Table of Contents

Locator Record

Title: Heavy Metals (L06HM_C )
Contact Number: 1-866-441-NCHS
Years of Content: 2003 - 2004
First Published: July, 2007
Revised: NA
Access Constraints: None
Use Constraints: None
Geographic Coverage: National
Subject:Heavy Metals
Record Source: NHANES 2003 - 2004
Survey Methodology: NHANES 2003 - 2004 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

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 screen urine specimens from subjects suspected to be exposed to a number of important toxic elements or to evaluate environmental or other nonoccupational exposure to these same elements.

Eligible Sample

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

Description of Laboratory Methodology

Inductively coupled plasma-mass spectrometry (ICP-MS) is a multi-element analytical technique (1). Liquid samples are introduced into the ICP through a nebulizer and spray chamber carried by a flowing argon stream. By coupling radio-frequency power into flowing argon, plasma is created in which the predominant species are positive argon ions and electrons. The sample passes through a region of the plasma that has a temperature of 6000–8000 K. The thermal energy atomizes the sample and then ionizes the atoms. The ions, along with the argon, enter the mass spectrometer through an interface that separates the ICP from the mass spectrometer, which is operating at an atmospheric pressure of 10–5 torr. The mass spectrometer permits ions at each mass to be detected in rapid sequence, allowing individual isotopes of an element to be determined. Electrical signals resulting from the detection of the ions are processed into digital information that is used to indicate first the intensity of the ions and then the concentration of the element. The ICP-MS method is used to measure the following 12 elements in urine: beryllium (Be), cobalt (Co), molybdenum (Mo), cadmium (Cd), antimony (Sb), cesium (Cs), barium (Ba), tungsten (W), platinum (Pt), thallium (TI), lead (Pb), and uranium (U). This method is based on the method by Mulligan et al. (2) Urine samples are diluted 1+9 with 2% (v/v), double-distilled, concentrated nitric acid containing both iridium (Ir) and rhodium (Rh) for multi-internal standardization. This procedure can be used for all 12 elements or subsets of the 12 elements.

Laboratory Quality Assurance and Monitoring

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

Detailed specimen collection and processing instructions are discussed in the NHANES Laboratory/Medical Technologists Procedures Manual (LPM). Vials are stored under appropriate frozen (–20°C) conditions until they are shipped to National Center for Environmental Health for testing.

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; testing procedures and constructive feedback are given to each staff. 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 heavy metals 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.

Variance estimation

The analysis of NHANES 2003-2004 laboratory data must be conducted with the key survey design and basic demographic variables. The NHANES 2003-2004 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 2003-2004 data files using the unique survey participant identifier SEQN.

Detection Limits

The detection limit was variable for many of the analytes in the data set. Two variables are provided for each of these analytes. 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. Urinary beryllium, cadmium, lead, platinum, tungsten, and uranium have multiple lower limits of detection in this data file. The other variable named LBX___ provides the analytic result for that analyte. In cases, where the result was below the limit of detection, the value for that variable is the detection limit divided by the square root of two.

URXUCD and URDUCD:

When comparing urine cadmium across two-year cycles please note that even though these two variables have different names the data is comparable. Variable URXUCD is used in 1999-2000 and 2003-2004 and variable URDUCD was used in 2001-2002. Variable URDUCD was derived to correct for molybdenum interference (Reference to 2001-2002 lab 6 heavy metal documentation). Beginning in 2003-2004 the urinary cadmium data is corrected at the testing laboratory for molybdenum interference.

Please refer to the Analytic Guidelines 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 - Two-year MEC weights of subsample A

Variable Name:
WTSA2YR
SAS Label:
Two-year MEC weights of subsample A
English Text:
Heavy Metals Subsample 2 year Mec Weight.
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 to 455771.88304 Range of Values 2673 2673
. Missing 0 2673

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
6 to 768 Range of Values 2586 2586
. Missing 87 2673

URXUBA - Barium, urine (ng/mL)

Variable Name:
URXUBA
SAS Label:
Barium, urine (ng/mL)
English Text:
Barium, urine (ng/mL).
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.15 to 108.1 Range of Values 2558 2558
-0.22 Fill Value of Limit of Detection 0 2558
. Missing 115 2673

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 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2374 2374
1 Below lower detection limit 184 2558
. Missing 115 2673

URXUBE - Beryllium, urine (ng/mL)

Variable Name:
URXUBE
SAS Label:
Beryllium, urine (ng/mL)
English Text:
Beryllium, urine (ng/mL).
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.11 to 0.13 Range of Values 24 24
0.05 First Fill Value of Limit of Detection 30 54
0.08 Second Fill Value of Limit of Detection 2504 2558
. Missing 115 2673

URDUBELC - Urinary beryllium comment code

Variable Name:
URDUBELC
SAS Label:
Urinary beryllium comment code
English Text:
Urinary beryllium 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 24 24
1 Below lower detection limit 2534 2558
. Missing 115 2673

