MEDDLING METALS
Mercury
Location and form
Elemental Mercury is a volatile metal. Mercury is released by volcanoes, rock erosion and human activity. Most Mercury exists in nature both as elemental Mercury and as a sulfide (a compound with sulfur). However, Mercury is found in different chemical forms:Inorganic Mercury
- Elemental or Metallic Mercury
- Mercurous Mercury (water solubility and intestinal absorption is poor) [1]. Mercuric Mercury is a present component of certain skin-lightening products and was used in the past as a preservative and in photographic film[1].
Organic Mercury
- Methylated Mercury is found in swamps, water bodies, or anaerobic (devoid of oxygen) environments with anaerobic bacteria. Skin and intestinal absorption of Methyl-Mercury is efficient [1].
- Other organic forms of Mercury form compounds with an ethyl, phenyl or other chemical groups. Ethyl-Mercury (Thimerosal) is used as a preservative in some formulations).
Mercury is exchanged between the atmosphere and the parts of earth where life exists, (biosphere), as Mercury is converted from inorganic to organic forms [2]. Methylated Mercury is the organic and more toxic state found in the biosphere. Under ideal conditions, Mercury will have a limited residence in the biosphere or terrestrial environments and cycle back to its volatile atmospheric form. These conversions are executed by anaerobic bacteria. Bacteria converts Mercury to Methyl-Mercury (the more toxic form) and back to elemental Mercury. Luckily, bacterial genes (mer A) for breaking Mercury bonds to produce the elemental form are more common than the genes for making the methyl bond. It appears that methylation of Mercury is part of an initial process of bacterial composting and is associated with other processes such as sulfate reduction [3]. Since Mercury bonds to most metals, acids, ammonia, etc., bacteria can make use of it as a holder of chemical compounds while working through its substrate during initial composting. The composting environment also provides a cue to bacteria for the expression of genes that will create or break Mercury bonds. Mercury bacterial methylation and oxidation is favored by low acidity and high carbon. See how soil microbial communities maintain soil fertility
The volatile form of inorganic Mercury, when deposited in lake sediments and wetlands, is occasionally transformed by bacterial action to Methyl-Mercury-Chloride or Methyl-Mercury-Cysteine (Mercury salts). These organic forms of Mercury could find their way to the food chain, e.g. fish. However, J.P. Bourdineaud et al. demonstrated that ingesting fish with artificially infused Mercury produced higher neurotoxicity than fish with naturally acquired Mercury. Unlike methyl-Mercury, Mercury salts are poorly absorbed and more stable, thus, less toxic. Conversely, large acute quantities of vapor Mercury can be toxic and traverse the blood brain barrier when inhaled/absorbed in sufficient quantities. Vapor Mercury can escape oxidation when entering the blood stream, e.g. the pressurized vapors released during excavations and mining. Pressurize Mercury vapors do not happen normally or habitually in nature.As a naturally occurring metal, Mercury has its role in nature but not a role in human or animal physiology.
Mercury toxic effects:
(dose, rate and form of Mercury are determinants of toxicity)- Alters the structure of proteins and has the potential to damage any organ in which any form of it is deposited.
- Affects human endothelial cell physiology [3].
- Methyl-Mercury has a disrupting effect on immunity, in particular natural killer cell activity disruption [1].
- Disrupts cell energy production and possibly DNA repair [1].
- Causes neurological toxicity in humans.
- Is an endocrine disruptor [4].
- Has potential carcinogenic effects on humans and affinity for mammary cell glands [1,4].
- A scientist’s death was reported following minimal skin contact with dimethyl Mercury [1].
- Affects the reproductive system of male rats [3].
- Causes renal and hepatic toxicity in fish [3].
Reported symptoms [1]:
- Lung inflammation (individuals exposed to large quantities of Mercury vapor). See Natural Inflammation Fighters.
- Gastrointestinal distress, weakness, fatigue, weight Loss.
- Immune disfunction
- Tremors
- Gingivitis with excess salivation
- Reduced visual acuity
- Polyarthritis, dermatitis.
- Mood abnormalities
- A form of cerebral palsy following massive pre-natal exposure.
- Renal failure following ingestion of large doses of mercuric salts.
- Paresthesia, visual, auditory disturbances.
- Impaired balance or coordination.
