Table of Contents

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

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

Description of Laboratory Methodology

1. Total arsenic

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.

Detailed instructions on specimen collection and processing can be found in the NHANES Laboratory Procedures Manual (LPM).

Refer to NHANES 2011-2012 Lab Methods for Antimony, Arsenic, Barium, Beryllium, Cadmium, Cesium, Cobalt, Lead, Manganese, Molybdenum, Platinum, Strontium, Thallium, Tin, Tungsten, and Uranium (for total arsenic) and Lab Methods for Arsenobetaine, Arsenocholine, Trimethylarsine Oxide, Monomethylarsonic Acid, Dimethylarsinic Acid, Arsenous (III) Acid, Arsenic (V) Acid (for speciated arsenics) for detailed description of the laboratory method used.

Data Processing and Editing

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

Laboratory Quality Assurance and Monitoring

The NHANES quality control and quality assurance protocols (QA/QC) meet the 1988 Clinical Laboratory Improvement Act mandates. Detailed QA/QC instructions are discussed in the NHANES Laboratory Procedures Manual (LPM).

Analytic Notes

Refer to the 2011-2012 Laboratory Data Overview for general information on NHANES laboratory data.

Subsample Weights

Urinary total arsenic and speciated arsenics were obtained 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.

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. 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 limit of detection (LLOD, in µg/L) for the total and speciated arsenics are:

Analyte Item ID LLOD
Urinary Total Arsenic URXUAS 1.25
Urinary Arsenous Acid URXUAS3 0.48
Urinary Arsenic acid URXUAS5 0.87
Urinary Arsenobetaine URXUAB 1.19
Urinary Arsenocholine URXUAC 0.28
Urinary Dimethylarsonic Acid URXUDMA 1.80
Urinary Monomethylarsonic Acid URXUMMA 0.89
Urinary Trimethylarsine Oxide URXUTM 0.25

Please refer to the NHANES Analytic Guidelinesand the on-line NHANES Tutorial for further details on the use of sample weights and other analytic issues.

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 - Subsample A weights

Variable Name:
WTSA2YR
SAS Label:
Subsample A weights
English Text:
Subsample A weights
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
12199.652219 to 643202.3505 Range of Values 2551 2551
. Missing 43 2594

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
4 to 800 Range of Values 2525 2525
. Missing 69 2594

URXUAS - Urinary arsenic, total (ug/L)

Variable Name:
URXUAS
SAS Label:
Urinary arsenic, total (ug/L)
English Text:
Urinary arsenic, total (ug/L)
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.88 to 1269 Range of Values 2504 2504
. Missing 90 2594

URDUASLC - Urinary arsenic, total comment code

Variable Name:
URDUASLC
SAS Label:
Urinary arsenic, total comment code
English Text:
Urinary arsenic, total 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 2408 2408
1 Below lower detection limit 96 2504
. Missing 90 2594

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
0.34 to 66.3 Range of Values 2517 2517
. Missing 77 2594

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
Hard Edits:
to
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 831 831
1 Below lower detection limit 1686 2517
. Missing 77 2594

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
0.62 to 42.5 Range of Values 2517 2517
. Missing 77 2594

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
Hard Edits:
to
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 77 77
1 Below lower detection limit 2440 2517
. Missing 77 2594

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
0.84 to 1140 Range of Values 2517 2517
. Missing 77 2594

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
Hard Edits:
to
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 1140 1140
1 Below lower detection limit 1377 2517
. Missing 77 2594

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
0.2 to 18.2 Range of Values 2517 2517
. Missing 77 2594

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
Hard Edits:
to
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 101 101
1 Below lower detection limit 2416 2517
. Missing 77 2594

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
1.27 to 136 Range of Values 2517 2517
. Missing 77 2594

URDUDALC - Urinary Dimethylarsonic acid comment cod

Variable Name:
URDUDALC
SAS Label:
Urinary Dimethylarsonic acid comment cod
English Text:
Urinary Dimethylarsonic acid comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Hard Edits:
to
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limlt 2031 2031
1 Below lower detection limit 486 2517
. Missing 77 2594

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
0.63 to 72.9 Range of Values 2517 2517
. Missing 77 2594

URDUMMAL - Urinary MMA acid comment code

Variable Name:
URDUMMAL
SAS Label:
Urinary MMA acid comment code
English Text:
Urinary Monomethylacrsonic acid comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Hard Edits:
to
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 665 665
1 below lower detection limit 1852 2517
. Missing 77 2594

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
0.18 to 6.34 Range of Values 2517 2517
. Missing 77 2594

URDUTMLC - Urinary TMO comment code

Variable Name:
URDUTMLC
SAS Label:
Urinary TMO comment code
English Text:
Urinary Trimethylarsine Oxide comment code
Target:
Both males and females 6 YEARS - 150 YEARS
Hard Edits:
to
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 68 68
1 below lower detection limit 2449 2517
. Missing 77 2594