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Overview
Results are presented from toxic heavy metals analyses of extractions from fresh vegetables and other foods grown and sold in Marin and Sonoma Counties, California, in 2014 and 2015.1 Laboratory findings from these samples (Pilot Study 3) indicated that 6 of 25 foods tested for thallium exhibited levels of thallium in excess of 0.26 ppm. In the human body, thallium levels above 0.5 ppm are considered excessive. Thallium has a half-life of 60 days, so the consumption of foods with thallium content of 0.26 ppm has the potential for harmful bioaccumulation in the body.
A majority of these elevated findings occurred in samples of kale (Brassica oleracea) sourced from local farms (both organic and non-organic), procured in farmer's markets and from food retailers. In parallel studies of heavy metals in humans (Pilot Studies 1 and 2), subjects exhibiting high urine thallium were found to be high consumers of some of the foods testing high in thallium, particularly cruciferous vegetables. Cessation of consumption of these foods resulted in reductions in urine thallium and reduction in symptoms associated with thallium toxicity. Further discussion regarding this pilot sample includes the possibility of toxic heavy metals in the food supply and hypotheses on sources of these heavy metals.
The genesis of this environmental pilot study (Pilot 3) dates to 2010 when the authors and colleagues were asked to conduct an independent clinical study of oral chelation (Pilot 1). This research was designed to document responses to a naturally-derived detoxification product developed by LifeHealth Science, LLC, a Cleveland, Ohio-based enterprise. The initial study indicated that the detoxification agent was effective in removing a spectrum of heavy metals from study participants, and no side effects of the chelator were observed.
Following the initial study, a second human study (Pilot 2) was undertaken in 2014 involving a refined version of the detoxification agent. During this follow-up study, a percentage of the participants exhibited higher-than-normal levels of toxic heavy metals, particularly thallium, aluminum, and cesium. The subjects with higher-than-normal thallium levels also exhibited varying degrees of symptoms consistent with thallium toxicity including cardiac arrhythmias, fatigue, and hair loss. No obvious sources for the detected thallium could be identified in Marin or Sonoma Counties (i.e. high concentration of coal-burning power plants and/or cement manufacturing facilities).
When research was found in the medical literature linking high levels of thallium to kale and other cruciferous vegetables, a survey of study participants was conducted and a high correlation was found between elevated urine thallium and high consumption of kale, cabbage, broccoli and other cruciferous vegetables.
Benchmarks for Thallium Toxicity in Humans
MR: We have good research on toxicity levels for thallium because cardiologists use thallium in cardiovascular studies, scans, and stress tests of the heart. Why thallium? Because thallium mimics potassium and there is a great deal of potassium in the heart. However, these tests use 1/4,000 of the amount that is considered to be toxic.
EH: Dosage and toxicity levels came from these medical studies, because the prescribed amount of thallium for the heart scan must take into account the half-life of thallium. That has provided benchmarks for toxicity.
Given the half-life of thallium, you can see how it starts to accumulate in the body. For example, simply having a kale smoothie every morning could create an exposure if the kale contains thallium. For an average kale user, half a bunch of kale a week is not a great deal. So we used the medical data as our baseline and found that within six to eight months you start seeing sub-clinical symptoms. That is what we actually were seeing in patients in our first and second pilot studies.
From a biochemical perspective, imagine what happens when a thallium atom lands where a potassium atom should have been, given that its atomic mass is about five times greater than that of a potassium atom with many more electrons. This is a hugely disruptive process in a very delicate mechanism, whether it is a nerve cell or a heart cell. Thallium is an enormously heavy metal that can bind to sulphur and lock up the potassium receptor sites, so it is no wonder that it can be so lethal.
Yet this is just one heavy metal. You could probably tell the same story about all the heavy metals in one way or another and then you must deal with all the combinations. Many of these patients have elevated levels of five or six toxic heavy metals; thallium is just one of them.
Search for the Source of the Thallium
EH: I began connecting the dots on these issues in 2014 when I came across a research paper from the Czech Republic entitled "Uptake of Thallium from Artificially Contaminated Soils by Kale." Once we realized that the thallium exposure might be present in the food chain, we decided to do a third pilot, procuring and preparing food samples for analysis, working with two different laboratories. By the end of 2014, we had submitted most of the food samples. As the lab reports came in, we found significant observable levels of thallium in some of the food, particularly in samples of cruciferous vegetables, primarily in kale. That led to all sorts of interesting questions. Were the samples that tested positive for thallium nonorganic or organic? What was the soil and the soil profile? Were the produce samples from different farms, and were they using different growing methods? We were in a scramble to find the source or sources of the thallium.
Pilot Study 3 of Sample Foods
In this pilot, food samples were prepared and submitted to two laboratories (Curtis & Thompkins and Doctor's Data) to analyze for the presence of thallium. These samples included 15 vegetables, 3 fruits, 3 protein sources, and 4 samples of commercial baby food.
Thallium. Of these, 24% showed evidence of thallium at levels with the potential for toxic effects, given the half-life of thallium in the body. Of the 10 dry-weight kale samples, 5 showed toxic levels of thallium.
Aluminum. Selected samples of kale and of commercial baby food were subjected to greater scrutiny, evaluated by Doctor's Data for 20 toxic metals. All 5 samples were found to have elevated levels of aluminum 15 to 25 times higher than the reference range.
Nickel. Two kale samples (of different varieties) evaluated for 20 metals had nickel levels 2 to 3 times the reference range.
Bioaccumulation in Crucifers
MR: We analyzed six different varieties and types of kale and the uptake was different in each of them. So we were not only looking at a particular plant, but all of the varieties of that plant.
