-carboxylic acid 11.2

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.

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

WTSA2YR - Subsample A weights

Variable Name:
WTSA2YR
SAS Label:
Subsample A weights
English Text:
Subsample A weights
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
12199.652219 to 643202.3505 Range of Values 2551 2551
0 No Lab Result 0 2551
. Missing 0 2551

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
4 to 800 Range of Values 2523 2523
. Missing 28 2551

URX1DC - N-Acel-S-(1,2-dichlorovinl)-L-Cys(ng/mL)

Variable Name:
URX1DC
SAS Label:
N-Acel-S-(1,2-dichlorovinl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S-(1,2-dichlorovinyl)-L-Cysteine (ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
8.9 to 14.3 Range of Values 2466 2466
. Missing 85 2551

URD1DCLC - N-Acel-S-(1,2-dichlorovinl)-L-Cys comt

Variable Name:
URD1DCLC
SAS Label:
N-Acel-S-(1,2-dichlorovinl)-L-Cys comt
English Text:
N-Acetyl-S-(1,2-dichlorovinyl)-L-Cysteine comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 1 1
1 Below lower detection limit 2465 2466
. Missing 85 2551

URX2DC - N-Acel-S-(2,2-Dichlorvinyl)-L-Cys(ng/mL)

Variable Name:
URX2DC
SAS Label:
N-Acel-S-(2,2-Dichlorvinyl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S-(2,2-Dichlorovinyl)-L-Cysteine (ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
3.32 to 19.4 Range of Values 2466 2466
. Missing 85 2551

URD2DCLC - N-Acel-S-(2,2-Dichlorvinyl)-L-Cys comt

Variable Name:
URD2DCLC
SAS Label:
N-Acel-S-(2,2-Dichlorvinyl)-L-Cys comt
English Text:
N-Acetyl-S-(2,2-Dichlorovinyl)-L-Cysteine comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 8 8
1 Below lower detection limit 2458 2466
. Missing 85 2551

URX2MH - 2-Methylhippuric acid (ng/mL)

Variable Name:
URX2MH
SAS Label:
2-Methylhippuric acid (ng/mL)
English Text:
2-Methylhippuric acid (ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
3.54 to 18200 Range of Values 2466 2466
. Missing 85 2551

URD2MHLC - 2-Methylhippuric acid comment code

Variable Name:
URD2MHLC
SAS Label:
2-Methylhippuric acid comment code
English Text:
2-Methylhippuric acid comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2352 2352
1 Below lower detection limit 114 2466
. Missing 85 2551

URX34M - 3-Methipurc acd & 4-Methipurc acd(ng/mL)

Variable Name:
URX34M
SAS Label:
3-Methipurc acd & 4-Methipurc acd(ng/mL)
English Text:
3-Methylhippuric acid & 4-Methylhippuric acid(ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
5.66 to 55000 Range of Values 2466 2466
. Missing 85 2551

URD34MLC - 3-Methipurc acd & 4-Methipurc acid comt

Variable Name:
URD34MLC
SAS Label:
3-Methipurc acd & 4-Methipurc acid comt
English Text:
3-Methylhippuric acid & 4-Methylhippuric acid comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2464 2464
1 Below lower detection limit 2 2466
. Missing 85 2551

URXAAM - N-Ace-S-(2-carbamoylethyl)-L-Cys(ng/mL)

Variable Name:
URXAAM
SAS Label:
N-Ace-S-(2-carbamoylethyl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S-(2-carbamoylethyl)-L-Cysteine(ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1.56 to 3120 Range of Values 2466 2466
. Missing 85 2551

URDAAMLC - N-Ace-S-(2-carbamoylethyl)-L-Cys comt

Variable Name:
URDAAMLC
SAS Label:
N-Ace-S-(2-carbamoylethyl)-L-Cys comt
English Text:
N-Acetyl-S-(2-carbamoylethyl)-L-Cysteine comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2463 2463
1 Below lower detection limit 3 2466
. Missing 85 2551

URXAMC - N-Ace-S-(N-methlcarbamoyl)-L-Cys(ng/mL)

