ACE: Biomonitoring - Perfluorochemicals (PFCs)
- Indicator B6 – Perfluorochemicals in women ages 16 to 49 years: median concentrations in blood serum, 1999-2016
- Background Text
- 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.
- PFCs are measured in blood samples obtained from individual survey participants.
- Between 1999-2000 and 2015-2016, median blood serum levels of PFOS in women of child-bearing age declined from 24 ng/mL in 1999-2000 to 3 ng/mL in 2015-2016. Median blood serum levels of PFOA in women of child-bearing age declined from 5 ng/mL in 1999-2000 to 1 ng/mL in 2015-2016. These decreasing trends were statistically significant.
- The median blood serum levels of PFHxS and PFNA were lower than those of PFOS and PFOA in women of child-bearing age. Median levels of PFHxS decreased from 1.3 ng/mL in 1999-2000 and 1.4 ng/mL in 2003-2004 to 0.6 ng/mL in 2015-2016. Between 1999-2000 and 2009-2010, median blood serum levels of PFNA showed an increasing trend, from 0.5 ng/mL in 1999-2000 to 1.0 ng/mL in 2009-2010, but then decreased to 0.4 ng/mL in 2015-2016.
- The decreasing trend in median PFHxS levels was statistically significant.
- The concentration of PFOS in blood serum at the 95th percentile in women of child-bearing age showed a decreasing trend from 50 ng/mL in 1999–2000 to 8 ng/mL in 2015–2016. The concentration of PFOA in blood serum at the 95th percentile in women of child-bearing age showed a decreasing trend from 8 ng/mL in 1999-2000 to 3 ng/mL in 2015–2016. The 95th percentile levels of PFHxS decreased from 4.9 ng/mL in 1999-2000 and 7.1 ng/mL in 2003-2004 to 2.5 ng/mL in 2015-2016.(See Table B6a.)
- The decreasing trends in 95th percentile PFOS and PFOA levels were statistically significant.
- For the years 2013–2016, women of child-bearing age living at or above poverty level had higher median but lower 95th percentile concentrations of PFOS in their blood serum compared with women living below poverty level. (See Tables B6b and 6c.)
- The differences between income groups were statistically significant, after adjustment for differences in race/ethnicity and age.
- For the years 2013–2016, median concentrations of PFOA were higher in White non-Hispanic women of child-bearing age (1.4 ng/mL) compared with Black non-Hispanic women (0.9 ng/mL), Mexican-American women (0.9 ng/mL), and women of “All Other Races/Ethnicities” (1.3 ng/mL). (See Table B6b.)
- These differences in median PFOA concentrations by race/ethnicity were statistically significant after accounting for other demographic characteristics (differences in age and income).
- • In 2013–2016, median and 95th percentile concentrations of PFOS were lower in Mexican-American women of child-bearing age at 2.0 ng/mL and 5.4 ng/mL, respectively, compared with White non-Hispanic women at 3.0 ng/mL and 8.4 ng/mL, respectively, Black non-Hispanic women at 2.8 ng/mL and 9.7 ng/mL, respectively, and women of “All Other Races/Ethnicities” at 2.8 ng/mL and 15.7 ng/mL, respectively. (See Tables B6b and 6c.)
- These differences were statistically significant both with and without adjustment for other demographic characteristics, with the following exceptions: the difference between Mexican-American women and Black non-Hispanic women was not statistically significant at the 95th percentile.
About the PFCs Indicator
Indicator B6 presents information about perfluorochemical (PFC) levels measured in women. The data are from a national survey that collects blood specimens from a representative sample of the population every two years, and then measures the concentration of various contaminants in the blood. The indicator focuses on women of child-bearing age because of concern for potential adverse effects in children born to women who have been exposed to PFCs.
Perfluorochemicals (PFCs) are a group of synthetic chemicals that have been used in many consumer products. The PFCs with the highest production volumes in the United States have been perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). Since 2000, efforts have been made toward phasing out production of PFOS and PFOA. However, the fact that some of these chemicals may be persistent in the environment and have a long half-life in humans means that they may continue to persist in the environment and in people for many years, despite reductions in emissions. The major sources of human exposure to PFCs are poorly understood, but may include food, water, indoor and outdoor air, breast milk, and dust. Some PFCs have been widely detected in pregnant women and in umbilical cord blood, suggesting that the developing fetus can be exposed to PFCs while in the womb.
Some human health studies have found associations between prenatal exposure to PFOS or PFOA and a range of adverse birth outcomes, such as low birth weight, decreased head circumference, reduced birth length, and smaller abdominal circumference. However, there are inconsistencies in the results of these studies, and other studies did not find an association between prenatal PFC exposure and birth weight. Animal studies have found a variety of developmental and reproductive effects, though typically at levels much higher than what humans are normally exposed to.
Indicator B6 presents PFC levels measured in blood serum of women from the National Health and Nutrition Examination Survey (NHANES). Data are presented for four PFCs: PFOS, PFOA, perfluorohexane sulfonic acid (PFHxS), and perfluorononanoic acid (PFNA).
More information about PFCs and Indicator B6 is provided in the updated PFC section of America's Children and the Environment, Third Edition.
Summary of Methods - PFCs
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 PFC levels in blood serum samples collected from NHANES participants.
Indicator B6 uses the NHANES data to present median concentrations of perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorohexane sulfonic acid (PFHxS), and perfluorononanoic acid (PFNA) measured in blood serum of women ages 16 to 49 years. These four PFCs were chosen because they are commonly detected in humans, and the bulk of PFCs health effects research in both humans and laboratory animals has focused on these contaminants—especially PFOS and PFOA.