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The Vegetable Detective

A molecular biologist found potentially dangerous levels of heavy metals in cruciferous "super food" vegetables, including kale, often called the “queen of greens." And these compounds have shown up most often in organic varieties.

Issue: Spring 2022

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When Ernie Hubbard started getting clients with model diets complaining of issues such as fatigue and hair loss, he was stunned, and confounded. Then he noticed a pattern in the vegetables they were eating.


  1. Behind Door Number One: Dirty Plants
  2. Door Number Two: Coal
  3. Door Number Three: Water

EDITOR’S NOTE: This story first appeared in our Summer 2015 issue, and although the questions and concerns it brought to light have continued to evolve, this version does not contain updated reporting. Several updates were later published in our Fall 2015 issue, exploring how thallium functions, its prodigious history in scientific literature, and how people should now think about eating kale and other vegetables. These are collected in an article entitled “The Vegetable Detective, Take Two.

Ernie Hubbard sees a very self-selecting group of patients and clients—“health fanatics,” he calls them—people who eat extremely well by current standards, exercise regularly, generally don’t smoke, do drugs, or drink to excess. In today’s world, however, especially in health-conscious Marin County, California, where Hubbard lives and works, these are the people increasingly showing up in doctors’ offices complaining of persistent but elusive problems: Chronic fatigue. Skin and hair issues. Arrhythmias and other neurological disorders. Foggy thinking. Gluten sensitivity and other digestive troubles. Sometimes even the possibility of Lyme Disease.

At one point, Hubbard got an opportunity to look more closely at what might be bothering some of these people. In 2010, a Cleveland company was developing a detoxification formula, called ZNatural. And its officers asked Hubbard and his colleagues at Preventive Medical Center of Marin, an alternative health clinic, if they would test the product.

Hubbard prepared all of his samples in his home laboratory, which he set up in the kitchen of his California houseboat.

As a molecular biologist with a background in biochemistry and genetics, Hubbard had been working with the clinic’s doctors to explore a range of tests and treatments not often found in traditional doctor’s offices. These include “bio-impedence” analyzers that measure cellular energy and “chelating” formulas like ZNatural, which aim to stimulate the body to release toxins. Chelating treatments have been controversial—some doctors consider them ineffective and, in some cases, even dangerous. After a bit of study, Hubbard and his colleagues concluded that ZNatural was far safer than its competitors, so they felt comfortable proceeding.

Before long, Hubbard had a pilot study underway, with 20 people happily peeing into cups. As he started gathering results on their samples—taken before, during, and after the detox regimens—he noticed an odd pattern: Several people registered high in thallium and cesium, two heavy metals generally not on anyone’s radar. “At first, I just thought, ‘Oh, another one of those. By the third or fourth, I started scratching my head.”

As the tests progressed, the detoxification regimens seemed to prove effective (and with no side-effects), but thallium kept showing up. Then, in July of 2014, he stumbled on a 2006 study out of the Czech Republic showing how the cruciferous family of vegetables behave as “hyperaccumulators” of thallium. Crucifers include many of our more intense green vegetables such as kale, cabbage, broccoli, cauliflower, and mustard and collard greens. These are also the vegetables often touted—and consumed—most heavily these days, supposedly for their outsized health benefits.

The most popular member of this family has been kale, promoted for its prodigious supplies of calcium, magnesium, potassium, Vitamin K, and various healthful phytochemicals and antioxidants. It’s even been described as “the queen of greens.” Not coincidentally, kale consumption has exploded. In 2007, according to the U.S. Department of Agriculture, kale was harvested on 954 farms across the country. By 2012, that figure had more than doubled, to roughly 2,500 growers. In the last 5 years, the number of restaurants serving kale has reportedly risen by some 400 percent. People are juicing it, cooking it, eating kale salads, even making chips and other food-oid products from this hearty plant. “It suddenly hit me,” Hubbard said, “I thought, ‘Oh, my God!’”

In fairness to the realities of industrial life, one can expect to find pollutants anywhere you look these days, if you look hard enough. “When I touch my desk right now, I’m picking up chemicals,” says Bernadette Burden, press officer for the U.S. Centers for Disease Control and its investigative little sister, the Agency for Toxic Substances and Disease Registry. “A lot of these elements occur in nature. For example, we now know there is arsenic in apple juice. And in rice.”

