• 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
  • WTSVOC2Y - VOC Subsample Weight
  • LBX2DF - Blood 2,5-Dimethylfuran (ng/mL)
  • LBD2DFLC - Blood 2,5-Dimethylfuran Comment Code
  • LBX4CE - Blood 1,1,1,2-Tetrachloroethane (ng/mL)
  • LBD4CELC - Blood 1,1,1,2-Tetrachloroethane Cmt Code
  • LBXV06 - Blood Hexane (ng/mL)
  • LBDV06LC - Blood Hexane Comment Code
  • LBXV07N - Blood Heptane (ng/mL)
  • LBDV07LC - Blood Heptane Comment Code
  • LBXV08N - Blood Octane (ng/mL)
  • LBDV08LC - Blood Octane Comment Code
  • LBXV1D - Blood 1,2-Dichlorobenzene (ng/mL)
  • LBDV1DLC - Blood 1,2-Dichlorobenzene Comment Code
  • LBXV2A - Blood 1,2-Dichloroethane (ng/mL)
  • LBDV2ALC - Blood 1,2-Dichloroethane Comment Code
  • LBXV3B - Blood 1,3-Dichlorobenzene (ng/mL)
  • LBDV3BLC - Blood 1,3-Dichlorobenzene Comment Code
  • LBXV4C - Blood Tetrachloroethene (ng/mL)
  • LBDV4CLC - Blood Tetrachloroethene Comment Code
  • LBXVBF - Blood Bromoform (ng/mL)
  • LBDVBFLC - Blood Bromoform Comment Code
  • LBXVBM - Blood Bromodichloromethane (ng/mL)
  • LBDVBMLC - Blood Bromodichloromethane Comment Code
  • LBXVBZ - Blood Benzene (ng/mL)
  • LBDVBZLC - Blood Benzene Comment Code
  • LBXVBZN - Blood Benzonitrile (ng/mL)
  • LBDVZBLC - Blood Benzonitrile Comment Code
  • LBXVC6 - Blood Cyclohexane (ng/mL)
  • LBDVC6LC - Blood Cyclohexane Comment Code
  • LBXVCB - Blood Chlorobenzene (ng/mL)
  • LBDVCBLC - Blood Chlorobenzene Comment Code
  • LBXVCF - Blood Chloroform (ng/mL)
  • LBDVCFLC - Blood Chloroform Comment Code
  • LBXVCM - Blood Dibromochloromethane (ng/mL)
  • LBDVCMLC - Blood Dibromochloromethane Comment Code
  • LBXVCT - Blood Carbon Tetrachloride (ng/mL)
  • LBDVCTLC - Blood Carbon Tetrachloride Comment Code
  • LBXVDB - Blood 1,4-Dichlorobenzene (ng/mL)
  • LBDVDBLC - Blood 1,4-Dichlorobenzene Comment Code
  • LBXVDE - Blood 1,2-Dibromoethane (ng/mL)
  • LBDVDELC - Blood 1,2-Dibromoethane Comment Code
  • LBXVDEE - Blood Diethyl Ether (ng/mL)
  • LBDVEELC - Blood Diethyl Ether Comment Code
  • LBXVEA - Blood Ethyl Acetate (ng/mL)
  • LBDVEALC - Blood Ethyl Acetate Comment Code
  • LBXVEB - Blood Ethylbenzene (ng/mL)
  • LBDVEBLC - Blood Ethylbenzene Comment Code
  • LBXVEC - Blood Chloroethane (ng/mL)
  • LBDVECLC - Blood Chloroethane Comment Code
  • LBXVFN - Blood Furan (ng/mL)
  • LBDVFNLC - Blood Furan Comment Code
  • LBXVIBN - Blood Isobutyronitrile (ng/mL)
  • LBDVIBLC - Blood Isobutyronitrile Comment Code
  • LBXVIPB - Blood Isopropylbenzene (ng/mL)
  • LBDVIPLC - Blood Isopropylbenzene Comment Code
  • LBXVMC - Blood Methylene Chloride (ng/mL)
  • LBDVMCLC - Blood Methylene Chloride Comment Code
  • LBXVME - Blood MTBE (ng/mL)
  • LBDVMELC - Blood MTBE Comment Code
  • LBXVMCP - Blood Methylcyclopentane (ng/mL)
  • LBDVMPLC - Blood Methylcyclopentane Comment Code
  • LBXVMIK - Blood Methyl Isobutyl Ketone (ng/mL)
  • LBDVMKLC - Blood Methyl Isobutyl Ketone Comt Code
  • LBXVNB - Blood Nitrobenzene (ng/mL)
  • LBDVNBLC - Blood Nitrobenzene Comment Code
  • LBXVOX - Blood o-Xylene (ng/mL)
  • LBDVOXLC - Blood o-Xylene Comment Code
  • LBXVTC - Blood Trichloroethene (ng/mL)
  • LBDVTCLC - Blood Trichloroethene Comment Code
  • LBXVTE - Blood 1,1,1-Trichloroethane (ng/mL)
  • LBDVTELC - Blood 1,1,1-Trichloroethane Comment Code
  • LBXVTFT - Blood aaa-Trifluorotoluene (ng/mL)
  • LBDVFTLC - Blood aaa-Trifluorotoluene Comment Code
  • LBXVTHF - Blood Tetrahydrofuran (ng/mL)
  • LBDVHTLC - Blood Tetrahydrofuran Comment Code
  • LBXVTP - Blood 1,2,3-Trichloropropane (ng/mL)
  • LBDVTPLC - Blood 1,2,3-Trichloropropane Comt Code
  • LBXVVB - Blood Vinyl Bromide (ng/mL)
  • LBDVVBLC - Blood Vinyl Bromide Comment Code
  • LBXVXY - Blood m-/p-Xylene (ng/mL)
  • LBDVXYLC - Blood m-/p-Xylene Comment Code

