America’s Dairyland May Have a PFAS Problem
By Susan Cosier
First there was Fred Stone, the third-generation dairy farmer in Maine who discovered that the milk from his cows contained harmful chemicals. Then came Art Schaap, a second-generation dairy farmer in New Mexico, who had to dump 15,000 gallons of contaminated milk a day.
While the pollutants in these cases were different, they both belong to the same class of chemicals: per- and polyfluoroalkyl substances, or PFAS for short. Numbering in the thousands, the chemicals are used to make a variety of products such as nonstick pans, stain-resistant rugs, water-repellent clothing and food packaging. Industries have been manufacturing most PFAS since the 1940s, but the effects these chemicals have on human health started surfacing only in the past decade or so. Exposure has been linked to serious conditions, including testicular and kidney cancer, colitis, thyroid disorders and suppressed immune systems in children.
Many states are just beginning to look for PFAS contamination in drinking water and elsewhere, and places like Michigan, where state officials are actively testing for (and finding) these chemicals, are starting to look like contamination hot spots. In reality, the PFAS problem is much more widespread.
While Teflon plants and military bases that use firefighting foams are common PFAS sources, another culprit is emerging: sludge produced by sewage treatment plants. Farmers all over the country use such sludge to fertilize their land, potentially contaminating the crops and livestock they produce. And it could be happening in the Midwest, too.
Wary in Wisconsin
Doug Oitzinger, the former mayor of Marinette, Wisconsin, was at a meeting to discuss a new community garden last year when he found out about his town's groundwater. Just 30 feet below where they stood, levels of PFAS were as high as 33,000 parts per trillion (ppt), more than 470 times the U.S. Environmental Protection Agency's health advisory level for drinking water of 70 ppt — a concentration many experts and states still consider a threat to human health. A few months later, Oitzinger knocked on a neighbor's door to see if anyone had told her about the pollution pooling below her home. She said she hadn't heard a thing.
In the beginning, he thought the contamination was limited to a specific area at the edge of town, close to the Tyco Fire Technology Center run by Johnson Controls International. But the more Oitzinger researched, the more concerned, and angry, he became. He's now pushing for Wisconsin politicians to make the PFAS issue a top priority. "I went from somebody who thought this was an unfortunate thing Tyco didn't know about, to ... well, let's just say their hands are covered in some pretty nasty stuff," he said.
Tyco knew back in 2013 of its PFAS problem, according to records it submitted to the Wisconsin Department of Natural Resources (DNR), but it wasn't until 2016 that the company documented the chemicals on its property and in the groundwater nearby. The public found out about it only in 2017, four years after Tyco's original admission, when the company acknowledged to the DNR that its pollution could be spreading.
When Tyco disclosed that PFAS pollution had contaminated groundwater in Marinette and nearby Peshtigo, the DNR directed the company to find affected wells. Since December 2017, Tyco has been voluntarily distributing bottled water to more than 120 households and installed 37 water treatment systems in the community. But it's not enough, and drinking water isn't the only thing in jeopardy. Just like other PFAS manufacturers, Tyco sent its waste to a local sewage treatment plant, where farmers obtain sludge for fertilizing their fields.
"We foolishly thought that we had institutions that would protect us from this sort of thing, that this couldn't happen anymore," said Oitzinger. "What we've discovered is that those institutions didn't protect us."
The DNR has since asked the wastewater treatment facility to stop selling sludge to farmers and launched a larger investigation into the matter earlier this year. For many farm owners, however, this action may have come too late — and there are no quick fixes. PFAS do not easily break down and can persist in the environment for decades, if not centuries.
A Message From Maine
The Stone family had been raising dairy cows in southern Maine for close to a century when, in 2016, Fred Stone voluntarily checked the farm's milk for PFAS. What he found, he said, destroyed his life: levels as high as 1,470 ppt.
"The toxic chemicals that I never used and had never even known about until two years ago contaminated my cows — which I really take exception to — and ruined my farming operation and hurt my family," he told reporters at a March press conference.
Stone had spread PFAS-contaminated sludge and paper mill ash on his fields for 20 years, but he stopped that practice in 2004. After 15 years, the substances were still there in amounts that could severely taint the milk of Stoneridge Farm, which is now out of business.
Stone went to Washington, DC, to ask Congress do something about PFAS contamination. Back in Maine, legislators set a PFOS action level of 210 ppt in milk, and the governor set up a PFAS task force. Maine's Department of Environmental Protection (DEP) temporarily stopped allowing farmers to spread sludge on their fields until it was tested. In 44 sludge samples taken by the agency, all but two had levels that exceeded the state's new limits for three PFAS chemicals: PFOA (2.5 parts per billion), PFOS (5.2 ppb), and PFBS (1,900 ppb). The DEP also tested retail and raw milk from three other farms, where PFAS levels did not exceed the state's reporting limit of 50 ppt.
So far, Stone's is the only Maine farm to shutter due to PFAS contamination, but others could follow and clean fields are still at risk. The Maine-based nonprofit Environmental Health Strategy Center has been pushing for the state to investigate other farms that received sludge from the same place as Stone, said Patrick MacRoy, deputy director of the group, but the group hasn't yet gotten a list of such farms, and testing isn't mandatory.
