• Component Description
• Eligible Sample
• Description of Laboratory Methodology
• Laboratory Method Files
• Laboratory Quality Assurance and Monitoring
• Data Processing and Editing
• Analytic Notes
• References
• Codebook
  • SEQN - Respondent sequence number
  • WTSA2YR - Subsample A Weights
  • URXP01 - 1-Hydroxynaphthalene (ng/L)
  • URDP01LC - 1-Hydroxynaphthalene Comment Code
  • URXP02 - 2-Hydroxynaphthalene (ng/L)
  • URDP02LC - 2-Hydroxynaphthalene Comment Code
  • URXP03 - 3-Hydroxyfluorene (ng/L)
  • URDP03LC - 3-Hydroxyfluorene Comment Code
  • URXP04 - 2-Hydroxyfluorene (ng/L)
  • URDP04LC - 2-Hydroxyfluorene Comment Code
  • URXP06 - 1-Hydroxyphenanthrene (ng/L)
  • URDP06LC - 1-Hydroxyphenanthrene Comment Code
  • URXP10 - 1-Hydroxypyrene (ng/L)
  • URDP10LC - 1-Hydroxypyrene Comment Code
  • URXP25 - 2 & 3-Hydroxyphenanthrene (ng/L)
  • URDP25LC - 2 & 3-Hydroxyphenanthrene Comment Code

National Health and Nutrition Examination Survey

2015-2016 Data Documentation, Codebook, and Frequencies

Polycyclic Aromatic Hydrocarbons (PAH) - Urine (PAH_I)

Data File: PAH_I.xpt

First Published: July 2020

Last Revised: NA

Component Description

PAHs constitute a group of chemicals formed during the incomplete combustion of coal, oil and gas, garbage, and other organic substances. In general, people are exposed to mixtures of PAHs, and the sources are widespread, including vehicle exhaust, asphalt, coal tar, wildfires, agricultural burning, charbroiled foods, and tobacco smoke. Upon entering the body, PAHs are readily metabolized and eliminated in urine. Urinary concentrations of PAH metabolites, specifically monohydroxylated PAHs (OH-PAHs), have been used as biomarkers of human exposure to select PAHs, including naphthalene, fluorene, phenanthrene, and pyrene.

Eligible Sample

All examined participants aged 3 to 5 years and a one-third subsample from examined participants aged 6 years and older were eligible.

Description of Laboratory Methodology

The specific analytes measured in this method are OH-PAHs, namely 1-hydroxynaphthalene, 2-hydroxynaphthalene, 2-hydroxyfluorene, 3-hydroxyfluorene, 1-hydroxyphenanthrene, 2- & 3-hydroxyphenanthrene, and 1-hydroxypyrene. The analytical procedure involves enzymatic hydrolysis of glucuronidated/sulfated OH-PAH metabolites in urine, extraction by on-line solid phase extraction, and separation and quantification using isotope dilution high performance liquid chromatography-tandem mass spectrometry (on-line SPE-HPLC-MS/MS) (Wang et al., 2016).

Refer to the Laboratory Method Files section for a detailed description of the laboratory methods used.

There were no changes to the lab method, lab equipment, or lab site for this component in the NHANES 2015-2016 cycle.

Laboratory Method Files

Polycyclic Aromatic Hydrocarbons (PAHs) (July 2020)

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 for analysis.

Detailed specimen collection and processing instructions are discussed in the NHANES Laboratory Procedures Manual (LPM). Vials were stored under appropriate frozen (-30°C) conditions until they were shipped to the National Center for Environmental Health 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 QA evaluation during unscheduled visits to evaluate both the quality of the laboratory work and the QC procedures. Each laboratory staff member is observed for equipment operation, specimen collection and preparation; testing procedures and constructive feedback are given to each staff member. 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% of all specimens.

