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Rolf Halden, PhD: Lessons Learned From Fighting Harmful Antimicrobial Personal Care Products

Interview by Craig Gustafson


Facilitated by the Environmental Health Symposium April 3 to 5, 2020, in Scottsdale, Arizona.


Rolf Halden, PhD, PE, is a professor at Arizona State University, where he founded the Biodesign Center for Environmental Health Engineering, the OneWaterOneHealth nonprofit initiative, and the Human Health Observatory. He has authored over 250 journal articles, book chapters, and patents exploring environmental and human health challenges in populations worldwide, and most recently for the 50th anniversary of Earth Day, the 2020 book Environment. He works to devise sustainability solutions for pollution prevention, resource recovery, and hazardous waste management, particularly as relating to the urban water cycle. Dr Halden serves on the Expert Team of the U.S. American Chemical Society and has been invited repeatedly to brief the U.S. Environmental Protection Agency, the U.S. Food and Drug Administration, the U.S. National Academies, and members of U.S. Congress on environmental health and sustainability challenges.


Integrative Medicine: A Clinician’s Journal (IMCJ): At the Environmental Health Symposium this spring, you’ll be talking about the immunotoxicology of triclosan and triclocarban. What distinguishes these compounds chemically?


Dr Halden: Actually, there is a very interesting story behind these chemicals because they look very similar to a lot of chemicals we have banned in the past. And that’s why they gained my attention back in the early 2000s, when we started to study them.

In the 1920s, we discovered the miracle chemistry of taking naturally occurring organic compounds, pulling off hydrogens from the carbon skeleton and substituting them with halogens to create a powerful, as well as potentially harmful, type of chemistry that is relatively rare in nature. And our favorite halogen, to start out with, was chlorine.


IMCJ: The same way sucralose is made?


Dr Halden: Yes. So, sucralose is an artificial sweetener obtained from the naturally occurring sugar, sucrose. Its synthetic look-alike is obtained by adding two chlorine atoms. This rather simple modification completely changes the way this sugar behaves. It’s a wonderful example how an intrinsically biodegradable molecule can be made environmentally persistent by the addition of carbon-halogen bonds. The two sugar molecules that form the disaccharide, sucrose, go from representing microbial candy to becoming essentially inert and nonmetabolizable.

This toxicological transformation was first exploited many decades back to create new, powerful pesticides, including the infamous DDT. While potential issues surfaced quickly, it took us several decades to better understand how the newly harnessed power of organohalogen chemistry can both help and harm us. So yes, synthetic organochlorines can kill mosquitoes and bacteria, but they can also wipe out a lot of other nontarget life forms—collateral damage that is causing harm to ecosystems and human health alike.

Doing this work for some 25 years, I see it is an ongoing story: We learn, we read the same storyline again and again, and we just don’t get the root cause—and we don’t do anything about it. It’s like the movie “Groundhog Day” where we are trapped in a cycle and then doomed to relive the same mistake over and over.

We started this storyline with aromatic rings, which look like chicken wire, which we decorated with chlorine to obtain polychlorinated biphenyls (aka PCBs), DDT, Agent Orange—and accidentally, dioxins as unwanted production byproducts or impurities. And we made millions and millions of pounds of them each year.

And so, if you look at the structures of triclosan and triclocarban, they look a lot like the dioxins that are famously toxic and carcinogenic. Indeed, triclosan had been labeled a precursor of dioxins by the EPA for many decades. Similarly, triclocarban looks like any other polychlorinated aromatic compound that we made back in the day. And most of these compounds have long been banned.


IMCJ: So, how did you study these chemicals?


Dr Halden: I was curious to see what happens to these chemicals upon use and disposal. We knew that they were produced in quantities of millions of pounds, but there was little information about what happens to them once we were done with them. In Watergate, answers were found by “following the money.” With the antimicrobials formulated into everyday personal care products, we suspected we had to follow the sewage into which the chemicals are disposed of. And that opened up a whole new scientific field of investigation for us. We learned a lot that we have shared with the world since then. When we looked at wastewater, we saw that these antimicrobial chemicals were released from our households from over 2,000 personal care products that were all labeled as being antimicrobial and antibacterial. And then we found that while the antimicrobials go to the biological wastewater treatment plant, they unfortunately do not degrade. They resist degradation in the wastewater treatment plant.


IMCJ: What would a half-life of triclosan or triclocarban be?


Dr Halden: It depends on where the chemical resides. In soil it may linger for years, as we have shown. In surface water it theoretically can be broken down by sunlight effectively, but in reality, the antimicrobials tend to bind to organic matter and sink to the sediments where they can persist for decades, as we showed with age-dating analyses. So, the half-lives of the compounds vary significantly and can span timescales of hours to years in certain environmental media.

