In 2012, an estimated 854 million pounds of conventional pesticides were used in the United States (EPA, 2017). Chlorpyrifos was the insecticide used the most in the agricultural market sector with 4-8 million pounds applied. 2,4-D was the most used herbicide in the home and garden sector and second most used in the commercial sector, and it was the fourth most used herbicide in the agricultural sector. Pyrethroids were the most used insecticides in the home and garden sector. In 2012, the United States used 24% of all pesticides applied throughout the world. The widespread use of pesticides and the scientific interest in potential adverse health effects of pesticides exposure have increased the demand for fast and robust analytical methods for measuring biomarkers of pesticides.
This component measures urinary concentrations of four organophosphorus insecticide metabolites: 3,5,6-trichloropyridinol, 2-isopropyl-6-methyl-4-pyrimidiol, para-nitrophenol, and 2-[(dimethoxyphosphorothioyl) sulfanyl] succinic acid; three synthetic pyrethroid metabolites: 3-phenoxybenzoic acid, 4-fluoro-3-phenoxybenzoic acid, and trans-3-(2,2-dichlorovinyl)-2,2-dimethyl-cyclopropane-1-carboxylic acid; and one herbicide: 2,4-dichlorophenoxyacetic acid.
All examined participants aged 3 to 5 years and a one-third subsample of examined participants aged 6 years and older were eligible.
Target analytes are extracted and concentrated from the urine matrix using an automated solid phase extraction system. Selective separation of the analytes is achieved using high-performance liquid chromatography with a gradient elution program. Sensitive detection of the analytes is performed by a triple quadrupole mass spectrometer with a heated electrospray ionization source. Analytes are identified using the specific m/z ion transition, the retention time and the ion ratio of the quantification and confirmation m/z ion transitions. Isotopically labeled internal standards are used for precise and accurate quantification. The approach followed is a modification of previous methodology (Beeson et. al., 1999; Olsson et. al., 2004).
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, and lab site for this component in the NHANES 2015-2016 cycle. URXMAL Malathion Diacid was a new component in the 2015-2016 survey cycle.
UPHOPM Laboratory Procedure Manual (May 2023)
Urine specimens 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 were stored under appropriate frozen (–30°C) conditions until they were shipped to National Center for Environmental Health for testing.
The NHANES quality control and quality assurance protocols (QA/QC) meet the 1988 Clinical Laboratory Improvement Amendments 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 QC 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 QC 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’ QA/QC 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.
There are over 800 laboratory tests performed on NHANES participants. However, not all participants provided biospecimens or enough volume for all the tests to be performed. The specimen availability can also vary by age or other population characteristics. Analysts should evaluate the extent of missing data in the dataset related to the outcome of interest as well as any predictor variables used in the analyses to determine whether additional re-weighting for item non-response is necessary.
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
Pyrethroids, Herbicides, & Organophosphorus Metabolites were measured in 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.
The analytes included in this dataset were measured for all examined participants aged 3 to 5 years, and in a one-third subsample of participants 6 years and older. For participants aged 3 to 5, their WTSBSYR is equivalent to their MEC exam sample weights. These participants have completed at least one physical exam component in the MEC; therefore, they all have an exam sample weight larger than “0”, regardless of their lab test results. For participants 6 years and older, special sample weights were created for the subsample. These special weights accounted for the additional probability of selection in to the subsample, as well as the additional nonresponse to these lab tests. Therefore, if participants 6 years and older were selected as part of the one-third subsample, but did not provide a urine specimen, they would have the sample weight value assigned as “0” in their records.
Demographic and Other Related Variables
The analysis of NHANES laboratory data must be conducted using the appropriate survey design and demographic variables. The NHANES 2015-2016 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.
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 limit were constant for all of the analyte in the data set. Two variables are provided for each of these analytes. The variable name ending in “LC” (ex., URD24DLC) 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., URX24D) provides the analytic result for that analyte. For analytes with analytic results below the lower limit of detection (ex., URD24DLC=1), an imputed fill value was placed in the analyte results field. This value is the lower limit of detection divided by the square root of 2 (LLOD/sqrt[2]).
The lower limit of detection (LLOD, in ug/L) for Pyrethroids, Herbicides, & Organophosphorus Metabolites - Urine:
| Variable Name | Analyte Description | LLOD |
|---|---|---|
| URX24D | 2,4-dicholorphenoxyacetic acid | 0.15 |
| URXCPM | 3,5,6-trichloropyridinol | 0.10 |
| URX4FP | 4-fluoro-3-phenoxy-benzoic acid | 0.10 |
| URXOPM | 3-phenoxybenzoic acid | 0.10 |
| URXOXY | 2-isopropyl-4-methyl-pyrimidinol | 0.10 |
| URXPAR | para-Nitrophenol | 0.10 |
| URXTCC | trans-dichlorovinyl dimethylcyclopropane carboxylic acid | 0.60 |
| URXMAL | Malathion diacid | 0.50 |
"Pesticides Industry Sales and Usage." EPA. Environmental Protection Agency, January 2017. US EPA - Pesticides Industry Sales and Usage 2008 - 2012
Beeson M.D., Driskell W.J., Barr D.B.. Isotope Dilution High-Performance Liquid Chromatography/Tandem Mass Spectrometry Method for Quantifying Urinary Metabolites of Atrazine, Malathion, and 2,4-Dichlorophenoxyacetic Acid. Anal. Chem., 71:3526-3530, 1999.
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.
Olsson A. O., Baker S. E., Nguyen J. V., Romanoff L. C., Udunka S. O., Walker R. D., Flemmen K. L., and Barr D. B.. A Liquid Chromatography-Tandem Mass Spectrometry Multiresidue Method for Quantification of Specific Metabolites of Organophosphorus Pesticides, synthetic Pyrethroids, selected Herbicides, and DEET in Human Urine. Anal. Chem., 76:2453-2461, 2004.
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.