• Component Description
• Eligible Sample
• Description of Laboratory Methodology
• Data Processing and Editing
• Laboratory Quality Assurance and Monitoring
• Analytic Notes
• Codebook
  • SEQN - Respondent sequence number
  • LBXIHG - Mercury, inorganic (ug/L)
  • LBDIHGSI - Mercury, inorganic (umol/L )
  • LBDIHGLC - Mercury, inorganic comment code
  • LBXBGE - Mercury, ethyl (ug/L)
  • LBDBGELC - Mercury, ethyl comment code
  • LBXBGM - Mercury, methyl (ug/L)
  • LBDBGMLC - Mercury, methyl comment code

National Health and Nutrition Examination Survey

2011-2012 Data Documentation, Codebook, and Frequencies

Mercury: Inorganic, Ethyl and Methyl - Blood (IHgEM_G)

Data File: IHgEM_G.xpt

First Published: September 2013

Last Revised: NA

Component Description

Blood mercury: inorganic, ethyl and methyl

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 total and 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, Ethyl and Methyl Mercury

The mercuries 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. However, ethyl and methyl mercury were added to this 2011-2012 cycle.

Detailed instructions on specimen collection and processing can be found in the NHANES Laboratory/Medical Technologists Procedures Manual (LPM).

Data Processing and Editing

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

Three calculated variables were created in this data file. The formula for their derivation is as follows:

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

LBXBGE and LBDBGESI
The ethyl mercury in µg/L was converted to nmol/L by multiplying by 4.99.

LBXBGM and LBDBGMSI
The methyl 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 were 0.27 µg/L for inorganic mercury, 0.16 µg/L for ethyl mercury, and 0.12 µg/L for methyl 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 Amendments mandates. Detailed QA/QC instructions are discussed in the NHANES Laboratory/Medical Technologists Procedures Manual (LPM).

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

Analytic Notes

Refer to the 2011-2012 Laboratory Data Overview for general information on NHANES laboratory data.

The analysis of NHANES 2011-2012 laboratory data must be conducted using the appropriate survey design and demographic variables. The NHANES 2011-2012 Demographics File contains demographic data, health indicators, and other related information collected during household interviews as well as the sample weight variables. The Fasting Questionnaire File includes auxiliary information such as fasting status, the time of venipuncture, and the conditions precluding venipuncture. The demographics and fasting questionnaire files may be linked to the laboratory data file using the unique survey participant identifier (i.e., 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