In our studies, when we found that the antimicrobials triclosan and triclocarban don’t degrade effectively in the wastewater treatment plant, we looked downstream of the sewage treatment facilities and found chemicals that were used as long ago as the late 1950s and early 1960s. It is incredible that the chemistry used over half a century ago is still sitting in the sediments without much degradation occurring there. We found in the sediments of Jamaica Bay near JFK airport in New York state antimicrobials that were used and disposed of while JFK was still alive and president. This persistence is similar to that of DDT, which was banned in 1972 but is still detectable in your blood right now, along with its major transformation products. We even can detect the antimicrobials along with the DDT compounds in babies born today. This is why I’m saying there was a lesson that we had to learn early that the chemicals persist for long periods of time. But unfortunately, we have continued to make this type of persistent chemistry and we continue to pay for this mistake by needlessly sacrificing our health and that of the ecosystems that support us.


IMCJ: When these chemicals get out into the environment, depending on what else is in the environment around them, rather than degrading, can they transform?


Dr Halden: They transform to some degree but that’s not necessarily helpful. We know that triclosan, for example, with residual chlorine from drinking water disinfection and sunlight available, can be transformed into more highly chlorinated chemicals, including polychlorinated carcinogenic dioxins. And if it is disinfected along with drinking water, then it can form formaldehyde. So there is a toxic chemical progeny, if you will, that can originate from the transformation of the antimicrobials.

Overall, transformation isn’t all that fast for organohalogen chemistry, because these are not naturally occurring chemicals, nature does not provide a lot of degradation mechanisms to destroy them. If they were a good food source and microorganisms had millions of years to adjust to them, then we would potentially have a nice and efficient catabolic machinery to degrade them. But we have only made these chemicals for about a hundred years and that wasn’t long enough for microorganisms to evolve the appropriate biochemical machinery to destroy them. The chemicals go into all kinds of environmental media—including biota—and can bioconcentrate, bioaccumulate and biomagnify.

But the good news is that we did achieve a ban of triclosan and triclocarban and similarly ineffective and risky antimicrobials in the U.S. I published a paper in 2014 making an evidence-based case for their removal from consumer products, and in 2017 the chemicals were banned by the FDA, the Food and Drug Administration. And so the message hit home and we are better off today. I wouldn’t claim that it was only due to the measurements we and others did. A lawsuit certainly helped, too. But eventually these antimicrobials were gone but only from those products regulated by the FDA. You can still buy carpets, sportswear, stationary, and children’s toys impregnated with triclosan, unfortunately.

Now, the big question is: Are we learning our lesson this time or do we continue to make chemicals that are incompatible with the natural environment and incompatible with our bodies and our good health? As far as we can tell right now, we still have not learned our lesson. If I would analyze your blood right now, I would find a lot of flame retardants, which look very similar to the chemicals Environmental Science and Technology put on its cover for the paper on antimicrobials back in 2014. In essence, it’s the same problematic chemistry with the notable difference that the aromatic rings of flame retardants carry bromines rather than chlorines. But these two elements are very closely related. Both belong to the group of halogens in the periodic table, and if you look at what chemicals have been banned throughout history and worldwide, you will note that a hallmark of these is their organohalogen structure.

Those compounds are cruising in your bloodstream right now and are detectable in babies at birth. And then there is another group of halogens, those using fluorines, another group of chemicals that we got heavily into. We are repeating the same mistake yet again. First, we made it with a polychlorinated chemistry, then we transitioned to polybrominated chemistry, and now we have transitioned to and are ramping up the use of polyfluorinated chemistry. A convenient but risky and extremely persistent chemistry.

This progression is a really bad idea and things will get worse rather than better, as far as we can tell. This is because the polyfluorinated compounds are almost indestructible. There are some microorganisms that can destroy polychlorinated chemicals and actually benefit by using them as an electron acceptor to maintain their metabolism. But there are very few microbes that degrade polybrominated chemicals and there are essentially none that can effectively degrade the polyfluorinated chemistry we are churning out today and which are embedded in our consumer products. We are talking about the chemistry that you might have on your skin right now if you wear a wrinkle-free shirt, if you wear sneakers with membranes, or if you have a jacket that is waterproof and made of a so-called “breathing” textile. Sports shoes, all this kind of stuff, contain polyfluorinated membranes.


IMCJ: That would be the PFAS?


Dr Halden: Yes, and you read a lot about them. But we still don’t read enough about these per- and polyfluoroalkyl substances. Once manufactured and short of incinerating it, this chemistry is doomed to stay with us essentially forever—there is just no mechanism known for destroying them in biological reactions. And even with the drinking water treatment technologies we have, if the raw water becomes contaminated like groundwater in West Virginia or someplace else, we have no good way of removing and destroying the polyfluorinated chemicals once they are out in the environment: in our drinking water, in our food, in our bodies.