Environmental concerns:
- Gold mines in the Brazilian Amazon use Mercury for amalgamation with gold. Some of the Mercury is not recovered and dumped in river, soil and atmosphere. The altered equilibrium of naturally occurring Mercury alters bacterial gene expression. Excess, not naturally occurring, Mercury surpasses the ability of human and animals to oxidate it. Excess Mercury is accumulated in rivers, travels with affected mammals, birds, fish and through the atmosphere.
- In dental amalgams or ‘silver fillings’ Mercury is the ‘glue’ that allows the mixing of metals. Dental amalgams not only affect the individuals who choose to work with this product, but also the eco-systems since some Mercury is disposed in our sewer systems. Consequently, Mercury can be released as vapor to the atmosphere adding to the naturally occurring Mercury in the environment.
Influences in Mercury toxicity:
- Microflora* of the intestinal track can break Mercury bonds thereby releasing Inorganic Mercury [3] (a less toxic form than methyl-Mercury). *See the effects of Microbiota on Brain function
- Approximately 90% of methyl-Mercury is excreted in the stool (about 70 days excretory half life) [1].
- The amount of excretion through breast milk is about 20%, but Mercury exposure amount influences excretion.
- Ca+, mitochondria, Glutamate influence neurotoxicity
- In mammalian cells marine omega-3 fatty acids, such as DHA decreases uptake of Methyl Mercury (O.J Nøstbakken et al.)
- Selenium* counteracts Mercury toxicity[1]. * See effect of Selenium on Poultry.
ALUMINUM
Location and forms:
Aluminum is a prevalent metal in the earth crust. In spite of Aluminum’s position as the third most abundant metal in earth crust, it has no function in plant, animal or human biology. Aluminum is mined from locations such as Australia where its precursor rock, bauxite, is found. Bauxite rock contains various oxide compounds, such as aluminum oxide, hydroxides, iron oxides, titanium dioxide and silicates. Aluminum is a light weight metal that is not found naturally. In fact, Aluminum is tightly bound to silicate in its most abundant form. The metal must be extracted via processing of bauxite rock and electrolysis. A resulting rich fluoride effluent is also by-product. The extracted aluminum metal retains high affinity for oxygen. Aluminum is inert as Aluminum oxide.
Some oil preparations with Aluminum will cause reactions with water resulting in production of Aluminum Hydroxide. Unlike Aluminum Oxide, the Hydroxide form provides no protection to the metal below the surface. The metal will continue reacting and producing this hydroxide, similar to the reaction of iron with water. Aluminum Hydroxide is toxic, a protein denaturant, akin to methyl Mercury [Bryan Corrin et al].
Aluminum has many applications in industry, e.g., construction material, pyrotechnics, rocket fuel, jewelry, metal polish, pigment for paints, nanoparticles in sunscreen lotions, toothpaste, pharmaceuticals, coffee pots, aluminum cans, aluminum foil, food additives, etc. Most human ingestion happens through food, food containers and utensils. Plants that grow in acidic soil can accumulate more aluminum (e.g. tea and subtropical fruits) [9].
Aluminum toxic effects:
- Aluminosis/Pulmonary fibrosis (Chronic Aluminum dust inhalation)
- Encephalopathy (in kidney disease patients).
- Osteomalacia (in kidney disease patients). Aluminum interacts with skeletal calcium.
- Anemia (often seen in dialysis patients).
- The role of Aluminum as an abetting factor in Breast Cancer and Alzheimers’ dementia has been addressed in some studies [13].
- True to most toxic metals, Aluminum also disrupts gut microbiota and influence growth of specific species.
- Consequently, some of microbial metabolites, such as short chain fatty acids, are also reduced [17]. Soil microbiota are affected by the same mechanisms as gut microbiota. See gut microbiota influence on brain function.
- Soil acidity is increased by sulfur, ammonium-based fertilizers, acid precipitation. In acidic soil, even microscopic amounts of Aluminum can have toxic effects in most plants. Aluminum inhibits root growth and plant development, as well as, limits uptake of water and nutrients. The presence of Aluminum in the soil can generate bursts of reactions with products such as hydrogen peroxide and other reactive oxygen species [15]. Some plants are able to overcome Aluminum toxic effects by expressing production of organic acids such as oxalate. Oxalate has been the subject of studies in medicine as a contributor to kidney disease [16]. Plants that use organic acids to tolerate Aluminum accumulate large quantities of this metal in leaves and stems [9]. Environmental pressures could make the expression of bacterial genes for oxalate production a common feature and render future generations of plants less beneficial to humans and animals.