Variable Name:
URXAMC
SAS Label:
N-Ace-S-(N-methlcarbamoyl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S-(N-methylcarbamoyl)-L-Cysteine(ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
4.43 to 4320 Range of Values 2466 2466
. Missing 85 2551

URDAMCLC - N-Ace-S-(N-methlcarbamoyl)-L-Cys comt

Variable Name:
URDAMCLC
SAS Label:
N-Ace-S-(N-methlcarbamoyl)-L-Cys comt
English Text:
N-Acetyl-S-(N-methylcarbamoyl)-L-Cysteine comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2461 2461
1 Below lower detection limit 5 2466
. Missing 85 2551

URXATC - 2-Amnothiazolne-4-carbxylic acid(ng/mL)

Variable Name:
URXATC
SAS Label:
2-Amnothiazolne-4-carbxylic acid(ng/mL)
English Text:
2-Aminothiazoline-4-carboxylic acid(ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
10.6 to 2420 Range of Values 2466 2466
. Missing 85 2551

URDATCLC - 2-Amnothiazolne-4-carbxylic acid comt

Variable Name:
URDATCLC
SAS Label:
2-Amnothiazolne-4-carbxylic acid comt
English Text:
2-Amnothiazolne-4-carbxylic acid comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2375 2375
1 Below lower detection limit 91 2466
. Missing 85 2551

URXBMA - N-Acetyl-S-(benzyl)-L-Cysteine(ng/mL)

Variable Name:
URXBMA
SAS Label:
N-Acetyl-S-(benzyl)-L-Cysteine(ng/mL)
English Text:
N-Acetyl-S-(benzyl)-L-Cysteine(ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.354 to 1180 Range of Values 2466 2466
. Missing 85 2551

URDBMALC - N-Acetyl-S-(benzyl)-L-Cysteine comt

Variable Name:
URDBMALC
SAS Label:
N-Acetyl-S-(benzyl)-L-Cysteine comt
English Text:
N-Acetyl-S-(benzyl)-L-Cysteine comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2450 2450
1 Below lower detection limit 16 2466
. Missing 85 2551

URXBPM - N-Acetyl-S-(n-propyl)-L-Cysteine(ng/mL)

Variable Name:
URXBPM
SAS Label:
N-Acetyl-S-(n-propyl)-L-Cysteine(ng/mL)
English Text:
N-Acetyl-S-(n-propyl)-L-Cysteine(ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.85 to 727 Range of Values 2396 2396
. Missing 155 2551

URDBPMLC - N-Acetyl-S-(n-propyl)-L-Cysteine comt

Variable Name:
URDBPMLC
SAS Label:
N-Acetyl-S-(n-propyl)-L-Cysteine comt
English Text:
N-Acetyl-S-(n-propyl)-L-Cysteine comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 1820 1820
1 Below lower detection limit 576 2396
. Missing 155 2551

URXCEM - N-Acetyl-S- (2-Carbxyethyl)-L-Cys(ng/mL)

Variable Name:
URXCEM
SAS Label:
N-Acetyl-S- (2-Carbxyethyl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S- (2-Carboxyethyl)-L-Cysteine(ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
4.92 to 3230 Range of Values 2466 2466
. Missing 85 2551

URDCEMLC - N-Acetyl-S-(2-Carbxyethyl)-L-Cys comt

Variable Name:
URDCEMLC
SAS Label:
N-Acetyl-S-(2-Carbxyethyl)-L-Cys comt
English Text:
N-Acetyl-S- (2-Carboxyethyl)-L-Cysteine comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2445 2445
1 Below lower detection limit 21 2466
. Missing 85 2551

URXCYM - N-Acetyl-S-(2-cyanoethyl)-L-Cyst(ng/mL)

Variable Name:
URXCYM
SAS Label:
N-Acetyl-S-(2-cyanoethyl)-L-Cyst(ng/mL)
English Text:
N-Acetyl-S-(2-cyanoethyl)-L-Cysteine(ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.354 to 1600 Range of Values 2466 2466
. Missing 85 2551

