Adult women's blood mercury concentrations vary regionally in the United States: association with patterns of fish consumption (NHANES 1999-2004).

BACKGROUND: The current, continuous National Health and Nutrition Examination Survey (NHANES) has included blood mercury (BHg) and fish/shellfish consumption since it began in 1999. NHANES 1999-2004 data form the basis for these analyses. OBJECTIVES: This study was designed to determine BHg distributions within U.S. Census regions and within coastal and noncoastal areas among women of childbearing age, their association with patterns of fish consumption, and changes from 1999 through 2004. METHODS: We performed univariate and bivariate analyses to determine the distribution of BHg and fish consumption in the population and to investigate differences by geography, race/ethnicity, and income. We used multivariate analysis (regression) to determine the strongest predictors of BHg among geography, demographic factors, and fish consumption. RESULTS: Elevated BHg occurred more commonly among women of childbearing age living in coastal areas of the United States (approximately one in six women). Regionally, exposures differ across the United States: Northeast > South and West > Midwest. Asian women and women with higher income ate more fish and had higher BHg. Time-trend analyses identified reduced BHg and reduced intake of Hg in the upper percentiles without an overall reduction of fish consumption. CONCLUSIONS: BHg is associated with income, ethnicity, residence (census region and coastal proximity). From 1999 through 2004, BHg decreased without a concomitant decrease in fish consumption. Data are consistent with a shift over this time period in fish species in women's diets.

Methylmercury and omega-3 fatty acids: co-occurrence of dietary sources with emphasis on fish and shellfish.

Despite many claims of broad benefits, especially for in utero development, derived from the consumption of fish as a source of omega-3 fatty acids, individual species of fish and shellfish provide substantially varied levels of these fatty acids. Likewise, mean methylmercury (MeHg) concentrations for fish and shellfish species differ by greater than an order of magnitude. Consideration of within-species variability would increase this variation farther. Exposures to both MeHg and to the omega-3 fatty acids reflect dietary choices including species consumed, frequency of consumption, and portion size. In view of these sources of variability, data on dietary patterns and blood mercury (microg/L) among women of child-bearing age (e.g., 16-49 years) provided an indication of exposures in the United States. Utilizing data from the National Health and Nutrition Examination Survey (NHANES) for survey years 1999--2002, calculated consumption of MeHg and omega-3 fatty acids from fish and shellfish have been estimated based on results from 3614 women who provided 30-day dietary recall and 24-hours records. Statistics from NHANES when appropriately weighted are representative of the US population. The association between dietary MeHg from fish and shellfish and dietary fish intake yielded a Pearson correlation of 0.68. The Pearson correlation between estimated 30-day intake from fish/shellfish consumption for omega-3 fatty acids and MeHg was 0.66. Evaluation of the most commonly consumed fish and shellfish species as sources of MeHg and omega-3 fatty acids indicated that salmon followed by shrimp are principal sources of omega-3 fatty acids and are lesser sources of MeHg, in contrast with tuna which provides omega-3 fatty acids, but considerably higher levels of MeHg. These data can be used to guide selection of individual fish and shellfish species that are higher in omega-3 content and low in MeHg concentrations. This more refined dietary approach contrasts with generic recommendations that simply advise increasing fish consumption as a path toward improving cardiovascular health and providing benefits for in utero development or avoiding fish altogether.

Serum TSH and total T4 in the United States population and their association with participant characteristics: National Health and Nutrition Examination Survey (NHANES 1999-2002).

OBJECTIVE: Describe thyrotropin (TSH) and thyroxine (T4) levels in the U.S. population and their association with selected participant characteristics. DESIGN: Secondary analysis of data from the National Health and Nutrition Examination Survey (NHANES) collected from 4392 participants, reflecting 222 million individuals, during 1999-2002. RESULTS: Hypothyroidism prevalence (TSH > 4.5 mIU/L) in the general population was 3.7%, and hyperthyroidism prevalence (TSH < 0.1 mIU/L) was 0.5%. Among women of reproductive age (12-49 years), hypothyroidism prevalence was 3.1%. Individuals aged 80 years and older had five times greater odds for hypothyroidism compared to 12- to 49-year-olds (adjusted odds ratio [OR] = 5.0, p = 0.0002). ORs were adjusted for sex, race, annual income, pregnancy status, and usage of thyroid-related medications (levothyroxine/thyroid, estrogen, androgen, lithium, and amiodarone). Compared to non-Hispanic whites, non-Hispanic blacks had a lower risk for hypothyroidism (OR = 0.46, p = 0.04) and a higher risk for hyperthyroidism (OR = 3.18, p = 0.0005), while Mexican Americans had the same risk as non-Hispanic whites for hypothyroidism, but a higher risk for hyperthyroidism (OR = 1.98, p = 0.04). Among those taking levothyroxine or desiccated thyroid, the adjusted risk for either hypothyroidism (OR = 4.0, p = 0.0001) or hyperthyroidism (OR = 11.4, p = 4 x 10(-9)) was elevated. CONCLUSIONS: Associations with known factors such as age, race, and sex were confirmed using this data set. Understanding the prevalence of abnormal thyroid tests among reproductive-aged women informs decisions about screening in this population. The finding that individuals on thyroid hormone replacement medication often remain hypothyroid or become hyperthyroid underscores the importance of monitoring.