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 mercury levels will be assessed in two subpopulations particularly vulnerable to the health effects from mercury exposure: children 1–5 years old and women of childbearing age.
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.
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 to the equipment or lab site from the previous 2 years.
Whole 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.
Detailed specimen collection and processing instructions are discussed in the NHANES LPM. Vials are stored under appropriate frozen (–20°C) conditions until they are shipped to National Center for Environmental Health for testing.
One derived variable was created in this data file. The formula for its derivation is as follows:
The inorganic mercury in μg/L was converted to nmol/L by multiplying by 4.99.
Detection Limits
The detection limits were variable for 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. 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.
Detailed instructions on specimen collection and processing can be found on the NHANES website.
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 LABDOC file for detailed QA/QC protocols.
A detailed description of the quality assurance and quality control procedures can be found on the NHANES website.
The analysis of NHANES 2005–2006 laboratory data must be conducted with the key survey design and basic demographic variables. The NHANES 2005–2006 Household Questionnaire Data Files contain demographic data, health indicators, and other related information collected during household interviews. The Household Questionnaire Data Files also contain all survey design variables and sample weights required to analyze these data. The Phlebotomy Examination file includes auxiliary information on duration of fasting, the time of day of the venipuncture, and the conditions precluding venipuncture. The Household Questionnaire and Phlebotomy Exam files may be linked to the laboratory data file using the unique survey participant identifier SEQN.
| Code or Value | Value Description | Count | Cumulative | Skip to Item |
|---|---|---|---|---|
| 0.35 to 15 | Range of Values | 2116 | 2116 | |
| 0.25 | First Below Detection Limit Fill Value | 6141 | 8257 | |
| 0.28 | Second Below Detection Limit Fill Value | 114 | 8371 | |
| . | Missing | 1069 | 9440 |
| Code or Value | Value Description | Count | Cumulative | Skip to Item |
|---|---|---|---|---|
| 1.75 to 74.85 | Range of Values | 2116 | 2116 | |
| 1.4 | First Below Detection Limit Fill Value | 114 | 2230 | |
| 1.25 | Second Below Detection Limit Fill Value | 6141 | 8371 | |
| . | Missing | 1069 | 9440 |
| Code or Value | Value Description | Count | Cumulative | Skip to Item |
|---|---|---|---|---|
| 0 | At or above the detection limit | 2116 | 2116 | |
| 1 | Below lower detection limit | 6255 | 8371 | |
| . | Missing | 1069 | 9440 |