Factors influencing Aluminum toxicity.
- Lactobacillus Plantarum in gut microbiota binds Aluminum [17].
- Iron deficiency increases absorption of Aluminum [18].
- Acids that increase Aluminum leaching from cooking utensils. Stahl et al, demonstrated that the tolerable weekly intake limit ( European Food Safety Authority) of Aluminum was exceeded when cooking with aluminum utensils in the presence of citric acid (such as the acid from lemon juice) but not with oil and water. A 15 kg. child could exceed weekly limit of Aluminum by 298%. Additionally, drinking apple juice with mineral water or tea from an aluminum can nearly reach the tolerable weekly intake limit [10,12].
- Plants can overcome toxicity with production of organic acids, such as oxalate.
- Kidney disease impairs Aluminum elimination.
- Soil acidity increases Aluminum toxicity in plants. Acidic soils constitute 40% of the cultivable land in the world.
- Boron may modulate plant toxicity [19].
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- Liu J, Bao Z, Wang C, Wei J, Wei Y, Chen M. Understanding of Mercury and methylMercury transformation in sludge composting by metagenomic analysis. Water Res. 2022.
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- Maniero MÁ, Wuilloud RG, Callegari EA, Smichowski PN, Fanelli MA. Metalloproteomics analysis in human mammary cell lines treated with inorganic Mercury. J Trace Elem Med Biol. 2020.
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- de Bakker LB, Gasparinetti P, de Queiroz JM, de Vasconcellos ACS. Economic Impacts on Human Health Resulting from the Use of Mercury in the Illegal Gold Mining in the Brazilian Amazon: A Methodological Assessment. Int J Environ Res Public Health. 2021 Nov 12;18(22):11869. doi: 10.3390/ijerph182211869. PMID: 34831624; PMCID: PMC8622153.
- Matsumoto H., Hirasawa E., Morimura S., Takahashi E. Localization of aluminium in tea leaves. Plant Cell Physiol. 1976
- Stahl T, Falk S, Rohrbeck A, Georgii S, Herzog C, Wiegand A, Hotz S, Boschek B, Zorn H, Brunn H. Migration of aluminum from food contact materials to food-a health risk for consumers? Part I of III: exposure to aluminum, release of aluminum, tolerable weekly intake (TWI), toxicological effects of aluminum, study design, and methods. Environ Sci Eur. 2017.
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- Stahl T, Falk S, Rohrbeck A, Georgii S, Herzog C, Wiegand A, Hotz S, Boschek B, Zorn H, Brunn H. Migration of aluminum from food contact materials to food-a health risk for consumers? Part III of III: migration of aluminum to food from camping dishes and utensils made of aluminum. Environ Sci Eur. 2017.
- Austrian Department of Health (2014) Bundesministerium für Gesundheit (BMG, 2014). Aluminium—toxikologie und gesundheitliche Aspekte körpernaher Anwendungen. Herausgeber, Medieninhaber und Hersteller:Bundesministerium für Gesundheit, Sektion IIRadetzkystraße 2, 1031 Wien, Österreich.
- Rahman MA, Lee SH, Ji HC, Kabir AH, Jones CS, Lee KW. Importance of Mineral Nutrition for Mitigating Aluminum Toxicity in Plants on Acidic Soils: Current Status and Opportunities. Int J Mol Sci. 2018.
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- Yu L, Duan H, Kellingray L, Cen S, Tian F, Zhao J, Zhang H, Gall GL, Mayer MJ, Zhai Q, Chen W, Narbad A. Lactobacillus plantarum-Mediated Regulation of Dietary Aluminum Induces Changes in the Human Gut Microbiota: an In Vitro Colonic Fermentation Study. Probiotics Antimicrob Proteins. 2021.
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- Riaz M, Yan L, Wu X, Hussain S, Aziz O, Jiang C. Mechanisms of organic acids and boron induced tolerance of aluminum toxicity: A review. Ecotoxicol Environ Saf. 2018.