Elementary mercury, sometimes called quicksilver, was once thought of as a supernatural, health-boosting, power-giving fluid. Mesmerized by its strange physical characteristics and the notion that it could grant him immortality, the first Chinese emperor, Qin Shi Huang, was buried in a mausoleum which is thought to feature an underground moat full of it.
Mercury will do anything but let you live forever, mind you: it’s a furiously toxic substance, one that can make you sick in numerous ways. As one tragic laboratory experiment clearly demonstrated, one particular mercury compound can kill you if you simply get a few drops on your hand.
Going by the chemical symbol, elemental mercury, Hg – meaning hydrargyrum, from the Greek meaning “water silver” – is a curiously heavy metal that’s liquid at room temperature. It’s quite volatile, and when left out, it can slowly change form a liquid into a gas.
Any exposure to it is potentially dangerous, particularly if you’re a young infant or you’re pregnant, but the dose, rate, and type of exposure will determine whether you’ll be merely afflicted with sickness, or you’ll be visited by the Grim Reaper. You also get various types of mercury – elemental, inorganic, and organic – and the type you’re exposed to can determine which fate befalls you.
Elemental mercury is the type you’ll find in old thermometers. Inorganic mercury generally appears in a solid state, and takes the form of more complex chemical compounds involving chlorine, sulfur, or oxygen. Organic mercury, which is synthesized by certain microorganisms, comes in methylated or ethylated forms.
Methylmercury, absorbed by a variety of aquatic critters, is one of the primary forms of mercury exposure to the general population; inorganic mercury found in several foodstuffs and in various industrial workplaces, and elemental mercury vapors that escape during industrial processes, make up the other two.
When it comes to organic mercury, it’s worth pointing out that ethylmercury is quite different from its deadlier chemical cousin. As noted by the World Health Organization: “Ethylmercury is used as a preservative in some vaccines and does not pose a health risk,” as it does not accumulate in the body and quickly breaks down.
Methylmercury is dangerous, however, and dimethylmercury is a beast. Just look at the case of the famed, deeply unfortunate chemistry professor from Dartmouth College who, back in 1996-7, spilled just a few small drops of dimethylmercury onto her lab glove during a fairly routine experiment.
The colorless substance passed through the latex immediately and was rapidly soaked up by her skin. It’s preferentially absorbed into fatty tissues thanks to its high lipophilicity, which means organs, from the kidney to the heart, quickly soak it up. It also crosses the blood-brain barrier, mostly in the form of elemental mercury. It is also broken down into methylmercury in the liver, which causes oxidative stress to tissues, and forms complexes that accelerate cell death.
According to the Centers for Disease Control and Prevention (CDC), unlike other forms of mercury poisoning, symptoms of any organic mercury poisoning are not often manifested straight away and can take weeks to emerge. The professor took 10 months to die, roughly half of which she spent comatose.
Headaches, the constriction of your visual field sometimes leading to blindness, and variations on deafness are commonly observed as the metal begins to disrupt the synaptic connections within your body. You may initially experience this disruption and damage as pins and needles (paraesthesia), and difficulty with motor control, a lack of balance, and speech difficulties (dysarthria) are also common symptoms as your central and peripheral nervous systems are corrupted.
Dimethylmercury was actually used as a fungicide, but, according to ScienceMag, it was outlawed in the 1970s after it killed 600 people in Iraq that ate contaminated wheat.
The symptoms of acute or chronic inorganic mercury compound poisoning aren’t exactly marvelous either. These include, but aren’t limited to, headaches, high blood pressure, chills, fever, chest tightness, coughs, and hand tremors. Skin discoloration and peeling can also be expected.
If you’re unlucky, you’ll also experience ejections of potentially bloody digestive fluids and other grim remnants from your upper and lower extremities, along with associated abdominal cramps.
Fancy exposing yourself to a larger amount of inorganic mercury in one go, perhaps through an industrial accident? You might go into hypovolemic shock as you profusely bleed from within, while organ failure, and possibly death, are around the corner. Even if you survive, you’ll have lasting skin, kidney, and neurological damage, as well as psychiatric disturbances including memory loss and depression.
Unlike organic mercury, however, inorganic mercury has a limited ability to cross cell membranes due to its low lipophilicity, so it’s arguably less dangerous in similar doses.
The effects of elemental mercury's acute toxicity are somewhat similar, although perhaps less deadly and vomity. It’s far more hazardous as a vapor, where the metal can get through blood-brain and placental barriers, as well as cell membranes, with ease.
You shouldn’t worry about breaking your mercury thermometer, though. The small amount of elemental mercury within is unlikely to be enough to cause major issues, but do be careful cleaning it up.