Your PFAS Questions Answered by Professor Rainer Lohmann

Prior to PFAS, I worked on legacy pollutants, typically chlorinated compounds like polychlorinated biphenyls (PCBs), and dichlorodiphenyltrichloroethane (DDT) – a lot of the early, first-generation pesticides that've been mostly banned. A lot of the work was dealing with contaminated sites, and then PFAS slowly came about. What was interesting to me, because I work in ocean systems, is that the eventual, final place where the PFAS end up is the ocean, and that's very different from a lot of the other contaminants. So, departments – and then some colleagues – reached out to get access to samples from across the ocean. We started collaborating, and that's how I started working in the field.

There’s a method being developed  to look at PFAS in stack emissions. The approach will follow established procedures for sampling stack gases; you take the effluent, use a little nozzle to get some of the gas and then cool it down very quickly. The EPA has been evaluating whether the method works or not, and it works reasonably well but only for fairly high concentration emissions.

There's a research arm of the US military that looks into environmental restoration, and it spends hundreds of millions of dollars to look at PFAS remediation approaches across a wide range of projects, from bench scale lab ideas to full remediation of contaminated sites. And of, course, the reason the military is funding this is because it has so many sites where it typically uses aqueous film forming form (AFFF) to train or extinguish real fires. 

So, at this point, there are several approaches that work. The most common, typically, is still to remove PFAS from water through filters, often with granular activated carbon. There are other approaches. If you have contamination with unique chemistries, you might have to go through ion exchange. And I believe the city of Wilmington has to use ion exchange resin because they have unique contamination in the drinking water where activated carbon doesn't do it anymore.

PFAS incineration works, probably not 100%, but it probably works. It's not popular in every country and every state to have special incinerators for fluorinated compounds. So, alternatives approaches are being tried. It's not entirely clear yet which one is going to be cost effective and proven to work at the field scale.

I think it depends on what you want to achieve. Typically, an incinerator is supposed to be above 850 °C  with a resonance time of two seconds, which will destroy most PFAS. What is less clear is how much is left, and if any other PFAS are formed that might be shorter or different in nature. There hasn’t been that much testing on stack emissions.

I think part of the challenge is to make sure, whatever incineration you have, that you don’t have some other products forming after the molecule has been broken apart, and suddenly fluorine starts finding new partners, and builds molecules up again. 

Yes. If you go through the literature, you find plenty of approaches that work really well in the lab. Unfortunately, they often only work really well in the lab under really ideal conditions and clean water. Once you start looking into real contaminated water, which has more than just PFAS, then, of course, the efficiency starts to drop. We looked at one sampling device that was made of really high-surface area, nano-graphene. Beautiful stuff – worked really well in the lab. We took it to the Delaware River, and the performance dropped by a roughly factor of 10.

We worked on some other carbon-based materials to prevent the release of PFAS from contaminated sites in Rhode Island. Again, in the lab, it works like magic. We’ll soon start with real water, which  will probably drop efficiency by quite a bit. Whether it's still technically and economically useful is another question. 

It depends a little bit on where you’re based. In the US, as of last year, the EPA said, basically four ppt is the only safe level for PFOA or PFOS and for a few others. Some [states] cannot exceed 10, and that’s roughly in line with some of the other states. In Rhode Island, Massachusetts, Vermont and Maine, I think they all have around 5 or 6 for 20 ppt – extremely low levels. In those states, public water suppliers have to come up with a method and cannot really offer water that is above those levels. Private well owners are on their own. There's nothing they can do. They have to put in their own filter.

It’s difficult for people who live in other states where there are no state rules yet. The EPA rule is being phased in, but it’s contested in the courts. So, there are a few years of transition here because of the costs and the technological challenge of installing filters in these different communities. I believe the EPA has performed testing around the country as part of what they call the unregulated contaminant monitoring rules.

I think every major water supplier should test a few times for PFAS, and the numbers should be public knowledge. I would strongly encourage people to put in filters at home, because that’s the only way you can detect PFAS in drinking water –  otherwise it should be removed already. 

Some groundwater systems are so contaminated, typically because of point sources that would have been military sites, airports or manufacturers. We also know that wastewater treatment plants are not really good at destroying or removing PFAS. They remove some, because they attach to the biosolids, but the others just get flushed out. We know, certainly for surface waters, the more wastewater treatment plants along a river, the higher the PFAS concentration. They don't break down; they just keep flowing with the water.

The concern is, if you have groundwater that might still be clean, if it rains, because there's a wastewater treatment plant, effluent will slowly also percolate through the soil and then might eventually contaminate the aquifer. So, the more you can do to make sure that groundwater stays clean, the easier and cheaper it's going to be.

There's one additional concern. The state of Maine, like many other states in the US, has had a practice of encouraging the use of bio-solids from treatment plants as fertilizers on agricultural fields, because you can re-use the nitrogen and the phosphorus. It has been controversial because of heavy metals and some other organics, but now because of PFAS. In the state of Maine, for whatever reason, sludge from paper mills has also ended up in agricultural fields, and several farmers had to shut down because their lands are so highly contaminated with PFAS that, when the cows eat the grass, it leads to the milk being highly contaminated. The state of Maine said, “we’re not going to use biosolids as fertilizer anymore”.

I don't know if there is work on such a label. I know that a lot of states in the US have started regulations and rules that basically say in certain consumer products there shall be no PFAS used. In my home state, Rhode Island, they’re something like this on the books for food contact material –so pizza boxes, take out products, etc. The challenge is that there’s no obvious way to verify whether the people who sell this in Rhode Island actually follow the rules.

I think there’s also an ongoing debate about what “PFAS-free” actually means. It means not intentionally added. PFAS are everywhere, so you can't really avoid them. I think that was recognized the hard way with recycled paper. There are different types of papers used to make the recycled paper and, of course, some have PFAS. So, recycled paper isn't actually PFAS-free, even though it's environmentally good. With the same logic, PFAS-free cannot mean that you can’t detect them, but you have to make a case that is not potentially added. 

The above content is a transcription of Professor Rainer Lohmann’s AMA interview. It has been edited for clarity and flow to ensure a better reading experience. While every effort has been made to preserve the original content and meaning, some minor adjustments have been made to improve readability.