Table of Contents

Component Description

Inorganic Mercury

Uncertainties exist regarding levels of exposure to methyl mercury from fish consumption and potential health effects resulting from this exposure. Past estimates of exposure to methyl mercury have been obtained from results of food consumption surveys and measures of methyl mercury in fish. Measures of a biomarker of exposure are needed for improved exposure assessments.

Blood measures of inorganic mercury will be important for evaluation of exposure from exposure to mercury in interior latex paints

Eligible Sample

Participants aged 1 year and older, who do not meet any of the exclusion criteria, are eligible.

Description of Laboratory Methodology

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

Inorganic Mercury

Inorganic mercury in blood is measured using stannous chloride as a reductant, also utilizing microwave digestion. Mercury vapor (reduced from inorganic mercury compounds) is measured via the same quartz cell at 253.7 nm.

The difference between total and inorganic mercury represents the organic mercury in blood. Mercury analysis identifies cases of mercury toxicity. The main organs affected by mercury are the brain and kidneys. Psychic and emotional disturbances are the initial signs of chronic intoxication by elemental mercury vapor or salts. Parasthesia and neuralgia may develop. Renal disease, digestive disturbances, and ocular lesions can also develop. Kidney toxicity is an important consequence of exposure to mercury salts.

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/Medical Technologists Procedures Manual (LPM).

Data Processing and Editing

Read the General Documentation on Laboratory Data General Documentation on Laboratory Data file for detailed data processing and editing protocols.

The analytical methods are described in the Description of the Laboratory Methodology section.

One calculated variable was created in this data file. The formula for its derivation is as follows:

LBXIHG and LBDIHGSI
The inorganic mercury in µg/L was converted to nmol/L by multiplying by 4.99.

Detection Limits

The detection limits were constant for the analytes in the data set.  The lower detection limits is 0.35 µg/L for Inorganic Mercury. 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.

Laboratory Quality Assurance and Monitoring

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 Laboratory/Medical Technologists Procedures Manual (LPM).

Read the General Documentation on Laboratory Data file for detailed QA/QC protocols.

The analytical methods are described in the Description of the Laboratory Methodology section.

Analytic Notes

The analysis of NHANES laboratory data must be conducted with the key survey design and basic demographic variables. The Demographic file contains: Status Variables providing core information on the survey participant including examination status, Recoded Demographic Variables including age, gender, race etc., and Interview and Examination Sample Weight Variables and Survey Design Variables. The Questionnaire Data Files contain socio-economic data, health indicators, and other related information collected during household interviews. The Phlebotomy Examination file includes auxiliary information on duration of fasting, the time of day of the venipuncture, and the conditions precluding venipuncture. The Demographic, Questionnaire and Phlebotomy Examination files may be linked to the laboratory data file using the unique survey participant identifier SEQN.

Exam sample weights should be used for analyses. 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.

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 1 YEARS - 150 YEARS

LBXIHG - Mercury, inorganic (ug/L)

Variable Name:
LBXIHG
SAS Label:
Mercury, inorganic (ug/L)
English Text:
Mercury, inorganic (ug/L)
Target:
Both males and females 1 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.35 to 42 Range of Values 1042 1042
0.25 First Below Detection Limit Fill Value 7691 8733
0.28 Second Below Detection Limit Fill Value 0 8733
. Missing 1102 9835

LBDIHGSI - Mercury, inorganic (umol/L )

Variable Name:
LBDIHGSI
SAS Label:
Mercury, inorganic (umol/L )
English Text:
Mercury, inorganic (umol/L )
Target:
Both males and females 1 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1.75 to 209.58 Range of Values 1042 1042
1.4 First Below Detection Limit Fill Value 0 1042
1.25 Second Below Detection Limit Fill Value 7691 8733
. Missing 1102 9835

LBDIHGLC - Mercury, inorganic comment code

Variable Name:
LBDIHGLC
SAS Label:
Mercury, inorganic comment code
English Text:
Mercury, inorganic comment code
Target:
Both males and females 1 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 At or above the detection limit 1042 1042
1 Below lower detection limit 7691 8733
. Missing 1102 9835