National Health and Nutrition Examination Survey

DEET is a widely used insect repellent, sometimes combined with sunscreen agents and available for use in concentrations ranging from 4 to 100%. Human exposure may occur when DEET is absorbed through the skin or inhaled from aerosol formulations. Because DEET is widely used in the U.S. population, measuring urinary DEET and its metabolites is important to evaluate human exposure and potential for health effects.

N,N-diethyl-3-methylbenzamide, commonly known as DEET, is the principle ingredient in many personal insect repellents worldwide and is highly effective against a broad spectrum of insect pests, including potential disease vectors such as mosquitoes, biting flies and ticks (including many ticks that may carry Lyme disease).

DEET was first developed and patented in 1946 by the U.S. Army for use by military personnel and later registered for general public use in 1975. Every year, approximately one-third of the U.S. population uses DEET-containing insect repellent products with concentrations ranging from 10 to 100% in a variety of liquids, lotions, gels, sprays, sticks and impregnated materials and more than 30 million packages of DEET-containing products are sold annually. Approximately 230 products containing DEET are registered with the Environmental Protection Agency by about 70 different companies.

Although the clinical relevance of this method, on rare occasions, may extend to quantifying concentrations for emergency responses, such as accidental poisonings, its design and intended use is to provide data in support of epidemiological studies. It does not directly test for any disease.

Examined participants aged 6 years and older from a one-third sample.

This method uses online solid phase extraction coupled with high performance liquid chromatography-tandem mass spectrometry (SPE-HPLC-MS/MS) for quantifying DEET and three of its metabolites, N,N-diethyl-3-hydroxymethylbenzamide (DHMB), N-ethyl-3-methylbenzamide (EMB), and 3-diethyl-carbamoyl benzoic acid (DCBA), in 100 µL of human urine. Sample preparation begins with an over-night enzymatic deconjugation of the glucuronide-bound metabolites. On the second day, the four compounds being measured are concentrated via online SPE and then chromatographically separated from each other and from other urine biomolecules using reversed phase HPLC. The eluting molecular ions are converted to gas phase ions using Atmospheric Pressure Chemical Ionization (APCI) and then selectively filtered by mass-to-charge ratios at unit resolution. Select molecular ions are then fragmented with chemical induced dissociation (CID) and the resulting product ions are filtered at unit resolution before detection via an electron multiplier.

Refer to NHANES 2007-2008 Lab Methods for DEET and metabolites laboratory for a detailed description of the laboratory method used.

There were no changes to the lab method, lab equipment or lab site for this component in the NHANES 2007-2008 cycle.

N,N-diethyl-3-methylbenzamide, N,Ndiethyl-3-hydroxymethylbenzamide, and 3-diethyl-carbamoyl benzoic acid (May 2016)

DEET and metabolites 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 are stored under appropriate frozen (-70°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 Laboratory/Medical Technologists Procedures Manual (LPM) Read the General Documentation on Laboratory Data file for detailed QA/QC protocols.

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.

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 the 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).

The data were reviewed. Incomplete data or improbable values were sent to the performing laboratory for confirmation.

Subsample weights

DEET and metabolites were measured in a one third subsample of persons 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.

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 named URDDEELC indicates whether the result was below the limit of detection. There are two values: “0” and “1.” “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 (i.e., URDDEELC=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., URXDEE) provides the analytic result for that analyte.

The lower limit of detection (LLOD in ug/L) for the atrazine and metabolites is:

NHANES Survey Design:

The analysis of NHANES laboratory data must be conducted with the key survey design and basic demographic variables. The Household Questionnaire Data Files contain demographic data, health indicators, and other related information collected during household interviews. The Household Questionnaire Data Files also contain all survey design variables and sample weights required to analyze these data. The Phlebotomy Examination file includes auxiliary information on duration of fasting, the time of day of the venipuncture, and the conditions precluding venipuncture. The Household Questionnaire and Phlebotomy Examination files may be linked to the laboratory data file using the unique survey participant identifier SEQN.

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.