• 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
  • URXNDEA - N-Nitrosodiethylamine (NDEA) (ng/L)
  • URDNDELC - NDEA Comment Code
  • URXNMEA - N-Nitrosoethylmethylamine (NMEA) (ng/L)
  • URDMEALC - NMEA Comment Code
  • URXNMOR - N-Nitrosomorpholine (NMOR) (ng/L)
  • URDMORLC - NMOR Comment Code
  • URXNPIP - N-Nitrosopiperidine (NPIP) (ng/L)
  • URDPIPLC - NPIP Comment Code
  • URXNPYR - N-Nitrosopyrrolidine (NPYR) (ng/L)
  • URDPYRLC - NPYR Comment Code

National Health and Nutrition Examination Survey

2013-2014 Data Documentation, Codebook, and Frequencies

Volatile N-Nitrosamine Compounds (VNAs) - Urine (VNA_H)

Data File: VNA_H.xpt

First Published: December 2018

Last Revised: NA

Component Description

Volatile nitrosamines (VNAs) are harmful ingredients in tobacco smoke. High levels of exposure have been reported during the consumption of smokeless or burned tobacco. Nitrate content in tobacco has significant influence on the tobacco smoke composition, cancer risk, and other disease risks relative to cigarette smoking. Nitrates are reduced to nitrites and can react with amines to form N-nitrosamine compounds. VNAs are well-established teratogens and carcinogens in animals, and are classified as probable (group 2A) or possible (group 2B) carcinogens in humans. These compounds have also been shown to have genotoxic effects. 

It has been reported that VNA exposure may play an important part in the etiology of esophageal cancer and schistosoma-associated bladder cancer. Studies have also shown correlations between VNA exposure and lipid peroxidation and oxidative stress (insulin-resistance and inflammation), chronic diseases (diabetes), and neurodegenerative diseases, such as Alzheimer’s.

Eligible Sample

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

Description of Laboratory Methodology

VNAs in human urine are measured using an isotope dilution gas chromatography tandem mass spectrometric (GC/MS-MS) method. Urine samples are collected and stored at -60 to -70ºC. Urine sample is spiked with a mixture of isotopically labeled internal standards, and VNAs are extracted from urine with dichloromethane. Isotopically labelled internal standards are used for accurate quantification. Standard solutions with known VNA concentrations are analyzed, and the reconstructed ion chromatogram peak area ratios of native analytes to labeled internal standards are used to determine VNAs levels in samples.

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

This is a new component in the NHANES 2013-2014 cycle.

Laboratory Method Files

Volatile N-Nitrosamine Compounds Laboratory Procedure Manual (December 2018)

Laboratory Quality Assurance and Monitoring

Urine samples were 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 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 quality assurance and quality control (QA/QC) protocols meet the 1988 Clinical Laboratory Improvement Act 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 competency assessment evaluation during visits to evaluate both the quality of the laboratory work and the quality-control 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 quality control 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 Environmental Health Laboratory Sciences 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 2013-2014 Laboratory Data Overview for general information on NHANES laboratory data.

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

Heterocyclic aromatic amines were measured in a one-third subsample of participants 6 years and older. 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 using the appropriate survey design and demographic variables. The NHANES 2013-2014 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).

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., URDDEALC) indicates whether the result was below the limit of detection: “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., URDDEALC=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 other variable prefixed URX (ex., URXNDEA) provides the analytic result for that analyte.

The lower limit of detection (LLOD, in ng/L) for Volatile N-Nitrosamines:

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

• Caudill, S.P., Schleicher, R.L., Pirkle, J.L. Multi-rule quality control for the age-related eye disease study. Statist. Med. (2008) 27(20):4094-40106.

• Westgard J.O., Barry P.L., Hunt M.R., Groth T. A multi-rule Shewhart chart for quality control in clinical chemistry. Clin Chem (1981) 27:493-501.

Codebook and Frequencies