PFCs: Facts & Figures
PFC blood levels
- In US population, by year
- In US population, by gender
- In US population, by race/ethnicity
- In two exposed MN communities
PFCs are common chemicals.
Perfluorochemicals (PFCs) are used to make products that resist heat, stains, grease, and water. There are many different PFCs. The three shown in the graphs below are detected in the blood of nearly all people studied: perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), and perfluorohexane sulfonate (PFHxS).
In communities where groundwater was contaminated with PFCs, like the East Metro of Minneapolis-St. Paul, people are often exposed through drinking water. Other exposures to PFCs are less well understood, but likely come from diet, house dust, and use of consumer products.
Scientists still do not fully understand the human health effects of PFC exposure. Studies in animals have found increased tumors and effects on some body systems such as the liver and thyroid, but it can be difficult to compare research findings in animals to human health effects. So far published studies in humans do not show clear evidence that PFCs increase the risk of disease, but many studies are actively being conducted and information will continue to emerge.
Biomonitoring shows levels of exposure to PFCs.
Biomonitoring measures the amount of a PFC in peoples' blood. It provides a measure of how much PFC a person actually took into their body from all different sources. Some PFCs are cleared from the body more quickly than others. PFOS, PFOA, and PFHxS all stay in the body for years, so a blood measurement reflects longer-term exposure. Currently, we have no clinical reference values for "safe" and "unsafe" levels of PFCs in the body.
Except where noted, the data shown in the graphs below are for the U.S. population as a whole, and are from the National Health and Nutrition Examination Survey (NHANES).
PFC levels in the U.S. population, by year
Blood levels of PFOS, both median and 95th percentile levels, declined in the U.S. population between 1999 and 2010, with a big drop between 1999-2000 and 2003-2004 (NHANES did not measure PFCs in people in 2001-2002).
The median blood level of PFOA declined somewhat from 1999-2000 to 2003-2004. After a period of insignificant change, PFOA levels again dropped from 2007-2010. Trends in PFHxS are less clear.
These changes are likely a result of reductions in the production and use of certain PFCs during this time period. 3M, formerly the primary manufacturer of PFOS world-wide, stopped producing PFOS and related chemicals in 2002, though these chemicals are still made in other countries. Efforts are also underway to reduce PFOA emissions to the environment.
Median PFC levels, by gender
For all three PFCs, U.S. men had significantly higher blood levels than women in 2009-2010. This was also true in earlier years of NHANES data, and in results from the East Metro PFC Biomonitoring Follow-up Project conducted in two Minnesota communities exposed to PFCs in drinking water. We do not fully understand the reasons for this difference by gender, but it may be related to biological differences in how men and women clear PFCs from their bodies or differences in the use of PFC-containing products.
Median PFC levels, by race
Of these three racial/ethnic groups, Mexican Americans had the lowest median blood levels for all three PFCs. Additionally, non-Hispanic whites had higher levels of PFOA and PFHxS compared to non-Hispanic blacks. Because we do not fully understand how people are exposed to PFCs, it is difficult to say why these differences by race/ethnicity exist. They are likely due to differences in exposure to PFCs from sources such as diet and use of consumer products.
PFC levels may be higher in children.
Biomonitoring in children is important. Because they are developing rapidly, babies in utero, infants, and young children may be particularly vulnerable to possible health effects from exposure to environmental chemicals. And, they tend to have higher exposures to certain chemicals than adults.
Because less blood can be collected from younger children, NHANES does not routinely measure PFCs in children under 12. Only a small handful of other studies have measured PFCs in children, and none are representative of children in the U.S. population or Minnesota.
To begin to determine whether children have higher blood levels than adults, NHANES pooled smaller amounts of available blood samples from children aged 3-11 and measured PFCs. Researchers compared blood levels in 3-5 and 6-11 year-olds to those in adolescents and adults, and concluded that mean levels of PFOS, PFOA, and PFHxS were higher in children. This seemed particularly true for PFHxS, a PFC used in the past as a stain-resistant finish for carpeting. More information on this study can be found here.
What is being done about PFCs in Minnesota?
MDH has conducted two PFC biomonitoring projects in Minnesota communities east of the Minneapolis-St. Paul metro area (called the "East Metro") exposed to PFCs in contaminated drinking water:
- The East Metro PFC Biomonitoring Pilot Project, in 2008, measured blood levels of PFCs in people from two communities known to be exposed to contaminated drinking water.
- In 2010, MDH conducted the East Metro PFC Biomonitoring Follow-up Project that collected a second blood sample from the same participants to determine the change in PFC levels over time and whether efforts made to reduce exposure were effective.
These projects were critical in helping MDH determine that:
- PFC exposures in these communities were higher than in the general U.S. population.
- Blood levels of PFOS, PFOA, and PFHxS declined substantially between 2008 and 2010, indicating that efforts to reduce the communities' exposure to PFCs in drinking water were effective. For more information, see the December 2011 Report to the Community [PDF: 3 pages/270 KB].
- Drinking water was a major source of exposure to PFCs in East Metro. The relationships between other sources of exposure, such as diet and product use, and PFCs were unclear for these communities. For more information, see the May 2013 Report to the Community [PDF: 4pages/266KB].
PFC levels in two exposed MN communities
The graph above shows median levels from the two MDH biomonitoring projects compared to the U.S. population. Levels of all three PFCs declined substantially between 2008 and 2010 in East Metro residents. Nevertheless, 2010 levels in the East Metro communities were still above the most recent NHANES levels. Given that these compounds stay in the body for a long time, this is not surprising. We expect that, over time, East Metro residents' blood levels will decline to general U.S. population levels.
What is being done about PFCs in Minnesota?
MDH, along with the Minnesota Pollution Control Agency (MPCA), has also been involved in testing PFC levels in public and private water supplies (see MDH's Perfluorochemicals (PFCs) and Water), and in the investigation of sites across the state where PFCs were released to the environment (see MDH's Perfluorochemicals (PFCs) and Minnesota Sites). MDH is responsible for developing Health Guidelines for Perfluorochemicals (PFCs) in Drinking Water. In addition, the MDH Fish Consumption Advisory Program offers recommendations (see Perfluorochemicals (PFCs) and Fish) about fish consumption from four Metro-area lakes where fish have been contaminated with PFOS.