Aldehydes are formed as thermal degradation byproducts released into the atmosphere from the burning of organic matter such as gasoline, food flavorants, and tobacco. Aldehydes are potentially carcinogenic and mutagenic; therefore, exposure to aldehydes has raised concerns about adverse health effects in humans.
Examined participants aged 12 years and older from a one-third subsample were eligible.
An automated analytical method was developed using solid phase microextraction (SPME) gas chromatography (GC) and high-resolution mass spectrometry (HRMS) with selected ion mass detection and isotope-dilution techniques. This analytical method quantifies trace levels of 12 aldehydes from protein adducts in human serum.
Because aldehydes have the tendency to react with biological molecules to form various products, including Schiff base protein adducts, free aldehydes released into the headspace of biological samples from the Schiff base protein adducts at low pH (~3) are analyzed. The method reproducibly hydrolyzes aldehyde adducts covalently bound to proteins, using automation to individually incubate samples prior to analysis with hydrochloric acid (Yeo 2004). Free aldehydes are captured by the SPME fiber; desorbed into the heated GC injector; and extracted aldehydes are focused at the head of the GC column using a cryogenically cooled trap (Cryo-trap). Analytes are then separated in a capillary column and quantified using multiple ion detection (MID) with mass spectrometry. This method employs isotope dilution to quantify precisely trace amounts of aldehydes with limits of detection in the low parts per trillion range. The linear calibration curve spanned over three orders of magnitude.
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.
Serum Aldehydes Laboratory Procedure Manual (April 2019)
Serum 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 refrigerated (2-8°C) conditions until they are 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 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 during “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 Sciences’ quality control and quality assurance
performance criteria for accuracy and precision, similar to the Westgard rules
(Caudill, et al., 2008).
The data were
reviewed. Incomplete data or improbable values were sent to the performing
laboratory for confirmation.
Refer to the 2013-2014 Laboratory Data Overview for general information on NHANES laboratory data.
Subsample Weights
Serum aldehydes were measured in a one-third 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 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.
The Fasting Questionnaire File includes auxiliary information such as fasting status, the length of fast, and the time of 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., LBD4ALLC) 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., LBD4ALLC=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., LBX4AL) provides the analytic result for that analyte.
The lower limit of detection (LLOD, in ng/mL) for serum aldehydes:
|
VARIABLE NAME |
SAS LABEL |
LLOD |
|
LBXBZAL |
Benzaldehyde (ng/mL) |
0.461 |
|
LBXCRAL |
Crotonaldehyde (ng/mL) |
0.147 |
|
LBXI5AL |
Isopentanaldehyde (ng/mL) |
0.119 |
|
LBXTLAL |
o-Tolualdehyde (ng/mL) |
0.142 |
|
LBX3AL |
Propanaldehyde (ng/mL) |
1.16 |
|
LBX4AL |
Butyraldehyde (ng/mL) |
0.313 |
|
LBX5AL |
Pentanaldehyde (ng/mL) |
0.119 |
|
LBX6AL |
Hexanaldehyde (ng/mL) |
0.693 |
|
LBX7AL |
Heptanaldehyde (ng/mL) |
0.312 |
|
LBX8AL |
Octanaldehyde (ng/mL) |
0.66 |
|
LBX9AL |
Nonanaldehyde (ng/mL) |
2.63 |
|
LBX10AL |
Decanaldehyde (ng/mL) |
3.9 |
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.