True enough, but the question is whether there has been a recent spike in these toxins, especially newcomers to the scene like thallium. That’s a difficult question to answer right now, given how recently people started gorging on kale.


As Hubbard poked around, he kept turning up more worrisome information. It turns out thallium was once a common ingredient in rat poison. It was also Saddam Hussein’s favorite poison to use on his enemies. (The metal works exquisitely for poison because it is tasteless, odorless, and nearly colorless.) While none of Hubbard’s test subjects had been consuming doses even close to poisonous levels, the medical and scientific literature linked low-level doses to many of the complaints brought to his clinic: fatigue, heart arrhythmia, and—in more extreme cases—nausea, neurological problems, and hair loss.

To test this link, Hubbard started playing a little game. Whenever the clinic would send him someone with the kind of chronic problems associated with thallium, or any other complaints that were hard to pin down, Hubbard would scribble kale on a little notecard and turn it face-down on his desk. After a short workup, he’d ask the patient to list his or her favorite vegetables. Over and over, people would mention the crucifers, especially kale. Hubbard would nod, say he expected as much, then show them the notecard on his desk to prove it.

One woman had always been admired for having beautiful hair, and now it was starting to fall out – “in clumps,” she says. Her favorite vegetable? Kale, and cabbage even more so. How often did she eat it? “Pretty much every day. I joke with my clients that I’m the cabbage queen.”

One such client was Laura Fenamore, an outwardly healthy, 52-year-old vegetarian. Fenamore works out vigorously—“for two hours every day,” she told me. “I’m in ridiculously great shape.” She even runs a body image consulting business. In fact, when she first joined Hubbard’s study group, Fenamore didn’t feel particularly unwell, by her recollection. (She enrolled, she said, primarily because Hubbard was a friend and she was curious.) She admits, however, that at times she felt fatigued and foggy in the brain. But there was one other problem: She had always been admired for having beautiful hair, and now it was starting to fall out—“in clumps,” she says. Fenamore’s favorite vegetable? Kale, and cabbage even more so. How often did she eat it? “Pretty much every day. I joke with my clients that I’m the cabbage queen.”

When Fenamore’s urine samples came back, even Hubbard was surprised. Her thallium levels measured at .7 parts per million (ppm), which is 7 times higher than what’s considered the “threshold” limit in the workplace. That threshold is according to a 2009 CDC report, the agency’s most recent statement on toxic exposures. Her test was not a perfectly accurate reflection of her toxicity levels, however. During the time she was drawing her urine samples, she had been taking the ZNatural detox formula, which infuses urine with more of the problem element than would normally be the case. Still, her urine measures were so high, the exaggeration created by ZNatural very likely pales by comparison.

For some frame of reference on this point, the CDC offers this data point: In one of the more widely studied instances of thallium contamination, at a cement plant in Germany decades ago, nearby residents suffered “a slight increase in nonspecific symptoms” when their urine showed thallium levels as low as .02 ppm. Fenamore’s thallium count was 35 times higher than that. And one more: The thallium levels in Fenamore’s urine were 4,700 times higher than the CDC found in most Americans—at least when the agency last measured. That was in 2012, when the kale craze was still warming up.

“This little lab was hummin’ for about four months, day and night!” Hubbard says.

“I couldn’t believe it,” Hubbard told me, regarding his reaction to Fenamore’s samples. He promptly put her on the clinic’s detox regimen, which tends to saturate the urine with any toxics as they are coaxed out of the body. Two months later, he tested Fenamore again and her numbers had more than doubled, to 1.8 ppm—nearly 12,000 times what the CDC found in the average population. Fenamore was also carrying around slight excesses of other metals, primarily cesium, cadmium, and arsenic—all toxins in their own right.

Fenamore was even more surprised by these numbers than Hubbard, given the mildness of her health problems. With reluctance, she cut way back on her cabbage consumption (which she now calls “getting off the sauce”), continued taking her detox potion, and watched her numbers slowly drop. “I do feel better now,” she says, “more even—hormonally, mentally, and emotionally. Energetically. And the brain fog cleared a lot.” Fenamore’s wife, Kathleen, also saw a change—a quick and marked difference in Fenamore’s alertness.