We as engineers are at a loss for what to do about removing them because these chemicals don’t behave like the other average hydrophobic chemicals—chemicals that only like fat. The PFAS are a somewhat schizophrenic chemistry, as they repel both water and oil, and instead of accumulating in fat tissue like many organochlorines do, prefer to stick to proteins present in our food and bodies.

The bottom line is that we stumbled into these chemicals—triclosan and triclocarban—and they didn’t get a lot of attention at the time. When we were done looking at them in the context of all the other chemicals that the EPA is interested in, in terms of pharmaceuticals and personal care products, ironically, the two chemicals we picked to study turned out to be the most frequently detected and the most abundant chemical pollutants across the United States out of 72 pharmaceuticals and personal care products. Consider the odds if you were to pick two chemicals to study and then you do a rank order years later, and you find out that you picked the winner and the runner up out of all the chemicals that there are. It was rather unlikely, but on the other hand not necessarily only luck, because the structural features of these two chemicals acted as red flags for us that we followed up on.

Another curiosity is that we not only discovered triclocarban as an environmental pollutant and called the chemical out, but we also got it banned. Completing this journey from a pollutant’s discovery to amassing data facilitating its nationwide ban was a unique experience for our team.


IMCJ: Wasn’t there an issue with being able to detect triclocarban?


Dr Halden: Exactly. So, it sailed under the radar, and that’s another interesting aspect. People were looking for pollutants and they were extracting tissue, breast milk and urine and all these various biospecimens but they wouldn’t find it. In tens of thousands of samples that scientists had in their laboratories, the chemical was there, but it was invisible to them because it wouldn’t show up on the instruments they were using.

The breakthrough for triclocarban really came when we introduced practical liquid chromatography mass spectrometry methods and made them broadly available. When using LC mass spectrometry and tandem mass spectrometry for these chemicals rather than gas chromatography, all of a sudden, people found them everywhere. If you look at the count of scientific papers, at how many papers got published, once the methods our lab pioneered were recognized and implemented, everyone detected triclocarban just about everywhere. And then we realized, “Wow, you can’t escape this chemistry, everyone gets exposed.” Those data collected across the nation in our monitoring campaign would later help to institute the ban. And I predict that a similarly unfortunate discovery for hundreds or even thousands of PFAS is still ahead of us.

We talked about immunotoxicity. Remember that when these antimicrobial organochlorine chemicals were made initially and tested with the rudimentary tests that we had at the time, we looked at whether a rat that eats this chemistry will die. If it didn’t die, then the assumption was that it’s probably okay. But we have learned so much in terms of toxicology since those days of early brute-force toxicity testing.


IMCJ: That would be determining median lethal dose, or the LD-50?


Dr Halden: Yes, exactly. But now we know that there are generational issues, that chemicals can affect epigenetics, that they can have an effect on the proteome, on the immune system, and on behavior as well. There are just so many outcomes. Endocrine disruption wasn’t really known or talked about at the time. And endocrine disruption can impact behavior and neurodevelopment and immune-system function. All these things were not known and they really have just bubbled up to the surface in recent years.

Now as we go back and look at these chemicals with toxicological assays, everything lights up, the whole dashboard starts blinking with red flags. You have got all these warning lights going off, visually speaking. This chemistry is really powerful, and yes, it was suitable to kill bacteria—but even that it didn’t do very well. The antimicrobials weren’t really good at killing bacteria. They are much better at killing crustaceans and fish—causing collateral damage—than they are at killing microorganisms, ironically.

We brought this to light and these two antimicrobial chemicals are gone now from personal care products, but my larger concern right now is that there are still hundreds of thousands of other organohalogens of very similar structure present in consumer products not regulated by the FDA. And I and my colleagues predict that they will give us a similar headache. If we refer now to the polyfluorinated chemicals, the floodgates have been opened to bring this chemistry into what we call the biosphere—the bubble in which we live, our atmosphere and everything we get exposed to—and there is no mechanism of removing the PFAS chemistry effectively. And so we are doomed and destined to live in that chemical soup for hundreds or even thousands of years, generation after generation.

Nobody is really paying attention to that and that is a scary development. We haven’t put the brakes on mass production of this persistent, risky PFAS chemistry. We don’t ask the question: “Do we really need this chemistry? Could you have your popcorn without the grease-repellent coating on the bag that you shove into the microwave? Is the convenience of having nongreasy popcorn bags and a wrinkle-free shirt worth the long-term contamination of the biosphere for centuries, or even millennia?” Those are questions we are not asking as consumers, and we’re certainly not making the regulatory decisions that are necessary to stop this ongoing and still accelerating global pollution.


