Table of Contents

Locator Record

Title: Urinary Total Arsenic and Speciated Arsenics (UAS_E )
Contact Number: 1-866-441-NCHS
Years of Content: 2007 - 2008
First Published: September, 2009
Revised: September, 2011
Access Constraints: None
Use Constraints: None
Geographic Coverage: National
Subject:Urinary total arsenic, Speciated arsenic
Record Source: NHANES 2007 - 2008
Survey Methodology: NHANES 2007 - 2008 is a stratified multistage probability sample of the civilian non-institutionalized population of the U.S.
Medium: NHANES Web site; SAS transport files

Component Description

Arsenic is widely distributed in the earth’s crust and is found most often in ground water rather than surface water. People encounter arsenic in many chemical forms that vary greatly in toxicity. The most toxic of the naturally-occurring arsenic compounds are inorganic forms of arsenic and their methylated metabolites. Less toxic are the organic arsenic compounds. Although this method does not reveal the chemical form of arsenic to which a person is exposed, it is sensitive enough to screen urine specimens rapidly from people thought to be exposed to arsenic or to evaluate total environmental or other total non-occupational exposure to arsenic.

Eligible Sample

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

Description of Laboratory Methodology

1. Total arsenc

The method described in this manual assesses arsenic exposure by analyzing urine through the use of inductively coupled-plasma dynamic reaction cell-mass spectrometry (ICP-DRC-MS). Urine is analyzed because urinary excretion is the major pathway for eliminating arsenic from the mammalian body (Vahter ME, 1988). This method achieves rapid and accurate quantification of total urinary arsenic.

Total urine arsenic concentrations are determined by using ICP-DRC-MS. This multielement analytical technique is based on quadrupole ICP-MS technology (Date AR et al., 1989) and includes DRC™ technology (Tanner SD et al. , 1999), which minimizes or eliminates much argon-based polyatomic interference. Coupling radio frequency power into a flowing argon stream seeded with electrons creates the plasma, the heat source, which is ionized gas suspended in a magnetic field. Predominant species in the plasma are positive argon ions and electrons. Diluted urine samples are converted into an aerosol by using a nebulizer inserted within a spray chamber. A portion of the aerosol is transported through the spray chamber and then through the central channel of the plasma, where it is exposed to temperatures of 6000-8000 ºK. This thermal energy atomizes and ionizes the sample. The ions and the argon enter the mass spectrometer through an interface that separates the ICP, which is operating at atmospheric pressure (approximately 760 torr), from the mass spectrometer, which is operating at approximately 10-5 torr. The mass spectrometer permits detection of ions at each mass-to-charge ratio in rapid sequence, which allows the determination of individual isotopes of an element. Once inside the mass spectrometer, the ions pass through the ion optics, then through DRC™, and finally through the mass-analyzing quadrupole before being detected as they strike the surface of the detector. The ion optics uses an electrical field to focus the ion beam into the DRC™. The DRC™ component is pressurized with an appropriate reaction gas and contains a quadrupole. In the DRC™, elimination or reduction of argon-based polyatomic interferences takes place through the interaction of the reaction gas with the interfering polyatomic species in the incoming ion beam. The quadrupole in the DRC™ allows elimination of unwanted reaction by-products that would otherwise react to form new interferences. Electrical signals, resulting from the detection of the ions, are processed into digital information that is used to indicate the intensity of the ions, and subsequently the concentration of the element. In this method, arsenic (isotope mass 75) and gallium (isotope mass 71) or tellurium (isotope mass 126) is measured in urine by ICP-DRC-MS, using argon/hydrogen (90%/10%, respectively) as a reaction gas (Neubauer K. et al., 1999). Urine samples are diluted 1:9 with 2% (v/v) double-distilled nitric acid containing gallium or tellurium for internal standardization.

