Table of Contents

Component Description

Trace metals have been associated with adverse health effects in occupational studies or laboratory studies, but have not been monitored in general population groups.

This method is used to achieve rapid and accurate quantifications of multiple elements of toxicological and nutritional interest. The method is sensitive and rapid enough to analyze urine specimens from subjects suspected of being exposed to a number of important toxic elements, or to evaluate environmental or other non-occupational exposure to these same elements.

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

This method directly measures multiple metals in urine specimens using mass spectrometry after a simple dilution sample preparation step. Liquid samples are introduced into the mass spectrometer through the inductively coupled plasma (ICP) ionization source, reduced to small droplets in an argon aerosol via a nebulizer, and then the droplets enter the ICP. The ions first pass through a focusing region, followed by the dynamic reaction cell (DRC), the quadrupole mass filter, and finally are selectively counted in rapid sequence at the detector allowing individual isotopes of an element to be determined.

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

Urinary Metals and Total Arsenic 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 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.

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) 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 (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 metals were measured 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.

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 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.

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 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., URDUBALC) 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., URDUBALC=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 other variable prefixed URX (ex., URXUBA) provides the analytic result for that analyte.

The lower limit of detection (LLOD, in µg/L) for the urinary metals in the data set is:

Variable Name SAS Label LLOD
URXUBA Urinary Barium 0.060
URXUCD Urinary Cadmium 0.036
URXUCS Urinary Cesium 0.086
URXUCO Urinary Cobalt 0.023
URXUMN Urinary Manganese 0.130
URXUMO Urinary Molybdenum 0.800
URXUPB Urinary Lead 0.030
URXUSB Urinary Antimony 0.022
URXUSR Urinary Strontium 2.340
URXUTL Urinary Thallium 0.018
URXUSN Urinary Tin 0.090
URXUTU Urinary Tungsten 0.018
URXUUR Urinary Uranium 0.002 

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

URXUBA - Barium, urine (ug/L)

Variable Name:
URXUBA
SAS Label:
Barium, urine (ug/L)
English Text:
Barium, urine (ug/L)
Target:
Both males and females 18 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.042 to 58.66 Range of Values 2373 2373
. Missing 89 2462

URDUBALC - Urinary Barium Comment Code

Variable Name:
URDUBALC
SAS Label:
Urinary Barium Comment Code
English Text:
Urinary Barium 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 2365 2365
1 Below lower detection limit 8 2373
. Missing 89 2462

URXUCD - Cadmium, urine (ug/L)

Variable Name:
URXUCD
SAS Label:
Cadmium, urine (ug/L)
English Text:
Cadmium, urine (ug/L)
Target:
Both males and females 18 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.025 to 7.59 Range of Values 2373 2373
. Missing 89 2462

URDUCDLC - Urinary Cadmium Comment Code

Variable Name:
URDUCDLC
SAS Label:
Urinary Cadmium Comment Code
English Text:
Urinary Cadmium 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 2241 2241
1 Below lower detection limit 132 2373
. Missing 89 2462

URXUCO - Cobalt, urine (ug/L)

Variable Name:
URXUCO
SAS Label:
Cobalt, urine (ug/L)
English Text:
Cobalt, urine (ug/L)
Target:
Both males and females 18 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.016 to 33.661 Range of Values 2373 2373
. Missing 89 2462

URDUCOLC - Urinary Cobalt Comment Code

Variable Name:
URDUCOLC
SAS Label:
Urinary Cobalt Comment Code
English Text:
Urinary Cobalt 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 2371 2371
1 Below lower detection limit 2 2373
. Missing 89 2462

URXUCS - Cesium, urine (ug/L)

Variable Name:
URXUCS
SAS Label:
Cesium, urine (ug/L)
English Text:
Cesium, urine (ug/L)
Target:
Both males and females 18 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.061 to 110.873 Range of Values 2373 2373
. Missing 89 2462

URDUCSLC - Urinary Cesium Comment Code

Variable Name:
URDUCSLC
SAS Label:
Urinary Cesium Comment Code
English Text:
Urinary Cesium 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 2372 2372
1 Below lower detection limit 1 2373
. Missing 89 2462

URXUMO - Molybdenum, urine (ug/L)

Variable Name:
URXUMO
SAS Label:
Molybdenum, urine (ug/L)
English Text:
Molybdenum, urine (ug/L)
Target:
Both males and females 18 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1.18 to 402.57 Range of Values 2372 2372
. Missing 90 2462