URDCYMLC - N-Acetyl-S-(2-cyanoethyl)-L-Cyst comt

Variable Name:
URDCYMLC
SAS Label:
N-Acetyl-S-(2-cyanoethyl)-L-Cyst comt
English Text:
N-Acetyl-S-(2-cyanoethyl)-L-Cysteine comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2251 2251
1 Below lower detection limit 215 2466
. Missing 85 2551

URXDHB - N-Ace-S- (3,4-Dihidxybutl)-L-Cys(ng/mL)

Variable Name:
URXDHB
SAS Label:
N-Ace-S- (3,4-Dihidxybutl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S- (3,4-Dihidroxybutyl)-L-Cysteine(ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
3.71 to 2410 Range of Values 2466 2466
. Missing 85 2551

URDDHBLC - N-Ace-S- (3,4-Dihidxybutl)-L-Cys comt

Variable Name:
URDDHBLC
SAS Label:
N-Ace-S- (3,4-Dihidxybutl)-L-Cys comt
English Text:
N-Acetyl-S- (3,4-Dihidroxybutyl)-L-Cysteine comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2465 2465
1 Below lower detection limit 1 2466
. Missing 85 2551

URXDPM - N-Ace-S-(dimethylphenyl)-L-Cys(ng/mL)

Variable Name:
URXDPM
SAS Label:
N-Ace-S-(dimethylphenyl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S-(dimethylphenyl)-L-Cysteine(ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.354 to 2.27 Range of Values 2466 2466
. Missing 85 2551

URDDPMLC - N-Ace-S-(dimethylphenyl)-L-Cys comt

Variable Name:
URDDPMLC
SAS Label:
N-Ace-S-(dimethylphenyl)-L-Cys comt
English Text:
N-Acetyl-S-(dimethylphenyl)-L-Cysteine comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 5 5
1 Below lower detection limit 2461 2466
. Missing 85 2551

URXGAM - N-Ac-S-(2-carbmo-2-hydxel)-L-Cys(ng/mL)

Variable Name:
URXGAM
SAS Label:
N-Ac-S-(2-carbmo-2-hydxel)-L-Cys(ng/mL)
English Text:
N-Acetyl-S-(2-carbamoyl-2-hydroxyethyl)-L-Cysteine(ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
6.65 to 455 Range of Values 2466 2466
. Missing 85 2551

URDGAMLC - N-Ac-S-(2-carbmo-2-hydxel)-L-Cys comt

Variable Name:
URDGAMLC
SAS Label:
N-Ac-S-(2-carbmo-2-hydxel)-L-Cys comt
English Text:
N-Acetyl-S-(2-carbamoyl-2-hydroxyethyl)-L-Cysteine comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 1100 1100
1 Below lower detection limit 1366 2466
. Missing 85 2551

URXHEM - N-Ace-S-(2-Hydroxyethyl)-L-Cys(ng/mL)

Variable Name:
URXHEM
SAS Label:
N-Ace-S-(2-Hydroxyethyl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S- (2-Hydroxyethyl)-L-Cysteine(ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.559 to 69.6 Range of Values 2466 2466
. Missing 85 2551

URDHEMLC - N-Ace-S-(2-Hydroxyethyl)-L-Cys comt

Variable Name:
URDHEMLC
SAS Label:
N-Ace-S-(2-Hydroxyethyl)-L-Cys comt
English Text:
N-Acetyl-S- (2-Hydroxyethyl)-L-Cysteine comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 1462 1462
1 Below lower detection limit 1004 2466
. Missing 85 2551

URXHP2 - N-Ace-S-(2-hydroxypropyl)-L-Cys(ng/mL)

Variable Name:
URXHP2
SAS Label:
N-Ace-S-(2-hydroxypropyl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S- (2-hydroxypropyl)-L-Cysteine(ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
3.75 to 9360 Range of Values 2466 2466
. Missing 85 2551

URDHP2LC - N-Ace-S-(2-hydroxypropyl)-L-Cys comt

Variable Name:
URDHP2LC
SAS Label:
N-Ace-S-(2-hydroxypropyl)-L-Cys comt
English Text:
N-Acetyl-S- (2-hydroxypropyl)-L-Cysteine comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2344 2344
1 Below lower detection limit 122 2466
. Missing 85 2551