Even though no federal PFAS standards exist, lawmakers in a few states such as Vermont, Michigan and New Hampshire have proposed or passed bills that limit various types of PFAS — at differing concentrations — in drinking water. For Wisconsin's water supplies, the state's Department of Health Services recently recommended limits for PFOA and PFOS, two of the most widely used types, at 20 ppt. These are moves in the right direction, but PFAS find their way into more than just water. Researchers have been detecting these substances in everything from fish to leafy greens and grains to iced chocolate cake.
According to a 2012 study conducted by the Center for Food Safety and Applied Nutrition, a branch of the U.S. Food and Drug Administration, "a number of researchers have concluded that food is often the primary human exposure route" for PFAS. (A 2016 EPA report agreed that diet is a primary source.)
Milk containing PFAS tends to be particularly potent because the substances bioaccumulate in cows. Farmers spread sludge on fields, plants take the contaminants up from the soil, then cows eat the grass in great amounts, concentrating the PFAS, which end up in their milk. That's bad for children, who tend to drink lots of milk and are also more vulnerable to these substances than adults are.
"Yes, exposure from milk is likely less than drinking water for adults, but for infants and children it's different," said Anna Reade, an NRDC staff scientist specializing in toxic chemicals. "It could be a significant source of exposure, and they're the most vulnerable in our population. We have a responsibility to protect them." Yet so far, no state except Maine has begun to develop a PFAS standard for milk — or any other food, for that matter.
The 2012 study showed that PFAS levels in 49 milk samples taken from around the country didn't contain levels higher than the EPA health advisory level of 70 ppt except for one — taken from a dairy farm where sludge was spread. Locations where we know farmers spread contaminated sludge are good places to be testing, said Erik Olson, NRDC's director of health and food.
In Wisconsin, the DNR has a map of where the state's farmers have spread biosolids from the wastewater treatment facility used by Tyco, and staff have tested the farms' soils and their surface water and groundwater. The results are expected this fall, but the agency hasn't yet indicated whether it will also test the foods grown on these farms.
Needless to say, tensions are high in these parts. "This is like coming to someone and saying your house is radioactive," said Oitzinger.
NRDC's Reade suggests that state agencies test sludge before it's spread on fields and milk before it goes to market. Then officials could see where the highest PFAS concentrations are coming from. But she knows that's not a popular idea. "PFAS is a huge, global public health threat," she said. "It's going to be hard to test for all this."
In July, the Wisconsin DNR urged 125 sewage treatment plants to test their waste products, but the agency has yet to set a PFAS standard for sludge or milk. Oitzinger hopes to change that. He's now working with a small group of activists and Wisconsin lawmakers to put PFAS standards on the books in his state, but he fears for the rest of the country, too.
The problems with these chemicals are complex, he said, and as Stone knows, they don't go away on their own. "It's like peeling an onion," he said. "Every time you take a layer off, there's another layer, and the more layers you take off, the more your eyes water. It just gets worse and worse."
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By Jacob L. Steenwyk and Antonis Rokas
From the mythical minotaur to the mule, creatures created from merging two or more distinct organisms – hybrids – have played defining roles in human history and culture. However, not all hybrids are as fantastic as the minotaur or as dependable as the mule; in fact, some of them cause human diseases.
When Looking Through a Microscope Isn’t Close Enough.<p>For the last few years, <a href="http://www.rokaslab.org/" target="_blank">our team at Vanderbilt University</a>, <a href="https://www.researchgate.net/lab/Gustavo-Goldman-Lab" target="_blank">Gustavo Goldman's team at São Paulo University in Brazil</a> and many other collaborators around the world have been collecting samples of fungi from patients infected with different species of <em>Aspergillus</em> molds. One of the species we are particularly interested in is <a href="https://doi.org/10.1006/rwgn.2001.0082" target="_blank"><em>Aspergillus nidulans</em>, a relatively common and generally harmless fungus</a>. Clinical laboratories typically identify the species of <em>Aspergillus</em> causing the infection by examining cultures of the fungi under the microscope. The problem with this approach is that very closely related species of <em>Aspergillus</em> tend to look very similar in their broad morphology or physical appearance when viewing them through a microscope.</p><p>Interested in examining the varying abilities of different <em>A. nidulans</em> strains to cause disease, we decided to analyze their total genetic content, or genomes. What we saw came as a total surprise. We had not collected <em>A. nidulans</em> but <em>Aspergillus latus</em>, a close relative of <em>A. nidulans</em> and, as we were to soon find out, <a href="https://doi.org/10.1016/j.cub.2020.04.071" target="_blank">a hybrid species that evolved through the fusion of the genomes</a> of two other <em>Aspergillus</em> species: <em>Aspergillus spinulosporus</em> and an unknown close relative of <em>Aspergillus quadrilineatus</em>. Thus, we realized not only that these patients harbored infections from an entirely different species than we thought they were, but also that this species was the first ever <em>Aspergillus</em> hybrid known to cause human infections.</p>
