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.

Eligible Sample

Participants aged 18 years and older, who met the regular one-third subsample selection criteria, were included in this special subsample. Additionally, to oversample adult smokers, those participants aged 18 years and older, not in the regular one-third subsample, who smoked at least 100 cigarettes in their entire lifetime (SMQ022=1) and now smoke cigarettes every day (SMQ040=1), were also included in this special subsample.

Description of Laboratory Methodology

Arsenobetaine, arsenocholine, 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.

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, or lab site for this component in the NHANES 2015-2016 cycle.

Laboratory Method Files

Arsenics - Speciated - Urine Laboratory Procedure Manual (June 2018)

Laboratory Quality Assurance and Monitoring

Urine samples 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 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 Amendment mandates. Detailed QA/QC instructions are discussed in the NHANES Laboratory Procedures Manual (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 quality-control 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 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 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 Sciences’ quality control and quality assurance performance criteria for accuracy and precision, similar to the Westgard rules (Caudill et al, 2008).

Data Processing and Editing

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

Analytic Notes

Refer to the 2015-2016 Laboratory Data Overview for general information on NHANES laboratory data.

Subsample Weights

Urinary speciated arsenics were measured in a one-third subsample of persons 18 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.

Demographic and Other Related Variables

The analysis of NHANES laboratory data must be conducted 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.

Starting in the 2015-2016 NHANES cycle, the variable URXUCR (urine creatinine) will not be reported in this file. URXUCR can be found in the data file titled Albumin & Creatinine – Urine.

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 limits were constant for all of the analytes in the data set. Two variables are provided for each of these analytes. The variable name ending in “LC” (ex., URDUASLC) 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. For analytes with analytic results below the lower limit of detection (ex., URDUASLC=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., URXUAS) provides the analytic result for the analyte.

The lower limit of detection (LLOD, in µg/L) for the speciated arsenics is:

Variable Name

SAS Label

LLOD

URXUAS3

Urinary Arsenous Acid

0.12

URXUAS5

Urinary Arsenic acid

0.79

URXUAB

Urinary Arsenobetaine

1.16

URXUAC

Urinary Arsenocholine

0.11

URXUDMA

Urinary Dimethylarsinic Acid

1.91

URXUMMA

Urinary Monomethylarsonic Acid

0.20

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.

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 18 YEARS - 150 YEARS

WTFSM - Two year smoking weights

Variable Name:
WTFSM
SAS Label:
Two year smoking weights
English Text:
Two year smoking weights
Target:
Both males and females 18 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
5682.8332946 to 708016.13026 Range of Values 2389 2389
0 No Lab Result 73 2462
. Missing 0 2462

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 18 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.08 to 8.77 Range of Values 2388 2388
. Missing 74 2462

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 18 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 1246 1246
1 Below lower detection limit 1142 2388
. Missing 74 2462

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 18 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.56 to 4.54 Range of Values 2388 2388
. Missing 74 2462

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 18 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 65 65
1 Below lower detection limit 2323 2388
. Missing 74 2462

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 18 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.82 to 662.24 Range of Values 2388 2388
. Missing 74 2462

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 18 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 1164 1164
1 Below lower detection limit 1224 2388
. Missing 74 2462

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 18 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.08 to 10.98 Range of Values 2388 2388
. Missing 74 2462

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 18 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 454 454
1 Below lower detection limit 1934 2388
. Missing 74 2462

URXUDMA - Urinary Dimethylarsinic acid (ug/L)

Variable Name:
URXUDMA
SAS Label:
Urinary Dimethylarsinic acid (ug/L)
English Text:
Urinary Dimethylarsinic acid (ug/L)
Target:
Both males and females 18 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1.35 to 149.62 Range of Values 2388 2388
. Missing 74 2462

URDUDALC - Urinary Dimethylarsonic acid coment code

Variable Name:
URDUDALC
SAS Label:
Urinary Dimethylarsonic acid coment code
English Text:
Urinary Dimethylarsinic acid comment code
Target:
Both males and females 18 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 1734 1734
1 Below lower detection limit 654 2388
. Missing 74 2462

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 18 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.14 to 5.74 Range of Values 2388 2388
. Missing 74 2462

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 18 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 1406 1406
1 Below lower detection limit 982 2388
. Missing 74 2462