Many millennia from now, when humans are long vanished from the Earth, intergalactic travelers visiting our planet may wonder about this world’s ancient inhabitants and their civilizations. One clue these visitors will be able to use in their investigations will be the presence of a class of manmade chemicals called per- and polyfluoroalkyl substances (PFASs). Dubbed “forever chemicals,” PFASs will likely outlast humanity.
PFASs have a wide range of uses thanks to their unique physico-chemical properties. They can be found in stain resistant textiles, greaseproof food packaging, nonstick cookware, firefighting foam, personal care products, pharmaceuticals, pesticides, and in over 200 other applications. Because of their widespread use, coupled with their persistence and mobility, PFASs can now be found everywhere researchers look for them—in our food, in our drinking water, and in our bodies.
Contamination of drinking water with one PFAS, called PFOA or C8 (because it contains eight carbon atoms), was first revealed two decades ago in Parkersburg, West Virginia, during a lawsuit filed by a cattle farmer against the chemical manufacturer DuPont. As part of the settlement for this case, DuPont agreed to fund an independent group of epidemiologists, known as the C8 Science Panel, to study the impacts on the local population of drinking PFOA-contaminated water. Based on data from over 69,000 participants from the nearby communities, they found probable links between exposure to PFOA in drinking water and testicular cancer, kidney cancer, thyroid disease, high cholesterol, ulcerative colitis, and pregnancy-induced hypertension. The story of how attorney Rob Bilott discovered the PFOA contamination and negotiated the settlement has been dramatized in the movie Dark Waters.
So what has happened since the early 2000s? Has the problem been solved? It’s a mixed picture at best. PFOA and other so-called long-chain PFASs were phased out in the U.S. and Europe by the end of 2015, but production continues in other parts of the world, such as in China. The replacement chemicals developed by industry are also PFASs—including shorter-chain PFASs, fluorinated ethers, and other fluorinated alternatives. These alternative chemicals are also extremely persistent and mobile and are increasingly found in the environment. Compared with PFOA, these newer PFASs are potentially just as, or even more, toxic. In other words, the contamination of our drinking water continues.
As of July 2020, several PFASs, including PFOA and its cousin, PFOS, had been found in drinking water samples collected at 2,230 sites in 49 U.S. states. A recent study estimated that more than 200 million Americans, or over 60 percent of the population, could be exposed to PFOA and PFOS in their drinking water at levels exceeding 1 part per trillion (ppt), which has been recommended by some experts as a maximum safe level for exposure.
Another newly published study compared available data for 526 samples from drinking water systems across 66 cities in China, which serve over 450 million inhabitants, against international drinking water standards. The study found that nearly 100 million people in 16 of the studied cities are likely using drinking water that exceeds the new maximum contaminant level (MCL) of 20 ppt for the sum of five PFASs (PFOA, PFOS, PFHxS, PFHpA, and PFNA) set by the U.S. state of Vermont. The PFAS levels in the drinking water of nearly all the Chinese cities included in this study exceeded 1 ppt.
Similar drinking water monitoring studies are lacking for other Asian countries, for most countries in Europe, and for all countries in Africa and South America. In Europe, for instance, most studies available to date have largely focused on hot spots near industrial and waste disposal sites that have led to high externalized socioeconomic costs. The general population exposures remain largely unknown.
To understand possible exposures and protect public health, we urgently need more targeted testing for PFASs in drinking water across the globe, as well as better analytical methods. We currently can measure only a small percentage of the PFASs found in environmental matrices. For example, the only accredited testing method for drinking water in the U.S. can quantitatively measure 18 of the over 6,000 PFASs described to date.
The burden of ensuring safe drinking water cannot fall on consumers. According to a recent study, the efficacy of home filters, such as under-sink, pitcher, and refrigerator filters, varies widely and tends to be worse for the shorter-chain PFASs, which have become generally more abundant in drinking water sources as the longer-chain compounds have been phased out. Switching to bottled water is not a good solution either, as it can also contain PFASs, sometimes at very high levels.
To ensure drinking water is properly monitored and treated to remove potentially harmful levels of PFASs, we need enforceable standards. On October 23, the Council of the European Union formally adopted a drinking water directive that includes a limit of either 500 ppt for the sum of all PFASs, or 100 ppt for the sum of 20 PFASs considered a concern for water intended for human consumption. If approved by the European Parliament, this will become the first drinking water limit for the sum of all PFASs in the world.
In contrast, China has only suggested health advisory levels for PFASs: 85 ppt for PFOA and 47 ppt for PFOS, as proposed in a recent scientific paper. Similarly, the U.S. Environmental Protection Agency (EPA) has set only a non-enforceable drinking water health advisory: 70 ppt for PFOA and PFOS combined. Some U.S. states have set lower limits than EPA’s, though most are also non-enforceable. California has recently set response levels of 10 ppt for PFOA and 40 ppt for PFOS. Drinking water systems whose water source exceeds those limits are now required to take that source out of service, treat or dilute the water to reduce the PFAS levels, or notify their customers. Additionally, six U.S. states have set enforceable MCLs for two or more PFASs, though the levels vary. Activists from communities impacted by firefighting foam or PFAS manufacturing discharges are pushing for an MCL of 1 ppt for the sum of all PFASs. However, there is currently no method that can measure all PFASs. An alternative could be setting a limit for the total amount of organic fluorine that would roughly correspond to a given limit for the sum of all PFASs.
Even if enforceable standards limiting the levels of PFASs in drinking water are established worldwide, one major issue remains: who pays for this expensive monitoring and treatment? Extended producer responsibility is largely missing in most countries, including in the EU and China. In the U.S., PFAS manufacturer 3M settled a lawsuit for drinking water contamination in Minnesota for $850 million, whereas DuPont and its spinoff Chemours settled 3,550 lawsuits in Ohio and West Virginia for $650 million. Nevertheless, large gaps in funding remain for most affected communities, placing still the burden for monitoring and treating the drinking water on taxpayers, local and state governments, and water utilities.
Ultimately, monitoring and treatment are not the solution to the problem of PFAS-contaminated drinking water. Because these “forever chemicals” tend to last—well—forever, if we don’t act now to reduce their emissions into the environment the drinking water contamination will continue to increase, making treatment ever more complicated and expensive. That is why concerned scientists are arguing that we need to identify and phase out all non-essential uses of PFASs and strictly control other uses. But even if we do, Earth’s future visitors from faraway galaxies will still find plenty of PFASs lingering around to clue them in on our civilization!