Glynn, A, U Berger, A Bignert, S Ullah, M Aune, S Lignell and PO Darnerud. 2012. Perfluorinated alkyl acids in blood serum from primiparous women in Sweden: Serial sampling during pregnancy and nursing, and temporal trends 1996-2010. Environmental Science and Technology http://dx.doi.org/10.1021/es301168c.
As the phased-out stain repellent PFOS steadily decreases in people, its replacement is rising rapidly at levels that are doubling every six years, a Swedish study shows. Levels of perfluorobutane sulfonate (PFBS) in the women’s blood rose 11 percent per year between 1996 and 2010. Whether there are any potential health effects of these exposures — which are still far lower than PFOS levels — is unknown.
What did they do?
The research is part of a larger study that examined time trends of persistent organic pollutants in the blood and breast milk of pregnant and nursing women in Uppsala County, Sweden.
Blood samples were collected from first-time mothers, aged 19 – 41 years, three weeks after delivery. Samples were collected each year between 1996 and 2010, except in 2003 and 2005. For each year, several individual blood samples were pooled together for analysis. In general, three pooled samples per year were analyzed.
The study investigated levels of 13 PFAAs, including PFBS and PFOS. The study also measured perfluorooctane sulfonamide (FOSA), which is known to degrade to PFOS.
A unique aspect of this study was the ability to measure PFBS levels at very low levels. It was this improved analytical capability that allowed the researchers to detect the PFBS trends over time.
In addition to examining time trends, the study also investigated PFAA trends at different stages during pregnancy and after delivery.
What did they find?
The study showed that PFBS blood concentrations in the Swedish women increased by 11 percent per year between 1996 and 2010. The levels doubled every 6.3 years. This is the first study to show increasing PFBS levels in humans.
However, during the same time period, PFOS levels decreased by 8.4 percent per year. The study also showed decreasing levels of perfluorodecane sulfonate (PFDS), PFOA and FOSA.
In contrast, blood levels of two PFCAs – perfluorononanoate (PFNA) and perfluorodecanoate (PFDA) – increased by 4.3 percent and 3.8 percent, respectively, from 1996 to 2010.
The study also looked for longer-chain length PFCAs: perfluorododecanoate (PFDoA), perfluorotridecanoate (PFTrA) and perfluorotetradecanoate (PFTA). But these PFCAs were not found in the women’s blood.
What does it mean?
Perfluorobutane sulfonate or PFBS – the chemical that replaced the PFOS-based fluorinated chemicals used as stain repellents – is building up in human blood with levels doubling every six years. This is the first study to show increasing PFBS levels in humans.
The study showed that PFBS levels in Swedish women are rapidly increasing. This means that humans are widely exposed to PFBS and its precursors. Exposure to these chemicals has increased dramatically from 1996 to 2010.
These findings were surprising because it was thought that PFBS would not accumulate in humans due to its very short half-life (26 days). But the new research shows that PFBS is building up at an alarming rate.
However, PFBS levels are still about 75 times lower than PFOS.
The study did not investigate whether there were any health effects associated with the increasing PFBS levels. There have been few toxicology studies on PFBS, and the toxic effects are generally less than PFOS and PFOA (Lieder et al. 2009).
PFBS-based chemicals were introduced as replacements for PFOS-based chemicals after 3M stopped their manufacture in 2002. In the current study, PFBS levels did not start increasing until 2002. Presumably, this increase in PFBS blood levels is a reflection of increased use of PFBS precursors in commercial products and their release into the environment after 2002.
The new study also showed that PFOS and FOSA levels are decreasing in Swedish women’s blood. FOSA is formed when PFOS precursors are metabolized in the body.
These results show that 3M’s PFOS ban in 2002 had a rapid effect on PFOS blood levels. Studies from the United States (Kato et al. 2011; Olsen et al. 2012) and Norway (Haug et al. 2009) have also shown decreasing PFOS blood levels after the 3M ban.