One might expect a person’s spouse to be biased, but her observations are credible for a few reasons. First, she didn’t completely buy Hubbard’s story, or his testing and detox procedures; and she does not like or eat cruciferous vegetables. Hubbard loved hearing that, because it handed him a convenient, mini-control on his study, suggesting that environmental factors may not have caused Fenamore’s toxicity. As coincidence would have it, two others in Hubbard’s study were twins, offering two people with the same genetic palate. “So I had a genetics control and an environmental control,” Hubbard says. “I had the kale haters and the kale lovers all getting their urine analyzed, and I think it’s hilarious.”

A strange subject to find amusing, maybe, but Hubbard is clearly having a ball with these inquiries. To follow these leads, Hubbard created a lab in his home (a houseboat). The first thing he wanted to confirm was exactly how much thallium was in the vegetables his clients were eating. He wanted to test everything he could, but time and resources wouldn’t permit it. So he focused on crucifer’s queen green: kale. After calling a few professional testing facilities, he came up with a set of protocols that turned the houseboat’s kitchen into a cross between a university laboratory and a movie set for a Frankenstein film. There were a few false starts. “I had an explosion that left glass and kale and molten slime all across this room,” he says.

Hubbard seems to thrive on obstacles. So he put his kitchen back together, and soon created some legitimate samples. Then he sent them to a well-established lab (Curtis & Tompkins, which was founded in 1878, in Berkeley, CA). When he got the samples back, he thought they weren’t analyzed in sufficient detail. So he looked for another lab. That led him to Doctor’s Data, a federally licensed laboratory near Chicago that does specialized testing, offering views of how elements function in the body on an intra-cellular level. By September of 2014, Hubbard was getting reports back showing heavy metals in virtually every kale sample he sent in. There were also traces of nickel, lead, cadmium, cesium, aluminum, and arsenic. Some of these metals are famously bad actors, or at least suspicious ones. For a touch of exploration, Hubbard also crunched a few jars of baby food. Lo and behold, they too contained heavy metals.


One day, Hubbard called Dr. David Quig, the lead scientist at Doctor’s Data, to better understand his lab results. Their conversation set off even more alarm bells. When Hubbard pointed out the prevalence of thallium in his subjects’ tests, Quig wasn’t terribly surprised. He said he, too, was seeing thallium in more and more tests from various clients. “It’s not high, it’s just frequent,” Quig told me, when I called him. “We never used to see thallium at all. Now, everybody who touches a report, it jumps out at them.”

“We now know that heavy metals are additive and synergistic,” he said. “If you get a little thallium, and a little lead, and a little cadmium in your system, you’ve got one plus one plus one equals five or six, not just three.” The reason, he said, is that metals and chemicals might each have different effects by themselves, but they “share similar sites of action where they disrupt metabolism.”

Quig suspects plenty of vegetables besides kale are picking up thallium, and other heavy metals. He already knew of one example, where a Seattle woman suffered from eating lettuce that turned out to be laced with thallium. “This happens with all leafy greens,” he said. “If it’s in the soil, the leafy greens are going to take it up.”

Hubbard has been wondering about other vegetables, too; he just didn’t have the budget, or the assistance, to test more than the obvious. But that’s been enough, in his mind, to build a case. At one point, he noticed that a rule from the U.S. Food and Drug Administration, called Title 21, prohibits the sale of food products containing more than 1 ppm of “mercury, lead, and all other such toxic metals.” The FDA was no more specific than that, but Hubbard thinks one could argue that a phrase like that is pretty inclusive. Hubbard is an experienced scientist (he is 65, and has been involved in several genetic engineering startups), so he knows his data is limited, and preliminary. But it also suggests the possibility of violations, in abundance. One kale sample reported thallium at 1.14 ppm, nickel at 20 ppm, and aluminum at a staggering 120 ppm.

Clearly, most of these excesses are minuscule, but they are enough to raise red flags for someone like Dr. Quig. Since Quig is regarded as something of an expert on toxicity—he is a former cardiovascular pharmacologist, with a PhD in nutritional biochemistry, and frequently gives presentations at medical conferences—I tested Burden’s argument on him. Potentially toxic chemicals are everywhere these days, so isn’t it foolish to overreact if we see trace signs of them in our urine? Quig’s answer, essentially, is no. “We now know that heavy metals are additive and synergistic,” he said. “If you get a little thallium, and a little lead, and a little cadmium in your system, you’ve got one plus one plus one equals five or six, not just three.”

