N,N-diethyl-3-methylbenzamide, commonly known as DEET, has become a widely used insect repellent in the United States. DEET is highly effective against a broad spectrum of insect pests, including potential disease vectors, such as mosquitoes, biting flies, and ticks (CDC, 2015). More than 500 products are currently registered with the Environmental Protection Agency in a variety of liquids, lotions, gels, sprays, sticks, and impregnated materials with DEET concentrations ranging from 5 to 98% (EPA, 2017). Every year, approximately one-third of the U.S. population uses DEET-containing insect repellents (CDC, 2009), and exposure to DEET is widespread (Calafat et al., 2016). Urinary metabolites of DEET are more sensitive biomarkers of exposure than DEET itself; in fact, relying on DEET as an exposure biomarker can lead to exposure misclassification (Calafat et al., 2016; ATSDR, 2017).
To better understand exposure to DEET, a surplus project testing 3-(Ethylcarbamoyl)benzoic acid (ug/L) was also performed in a one-third subsample of participants 3+ years of age from NHANES 2015-2016 (SSDEET_I), in addition to the one measured DEET metabolite in this dataset (3-(diethylcarbamoyl)benzoic acid).
All examined participants aged 3 to 5 years were eligible and participants aged 6 years and older from a one-third subsample were eligible.
The method uses 0.2 mL of urine for quantifying two DEET metabolites: 3-(diethylcarbamoyl)benzoic acid and 3-(ethylcarbamoyl)benzoic acid; four neonicotinoid insecticides: acetamiprid, clothianidin, imidacloprid, and thiacloprid; and two neonicotinoid metabolites: N-desmethyl-acetamiprid and 5-hydroxy-imidaclopridand. The method is based on enzymatic hydrolysis of urinary conjugates of the target analytes, online solid phase extraction, reversed phase high-performance liquid chromatography separation, and isotope dilution-electrospray ionization tandem mass spectrometry detection (Baker et al., 2018).
Refer to the Laboratory Method Files section for a detailed description of
the laboratory methods used.
There were no changes to the lab equipment
or lab site for this component in the NHANES 2015-2016 cycle. However, the lab
method was changed to include neonicotinoid insecticide biomarkers, and one
additional DEET metabolite. These data can be found in the Neonicotinoids – Urine (Surplus)
(SSNEON_I) and DEET Metabolite – Urine (Surplus) (SSDEET_I) datasets on this
website.
DEET Metabolite (August 2019)
Urine specimens are 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 were stored under appropriate
frozen (-30°C) conditions until they were 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 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 2015-2016 Laboratory Data Overview for general information on NHANES laboratory data.
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.
Subsample weights
DEET and metabolites were measured in a full sample of participants ages 3-5 and 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 Demographic Data 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: 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., URXDEA) provides the analytic result for that analyte. For analytes with analytic results below the lower limit of detection (i.e., 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 lower limit of detection (LLOD in ng/mL) for DEET metabolite is:
|
Variable Name |
Analyte Description |
LLOD |
|
URXDEA |
3-(diethylcarbamoyl)benzoic acid (DEET acid) (ng/mL) |
0.20 |
| Code or Value | Value Description | Count | Cumulative | Skip to Item |
|---|---|---|---|---|
| 6552.119284 to 874638.01159 | Range of Values | 3149 | 3149 | |
| 0 | No Lab Result | 56 | 3205 | |
| . | Missing | 0 | 3205 |
| Code or Value | Value Description | Count | Cumulative | Skip to Item |
|---|---|---|---|---|
| 0.1414 to 43700 | Range of Values | 2989 | 2989 | |
| . | Missing | 216 | 3205 |
| Code or Value | Value Description | Count | Cumulative | Skip to Item |
|---|---|---|---|---|
| 0 | At or above detection limit | 2757 | 2757 | |
| 1 | Below lower detection limit | 232 | 2989 | |
| . | Missing | 216 | 3205 |