URXHPM - N-Ace-S-(3-Hydroxypropyl)-L-Cys(ng/mL)

Variable Name:
URXHPM
SAS Label:
N-Ace-S-(3-Hydroxypropyl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S- (3-Hydroxypropyl)-L-Cysteine(ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
9.2 to 8970 Range of Values 2466 2466
. Missing 85 2551

URDHPMLC - N-Ace-S-(3-Hydroxypropyl)-L-Cys comt

Variable Name:
URDHPMLC
SAS Label:
N-Ace-S-(3-Hydroxypropyl)-L-Cys comt
English Text:
N-Acetyl-S- (3-Hydroxypropyl)-L-Cysteine comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2464 2464
1 Below lower detection limit 2 2466
. Missing 85 2551

URXMAD - Mandelic acid(ng/mL)

Variable Name:
URXMAD
SAS Label:
Mandelic acid(ng/mL)
English Text:
Mandelic acid(ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
8.5 to 27500 Range of Values 2466 2466
. Missing 85 2551

URDMADLC - Mandelic acid comment code

Variable Name:
URDMADLC
SAS Label:
Mandelic acid comment code
English Text:
Mandelic acid comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2441 2441
1 Below lower detection limit 25 2466
. Missing 85 2551

URXMB1 - N-A-S-(1-HydrxMet)-2-Prpn)-L-Cys(ng/mL)

Variable Name:
URXMB1
SAS Label:
N-A-S-(1-HydrxMet)-2-Prpn)-L-Cys(ng/mL)
English Text:
N-Acetyl-S-(1-HydroxyMethyl)-2-Propenyl)-L-Cysteine(ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.495 to 2.22 Range of Values 2466 2466
. Missing 85 2551

URDMB1LC - N-A-S-(1-HydrxMet)-2-Prpn)-L-Cys comt

Variable Name:
URDMB1LC
SAS Label:
N-A-S-(1-HydrxMet)-2-Prpn)-L-Cys comt
English Text:
N-Acetyl-S-(1-HydroxyMethyl)-2-Propenyl)-L-Cysteine comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 24 24
1 Below lower detection limit 2442 2466
. Missing 85 2551

URXMB2 - N-Ac-S-(2-Hydrxy-3-butnyl)-L-Cys(ng/mL)

Variable Name:
URXMB2
SAS Label:
N-Ac-S-(2-Hydrxy-3-butnyl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S- (2-hydroxy-3-butenyl)-L-Cysteine (ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.495 to 30.9 Range of Values 2466 2466
. Missing 85 2551

URDMB2LC - N-Ac-S-(2-Hydrxy-3-butnyl)-L-Cys comt

Variable Name:
URDMB2LC
SAS Label:
N-Ac-S-(2-Hydrxy-3-butnyl)-L-Cys comt
English Text:
N-Acetyl-S- (2-hydroxy-3-butenyl)-L-Cysteine comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 256 256
1 Below lower detection limit 2210 2466
. Missing 85 2551

URXMB3 - N-A-S-(4-hydrxy-2butn-l-yl)-L-Cys(ng/mL)

Variable Name:
URXMB3
SAS Label:
N-A-S-(4-hydrxy-2butn-l-yl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S- (4-hydroxy-2-butenyl)-L-Cysteine (ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.424 to 261 Range of Values 2466 2466
. Missing 85 2551

URDMB3LC - N-A-S-(4-hydrxy-2butn-l-yl)-L-Cys comt

Variable Name:
URDMB3LC
SAS Label:
N-A-S-(4-hydrxy-2butn-l-yl)-L-Cys comt
English Text:
N-Acetyl-S- (4-hydroxy-2-butenyl)-L-Cysteine comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2399 2399
1 Below lower detection limit 67 2466
. Missing 85 2551

URXPHE - N-Ace-S-(phenl-2-hydxyetl)-L-Cys(ng/mL)

Variable Name:
URXPHE
SAS Label:
N-Ace-S-(phenl-2-hydxyetl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S-(phenyl-2-hydroxyethyl)-L-Cysteine(ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.495 to 550 Range of Values 2466 2466
. Missing 85 2551