IMCJ: Science is developing so rapidly in so many different areas that many advances seem to lack that kind of reflection.


Dr Halden: Yes. So, we have the short-term gains and then we have the long-term pains. And we have so many of the latter. If you look at many diseases, possibly more than half of them have some environmental component. And we in the environmental health sciences often say that genes load the gun—our inherited genes—but that the environment pulls the trigger. Meaning that we are susceptible to a disease, but whether it manifests or not is really a function of what we do, what we eat, how we behave, and what we get exposed to. That becomes more and more clear.

We also have a lot of diseases for which we are at a loss for explaining why they are escalating so quickly. Allergies, a function of the immune system, is one of them. I don’t know how old you are, but I am 55 years old. When I had birthday parties when I was young, nobody was asking what we would be eating and whether the children had any sensitivities. Today you can’t have a birthday party without doing a food survey with the parents first to find out about all the various allergies and potential health issues. And you have to have your EpiPen ready. That is just one example.

We also suffer from what could be called an epidemic of behavioral disorders. We have autism and we have attention deficit disorder. There are so many things happening. We now understand that chemicals do not just inflict physical pain or disease, but that they also impact our behavior and a lot of other bodily functions. That realization is setting in more and more. We become, if you will, medicated by the environmental contaminants—and it’s not for the better. It does damage and reduces our quality of life.

It is all quite depressing but fascinating at the same time. I tried to capture our current population health challenges in a little book that I wrote. It will be published in April of 2020, and is titled Environment. While it comes out of the same publishing house as the Harry Potter books, it remains a challenge to reach a broader audience and to inform the public about chemistry. It’s just not everyone’s favorite topic. In the book, I tried to look back at the history of humanity and the chemistry we put out into our living spaces and into our bodies—and now by using opportunities stemming from the new tools that we have developed—to see what really is going on and how we may be able to better care for our health and the health of the planet.


IMCJ: Can we afford to look at these exposures individually, from a more-or-less reductionist viewpoint?


Dr Halden: I’m not sure whether you’re familiar with the term exposome—everything has an “ome” these days. So in exposure science, we now define the totality of everything that comes at us as the exposome. The advanced analytical tools we have today allow us to see that we are exposed to tens of thousands of chemicals on a daily basis and to biological agents as well, all arriving in a very complex mixture. If you don’t believe me, just read the ingredient list of any of the personal care products that you have standing around in your bathroom.

There is no hope that we will fully understand how these chemicals all interact singularly and then as a mixture. So, we just increase the complexity and we continuously introduce new chemicals. Unfortunately, we are not instituting the design principles that nature has taught us. If we would follow those, our everyday chemistry would be much safer, would be much more biodegradable and less risky. This implies that we would have less exposures and would be healthier overall. But instead we are mass producing risky chemicals at very high rates, and that continues to create big problems for us now and into the future, unfortunately.

Triclosan and triclocarban are just two examples of how long it can take to identify that there is a problem, that there is widespread pollution, and to then pull the plug on them. Oftentimes, what you get is what we call regrettable substitutions. We take the twin chemical that looks identical to the original. If you are not a chemist, you can’t even tell the difference between the known chemical hazard and the replacement chemical we choose. Then, we drop that in and say, “Yeah, everything’s awesome because we know nothing harmful is known about this chemical.” Until once we study it, and we learn sure enough, it has the same downsides as the one that we just removed.


IMCJ: Like bisphenol-A and bisphenol-AF.


Dr Halden: Yes. Some people say that this type of replacement is bordering on criminal behavior, because if you know that the bisphenol chemistry is endocrine disrupting, adding for example multiple fluorine substituents to it will make it only more persistent and potentially more potent. When people wanted to buy bisphenol-A-free plastics, manufacturers came up with bisphenol AF. And well, yes, it’s not bisphenol-A, now it’s fluorinated bisphenol A. But it has the very same structural features—even worse because it is polyfluorinated now, it doesn’t even break down. And so, you have lots of these regrettable substitution issues that we are fighting.


IMCJ: What more will attendees learn from your address at the Environmental Health Symposium this spring?


Dr Halden: I look forward to talking to the environmental health sciences community and sharing with them my journey of studying antimicrobials. It kept me busy for 14 years between the discovery and then the banning of the chemical nationwide. In 2015, my team reviewed some 14 318 pieces of literature and published a review article on how long it takes after we recognize a problem to then institute some sort of regulatory action. On average, it takes 14 years. Ironically, it took exactly 14 years for triclocarban to get regulated after we discovered it as a widespread environmental pollutant and toxicant. But there are many more chemicals lingering. I hope we can put the spotlight on the root cause of this and make some progress so that we don’t have to swim in an ever-more-complex chemical soup moving into the future.


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