Don't be one to bite the dust! Toxic heavy metal Hg – University of Copenhagen

14 January 2019

Don't be one to bite the dust! Toxic heavy metal Hg

You might have guessed what these pictures might have in common. It is Mercury (Hg): Freddie Mercury (the lead singer of Queen), a band of heavy metals (where lead is a lead singer and mercury playing bass), Cloud Gate sculpture (which was designed by Sir Anish Kapoor and inspired by liquid mercury), and a symbol of planet Mercury (which was once used to represent the element). Here are several facts about the heavy metal Hg.

Hg is also commonly known as a quick or liquid silver. It has the atomic number 80, the standard atomic weight of 200.5924(8), a melting point of – 38°C, a boiling point of 356.7°C. It is highly volatile, at 24°C a saturated atmosphere of mercury vapour has roughly 18 mg Hg/m3. Hg has silver colour, and is the only metal which is liquid at a room temperature. Hg can have three oxidation states: 0 (elemental or metallic mercury), I (monovalent or mercurous mercury), and II (divalent or mercuric mercury). There is a distribution of different metal species in the environment: vast majority (more than 95%) in the atmosphere is elemental Hg vapour; in water, soils and sediments most abundant is inorganic Hg(II) form; and in biota – (mono)methylmercury (MeHg, CH3Hg+), which is highly toxic.

The exposure to mercury can be carcinogenic and can also cause cardiovascular, reproductive, and developmental toxicity, neurotoxicity, nephrotoxicity, and immunotoxicity. Two origins of Hg in the environment: natural and anthropogenic. The sources of Hg are volcanoes, forest fires, from solid waste incineration, fossil fuel combustion, and mining. The most common cause of mercury poisoning is from eating contaminated food. 

Methelation of Hg is a critical point for Hg migration into the food chain. MeHg forms due to Hg(II) bioavailability and microbial activity. Production of MeHg in most terrestrial environments is relatively low, and thus bioaccumulation of MeHg in plants is considered to be small. However, MeHg efficiently bioaccumulates and biomagnifies in aquatic ecosystems, which makes it a human health threat due to consumption of primarily fish or fish predators (where MeHg concentration can be especially high).

References:

  1. Beckers, F.; Rinklebe, J., Cycling of mercury in the environment: Sources, fate, and human health implications: A review. Critical Reviews in Environmental Science and Technology 2017, 47, 693-794.
  2. Genchi, G.; Sinicropi, S. M.; Carocci, A.; Lauria, G.; Catalano, A., Mercury Exposure and Heart Diseases. International Journal of Environmental Research and Public Health 2017, 14.
  3. Edelstein, M.; Ben-Hur, M., Heavy metals and metalloids: Sources, risks and strategies to reduce their accumulation in horticultural crops. Scientia Horticulturae 2018, 234, 431-444.

Image copyrights:

  • Fig 1. elpais.com
  • Fig 2. reddit.com
  • Fig 3. inspiredimperfection.com
  • Fig 4. wikipedia.org
  • Fig 5. www.nih.gov