Rachel Shaffer is a research assistant.
What do waterproof jackets, car wax, and non-stick pans have in common?
Aside from being great Father’s Day presents (Dad, I’m thinking ahead this year!), they also all are made with perfluorinated compounds, or PFCs. There are hundreds of different PFCs, and their oil- and water-resistant properties make them useful in a variety of products, from cookware and carpets to food-packaging and electronics.
Unfortunately, these chemicals have less desirable properties as well. Thanks to their strong molecular bonds, PFCs do not readily break down; they persist in the environment and in our bodies. And, widespread use has led to extensive human exposure. The Centers for Disease Control’s (CDC) human biomonitoring program, the National Health and Nutrition Examination Survey (NHANES), detected four types of PFCs in over 98% of samples representative of the U.S. population collected in 2003-2004.
Two of the compounds detected in NHANES, perfluorooctane sulfonic acid (PFOS) and perfluorootanoic acid (PFOA), are the focus of three new studies published this month in Environmental Health Perspectives. These studies, one reporting an association with osteoarthritis in women, another an association with semen quality in men, and a third an association with asthma in children, add to a growing concern about the potential adverse effects of these ubiquitous chemicals.
What follows is a brief overview of the findings of these new studies.
Osteoarthritis is the most common form of arthritis, affecting over 27 million people in the U.S. In this disease, cartilage breaks down, resulting in chronic pain and joint stiffness. Though not fully understood, some have hypothesized that the disease may be related to inflammation, changes in calcium levels, and oxidative stress. Because some animal studies have linked PFOA and PFOS to these same mechanisms (see here, here, and here), researchers set out to explore the associations between levels of these two compounds and the prevalence of osteoarthritis in the U.S. population.
Through an analysis of recent NHANES data, researchers found statistically significant associations between blood serum concentrations of PFOA and osteoarthritis in women, but not men. Women in the highest exposure group were almost twice as likely to have the disease as those in the lowest exposure group.
The sex differences will need to be confirmed through further research, but these initial results indicate that males and females may exhibit differing susceptibility to these compounds. This may in part be due to variations in the ways that PFOA are processed in the male and female systems (as demonstrated in previous animal studies), and it also suggests that the compounds may interact with sex-specific hormones to promote inflammation that leads to disease.
The authors are careful to note that because of limitations inherent in the study, they cannot make any definitive conclusions about causation (i.e., that the PFOA exposure resulted in the osteoarthritis). Nevertheless, the observed associations – seen at concentrations found in the general population – are of real concern and highlight an urgent need for future research.
Previous animal studies have indicated that PFOA and PFOS may cause changes to the development of the male reproductive system, which could lead to reduced testosterone levels and lower sperm counts, among other effects. The authors of the second study set out to answer the question that logically follows: do these chemicals affect human males in similar ways?
Because the developing fetus may be especially vulnerable to environmental chemicals and because PFOA and PFOS are able to cross the placental barrier, researchers investigated the connection between the level of these compounds in maternal blood during pregnancy and specific reproductive endpoints in their sons, 20 years later.
Their findings are troubling. Higher exposure to PFOA during pregnancy was associated with lower sperm concentrations, lower total sperm counts, and higher concentrations of two reproductive hormones (LH and FSH) in the sons as adults. No association was found with PFOS.
Based on their results, the authors of this study suggest that PFOA may act as a reproductive toxicant. Once again, though, more research is needed to show causation.
PFCs have also been shown to exacerbate asthma in animal models, and this final study investigated the possible connection between levels of these contaminants and asthma in children.
Researchers looked at levels of 11 PFCs, including PFOA and PFOS, present in the blood of several hundred Taiwanese children aged 10-15 years old and then compared the incidence of asthma in the highest exposed group to the lowest exposed group. They found that children with the highest concentrations of PFOS were about twice as likely to have asthma. And those with the highest concentrations of PFOA were four times as likely to have asthma. Significant associations were also found for a variety of the other PFCs. In addition, the authors noted a relation between markers of elevated immune system sensitivity – which indicate increased likelihood of airway swelling in response to certain triggers – and concentrations of PFCs.
Numerous factors are contributing to rising asthma rates, but this study indicates that exposure to chemicals like PFCs may play a role.
One chemical, many effects?
The studies described here examined PFCs in relation to three adverse effects, but previous studies in both animals and people have linked PFCs to a variety of others, including liver toxicity, developmental changes, immune system alterations, and cancer.
It may seem implausible that one group of chemicals could cause such diverse health problems. But the networks in our bodies are highly linked and coordinated, which, unfortunately, means that a single chemical may have the power to interfere with a range of processes. Changes to the immune system, for example, could result in increased susceptibility to inflammation or decreased ability to fight cancer-causing agents. A disruption to normal hormonal functioning could have an impact on the development of the reproductive, immune, skeletal and nervous systems.
Governments are beginning to act – but more is needed
International and federal agencies are starting to take action, driven especially by the fact that these compounds are extremely persistent and tend to accumulate in the environment and in organisms. The Stockholm Convention recently listed PFOS as a Persistent Organic Pollutant (POP), which means that signatory countries are required to restrict its production. (Note: The U.S. has not yet ratified this international treaty).
And despite limited authority under the outdated Toxic Substances Control Act (TSCA), the U.S. Environmental Protection Agency (EPA) has taken a number of steps to address certain PFCs:
- In 2006, the agency initiated the 2010/2015 PFOA Stewardship Program, a commitment by major PFOA manufacturers to eliminate PFOA and related compounds in their products and manufacturing facility releases by 2015.
- In 2009, EPA issued an action plan for several of the PFCs that includes conducting further studies to investigate health effects and initiating regulations on production and use of PFCs found to pose high risks.
- In 2012, the EPA proposed a Significant New Use Rule (SNUR) and a test rule for a subset of these compounds, which, when finalized, will require companies to report to EPA before using them in new ways and to conduct testing on current uses they plan to continue.
While the steps taken by the EPA represent important progress, they are limited in scope and were initiated after widespread exposure. The story of PFCs is another example that points to the need for the U.S. to adopt a stronger chemicals policy, which would, among other important provisions, ensure that chemicals are tested for potential health effects before being used in products.
Meanwhile, I guess I’ll have to keep looking around for a good Father’s Day present.