NCHS developed and distributed a QC protocol for all CDC and contract laboratories, which outlined the use of Westgard rules (Westgard et al., 1981) 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 Division of Laboratory Sciences’ QA/QC 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 2015-2016 Laboratory Data Overview for general information on NHANES laboratory data.

There are over 800 laboratory tests performed on NHANES participants. However, not all participants provided biospecimens or enough volume for all the tests to be performed. The specimen availability can also vary by age or other population characteristics. Analysts should evaluate the extent of missing data in the dataset related to the outcome of interest as well as any predictor variables used in the analyses to determine whether additional re-weighting for item non-response is necessary.

Please refer to the NHANES Analytic Guidelines and the on-line NHANES Tutorial for details on the use of sample weights and analytic issues.

Subsample Weights

The analytes included in this dataset were measured for all examined participants aged 3-5 years, and in a one-third subsample of participants 6 years and older. For participants aged 3-5, their WTSA2YR are equivalent to their MEC exam sample weights. These participants have completed at least one physical exam component in the MEC; therefore, they all have an exam sample weight larger than “0,” regardless of their lab test results. For participants 6 years and older, special sample weights were created for the subsample. These special weights accounted for the additional probability of selection into the subsample, as well as the additional nonresponse to these lab tests. Therefore, if participants 6 years and older were selected as part of the one-third subsample, but did not provide a urine specimen, they would have the sample weight value assigned as “0” in their records.

Demographic and Other Related Variables

The analysis of NHANES laboratory data must be conducted using the appropriate survey design and demographic variables. The NHANES 2015-2016 Demographics File contains demographic data, health indicators, and other related information collected during household interviews as well as the 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 (i.e., SEQN).

Starting in the 2015-2016 NHANES cycle, the variable URXUCR (urine creatinine) will not be reported in this file. URXUCR can be found in the data file titled “Albumin & Creatinine – Urine”.

Detection Limits

The detection limits were constant for all of the analytes in the data set. Two variables are provided for each of these analytes. The variable name ending in “LC” (ex., URDP04LC) 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. The other variable prefixed URX (ex., URXP04) provides the analytic result for that analyte. For analytes with analytic results below the lower limit of detection (ex., URDP04LC=1), an imputed fill value was placed in the analyte results field. This value is the lower limit of detection divided by square root of 2 (LLOD/sqrt [2]). The lower limit of detection (LLOD in ng/L) for urinary OH-PAHs:

Variable Name	Analyte Description	LLOD
URXP01	1-Hydroxynapthalene (1-Naphthol)	60
URXP02	2-Hydroxynapthalene (2-Naphthol)	90
URXP03	3-Hydroxyfluorene	8
URXP04	2-Hydroxyfluorene	8
URXP06	1-Hydroxyphenanthrene	9
URXP10	1-Hydroxypyrene	70
URXP25*	2-Hydroxyphenanthrene & 3-Hydroxyphenanthrene	10

*URXP25 values are comparable to the sum of urinary levels of 2-hydroxyphenanthrene and 3-hydroxyphenanthrene reported as two separate variables (URXP07 and URXP05, respectively) in NHANES cycles prior to 2013-2014.

 

References

• Caudill SP, Schleicher RL, Pirkle JL. Multi-rule quality control for the age-related eye disease study. Statist Med 2008;27:4094-41-06.
• Wang Y, Meng L, Pittman EN, Etheredge A, Hubbard K, Trinidad DA, Kato K, Ye X, Calafat AM (2016) Quantification of Urinary Mono-hydroxylated Metabolites of Polycyclic Aromatic Hydrocarbons by on-line Solid Phase Extraction-High Performance Liquid Chromatography-Tandem Mass Spectrometry. Anal Bioanal Chem. 2017 Feb;409(4):931-937.
• Westgard JO, Barry PL, Hunt MR, Groth T. A multi-rule Shewhart chart for quality control in clinical chemistry. Clin Chem. 1981 Mar; 27(3):493-501.

Codebook and Frequencies