URXUCD - Cadmium, urine (ng/mL)

Variable Name:
URXUCD
SAS Label:
Cadmium, urine (ng/mL)
English Text:
Cadmium, urine (ng/mL).
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.03 to 14.94 Range of Values 2543 2543
-0.03 First Fill Value of Limit of Detection 0 2543
-0.04 Second Fill Value of Limit of Detection 0 2543
. Missing 130 2673

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 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2317 2317
1 Below lower detection limit 226 2543
. Missing 130 2673

URXUCO - Cobalt, urine (ng/mL)

Variable Name:
URXUCO
SAS Label:
Cobalt, urine (ng/mL)
English Text:
Cobalt, urine (ng/mL).
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.08 to 127.87 Range of Values 2463 2463
0.06 Fill Value of Limit of Detection 95 2558
. Missing 115 2673

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 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2463 2463
1 Below lower detection limit 95 2558
. Missing 115 2673

URXUCS - Cesium, urine (ng/mL)

Variable Name:
URXUCS
SAS Label:
Cesium, urine (ng/mL)
English Text:
Cesium, urine (ng/mL).
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.34 to 552.12 Range of Values 2558 2558
. Missing 115 2673

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 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2558 2558
1 Below lower detection limit 0 2558
. Missing 115 2673

URXUMO - Molybdenum, urine (ng/mL)

Variable Name:
URXUMO
SAS Label:
Molybdenum, urine (ng/mL)
English Text:
Molybdenum, urine (ng/mL).
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1.7 to 1215.9 Range of Values 2555 2555
1.06 Fill Value of Limit of Detection 3 2558
. Missing 115 2673

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 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2555 2555
1 Below lower detection limit 3 2558
. Missing 115 2673

URXUPB - Lead, urine (ng/mL)

Variable Name:
URXUPB
SAS Label:
Lead, urine (ng/mL)
English Text:
Lead, urine (ng/mL).
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.07 to 12.9 Range of Values 2558 2558
-0.07 First Fill Value of Limit of Detection 0 2558
-0.23 Second Fill Value of Limit of Detection 0 2558
. Missing 115 2673

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 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2170 2170
1 Below lower detection limit 388 2558
. Missing 115 2673

URXUPT - Platinum, urine (ng/mL)

Variable Name:
URXUPT
SAS Label:
Platinum, urine (ng/mL)
English Text:
Platinum, urine (ng/mL).
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.01 to 1.7 Range of Values 2558 2558
-0.01 First Fill Value of Limit of Detection 0 2558
-0.05 Second Fill Value of Limit of Detection 0 2558
. Missing 115 2673

URDUPTLC - Urinary platinum comment code

Variable Name:
URDUPTLC
SAS Label:
Urinary platinum comment code
English Text:
Urinary platinum 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 10 10
1 Below lower detection limit 2548 2558
. Missing 115 2673

URXUSB - Antimony, urine (ng/mL)

Variable Name:
URXUSB
SAS Label:
Antimony, urine (ng/mL)
English Text:
Antimony, urine (ng/mL).
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.02 to 3.73 Range of Values 2558 2558
-0.02 First Fill Value of Limit of Detection 0 2558
-0.05 Second Fill Value of Limit of Detection 0 2558
. Missing 115 2673

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 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 1601 1601
1 Below lower detection limit 957 2558
. Missing 115 2673

URXUTL - Thallium, urine (ng/mL)

Variable Name:
URXUTL
SAS Label:
Thallium, urine (ng/mL)
English Text:
Thallium, urine (ng/mL).
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.02 to 1.41 Range of Values 2539 2539
0.011 Fill Value of Limit of Detection 19 2558
. Missing 115 2673

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 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2539 2539
1 Below lower detection limit 19 2558
. Missing 115 2673

URXUTU - Tungsten, urine (ng/mL)

Variable Name:
URXUTU
SAS Label:
Tungsten, urine (ng/mL)
English Text:
Tungsten, urine (ng/mL).
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.01 to 3.93 Range of Values 2558 2558
-0.01 First Fill Value of Limit of Detection 0 2558
-0.02 Second Fill Value of Limit of Detection 0 2558
-0.03 Third Fill Value of Limit of Detection 0 2558
. Missing 115 2673

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 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 2115 2115
1 Below lower detection limit 443 2558
. Missing 115 2673

URXUUR - Uranium, urine (ng/mL)

Variable Name:
URXUUR
SAS Label:
Uranium, urine (ng/mL)
English Text:
Uranium, urine (ng/mL).
Target:
Both males and females 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.001 to 0.979 Range of Values 2557 2557
-0.001 First Fill Value of Limit of Detection 0 2557
-0.004 Second Fill Value of Limit of Detection 0 2557
. Missing 116 2673

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 6 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 1795 1795
1 Below lower detection limit 762 2557
. Missing 116 2673