Forever Chemicals: What’s going on
You have likely heard a lot about PFAS (perfluoroalkyl and polyfluoroalkyl) in the last few weeks. Companies involved in PFAS manufacture faced congressional hearings where they were asked to explain why they concealed the health risks posed by the chemicals and how they plan to address widespread PFAS contamination. PFAS can be found in food packaging, nonstick cookware, cleaning products, paints, waxes, firefighting foams, drinking water, etc. It has also been found in the blood of many humans who were tested for these chemicals.
PFAS are a group of nearly 5000 synthetic chemicals that have been produced since the 1950s. The most common PFAS chemicals are perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS). These are no longer manufactured in the U.S., but they are still present in the environment. PFAS have been nicknamed the “forever chemicals” because they don’t break down, so they accumulate over time.
PFAS first made the news when it was observed that livestock were being killed and humans were being made sick and deformed by exposure to PFAS through drinking water in certain places in West Virginia. A DuPont site nearby, which was manufacturing the chemical, was releasing large amounts into local water bodies. Since most of the human population is not exposed to this high levels of PFAS, it is important to quantify exposure levels and determine if these exposure levels are safe.
Study selection
Many published studies have explored the effects of PFAS on human populations. However, individual studies alone can rarely capture the entire impact of a chemical. Apart from the need for consistent replication of results, individual studies can have biases or a small number of participants, which makes it difficult to draw a conclusion. Thus, I chose a review that analyzed multiple published studies using sound scientific methods to find out what effects PFAS have on humans. The review was conducted by the Australian National University (ANU) and funded by the Australian Government Department of Health.
The authors looked at electronic databases and grey literature sources (i.e., reports, government documents, white papers, etc.) to identify all studies that examined a link between PFAS and human health effects up until February 2017. They selected 221 separate studies that fit the criteria. The studies looked for PFAS effects on major organ systems, reproduction, metabolism, immune and thyroid gland function, and on specific conditions like obesity, diabetes, and cancer. These effects were studied in workers who were manufacturing PFAS, firefighters (as they use firefighting foams that contain PFAS), people exposed to PFAS through drinking water contamination, and people in the general community. They also looked at PFAS effects on newborns, infants, and pregnant women, who are often more sensitive to chemicals than the rest of the population.
Study findings
Based on the strength of evidence, the authors used four terms to classify PFAS’s role in different health outcomes:
Sufficient evidence of health effect: There is enough evidence to say PFAS causes the heath effect
Limited evidence of health effect: There is enough evidence to say PFAS possibly or probably causes the heath effect
Inadequate evidence of health effect: There is not enough evidence to say PFAS causes the health effect
Evidence suggesting lack of effect: There is enough evidence to say PFAS does not cause the health effect
The authors found sufficient evidence to link two PFAS chemicals (PFOA and PFOS) to increased blood cholesterol level in humans. While the increase in cholesterol level was small, high blood cholesterol level can lead to heart attacks. For the other PFAS chemicals studied, there was inadequate evidence to link them to cholesterol increase.
The authors found limited evidence to link PFAS to increases in uric acid levels (a normal byproduct of human body), and reduced kidney function and chronic kidney disease. However, the authors suggest it is possible that poor kidney function (caused by something else) could lead to increased PFAS levels and increased uric acid levels (PFAS and uric acid are both excreted by kidneys).
The authors found limited evidence to link PFAS exposure to kidney and testicular cancer, and to lower levels of antibodies following vaccination. This could indicate that vaccines are less effective in people with comparatively high PFAS levels in blood.
The authors found inadequate evidence to link PFAS to the other health effects.
Study limitations
After identifying all relevant studies, the authors tried to combine and analyze studies that examined the same health effect to determine the role PFAS plays in each of the health effects. However, for this to happen, the studies must have been conducted and reported similarly. In several instances, this was not the case. And sometimes, only a few studies showed a link between PFAS and a health effect, which made it difficult to confidently draw a conclusion. The authors say more high-quality studies are needed to further our understanding of the health effects of PFAS chemicals (further research has been published since this review was done).
The authors note that difficulties in accessing international government reports, variabilities in exposed populations, and reviews by different scientists (multiple scientists were involved in conducting this review) could have influenced their findings. Finally, while there are many PFAS chemicals in the environment, health effects have been studied for only a few.
Conclusions
There are several ongoing PFAS studies on human populations, including one by the Australian government which commissioned ANU to write up this report. The current focus of the U.S. government is on reducing exposure to PFAS through drinking water, as many water bodies have been found to contain PFAS. By regulating the concentration of PFAS in drinking water, we can reduce human exposure to the chemicals, thereby reducing any health risk. When it comes to consumer products, it is important to consider what chemicals, if any, might replace PFAS and if their safety profiles are better understood.
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