URDUMOLC - Urinary Molybdenum Comment Code

Variable Name:
URDUMOLC
SAS Label:
Urinary Molybdenum Comment Code
English Text:
Urinary Molybdenum 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 2372 2372
1 Below lower detection limit 0 2372
. Missing 90 2462

URXUMN - Manganese, urine (ug/L)

Variable Name:
URXUMN
SAS Label:
Manganese, urine (ug/L)
English Text:
Manganese, urine (ug/L)
Target:
Both males and females 18 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.092 to 18.17 Range of Values 2373 2373
. Missing 89 2462

URDUMNLC - Urinary Mn Comment Code

Variable Name:
URDUMNLC
SAS Label:
Urinary Mn Comment Code
English Text:
Urinary Mn 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 694 694
1 Below lower detection limit 1679 2373
. Missing 89 2462

URXUPB - Lead, urine (ug/L)

Variable Name:
URXUPB
SAS Label:
Lead, urine (ug/L)
English Text:
Lead, urine (ug/L)
Target:
Both males and females 18 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.02 to 18.53 Range of Values 2373 2373
. Missing 89 2462

URDUPBLC - Urinary Lead Comment Code

Variable Name:
URDUPBLC
SAS Label:
Urinary Lead Comment Code
English Text:
Urinary Lead 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 2363 2363
1 Below lower detection limit 10 2373
. Missing 89 2462

URXUSB - Antimony, urine (ug/L)

Variable Name:
URXUSB
SAS Label:
Antimony, urine (ug/L)
English Text:
Antimony, urine (ug/L)
Target:
Both males and females 18 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.016 to 14.291 Range of Values 2373 2373
. Missing 89 2462

URDUSBLC - Urinary Antimony Comment Code

Variable Name:
URDUSBLC
SAS Label:
Urinary Antimony Comment Code
English Text:
Urinary Antimony 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 1926 1926
1 Below lower detection limit 447 2373
. Missing 89 2462

URXUSN - Tin, urine (ug/L)

Variable Name:
URXUSN
SAS Label:
Tin, urine (ug/L)
English Text:
Tin, urine (ug/L)
Target:
Both males and females 18 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.064 to 86.39 Range of Values 2372 2372
. Missing 90 2462

URDUSNLC - USN Comment Code

Variable Name:
URDUSNLC
SAS Label:
USN Comment Code
English Text:
USN 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 2227 2227
1 Below lower detection limit 145 2372
. Missing 90 2462

URXUSR - Strontium, urine (ug/L)

Variable Name:
URXUSR
SAS Label:
Strontium, urine (ug/L)
English Text:
Strontium, urine (ug/L)
Target:
Both males and females 18 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
2.73 to 1097.34 Range of Values 2373 2373
. Missing 89 2462

URDUSRLC - USR Comment Code

Variable Name:
URDUSRLC
SAS Label:
USR Comment Code
English Text:
USR 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 2373 2373
1 Below lower detection limit 0 2373
. Missing 89 2462

URXUTL - Thallium, urine (ug/L)

Variable Name:
URXUTL
SAS Label:
Thallium, urine (ug/L)
English Text:
Thallium, urine (ug/L)
Target:
Both males and females 18 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.013 to 7.658 Range of Values 2373 2373
. Missing 89 2462

URDUTLLC - Urinary Thallium Comment Code

Variable Name:
URDUTLLC
SAS Label:
Urinary Thallium Comment Code
English Text:
Urinary Thallium 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 2363 2363
1 Below lower detection limit 10 2373
. Missing 89 2462

URXUTU - Tungsten, urine (ug/L)

Variable Name:
URXUTU
SAS Label:
Tungsten, urine (ug/L)
English Text:
Tungsten, urine (ug/L)
Target:
Both males and females 18 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.013 to 5.178 Range of Values 2372 2372
. Missing 90 2462

URDUTULC - Urinary Tungsten Comment Code

Variable Name:
URDUTULC
SAS Label:
Urinary Tungsten Comment Code
English Text:
Urinary Tungsten 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 2042 2042
1 Below lower detection limit 330 2372
. Missing 90 2462

URXUUR - Uranium, urine (ug/L)

Variable Name:
URXUUR
SAS Label:
Uranium, urine (ug/L)
English Text:
Uranium, urine (ug/L)
Target:
Both males and females 18 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.0014 to 1.6664 Range of Values 2373 2373
. Missing 89 2462

URDUURLC - Urinary Uranium Comment Code

Variable Name:
URDUURLC
SAS Label:
Urinary Uranium Comment Code
English Text:
Urinary Uranium 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 1990 1990
1 Below lower detection limit 383 2373
. Missing 89 2462