Several Different Fungal Hybrids Cause Human Disease.<p>Hybrid fungi that can cause infections in humans are well known to occur in several different lineages of single-celled fungi known as yeasts. Notable examples include multiple different species of <a href="https://doi.org/10.1002/yea.3242" target="_blank">yeast hybrids</a> that cause the human diseases <a href="https://rarediseases.info.nih.gov/diseases/6218/cryptococcosis" target="_blank">cryptococcosis</a> and <a href="https://www.cdc.gov/fungal/diseases/candidiasis/index.html" target="_blank">candidiasis</a>. Although pathogenic yeast hybrids are well known, our discovery that the <em>A. latus</em> pathogen is a hybrid is a first for molds that cause disease in humans.</p>
(Left) Candida yeasts live on parts of the human body. Imbalance of microbes on the body can allow these yeasts, some of which are hybrids, to grow and cause infection. (Right) Cryptococcus yeasts, including ones that are hybrids, can cause life-threatening infections in primarily immunocompromised people. Centers for Disease Control and Prevention<p><a href="https://doi.org/10.1371/journal.ppat.1008315" target="_blank">Why certain <em>Aspergillus</em> species are so deadly</a> while others are harmless remains unknown. This may in part be because <a href="https://doi.org/10.1016/j.fbr.2007.02.007" target="_blank">combinations of traits, rather than individual traits</a>, underlie organisms' ability to cause disease. So why then are hybrids frequently associated with human disease? Hybrids inherit genetic material from both parents, which may result in new combinations of traits. This may make them more similar to one parent in some of their characteristics, reflect both parents in others or may differ from both in the rest. It is precisely this mix and match of traits that hybrids have inherited from their parental species that <a href="https://www.nytimes.com/2010/09/14/science/14creatures.html" target="_blank">facilitates their evolutionary success</a>, including their ability to cause disease.</p>
The Evolutionary Origin of an Aspergillus Hybrid.<p>Multiple evolutionary paths can lead to the emergence of hybrids. One path is through mating, just as the horse and donkey mate to create a mule. Another path is through the merging or fusion of genetic material from cells of different species.</p><p>It is this second path that appears to have been taken by our fungus. <em>A. latus</em> appears to have two of almost everything compared to its parental species: twice the genome size, twice the total number of genes and so on. But unlike other hybrids, which are often sterile like the mule, we found that <em>A. latus</em> is capable of reproducing both asexually and sexually.</p><p>But how distinct were the parents of <em>A. latus</em>? By comparing the parts contributed by each parent in the <em>A. latus</em> genome, we estimate that its parents are approximately 93% genetically similar, which is about as related as we humans are with lemurs. In other words, <em>A. latus</em>, an agent of infectious disease, is the fungal equivalent of a human-lemur hybrid.</p>
How A. Latus Differs From its Parents.<p>Elucidating the identity of closely related fungal pathogens and how they differ from each other in infection-relevant characteristics is a key step toward reducing the burden of fungal disease. For example, we found that <em>A. latus</em> was three times more resistant than <em>A. nidulans</em>, the species it was originally identified as using microscopy-based methods, to one of the most common antifungal drugs, <a href="https://www.drugbank.ca/drugs/DB00520" target="_blank">caspofungin</a>. This result provides a clear example of the potential importance of accurate identification of the <em>Aspergillus</em> pathogen causing an infection.</p><p>We also examined how <em>A. latus</em> and <em>A. nidulans</em> interact with cells from our immune system. We found that immune cells were less efficient at combating <em>A. latus</em> compared to <em>A. nidulans</em>, suggesting the hybrid fungus may be trickier for our immune systems to identify and destroy.</p><p>In the midst of the COVID-19 pandemic, our quest to understand <em>Aspergillus</em> pathogens is becoming more urgent. Growing evidence suggests that <a href="https://doi.org/10.1111/myc.13096" target="_blank">a fraction of COVID-19 patients are also infected with <em>Aspergillus</em>.</a> More worrying is that these <a href="https://doi.org/10.3201/eid2607.201603" target="_blank">secondary <em>Aspergillus</em> infections</a> can worsen the clinical outcomes for those infected with the novel coronavirus. That being said, we stress that little is known about <em>Aspergillus</em> infections in COVID-19 patients due to a lack of systematic testing, and none of the infections identified so far appear to have been caused by hybrids.</p><p>So, when it comes to hybrids, some are fantastic (the minotaur), some are helpful (the mule) and some are dangerous (<em>Aspergillus latus</em>). Understanding more about the biology of <em>Aspergillus latus</em> may help in our understanding of how microbial pathogens arise and how to best prevent and combat their infections.</p>
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Growing Contribution<img lazy-loadable="true" src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzM3NDY5Ny9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTY0NjM4MTgyM30.IuQTKQs1stvYYKD6vaVTrqAyoBsUG0BhDvlhxsyKwPA/img.png?width=980" id="02a05" class="rm-shortcode" data-rm-shortcode-id="2841f82b1785df5d5ed7bf64d3bb882b" data-rm-shortcode-name="rebelmouse-image" />
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