National Health and Nutrition Examination Survey

2003 - 2004 Data Documentation, Codebook, and Frequencies

Volatile Organic Compounds in Blood and Water (L04VOC_C)

Data File: L04VOC_C.xpt

First Published: August, 2008

Last Revised: June, 2009

Locator Record

Title: Volatile Organic Compounds in Blood and Water (L04VOC_C )
Contact Number: 1-866-441-NCHS
Years of Content: 2003 - 2004
First Published: August, 2008
Revised: June, 2009
Access Constraints: None
Use Constraints: None
Geographic Coverage: National
Subject:Lab 04 Volatile Organic Compounds Questionnaire, Blood and Water
Record Source: NHANES 2003 - 2004
Survey Methodology: NHANES 2003 - 2004 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

Both the lab data and questionnaire items will be released in this file.

Volatile Organic Compound Questions:

The volatile organic compound section of the Mobile Examination Center (MEC) Interview and Phlebotomy Component (PH) provide personal interview data.

Volatile Organic Compounds (Human Blood):

Exposure to volatile organic compounds (VOCs) is ubiquitous. Chronic exposure to extremely high levels of some VOCs can lead to cancer and neurocognitive dysfunction.

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 levels in blood is essential to determine the need for regulatory mechanisms to reduce the levels of hazardous air pollutants to which the general population is exposed.

Volatile Organic Compounds (Home Tap Water):

In addition to assessing levels of VOCs in blood, VOC levels were measured in home tap water specimens provided by NHANES participants. Specifically, trihalomethanes (THMs) and the fuel additive methyl tertiary-butyl ether (MTBE) are measured in these samples.

Eligible Sample

Participants aged 20 to 59 years on a one-half sample had questions administered and whole blood and water specimens tested.

Description of Laboratory Methodology

Interview Setting and Mode of Administration

The questions were asked during the physical examination, in the mobile examination center (MEC). The questions were administered by the phlebotomist or the MEC interviewers.

Measurements of Trihalomethanes (THMs) and MTBE in Tap Water:

The prevalence of water disinfection by-products in drinking water supplies has raised concerns about possible health effects from chronic exposure to these compounds. The objective is to support studies exploring the relationship between exposure to THMs and health effects.

This automated analytical method uses headspace solid-phase microextraction (SPME) coupled with capillary gas chromatography and mass spectrometry. This method quantitates trace levels of THMs (chloroform, bromodichloromethane, dibromochloromethane, and bromoform) and MTBE in tap water. Detection limits of less than 100 pg/mL for all analytes and linear ranges of three orders of magnitude are adequate for measuring the THMs in tap water samples tested from across the United States. THMs are stable for extended periods in tap water samples after quenching of residual chlorine and buffering to pH 6.5, thus enabling larger epidemiologic field studies with simplified sample collection protocols.

Measurements of THMs and MTBE in Whole Blood

The prevalence of water disinfection by-products (e.g. THMs) in tap water has raised concerns about possible health effects from chronic exposure to these compounds. Exposure to the fuel oxygenate MTBE has also raised concerns. People can be exposed to THMs and MTBE through a variety of sources, including use of household tap water that contains these chemicals. The objective of this study is to support studies exploring the relationship between health effects and exposure to THMs and MTBE. THMs and MTBE were quantified in human blood using capillary gas chromatography (GC) and high-resolution mass spectrometry (MS) with selected ion mass detection and isotope-dilution techniques. This method quantified trace levels of THMs (chloroform, bromodichloromethane, dibromochloromethane, and bromoform) and MTBE in human blood. Analyte responses were adequate for measuring background levels after extraction of these volatile organic compounds with headspace SPME. Detection limits ranged from 0.3–2.4 pg/mL, with linear ranges of three orders of magnitude. This method provided adequate sensitivity for measuring the THMs and MTBE in most blood samples tested from diverse U.S. reference population.

Measurements of other VOCs in Whole Blood

Additional VOCs were measured in human blood using SPME in conjunction with gas chromatography and bench top quadrupole mass spectrometer. A combination of SPME and multiple single-ion monitoring minimizes the interferences and chemical noise associated with whole-blood samples. Detection limits are below 50 ppt (pg/mL) for a majority of the VOCs tested.