In contrast, PFNA and PFDA levels were shown to increase in the Swedish women. These chemicals are breakdown products of fluorotelomer-based compounds that are used in some polymers and surfactants. They have similar uses as the PFOS-related chemicals. In addition, PFNA is used in the production of polyvinylidene fluoride (PVDF) and trace amounts can be detected in the final products. Production of fluorotelomer chemicals increased after the 3M PFOS ban. The increasing blood levels of these chemicals most likely represents the increased use of their precursors in commercial products.
Because the study only monitored Swedish women, it will be necessary to confirm the trends in other regions of the world. This is because fluorinated chemical use varies in different areas of the world. For example, China began producing PFOS-chemicals in 2003. Their production in China may represent a new source of PFOS to the world.
Scientists are concerned when blood levels of a chemical increase in our bodies because it shows that our exposure is increasing. However, it is necessary to determine if the contaminant levels are enough to cause harmful effects in wildlife and people. Future research is needed to determine if the increasing PFBS levels are affecting human health.
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Lieder, PH, RG York, DC Hakes, S-C Chang and JL Butenhoff. 2009. A two-generational gavage reproduction study with potassium perfluorobutanesulfonate (K+PFBS) in Sprague Dawley rat. Toxicology 259:33-4.
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Olsen, GW, CC Lange, ME Ellefson, DC Mair, TR Church, CL Goldberg, RM Herron, Z Medhdizadehkashi, JB Nobiletti, JA Rios, WK Reagen and LR Zobel. 2012. Temporal trends of perfluoroalkyl concentrations in American Red Cross adult blood donors, 2000-2010. Environmental Science & Technology 46:6330-6338.
Polyfluorinated and perfluorinated chemicals (PFASs) are applied to clothing, furniture, carpeting, cookware and food packaging to make the products stain repellent. PFASs – commonly referred to as PFCs – are a large group of chemicals that are unique because they repel both grease and water.
The PFAS chemicals used in commercial products fall into two main categories: the large fluorinated polymers that are used in clothing, furniture and carpet treatments and the phosphate surfactants that are used to coat paper.
Commercial products often contain the parent PFAS chemicals used to make the polymers and phosphate surfactants – called precursors – as impurities. PFASs break down in the atmosphere and in our bodies to form very long-lived perfluorinated alkyl acids (PFAAs).
People are exposed to PFAAs and their precursors mainly through food, air and water. Studies suggest the chemicals may contribute to kidney damage, and prenatal exposures have been linked to low birth weight.
Two of the most well-known and well-studied PFAA varieties are perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA). In addition to forming as breakdown products, small amounts of PFOS and PFOA were directly produced for specialized products. PFOS was used in fire-fighting foams as well as in the semiconductor industry. PFOA was used in the production of Teflon, but is typically not detected in the final products.
In 2002, the 3M Company – a leading manufacturer of PFOS and PFOA – voluntarily stopped manufacturing both PFOS and the chemicals that degrade to form PFOS because they were accumulating in humans globally and in animals – such as polar bears – that live in remote areas (Hansen et al. 2001; Giesy and Kannan 2001; Butt et al. 2010).
The company has substituted PFOS-based chemicals with another PFAA variety that is based on perfluorobutane sulfonate (PFBS). PFBS has four carbons whereas PFOS has eight. Otherwise, their molecular makeup is identical.
The smaller PFBS clears from the human body much faster than PFOS. PFOS has a half-life in people of 4 – 5 years, but PFBS’s half-life is only 26 days (Olsen et al. 2009).
After 3M stopped making PFOS-based compounds, production of other compounds made by another manufacturing process rapidly increased. These are called fluorotelomer-based chemicals. The fluorotelomer compounds are used for the same purpose as the PFOS-based compounds were: to make fluorinated polymers and surfactants. However, these chemicals degrade to form perfluorinated carboxylates (PFCAs), including PFOA.
Due to the increasing concern about PFOA, the eight major manufacturers have committed to eliminate PFOA emissions by 2015.