title: Total and methyl mercury in whole blood measured for the first time in the U.S. population: NHANES 2011-2012.
abstract: BACKGROUND
  Despite the public health and toxicologic interest in methyl mercury (MeHg) and ethyl mercury (EHg), these mercury species have been technically difficult to measure in large population studies.
  
  
  METHODS
  Using NHANES 2011-2012 data, we calculated reference ranges and examined demographic factors associated with specific mercury species concentrations and the ratio of MeHg to THg. We conducted several multiple regression analyses to examine factors associated with MeHg concentrations and also with the ratio of MeHg to THg.
  
  
  RESULTS
  Asians had the highest geometric mean concentrations for MeHg, 1.58 µg/L (95% CI 1.29, 1.93) and THg, 1.86 µg/L (1.58, 2.19), followed by non-Hispanic blacks with MeHg, 0.52 µg/L (0.39, 0.68) and THg, 0.68 µg/L (0.54, 0.85). Greater education attainment in adults and male sex were associated with higher MeHg and THg concentrations. Race/ethnicity, age, and sex were significant predictors of MeHg concentrations, which increased with age and were highest in Asians in all age categories, followed by non-Hispanic blacks. Mexican Americans had the lowest adjusted MeHg concentrations. The ratio of MeHg to THg was highest in Asians, varied by racial/ethnic group, and increased with age in a non-linear fashion. The amount of increase in the MeHg to THg ratio with age depended on the initial ratio, with a greater increase as age increased. Of the overall population, 3.05% (95% CI 1.77, 4.87) had MeHg concentrations >5.8 µg/L (a value that corresponds to the U.S. EPA reference dose). The prevalence was highest in Asians at 15.85% (95% CI 11.85, 20.56), increased with age, reaching a maximum of 9.26% (3.03, 20.42) at ages 60-69 years. Females 16-44 years old had a 1.76% (0.82-3.28) prevalence of MeHg concentrations >5.8 µg/L.
  
  
  CONCLUSIONS
  Asians, males, older individuals, and adults with greater educational attainment had higher MeHg concentrations. The ratio of MeHg to THg varied with racial/ethnic group, increased with age, and was nonlinear. U.S. population reference values for MeHg and the ratio of MeHg to THg can assist in more precise assessment of public health risk from MeHg consumed in seafood.
authors.affiliation: Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, MS F-20, 4770 Buford Highway, Atlanta, GA 30341, USA. Electronic address: MMortensen@cdc.gov.
authors.forename: Mary E
authors.initials: ME
authors.lastname: Mortensen
authors.affiliation: Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, MS F-20, 4770 Buford Highway, Atlanta, GA 30341, USA.
authors.forename: Samuel P
authors.initials: SP
authors.lastname: Caudill
authors.affiliation: Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, MS F-20, 4770 Buford Highway, Atlanta, GA 30341, USA.
authors.forename: Kathleen L
authors.initials: KL
authors.lastname: Caldwell
authors.affiliation: Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, MS F-20, 4770 Buford Highway, Atlanta, GA 30341, USA.
authors.forename: Cynthia D
authors.initials: CD
authors.lastname: Ward
authors.affiliation: Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, MS F-20, 4770 Buford Highway, Atlanta, GA 30341, USA.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Jones
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008628:Mercury / Q000097:blood*; D008767:Methylmercury Compounds / Q000097:blood*; D008875:Middle Aged; D009749:Nutrition Surveys; D014481:United States; D055815:Young Adult
chemical_list: D008767:Methylmercury Compounds; D008628:Mercury
keywords: Biomonitoring; Blood mercury; Mercury species; Methyl mercury; NHANES