EH: What we know now is that certain species of kale can absorb 15 times the thallium from low thallium soil and sequester so much thallium that it is probably not healthy to consume kale—especially raw kale—in large quantities. Kale is a hyper-accumulator, and there is genetic variation for this. Of the different types of kale that we have tested, we have seen significant variation in the uptake of metals in kale, even in different kale species grown in the same soil. Once you see the preponderance of information on the capacity of the crucifers as bioaccumulators, it is almost undeniable. Biochemically, it is easy to understand how they would be hyper-accumulators of thallium.
The bottom line is that anyone who is developing symptoms and eating a lot of crucifers should change their diet and get tested for heavy metal exposure.
Plant Biosorption and Bioaccumulation
The capacity of certain plants as bioaccumulators has been recognized for more than a decade. Researchers have studied both the risk of toxicity and the potential role of these plants in the remediation of toxic soils. A German study published in 2004 explored the removal of heavy metals from the environment by plant biosorption. Brassica species in particular have been evaluated for their bioaccumulation capacity: A Polish study published in the International Journal of Molecular Sciences in 2011, explored the role of mustard seed in toxic clean-up. Other Polish research published in 2012 documented absorption of heavy metals, nitrates, and nitrites by various species of cabbage. Additional research in this area has focused on food safety in the context of novel soil media. A 2006 U. of Illinois study of heavy metals in garden vegetables, including broccoli, evaluated the safety of river sediment as a food medium, finding levels of molybdenum three-fold higher than those associated with toxicity in grazing animals. A 2008 Chinese study evaluated the safety of cabbage grown in sludge, reporting toxic levels of arsenic, cadmium, chromium, and zinc. There is a need for comparable studies on cruciferous vegetables and other bioaccumulating plants grown in soils with heavy metal accumulation.
Environmental Contaminants
Thallium in Fertilizer
EH: We have reason to believe that some growers (on both non-organic and organic farms) may be using coal-ash-based fertilizer or manure that contains thallium. You can track the history of the coal-ash industry, the rise of coal-fired electrical generating plants in this country, and their track record on waste disposal. The picture that emerges is that the environment has been polluted by toxic heavy metals, including thallium, for at least a decade.
Coal Ash in the Environment
By 2007, the EPA had tracked at least 70 cases in which coal ash had caused fish kills, or tainted drinking water and land.2 In 2008, coal ash overflowed a holding pond at a power plant in Tennessee, engulfing over 300 acres in sludge, and contaminating drinking water with arsenic and radioactive radium. (The cleanup was projected to cost about $1 billion.) A spill occurred in Alabama just a few weeks later. In Virginia, a golf course built on 1.5 million tons of fly ash was considered a model of landfill recycling until tests of nearby ground water wells showed arsenic and lead levels exceeding safety standards.3 In 2011 the Tennessee Valley Authority reevaluated groundwater sources for toxins and found contaminants leaching out of coal ash dumps at eight of the nine plants being monitored.
Synthetic Gypsum
One form of coal ash is known as synthetic gypsum, a whitish, calcium-rich material also termed flue gas desulfurization (FGD) gypsum.4 The Environmental Protection Agency has formally stated, "EPA believes that the use of FGD gypsum in agriculture is safe in appropriate soil and hydrogeologic conditions." The EPA indicates that heavy metals in the material are far less than the amount considered a threat to human health. Field studies have shown that mercury, the primary heavy metal of concern, does not accumulate in crops or run off fields in surface water at "significant" levels.
EH: Coal ash has been used in agriculture since the 1990s as a fertilizer that is labeled as coal-ash or fly-ash, approved by the USDA. There are numerous agronomic studies that show just how much you can use before it is toxic to plants. But there is a major story in Georgia about a dairy farmer who lost about 600 head of cattle because the city of Atlanta had given him all their coal-ash to use as fertilizer. He lost his entire herd and went bankrupt. His neighbor, who was using the same coal ash, had the common sense to have his own herd's milk tested, and it turned out that it was extremely high in thallium. They did necropsies on the cattle and found high thallium. There was a huge settlement with this farmer over the thallium poisoning.
There is a history of thallium use in agriculture and its toxic effects, but no one is really regulating it. 60 Minutes did a piece on Duke Energy in North Carolina because there was a toxic spill of coal-ash sludge in a pond and it destroyed an entire ecosystem in North Carolina. Yet we know that the American Coal Ash Association petitioned the EPA, requesting that coal ash be officially approved by the USDA for use as an organic fertilizer.
Final EPA Ruling on Coal Combustion Residuals
On April 17, 2015, EPA published its final rule establishing comprehensive regulations for the disposal of CCRs [Coal Combustion Residual] from coal-fired power plants under subtitle D of the Resource Conservation and Recovery Act (RCRA), classifying CCRs as nonhazardous solid waste. EPA issued the final rule under a self-implementing approach because EPA lacks the authority under subtitle D of the RCRA to require states to issue permits in this context. Therefore, EPA requires the minimum federal criteria to be administered by each owner and/or operator that manages CCRs in surface impoundments and landfills. The final rule continues to exclude the beneficial use of CCRs from regulation.5
EH: The landfills and the ponds are overflowing with coal ash, so industry turned to agriculture for disposal, and now these metals are showing up in our food supply. Periodically Michael and I step back and say, ‘This is just thallium, and this is just kale. Let's look at baby food, let's look at flesh foods, at fish.' The discovery that we made in these pilot studies was the proverbial tip of the iceberg.
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