The reason, Quig says, is that metals and chemicals might each have different effects by themselves, but they “share similar sites of action where they disrupt metabolism.” The problem multiplies, he believes, when patients see their doctors complaining about not feeling well in vague, general terms. Some doctors dismiss such complaints; some suggest remedies that might prove unrelated (such as medication, or lifestyle changes to reduce stress); and some will order tests, to look at issues such as thyroid function or blood content. When the results come back, there’s often no sign of toxicity at levels considered poisonous, or any other severe problems. So everybody throws up their hands and, in Quig’s view, misses the point. “Of course the symptoms are vague,” Quig says. “That’s the point. This stuff bioaccumulates. Down the road, it’s going to kick you in the ass one way or another.”

The more Hubbard nosed around in the circle of toxicity, the more he thought he smelled a rat. He just wasn’t sure where it was. He spent hours on the internet, figuring out where thallium comes from. Answer: It’s a natural part of the Earth’s crust, but usually only in the faintest quantities. Whenever it has been found in amounts large enough to sicken people or contaminate farms, it’s been traced to nearby cement plants, oil drilling, smelting, and, most of all, in the ash that results from coal-burning.

For a while, Hubbard was obsessed with the possibility that coal ash, which is produced at a rate of about 70 million tons a year and steadily growing, might be the culprit. The circle was perfect. A Seattle Times reporter named Duff Wilson ably reported as much in 2001, in a swaggering account of his investigative conquests entitled “Fateful Harvest: The True Story of a Small Town, a Global Industry, and a Toxic Secret.” The circle works this way: When energy companies burn coal, they need a cheap way to get rid of the ash. So they sell it as fertilizer, where it’s most generously used on the miles of corn and soybeans that are grown for animal feed across the Midwest. The crops absorb the thallium; the animals eat what the plants produce; then they poop out thallium and anything else the animal’s digestive system rejects. In honor of the modern ethic to recycle whenever possible, we gather the manure and use it again—for more fertilizer, often on organic farms.

When the numbers for heavy metals in kale started coming in, Hubbard was stunned. One really stood out: thallium, which for years was Saddam Hussein’s favorite poison.

The final stage of this cycle—the possibility of contaminated fertilizer on organic vegetables—really got Hubbard fired up. In an attempt to figure this out, he collected two kinds of kale samples—organic varieties, and several that were conventionally grown.  The results were perplexing. Thallium—along with other toxic metals such as cadmium, lead, and mercury—showed up slightly more often, and in slightly higher quantities, in the organic varieties.

The limited number of his samples made Hubbard wary of drawing any definitive conclusions about organic vegetables containing more toxic metals than their conventional counterparts. But the pattern, tiny as it was, was clearly worrisome. Could it be, he wondered, that organically grown kale is higher in sulfur, which is known to attract thallium? If not, its presence had to come from something else that farmers are using in their fields. Whatever the case, Hubbard’s growing body of evidence was enough to make him suspect what he calls “a perfect storm”: contaminated vegetables, misleadingly pushed on the public as nutritious—and clean—leading to misdiagnosed ailments. “Where does this list end?” he wrote in one of his numerous messages emphasizing these points. “There is undoubtedly a series of similar perfect storms at work in other heavy metals and our food supply, including infant and baby foods, pet foods, and beyond.”

The crops absorb the thallium; the animals eat what the plants produce; then they poop out thallium and anything else the animal’s digestive system rejects. In honor of the modern ethic to recycle whenever possible, we gather the manure and use it again—for more fertilizer, often on organic farms.

The potential of this storm so bothered Hubbard that he decided to test his theories himself. And he thought he had the perfect petri dish: a few acres in Sonoma County, farmed by a friend, that had been mostly abandoned over the years. This created the possibility of something close to a blank slate. Within days, he was testing the soil and planting kale. Then came another surprise. The soil showed very little thallium in comparison with others he had tested, but the kale he grew contained quite a bit. This proved kale’s powers as a hyperaccumulator, but it disproved, or at least shook, his belief that coal ash was the culprit. “Now I’m not so sure where it’s coming from,” Hubbard says.

