Biomonitoring - Mercury
Mercury can be found in some devices such as thermometers and lightbulbs, foods, and the environment. The most common source of mercury exposure in people is consuming contaminated fish. Higher levels of exposure to certain types of mercury, especially prenatal and early life exposures, can result in neurotoxic and developmental effects in humans.
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Indicators
B3: Mercury in women
Web update: 2022
Key Information
- The median level of mercury in the blood of women of child-bearing age decreased from 0.9 µg/L in 1999–2000 to 0.6 µg/L in 2017-2018. The median represents the midpoint of exposure.
- In 2017-2018, the 95th percentile level of mercury in the blood of women was 3.8 µg/L. This level decreased from 7.4 µg/L in 1999–2000 to 3.7 µg/L in 2001-2002, and has remained relatively steady since. The 95th percentile represents higher exposure.
- Differences in mercury in blood were observed across race/ethnicity groups, especially among women with higher exposures. For the years 2015–2018, White non-Hispanic women had a 95th percentile blood mercury level of 3.6 µg/L, Black non-Hispanics had 3.5 µg/L, Mexican-American women had 2.6 µg/L, and women in the "All Other Races/Ethnicities" group had 5.8 µg/L.
Data Characterization
Data for this indicator are obtained from an ongoing continuous survey conducted by the National Center for Health Statistics.
Survey data are representative of the U.S. civilian noninstitutionalized population.
Mercury is measured in blood samples obtained from individual survey participants.
B4: Mercury in Children
Web update: 2022
Key Information
- In 2017-2018, the median level of mercury in the blood of children ages 1 to 5 was was 0.2 µg/L.
- The 95th percentile level of mercury in the blood of children ages 1 to 5 decreased from 2.3 µg/L in 1999-2000 to 1.0 µg/L in 2017-2018.
- Blood mercury levels generally increase with age, in part because mercury accumulates in the body over time. In 2015–2018, children ages 6 years and older had higher blood mercury levels than younger age groups.
Data Characterization
Data for this indicator are obtained from an ongoing continuous survey conducted by the National Center for Health Statistics.
Survey data are representative of the U.S. civilian noninstitutionalized population.
Mercury is measured in blood samples obtained from individual survey participants.
About the Mercury Indicators
Mercury is a metal that is liquid at room temperature. There are three major forms of mercury -- inorganic mercury (used in some batteries, disinfectants, and health products and creams); elemental mercury (used in some thermometers, fluorescent bulbs, and dental fillings); and organic mercury or methylmercury (found in the environment when mercury is deposited into water systems and converted by microorganisms).
Methylmercury is particularly concerning because it bioaccumulates in the aquatic food web. Eating contaminated fish is the main way that people are exposed to methylmercury. Each person's exposure depends on the amount of methylmercury in the fish that they eat and how often they eat fish. Higher levels of mercury are more common in certain types of fish. This is particularly important for women of child-bearing age because methylmercury can easily cross the placenta and blood-brain barrier. As a result, the prenatal period is considered the most sensitive period of exposure.
Although ingesting methylmercury from fish can be harmful, many compounds naturally present in most fish (such as high-quality protein and other essential nutrients) are beneficial. EPA and the Food and Drug Administration (FDA) have issued a fish consumption advisory for young children and pregnant and breastfeeding women. The advisory encourages consumption of up to 12 ounces per week of a variety of fish and shellfish that are lower in mercury and avoiding consumption of fish species that contain high levels of mercury.
For historic and contextual information about mercury and these indicators, see the Mercury section of America's Children and the Environment, Third Edition (pdf) .
Data Sources and Methods - Mercury
The National Center for Health Statistics, a division of the Centers for Disease Control and Prevention, conducts the National Health and Nutrition Examination Surveys (NHANES), a series of U.S. national surveys of the health and nutrition status of the noninstitutionalized civilian population. Interviews and physical examinations are conducted with approximately 10,000 people in each two-year survey cycle. The survey measures mercury levels in blood samples collected from NHANES participants. These indicators focus on children and women of child-bearing age because of concern for potential adverse effects in children born to women who have been exposed to mercury. The concentration of total mercury in blood is a marker of exposure to methylmercury in populations where fish consumption is the predominant source of mercury exposure.
- Detailed Methods for Indicator B3 (pdf)
- Metadata for National Health and Nutrition Examination Surveys (NHANES)
Related Links
- U.S. EPA: Fish and Shellfish Advisories
- U.S. EPA: Mercury
- U.S. EPA: Methylmercury (MeHg) (CASRN 22967-92-6)
- U.S EPA: Choose Fish and Shellfish Wisely
- Centers for Disease Control and Prevention (CDC): Mercury and Breastfeeding
- Centers for Disease Control and Prevention (CDC): National Report on Human Exposure to Environmental Chemicals
- Centers for Disease Control and Prevention (CDC): Thimerosal