Why Is Mercury Dangerous to Humans?

mercury vapors detrimental to nervous system, lungs, kidneys

By Jonny Lupsha, Wondrium Staff Writer

Mercury has been used for so long its discoverers are unknown. It’s been found in Egyptian tombs as old as 1500 BCE and was once believed to have healing properties. Unfortunately, it’s also particularly toxic.

Shiny Mercury drops on a pit black background
On the periodic table of elements, Mercury has the symbol “Hg” and its atomic number is 80. Photo by Ventin / Shutterstock

The element mercury occurs naturally in rocks in the Earth’s crust. It gets its symbol, Hg, from its former name hydrargyrum. This comes from the Greek words hydor, meaning “water,” and argyros, meaning “silver.” It has had a wide range of uses in society, from thermometers to fishing lures and from nuclear reactor coolant to hydraulic gold mining.

In the modern world, mercury is commonly associated with its toxic properties. Last week, the Environmental Protection Agency (EPA) announced that it would further restrict permitted emissions of mercury from coal-fired power plants in order to better protect public health. This restriction would further the EPA’s Mercury and Air Toxics Standards, which have already reduced mercury emissions by 90% since its implementation in 2012.

Why is mercury so bad for us? In his video series Understanding the Periodic Table, Dr. Ron B. Davis, Jr., Associate Teaching Professor of Chemistry at Georgetown University, discusses what makes mercury such a danger to our health.

Why Is Mercury So Toxic?

Mercury, in its liquid state, certainly causes health problems.

“Those health problems are thought to be linked to mercury’s chalcophile or ‘sulfur-loving’ nature,” Dr. Davis said. “Mercury, much like its famously poisonous neighbor, thallium, associates strongly with sulfur atoms in critical enzymes in the body, disrupting our biochemistry and making us sick.”

Due to mercury’s similarities with thallium, acute mercury poisoning can sometimes be treated with selenium, which is also a treatment for thallium poisoning. Selenium is another metalloid that’s far less toxic. It can also “impersonate” sulfur, attracting mercury and keeping it tied up so mercury won’t cause problems for our biochemistry.

“Mercury is also responsible for the famous trope ‘mad as a hatter,'” Dr. Davis said. “This expression originated in 1830s England, where it was commonly known that those in the hat-making profession seemed to have a high incidence of mental illness in their later years. At the time, felt production for hats involved a process known as ‘carroting,’ in which fur was matted down and a pleasant orange color was imparted to the material.”

One common chemical used in carroting was mercurous nitrate. Mercurous nitrate is a salt of mercury which proved fatal when inhaled on a daily basis over the course of one’s career in the hat-making business. Over the course of the 20th century, it was increasingly banned in various countries around the world.

“Yet in spite of its known dangers, elemental mercury’s other properties have continued to make it a widely used material, even in more recent decades,” Dr. Davis said. “Mercury used in thermometers can measure temperatures as low as minus 39° Celsius before the mercury freezes. Electrical switches used the movement of liquid mercury to create or interrupt a circuit.”

Americans living downwind of coal power plants will likely be glad to hear about the new EPA regulations, though coal plant owners may not share their exuberance.

Understanding the Periodic Table is now available to stream on Wondrium.

Edited by Angela Shoemaker, Wondrium Daily