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In February 2019, the U.S. Environmental Protection Agency (EPA) unveiled (1) a comprehensive plan to deal with one of today’s most persistent and pervasive classes of pollutants: per- and polyfluoroalkyl substances (PFAS). Used since the 1940s in a vast array of industrial and consumer products including food packaging, firefighting foams, and fabric protectants, PFAS have been associated with reproductive and developmental problems, liver and kidney function, immunological effects, and cancer in laboratory studies. Among other actions, the EPA plans to develop new tools to characterize PFAS in the environment and set maximum levels for two common PFAS chemicals—perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA)— in drinking water.
The new EPA policies build on the agency’s 2018 expansion of its Method 537 (2, 3), which specifies the use of solid-phase extraction (SPE) and liquid chromatography–tandem mass spectrometry (LC–MS/MS) for the determination of PFAS in drinking water. The changes reflect a move to regulate a wider range of PFAS compounds, including so-called GenX chemicals and other newer products developed to replace specific PFAS compounds no longer on the market.
Although some environmental activists have welcomed the plan as a step in the right direction, the PFAS story is emblematic of a larger challenge facing today’s environmental laboratories. Tens of thousands of chemicals of emerging ecological concern are introduced into the environment daily, posing a daunting array of scientific and regulatory issues for analytical chemists working in analytical testing laboratories, academia, and the scientific instrument manufacturing industry. New findings about the health impacts of compounds such as glyphosate-based herbicides, microplastics, and dioxane are currently making headlines. The myriad of largely undisclosed chemicals used by the oil and gas industry in hydraulic fracturing (“fracking”) are a source of ongoing public controversy. Meanwhile, a large class of persistent organic compounds including dichloro-diphenyl-trichloroethane (DDT) and polychlorinated biphenyls (PCBs) continue to cycle through the environment, appearing decades after they were last manufactured. Whether working in commercial environmental laboratories or academia, many analytical chemists agree that the number and variety of pollutants requiring analysis today is straining the capabilities of current methods and technologies, that the introduction of new standard methods is far too slow, and that the community sorely needs a system by which new and up-to-date methods are more easily developed, shared, and adopted. These issues were all raised in some recent LCGC roundtable discussions.
Testing laboratories are often unsure of which regulatory statutes apply to certain sample types, says William A. Lipps, chief science officer at Eurofins Eaton Analytical (Monrovia, California). For example, although the existing EPA guidelines for PFAS analysis in drinking water take the guesswork out of that particular application, the guidelines don’t address one of the largest sources of PFAS contamination: wastewater. “As far as I know, there’s really no activity to make a method for wastewater,” Lipps says.
Lipps says with more than 6000 known PFAS in the environment, more up-to-date methods could help laboratories face an array of tough questions: “Who knows which ones to look for? How do you run them? Do you use this column or that column? This mobile phase or that mobile phase? Is it an ion? Is it an organic? At commercial laboratories, we don’t really have time to deal with that stuff anymore.”
PFAS compounds as a class comprise molecules across a wide size range, and the challenge of selecting the appropriate chromatographic technique is yet another consequence of the lack of PFAS standards, says Kevin Schug, PhD, the Shimadzu Distinguished Professor of Analytical Chemistry at the University of Texas at Arlington. “If you look at the thousands of variants of these PFAS compounds, you’re talking about small molecules that are easily LC-able and then [on the other end] you have really big polymeric species,” he says. “There are very different analytical challenges with characterizing those and—again—there are no standards.”
Similar ambiguity surrounds the selection of analytical methods for recycled water: processed wastewater that’s increasingly being used in agriculture, landscaping, and other applications that increase the risks of human exposures to hazardous pollutants. In principle, Lipps notes, recycled water could fall under either wastewater or drinking water regulations, but there are consequences of the choice, and important implications for methods would be used and how the laboratory would apply quality control. “Wastewater methods allow you to make some modifications, but drinking water methods don’t,” he explains. “If there’s significant turbidity, the drinking water method won’t work. You’re probably going to need a combination of both, but there’s really no EPA statute that handles recycled water as it is.”
Laboratories working to measure the environmental impact of fracking chemicals face special challenges due to the large array of chemicals currently in use by the oil and gas industry, most of which are not publicly reported because they’re part of proprietary processes. “Even the oil and gas operators don’t know exactly what they’re using in some cases,”Schug adds. One of the many issues is that there are a lot of different chemicals being used, in extremely high volumes, to stimulate the ground when companies are trying to extract oil and gas. “There’s the potential for waste to be mishandled and to touch the environment, to get into drinking water and groundwater,” Schug says. “There’s not the kind of EPA standard methods to look at water quality through the lens of all those different chemicals.”
Lipps agrees. “Nobody knows what they’re sticking down that hole, and they’re not going tell anybody because it’s proprietary,” he says. “And so [fracking involves] all these different compounds. We have no methods for them. We don’t know what they are.”
Industry’s response to the regulation of certain toxic compounds is often to develop chemically similar variants that offer similar performance but sidestep existing regulatory statues. The manufacturer creates a new compound that does the same job as the original substance but has an unknown toxicity profile. “It’s almost like a designer street drug type of situation” Schug says. These issues underscore the concern raised by many environmental chemists that EPA’s development of new methods has simply not kept pace with the dramatic changes in the volume and variety of pollutants needing analysis these days. They say the agency’s methods are largely focused on compounds that are no longer manufactured and, that when the EPA does develop a new method, it often is based on the capabilities of outdated analytical equipment.