2. Speciated arsenics

 (arsenobetaine, arsenocholine, trimethylarsine oxide, monomethylarsonic acid, dimethylarsinic acid, arsenous (III) acid, arsenic (V) acid)

The concentration of speciated arsenics is determined by using high performance liquid chromatography (HPLC) to separate the species coupled to an ICP-DRC-MS to detect the arsenic species. This analytical technique is based on separation by anion-exchange chromatography (IC), followed by detection using quadrupole ICP-MS technology, and includes DRC™ technology (Baranov VI et al., 1999), which minimizes or eliminates many argon-based polyatomic interferences (Tanner S et al., 2000) will require 0.5 mL of urine. Arsenic species column separation is largely achieved due to differences in charge-charge interactions of each negatively-charged arsenic component in the mobile phase, with the positively-charged quaternary ammonium groups bound at the column’s solid-liquid interface. Upon exit from the column, the chromatographic eluent goes through a nebulizer, where it is converted into an aerosol upon entering the spray chamber.

Carried by a stream of argon gas, a portion of the aerosol is transported through the spray chamber and then through the central channel of the plasma, where it is heated to temperatures of 6000-8000° K. This thermal energy atomizes and ionizes the sample. The ions and the argon enter the mass spectrometer through an interface that separates the ICP, which is operating at atmospheric pressure (approximately 760 torr), from the mass spectrometer, which is operating at approximately 10-5 torr.

The mass spectrometer permits detection of ions at each mass-to-charge ratio in rapid sequence, which allows the determination of individual isotopes of an element. Once inside the mass spectrometer, the ions pass through the ion optics, then through the DRC™, and finally through the mass-analyzing quadrupole before being detected as they strike the surface of the detector. The ion optics uses an electrical field to focus the ion beam into the DRC™.

The DRC™ component is pressurized with an appropriate reaction gas and contains a quadrupole. In the DRC™, elimination or reduction of argon-based polyatomic interferences takes place through the interaction of the reaction gas with the interfering polyatomic species in the incoming ion beam. The quadrupole in the DRC™ allows elimination of unwanted reaction by-products that would otherwise react to form new interferences.

There were no changes (from the previous 2 years of NHANES) to equipment, lab methods or lab site.

Laboratory Quality Assurance and Monitoring

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, and testing procedures. Constructive feedback are given to each staff person. Formal retraining sessions are conducted annually to ensure that required skill levels were maintained.

The NHANES 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 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 and Westat 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 Science’s quality control and quality assurance performance criteria for accuracy and precision (similar to specifications outlined by Westgard (1981).

Analytic Notes

Subsample weights

Measures of urinary speciated arsenic were obtained in a one-third subsample of persons 6 years and over. Therefore, special sample weights (WTSA2YR) 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.

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 arsenics in the data set.

Lower detection limits for the total and speciated arsenics
Urinary total arsenic 0.74 µg/L
Urinary arsenous acid 1.2 µg/L
Urinary Arsenic acid 1.0 µg/L
Urinary Arsenobetaine 0.4 µg/L
Urinary Arsenocholine 0.6 µg/L
Urinary Dimethylarsonic acid 1.7 µg/L
Urinary Monomethylarsonic acid 0.9 µg/L
Urinary Trimethylarsine Oxide 1.0 µg/L

The variable named URX___ provides the analytic result for that analyte.

Please refer to the Analytic Guidelines for further details on the use of sample weights and other analytic issues. The Analytic Guidelines are available on the NHANES website.

References

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

WTSA2YR - Environmental A two year weights

Variable Name:
WTSA2YR
SAS Label:
Environmental A two year weights
English Text:
Environmental A two year weights
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 to 604864.71127 Range of Values 2720 2720
. Missing 0 2720

URXUCR - Urinary creatinine (mg/dL)

Variable Name:
URXUCR
SAS Label:
Urinary creatinine (mg/dL)
English Text:
Urinary creatinine (mg/dL)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
7 to 528 Range of Values 2657 2657
. Missing 63 2720

URXUAS - Urinary total arsenic (ug/L)

Variable Name:
URXUAS
SAS Label:
Urinary total arsenic (ug/L)
English Text:
Urinary total arsenic (ug/L)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.52 to 1195 Range of Values 2605 2605
. Missing 115 2720

URDUASLC - Urinary Arsenic comment code

Variable Name:
URDUASLC
SAS Label:
Urinary Arsenic comment code
English Text:
Urinary Arsenic 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 2594 2594
1 Below lower detection limit 11 2605
. Missing 115 2720