Tom Willey is equally mystified. Willey farms 75 acres of organic vegetables in Madera, California, and is one of the state’s most experienced and knowledgeable organic farmers. And, by coincidence, two of Willey’s vegetables—baby bok choy and carrots—ended up among the 30 different foods Hubbard chose to study. Both turned up entirely clean—of thallium and any other heavy metals the lab tested. But those tests were done by Hubbard’s first lab, which did not find thallium in any of the 19 samples it tested. But obviously something slipped through somewhere: “We definitively have aluminum in our soil,” Willey told me. “We’ve seen it in our soil tests.”

Willey has never seen thallium in soil tests—then again, he’s never looked for it. But he might not find it even if he did. As Hubbard discovered in his own test garden, plants and soil play an expert shell game with heavy metals—some of which, in farming parlance, are also called micronutrients. Take iron, for example. One year, when Willey found low levels of iron in a few soil tests, he decided to test his crops’ plant tissues to see just how bad the situation was. When the test results came back, they showed iron levels to be perfectly adequate. By that time, Willey had already added fertilizer to increase the soil’s iron content, which he then realized was unnecessary, and potentially overloading his crops. Iron, however, is pretty well understood in both health and farming circles. Thallium is a new one. “It may have a value to a plant that we don’t understand yet,” Willey said. “We’re just now learning how a lot of these micronutrients function.”


Once Hubbard had ground, boiled and dried his vegetable samples into a form that could be tested, he sent them to Doctor’s Data, a specialty testing laboratory in Illinois.

While nosing around all these dark, toxic corridors, Hubbard did find a few promising doors. One arose from a bizarre discovery in his kale samples: Some varieties, such as “Dino” and baby kale, accumulated large amounts of thallium; others pulled in less than half as much, even though they had been grown in the very same ground. This gave Hubbard an idea: Breed a kale variety that isn’t attracted to thallium. “We breed special tomatoes, and everything else,” he said one morning, while showing me his array of testing apparatus. “Why not kale?” To further explore this possibility, and his many other ideas, Hubbard is setting up his own study program (called The Sage Center) to promote new kale varieties, toxicity testing, and whatever else he has found that might lead to optimal health.

As Hubbard’s efforts continue, it would obviously help matters if we could pinpoint the sources of these metals. David Quig has his suspicions. With all the fracking and oil drilling being done around Kern County, where much of the state’s fabled produce is grown, he thinks there is a chance that various heavy metals are making their way into irrigation water. The reason, as has been well-reported, is that both fracking and oil drilling require massive amounts of fresh water. “Even if you clean it up, and put the leftover sediment in a landfill, it’s going to make its way back into the water supply anyway.”

That’s a heavy charge, so I called the California Regional Water Quality Control Board, which is the state agency that watches these issues. I learned some good news and some bad news.

The good news is that in most areas of the state, wastewater from fracking and oil drilling isn’t used on farms—whether polluted or not, it’s too salty. The bad news is that there is at least one glaring exception.

In one area of Kern County, said Clay Rogers, the assistant executive officer for the Central Valley Water Control Board, the oil-field wastewater has been clean enough to use for irrigation. So they have allowed the practice for decades. Just recently, however, community members have begun asking about chemicals and other elusive toxins that the agency has never regulated, or watched for. “Out of an abundance of caution,” Rogers said, they have been gathering test data. As it happens, the first reports just arrived, in June, and the agency hopes to have an analysis available soon.

In the meantime, Hubbard, not one to leave a stone unturned, has been wondering what he can find in agricultural water supplies. So he tried another experiment at his friend’s farm—the one that inexplicably grew thallium-tainted kale. Due to California’s historic drought, the farm’s landowner had recently drilled a new well, which had to go down 360 feet before it struck water. At that depth, you don’t know what’s generating any metals that might surface. It could be old seepages from the dairy operation that apparently used to work this land. Or it could be metals from under the earth’s surface, where they often lie in a more concentrated form than is found in topsoil. Either way, maybe this was the source of the thallium found in Hubbard’s test kale.

When he tested the water, however, the reports came back entirely clean.” So the mystery continues. “It’s really difficult to know where this circle ends,” Hubbard says.

More stories from this issue:

The Vegetable Detective

Tips and Inspiration from England’s Great Dixter Gardens

The Drought Fighter

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