URDPHELC - N-Ace-S-(phenl-2-hydxyetl)-L-Cys comt

Variable Name:
URDPHELC
SAS Label:
N-Ace-S-(phenl-2-hydxyetl)-L-Cys comt
English Text:
N-Acetyl-S-(phenyl-2-hydroxyethyl)-L-Cysteine comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 863 863
1 Below lower detection limit 1603 2466
. Missing 85 2551

URXPHG - Phenylglyoxylic acid(ng/mL)

Variable Name:
URXPHG
SAS Label:
Phenylglyoxylic acid(ng/mL)
English Text:
Phenylglyoxylic acid(ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
8.5 to 32200 Range of Values 2466 2466
. Missing 85 2551

URDPHGLC - Phenylglyoxylic acid comment code

Variable Name:
URDPHGLC
SAS Label:
Phenylglyoxylic acid comment code
English Text:
Phenylglyoxylic acid comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2444 2444
1 Below lower detection limit 22 2466
. Missing 85 2551

URXPMA - N-Acetyl-S-(phenyl)-L-Cysteine(ng/mL)

Variable Name:
URXPMA
SAS Label:
N-Acetyl-S-(phenyl)-L-Cysteine(ng/mL)
English Text:
N-Acetyl-S-(phenyl)-L-Cysteine(ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.424 to 19.1 Range of Values 2466 2466
. Missing 85 2551

URDPMALC - N-Acetyl-S-(phenyl)-L-Cysteine comt

Variable Name:
URDPMALC
SAS Label:
N-Acetyl-S-(phenyl)-L-Cysteine comt
English Text:
N-Acetyl-S-(phenyl)-L-Cysteine comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 1158 1158
1 Below lower detection limit 1308 2466
. Missing 85 2551

URXPMM - N-A-S-(3-hydrxprpl-1-metl)-L-Cys(ng/mL)

Variable Name:
URXPMM
SAS Label:
N-A-S-(3-hydrxprpl-1-metl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S-(3-hydroxypropyl-1-methyl)-L-Cysteine(ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
2.85 to 20700 Range of Values 2466 2466
. Missing 85 2551

URDPMMLC - N-A-S-(3-hydrxprpl-1-metl)-L-Cys comt

Variable Name:
URDPMMLC
SAS Label:
N-A-S-(3-hydrxprpl-1-metl)-L-Cys comt
English Text:
N-Acetyl-S-(3-hydroxypropyl-1-methyl)-L-Cysteine comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2466 2466
1 Below lower detection limit 0 2466
. Missing 85 2551

URXTCV - N-Acetyl-S-(trichlorovinyl)-L-Cys(ng/mL)

Variable Name:
URXTCV
SAS Label:
N-Acetyl-S-(trichlorovinyl)-L-Cys(ng/mL)
English Text:
N-Acetyl-S-(trichlorovinyl)-L-Cysteine(ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
2.12 to 4.94 Range of Values 2466 2466
. Missing 85 2551

URDTCVLC - N-Acetyl-S-(trichlorovinyl)-L-Cys comt

Variable Name:
URDTCVLC
SAS Label:
N-Acetyl-S-(trichlorovinyl)-L-Cys comt
English Text:
N-Acetyl-S-(trichlorovinyl)-L-Cysteine comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2 2
1 Below lower detection limit 2464 2466
. Missing 85 2551

URXTTC - 2-Thoxothazlidne-4-carbxylic acid(ng/mL)

Variable Name:
URXTTC
SAS Label:
2-Thoxothazlidne-4-carbxylic acid(ng/mL)
English Text:
2-Thioxothiazolidine-4-carboxylic acid(ng/mL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
7.9 to 2320 Range of Values 2466 2466
. Missing 85 2551

URDTTCLC - 2-thoxothazlidne-4-carbxylic comt

Variable Name:
URDTTCLC
SAS Label:
2-thoxothazlidne-4-carbxylic comt
English Text:
2-thioxothiazolidine-4-carboxylic acid comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 876 876
1 Below lower detection limit 1590 2466
. Missing 85 2551