“The EPA methods were written for priority pollutants like organochlorine pesticides, or organochlorine solvents,” Lipps says. “We’re sitting around monitoring things that were banned 40 years ago, and yet there are absolutely no methods for the new things that are coming out. EPA just doesn’t move fast enough.” And by the time the agency does release a new method, he says, it may have been developed on a piece of equipment that may be more than a decade old. Jennifer Field, PhD, a professor in the Department of Environmental and Molecular Toxicology at Oregon State University (Corvallis, OR), says although she isn’t required to follow EPA methodology in her research, she too believes that EPA existing methods often call for the use of older techniques that add complexity to the analytical process without substantially improving performance. “PFAS are where my laboratory spends 99% of its time now so we’re watching the development of EPA methods,” she says. “EPA methods tend to be lagged in time, technology-wise.”
Field points to the mandated use of SPE in many EPA methods as a prime example of the agency’s adherence to older technologies that may not be necessary or even appropriate. “I personally want to see the use of SPE decline,” she says. “It’s really not necessary for so many applications. I think SPE has a history and it (exists for) a reason, but there are a lot of problems that come with it in terms of cost, time, and waste.”
Field considers SPE a “crude tool” that requires inordinate amounts of time, labor, and sample matrix to obtain just the few microliters needed for analysis. “People have been told from infancy that SPE protects columns and mass spectrometers. I haven’t had an application yet where that’s true,” she says, citing her laboratory’s alternative practice of using the mass spectrometer’s divert valve to eliminate salts and other components that are eluted prior to the analytes of interest. “I get the same functionality with much better control and resolution [than with SPE]. If you know your LC instrument very well, you can essentially achieve everything for water samples you can achieve with SPE. It’s greener, faster, there’s less labor, there are fewer problems with lot changes, and you just have much finer control. But this is a hard sell.”
Lipps says he shares Field’s concerns about SPE but has no choice other than to use it. “As a commercial lab, we’re stuck with it, especially for drinking water. There’s really no reason for it, but we have to do it. So, we take an analysis that is maybe 15–30 minutes per sample on the instrument and we add four hours to a day of sample preparation to it.”
Filling the method development void
Academic environmental laboratories and volunteer organizations such as ASTM International are positioned to fill the void in analytical method development. However, many chemists say it’s difficult to secure the time, resources, and human capital for a task that is typically under-valued inside an organization and under-utilized by the chemistry community at large.
“Developing methods for wider use is kind of the goal,” says Sascha Usenko, PhD, an associate professor in the Department of Environmental Science at Baylor University (Waco, Texas). “But with the variations in approaches and technologies—which are somewhat competitive—it’s kind of hard to get even a good method broadly accepted.”
Field agrees that academic laboratories face barriers in transferring methods to the broader community and commercial environment. “For example, our main vector is to put papers in peer-reviewed journals,” she says. “But not everybody outside academia has subscriptions to those, nor wants them.” The open-source vehicles for disseminating methods might facilitate more efficient technology transfer, she adds.
As a contract laboratory scientist who also serves as a volunteer chairman of ASTM International’s Committee D19 on Water, Lipps views the issue of standard method development from a unique vantage point. “ASTM is all-volunteer, so the speed at which we can bring a method forward is based on the speed of the volunteers and the voting process,” he explains. “We’ve had some methods go through in as fast as a year and others take five years.” Finding qualified volunteers willing to sign on for the tedious, time-consuming work of ASTM method development is no small task, he adds. “For the most part, it’s roughly 20 or 30 people in the United States doing all the methods being developed at ASTM,” he says. “There is just not that much interest. It’s hard, it’s a challenge, it takes a lot of time. And it’s a very expensive endeavor.”
Lipps says the environmental analysis community is reluctant to adopt non-EPA methods, even though the agency recognizes many standards developed by others. He cites past efforts to develop three EPA-approved ASTM methods for cyanide that significantly reduced sample preparation time. “Roughly eight years after the fact, I only know of two laboratories that are running one of them,” he says. “You would think that commercial laboratories would jump right at this, but the adoption is almost nothing.”
ASTM has developed “probably about 10 LC–MS/MS methods that don’t use SPE…Polar pesticides, herbicides, other organic compounds like glycols—those are the types of methods we’re developing at ASTM that do a modified form of direct injection LC–MS/MS. They are published, they are standardized, and the world just absolutely rejects them,” he says.
A fundamental challenge for academics who seek to spend time or money on method development is the widespread lack of appreciation for the complexity of the method development process itself. “In the environmental world, a lot of my colleagues and collaborators are engineers,” Field says. “They just want you to measure stuff. They think these methods to grow on trees. They don’t realize that method development is a whole discipline that requires a very systematic validation for each matrix of interest. The time and effort are simply undervalued by everybody except an analytical chemist.” As a result, she says, academic chemists are rarely able to secure funding specifically for the time and materials required to develop new methods and often end up doing the work while in the process of performing other funded studies.
Click here to read part II of this article.