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
Participants aged 1 year and older, who do not meet any of the exclusion criteria, are eligible.
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).
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.
The NHANES quality assurance and quality control (QA/QC) protocols meet the 1988 Clinical Laboratory Improvement Amendments 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.
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.
| 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 |
| 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 |
| 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 |