Data Processing and Editing

Automated data collection procedures for the survey were introduced in NHANES 2003–2004. In the MECs and analytical laboratories, data for the laboratory component are recorded directly onto a computerized data collection form. The system is centrally integrated, and it allows for ongoing monitoring of much of the data. Although the complete blood count and pregnancy analyses are performed in the MEC laboratory, most analyses are conducted elsewhere by approximately 21 laboratories across the United States.

Guidelines have been developed that provide standards for naming variables, filling missing values, and handling missing records. NCHS staff, assisted by contract staff, has developed data-editing specifications that check data sets for valid codes, ranges, and skip-pattern consistencies and examine the consistency of values between interrelated variables. Comments have been reviewed and recoded. NCHS staff verifies extremely high and low values whenever possible, and numerous consistency checks are performed. Nonetheless, users should examine the range and frequency of values before analyzing data.

Data Editing

The data editing specifications are as follows:

• Age and gender checks
• Total number of observations complete for each field
• No field overlap, truncated values, or atypical results
• Direct data entry errors
• Abnormal results confirmed by lab
• Test algorithm performed
• Checked comment codes to resolve missing results and missing records
• All missing results and missing MEC-examined records are accounted
• Duplicate records were verified and deleted

Laboratory Quality Assurance and Monitoring

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.

The NHANES QA/QC protocols meet the 1988 Clinical Laboratory Improvement Act mandates. Detailed QA/QC instructions are discussed in the NHANES LPM.

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 Westgaard 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 and Westat quarterly. The reports are reviewed for trends or shifts in the data. The laboratories are required to explain any identified areas of concern.

NCHS/Westat is currently reviewing these reports.

Analytic Notes

Measures of volatile organic compounds in blood and water were assessed in a subsample of participants aged 20–59. Use the special weights (WTSVOC2Y) included in this data file when analyzing data. Please refer to the Analytic Guidelines for further details on the use of sample weights and other analytic issues.

The analysis of NHANES 2003-2004 laboratory data must be conducted with the key survey design and basic demographic variables. The recommended procedure for variance estimation requires use of stratum and PSU variables (SDMVSTRA and SDMVPSU, respectively), which are included in the demographic data file for each data release. The NHANES 2003-2004 Household Questionnaire and Demographic Data Files contain demographic data, health indicators, and other related information collected during household interviews. The phlebotomy file includes auxiliary information such as the conditions precluding venipuncture. The demographic, household questionnaire and phlebotomy files may be linked to the laboratory data file using the unique survey participant identifier SEQN.

Detection limits

The detection limit was variable for many of the analytes in the data set. In addition two variables are provided for each of these analytes. The variable named LBD___LC indicates whether the result was below the limit of detection. There are three values: “0”, “1”, and “2”. “0” means that the result was at or above the limit of detection. “1” indicates that the result was below the limit of detection. “2” means the result was above the limit of detection and exceeds calibrated range of assay.

The other variable named LBX___ provides the analytic result for that analyte. In cases, where the result was below the limit of detection, the value for that variable is the detection limit divided by the square root of two.

References

• Blount BC, Kobelski RJ, McElprang DO, Ashley DL, Morrow JC, Chambers DM, Cardinali FL (2006) Quantification of 31 Volatile Organic Compounds in Whole Blood Using Solid-Phase Microextraction and Gas Chromatography/Mass Spectrometry. J. Chromatography B. 832(2):292-301.
• Bonin MA, Silva LK, Smith MM, Ashley DL, Blount BC (2005) Measurement of trihalomethanes and methyl tert-butyl ether in whole blood using gas chromatography with high-resolution mass spectrometry. J Anal Toxicol. 29(2):81-89.
• Cardinali FL, Ashley DL, Morrow JC, Moll DM, Blount BC (2004), Measurement of Trihalomethanes and Methyl Tertiary-Butyl Ether in Tap Water Using Solid-Phase Microextraction GC/MS, Journal of Chromatographic Sciences, 42:200-206.
• Morandi MT, Stock TH. Personal Exposures to Toxic Air Pollutants, Vol. 2. Houston, TX; The University of Texas – Houston, Health Science Center, School of Public Health: 1998.
• U.S. Occupational Safety and Health Administration (OSHA). Organic Vapors, Method 07 in Analytical Methods Manual. Salt Lake City, Utah; OSHA Analytical Laboratory: 1985.

Codebook and Frequencies