The Green Drink Conundrum:
Potential Thallium Exposure and Neurological Risks
By Julia Malkowki, ND, DC | May 29, 2019

Thallium (Tl) is a highly toxic heavy metal that has no
physiological function. More toxic to humans than mercury, cadmium or
lead, Tl is increasingly prevalent in the environment partly as a result of
modern industrial practices and crop irrigation. Vegetables most heavily
contaminated with Tl are the Spinacia and Brassica groups
inclusive of spinach, kale and lettuces. Direct sources of exposure include
cement dust, combustion of some types of coal and leakage of fracking
wastewater from legal and illegal storage pits and wells. Unfortunately
there is a man-induced omnipresence of yet another toxic metal that has great
potential to diminish health and well-being. 

Thallium elicits neurotoxic effects as it inhibits DNA and
protein synthesis, binds sulfhydryl groups on proteins of neurons and
mitochondria, impairs the production of ATP, and competes with
potassium. Thallium accumulates in the tissues with high potassium content
such as skeletal and cardiac muscle, and the central and peripheral nervous
systems. Thallium toxicity may manifest as alopecia areata, fatigue,
headaches, depression, sleeplessness, ataxia, neuropathy, vision disturbances,
psychoses, gastric antacidity, loss of appetite and/or weight, cardiac
arrhythmias, angina-like pain, hypertension and irregular pulse. Thallium
is primarily excreted via the kidneys and secondarily in bile. It may be
found in urine as long as two months after exposure. Urine levels are an
appropriate measure of Tl exposure and possible body burden.

The greatest exposure to thallium is from food, although
exposure from air and water may occur from industrial operations. Smokers
have been shown to have twice as much Tl exposure than non-smokers. In
1972 Tl-containing rat poison was discontinued due to the risk to human
health. Current irrigation practices permit the use of fracking wastewater
for irrigation of crops such as vegetables and fruit. An Environmental
Working Group report found that 95,000 acres of produce in California was
irrigated with fracking wastewater brine. Analyses of surface stream water near
a fracking site indicated significant Tl contamination. Spinacia
and Brassica group vegetables, such as kale, cabbage, spinach and
lettuce, efficiently assimilate Tl from soil. Alarmingly, this has made
dark green leafy vegetables one of the most common sources of Tl
exposure. Thallium has been detected in prenatal vitamins, and clinicians
should be aware that the neurotoxic metal readily crosses the placenta to the
developing fetus.

The human health issue appears to relate predominately to
chronic low-dose exposure via air, water and food sources over time, as opposed
to acute high-dose exposure. The more neurologically vulnerable
populations such as pregnant women, infants and children are of greater concern
and warrant more consideration. Particular caution is to be exercised in
instances of large amounts of Spinacia and Brassica group
vegetables, such as juicing, in the diet. The current culture strongly
advocates dark green leafy vegetables as healthy due to their mineral and
folate contents, yet the health risks of Tl exposure must be weighed against
the benefits. Furthermore, in sensitive populations and those consuming
large amounts of Spinacia and Brassica group vegetables,
urine levels of Tl may be clinically relevant. Clinicians should be aware
of the neurotoxic potential of Tl. Mitigating Tl exposure could benefit
human health on the individual and greater community levels. 

Ind J Occup Environ Med (2005)9:53-55 CDC/NIOSH 2016Peter AL, Viraraghavan T. Thallium: a review of public health and environmental concerns. Environ Int. 2005 May;31(4):493-501.Public Health Statement Thallium CAS#: 7440-28-0. and Analysis of Water Streams Associated with the Development of Marcellus Shale Gas: Final Report Dec. 31, 2009.Schwalfenberg, et all. Heavy metal contamination of prenatal vitamins. Toxicology Reports. March 2018. DOI: 10.1016/j.toxrep.2018.02.015Stoiber, Tasha. Toxic Chemicals May Contaminate Oil Field Wastewater Used to Grow Calif. Crops. October26, 2019.

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