Table of Contents

Component Description

Ethylene thiourea (ETU) is a metabolite and environmental breakdown product of several fungicides in the dithiocarbamates class of chemicals, of which zineb, maneb, metiram, and mancozeb are examples. Propylenethiourea (PTU) is the metabolite and environmental breakdown product of propineb. These fungicides can be applied to fruits, vegetables, field crops, and ornamental plants, but they are not registered for residential use. ETU and related chemicals have numerous industrial uses and have also been used as scavengers in waste water treatment. ETU and PTU do not bioaccumulate and are rapidly eliminated in urine following human exposure.

Two organophosphorus insecticides and their metabolites have been measured: dimethoate and its metabolite, omethoate; acephate; and methamidophos, which is also a metabolite of acephate. Dimethoate and methamidophos are not registered for use in the U.S. Acephate has been used to control insects on field and food crops, on ornamental plants, sods and turf, and in food handling establishments and around commercial and residential buildings. Acephate and its metabolite, methamidophos, do not bioaccumulate and they break down in soils after several days. Measuring these pesticides and the metabolites in urine are important to evaluate human exposure and potential for health effects.

Eligible Sample

Participants aged 6 years and older who met the subsample requirements.

 

Description of Laboratory Methodology

This method is used for determining concentrations of specific organophosphorous
and carbamate metabolites, in particular, AP, MMP, Omet, Dmet, ETU and PTU
from a urine matrix. The general sample preparation includes lyophilization of the
urine followed by extraction with dichloromethane using a 96-well plate automated sample handler. The analytical separation is performed by high-performance liquid chromatography, and detection by a triple quadrupole mass spectrometer with APCI source in positive ion mode using MS/MS. Isotopically labeled internal standards were used for three of the analytes.

Laboratory Quality Assurance and Monitoring

Urine specimens are processed, stored, and shipped to the Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention for analysis.

Detailed instructions on specimen collection and processing are discussed in the NHANES Laboratory Procedures Manual (LPM). Vials are stored under appropriate frozen (–30°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 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 blind split samples collected on “dry run” sessions. In addition, contract laboratories randomly perform repeat testing on 2.0% of all specimens.

NCHS developed and distributed a quality control protocol for all the contract laboratories which outlined the Westgard rules (Westgard et al, 1981) 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 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.

 

Analytic Notes

Refer to the NHANES 2011–2012 Lab Data Overview for general information on NHANES laboratory data.

Subsample weights 
Uurinary carbamate and phosphorus pesticides were measured in a one third subsample of persons 6 years and over. 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.

Please refer to the Analytic Guidelines for further details on the use of sample weights and other analytic issues.

Variance Estimation
The analysis of NHANES laboratory data must be conducted with the key survey design and basic demographic variables. The NHANES Demographic Data File contains demographic and 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.

 Links to NHANES Data Files
This laboratory data file can be linked to the other NHANES data files using the unique survey participant identifier SEQN.

Detection Limits
The detection limits were constant for all of the analytes in the data set. The variable named LBD__LC 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., URD___LC=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 limits of detection (LLOD, in ng/mL) for these analytes are:

Analyte   Item ID LLOD 
 Acephate  URXAPE  0.27
 Ethylene thiourea  URXETU  0.21
 Methamidophos  URXMMI  0.41
 Dimethoate  URXMTO  0.10
 Omethoate  URXOMO  0.10
 Propylene thiourea  URXPTU  0.36

Please refer to the Analytic Guidelines for further details on the use of sample weights and other analytic issues.

 

Codebook and Frequencies

SEQN - Respondent sequence number

Variable Name:
SEQN
SAS Label:
Respondent sequence number
English Text:
Respondent sequence number.
Target:
Both males and females 6 YEARS - 150 YEARS

WTSC2YR - Environmental C 2 year weights

Variable Name:
WTSC2YR
SAS Label:
Environmental C 2 year weights
English Text:
Environmental C 2 year weights
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 to 520135.04901 Range of Values 2694 2694
. Missing 0 2694

URXAPE - Acephate (ug/L)

Variable Name:
URXAPE
SAS Label:
Acephate (ug/L)
English Text:
Acephate (ug/L)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.19 to 21.47 Range of Values 2505 2505
. Missing 189 2694

URDAPELC - Acephate comment code

Variable Name:
URDAPELC
SAS Label:
Acephate comment code
English Text:
Acephate comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 45 45
1 Below lower detection limit 2460 2505
. Missing 189 2694

URXETU - Ethylenethio urea (ug/L)

Variable Name:
URXETU
SAS Label:
Ethylenethio urea (ug/L)
English Text:
Ethylenethio urea (ug/L)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.15 to 12.22 Range of Values 2571 2571
. Missing 123 2694

URDETULC - Ethylenethio urea comment code

Variable Name:
URDETULC
SAS Label:
Ethylenethio urea comment code
English Text:
Ethylenethio urea comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 192 192
1 Below lower detection limit 2379 2571
. Missing 123 2694

URXMMI - Methamidaphos (ug/L)

Variable Name:
URXMMI
SAS Label:
Methamidaphos (ug/L)
English Text:
Methamidaphos (ug/L)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.29 to 0.98 Range of Values 2573 2573
. Missing 121 2694

URDMMILC - Methamidaphos comment code

Variable Name:
URDMMILC
SAS Label:
Methamidaphos comment code
English Text:
Methamidaphos comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 9 9
1 Below lower detection limit 2564 2573
. Missing 121 2694

URXMTO - Dimethoate (ug/L)

Variable Name:
URXMTO
SAS Label:
Dimethoate (ug/L)
English Text:
Dimethoate (ug/L)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 0.65 Range of Values 2573 2573
. Missing 121 2694

URDMTOLC - Dimethoate comment code

Variable Name:
URDMTOLC
SAS Label:
Dimethoate comment code
English Text:
Dimethoate comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 1 1
1 Below lower detection limit 2572 2573
. Missing 121 2694

URXOMO - O-methoate (ug/L)

Variable Name:
URXOMO
SAS Label:
O-methoate (ug/L)
English Text:
O-methoate (ug/L)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 0.55 Range of Values 2574 2574
. Missing 120 2694

URDOMOLC - O-methoate comment code

Variable Name:
URDOMOLC
SAS Label:
O-methoate comment code
English Text:
O-methoate comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 4 4
1 Below lower detection limit 2570 2574
. Missing 120 2694

URXPTU - Propylenethio urea (ug/L)

Variable Name:
URXPTU
SAS Label:
Propylenethio urea (ug/L)
English Text:
Propylenethio urea (ug/L)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.25 to 2.82 Range of Values 2573 2573
. Missing 121 2694

URDPTULC - Propylenethio urea comment code

Variable Name:
URDPTULC
SAS Label:
Propylenethio urea comment code
English Text:
Propylenethio urea comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 8 8
1 Below lower detection limit 2565 2573
. Missing 121 2694

URXUCR - Creatinine, urine (mg/dL)

Variable Name:
URXUCR
SAS Label:
Creatinine, urine (mg/dL)
English Text:
Creatinine, urine (mg/dL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
3 to 724 Range of Values 2596 2596
. Missing 98 2694