URXUAS3 - Urinary Arsenous acid (ug/L)

Variable Name:
URXUAS3
SAS Label:
Urinary Arsenous acid (ug/L)
English Text:
Urinary Arsenous acid (ug/L)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.85 to 156 Range of Values 2576 2576
. Missing 144 2720

URDUA3LC - Urinary Arsenous acid comment code

Variable Name:
URDUA3LC
SAS Label:
Urinary Arsenous acid comment code
English Text:
Urinary Arsenous acid 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 89 89
1 Below lower detection limit 2487 2576
. Missing 144 2720

URXUAS5 - Urinary Arsenic acid (ug/L)

Variable Name:
URXUAS5
SAS Label:
Urinary Arsenic acid (ug/L)
English Text:
Urinary Arsenic acid (ug/L)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.71 to 148 Range of Values 2576 2576
. Missing 144 2720

URDUA5LC - Urinary Arsenic acid comment code

Variable Name:
URDUA5LC
SAS Label:
Urinary Arsenic acid comment code
English Text:
Urinary Arsenic acid 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 28 28
1 Below lower detection limit 2548 2576
. Missing 144 2720

URXUAB - Urinary Arsenobetaine (ug/L)

Variable Name:
URXUAB
SAS Label:
Urinary Arsenobetaine (ug/L)
English Text:
Urinary Arsenobetaine (ug/L)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.28 to 874 Range of Values 2576 2576
. Missing 144 2720

URDUABLC - Urinary Arsenobetaine comment code

Variable Name:
URDUABLC
SAS Label:
Urinary Arsenobetaine comment code
English Text:
Urinary Arsenobetaine 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 1441 1441
1 Below lower detection limit 1135 2576
. Missing 144 2720

URXUAC - Urinary Arsenocholine (ug/L)

Variable Name:
URXUAC
SAS Label:
Urinary Arsenocholine (ug/L)
English Text:
Urinary Arsenocholine (ug/L)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.42 to 10.9 Range of Values 2576 2576
. Missing 144 2720

URDUACLC - Urinary Arsenocholine comment code

Variable Name:
URDUACLC
SAS Label:
Urinary Arsenocholine comment code
English Text:
Urinary Arsenocholine 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 50 50
1 Below lower detection limit 2526 2576
. Missing 144 2720

URXUDMA - Urinary Dimethylarsonic acid (ug/L)

Variable Name:
URXUDMA
SAS Label:
Urinary Dimethylarsonic acid (ug/L)
English Text:
Urinary Dimethylarsonic acid (ug/L)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1.2 to 270 Range of Values 2576 2576
. Missing 144 2720

URDUDALC - Urinary Dimethylarsonic acid comment

Variable Name:
URDUDALC
SAS Label:
Urinary Dimethylarsonic acid comment
English Text:
Urinary Dimethylarsonic acid comment
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 2199 2199
1 Below lower detection limit 377 2576
. Missing 144 2720

URXUMMA - Urinary Monomethylacrsonic acid (ug/L)

Variable Name:
URXUMMA
SAS Label:
Urinary Monomethylacrsonic acid (ug/L)
English Text:
Urinary Monomethylacrsonic acid (ug/L)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.64 to 54.2 Range of Values 2576 2576
. Missing 144 2720

URDUMMAL - Urinary Monomethylacrsonic acid comment

Variable Name:
URDUMMAL
SAS Label:
Urinary Monomethylacrsonic acid comment
English Text:
Urinary Monomethylacrsonic acid comment
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 947 947
1 Below lower detection limit 1629 2576
. Missing 144 2720

URXUTM - Urinary Trimethylarsine Oxide (ug/L)

Variable Name:
URXUTM
SAS Label:
Urinary Trimethylarsine Oxide (ug/L)
English Text:
Urinary Trimethylarsine Oxide (ug/L)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.71 to 19.6 Range of Values 2576 2576
. Missing 144 2720

URDUTMLC - Urinary Trimethylarsine Oxide comment

Variable Name:
URDUTMLC
SAS Label:
Urinary Trimethylarsine Oxide comment
English Text:
Urinary Trimethylarsine Oxide comment
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 15 15
1 Below lower detection limit 2561 2576
. Missing 144 2720