National Health and Nutrition Examination Survey

2017-2018 Data Documentation, Codebook, and Frequencies

Volatile Organic Compounds and Trihalomethanes/MTBE - Blood (VOCWB_J)

Data File: VOCWB_J.xpt

First Published: October 2020

Last Revised: NA

Component Description

Volatile Organic Compounds and Trihalomethanes/MTBE (Whole Blood)

Volatile organic compounds (VOCs) are a large group of chemicals that have been used as solvents, degreasers, and cleaning agents in industry and consumer products. Many of the VOCs were found to contaminate ground water and drinking water sources. Because of human health concerns, these VOCs have been banned or restricted from most uses.

The halogenated solvents are VOCs consisting of a hydrocarbon chain or one hydrocarbon substituted with one or more chlorine or bromine atoms. Most of these chemicals are used as degreasers and solvents in various products, such as paint. In the past, 1,1,1-trichloroethane was used as a dry cleaning agent, insect fumigant, and solvent in consumer products. Methylene chloride, tetrachloroethene, and trichloroethene are other VOCs that were widely used in the past.

Benzene, ethylbenzene, and xylene collectively referred to as BTEXS, are components of tobacco smoke. Along with 2,5-dimethylfuran, these VOCs are usually detected in the blood of cigarette smokers at higher levels than in non-smokers. Chlorobenzene (monochlorobenzene) and the three dichlorobenzenes are halogenated aromatic hydrocarbons primarily used in industrial and chemical synthetic processes. Chlorobenzene has been used to produce DDT, phenol, and nitrobenzene. The dichlorobenzenes are also chemical intermediates in the synthesis of dyes, pesticides, and other industrial products. 1,4-Dichlorobenzene (para-dichlorobenzene) is used also as a moth repellent and as a deodorizer. Disinfection by-products (DBP), including bromodichloromethane, dibromochloromethane, bromoform, and chloroform are formed when chlorine interacts with natural organic materials found in water. Primary sources of DBPs are chlorinated drinking water and recreational water bodies, such as swimming pools.

The prevalence of disinfection by-products in drinking water supplies has raised concerns about possible adverse health effects from chronic exposure to these potentially carcinogenic compounds. Methyl-tert-butyl ether (MTBE) was used as an additive to replace lead in gasoline, but its use was banned after widespread ground water contamination was discovered.

Inhalation is the most common VOC route of exposure in the general population, including indoor sources such as paints, adhesives, cleaning solutions, and aerosolized insecticide sprays; industries producing these solvents; and contaminated waste disposal sites. Drinking water may contribute to exposure when underground drinking water supplies are contaminated. After they are absorbed in the body, VOCs are rapidly eliminated in exhaled breath, or may be rapidly metabolized and eliminated in the urine.

Eligible Sample

Examined participants aged 12 years and older from a one-half sample were eligible.

Description of Laboratory Methodology

An automated analytical method was developed using capillary gas chromatography (GC) and mass spectrometry (MS) with selected-ion monitoring (SIM) detection and isotope-dilution. This method quantifies levels of individual VOCs and Trihalomethanes (THMs) and methyl tert-butyl ether (MTBE) in whole blood to low-parts-per-trillion range. Because non-occupationally exposed individuals have blood VOC concentrations within this range, this method is applicable for determining these quantities and investigating cases of sustained or recent low-level exposure.

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 2017-2018 cycle.

Laboratory Method Files

Volatile Organic Compounds (VOCs) & Trihalomethanes/MTBE Laboratory Procedure Manual (October 2020)

Laboratory Quality Assurance and Monitoring

Whole blood specimens were processed, stored, and shipped to 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 refrigerated (2-8°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 Laboratory Services’ 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 2017-2018 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.

Volatile Toxicant Questionnaire

 A volatile toxicant questionnaire (VTQ) was administered on the mobile examination center (MEC), by trained interviewers, using the Computer-Assisted Personal Interview (CAPI) system. The VTQ section includes data about the participant’s home, activities, amount of time spent in various locations, and exposure to different chemicals over the past 48 hours. This questionnaire data can be used in conjunction with the VOC laboratory dataset and found in the Volatile Toxicant Data File in the NHANES 2017-2018 Questionnaire Data section.

Subsample Weights

Whole blood VOCs were measured in a one-half subsample of participants 12 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 2017-2018 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.

The Fasting Questionnaire file includes auxiliary information such as fasting status, the time of venipuncture, and the conditions precluding venipuncture.

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., LBD2DFLC) 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., LBD2DFLC=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 LBX (ex., LBX2DF) provides the analytic result for that analyte. All data are rounded to three significant figures or three decimal places, whichever is less precise.

Lower Limit of Detection (LLOD, in ng/mL) for Whole Blood VOCs:

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