Elemental (metallic) mercury and all of its compounds are toxic. Excessive exposure to this metal can lead to permanent damage to the brain and kidneys. Organic compounds of mercury such as methyl mercury are considered the most toxic forms of this element. Exposure to very small amounts of such compounds can cause devastating neurological damage and even death. This was the case of Karen E. Wetterhahn, a Dartmouth College Chemistry professor who died because of liquid mercury poisoning.
The tragedy happened in 1997, in Hanover, New Hampshire. The professor was a specialist in toxic metals. However, she was poisoned in her own laboratory by a few drops of the rare, extremely toxic compound dimethyl mercury. The compound is a synthetic, colorless liquid used almost exclusively as a reference standard in a particular type of specialized chemical analysis.
Ironically, the professor was investigating the toxic properties of another metal, cadmium. She was only using the dimethyl mercury as a reference for her instrumentation. Little did she know that this compound would kill her. The dimethyl mercury accidentally penetrated her protective glove when it spilled. However, symptoms of the mercury poisoning did not start to develop until 6 months after the accident.
At that time, the poisoning was already irreversible. The professor became ill out of the sudden and was hospitalized. However, she rapidly went into a coma and died the same month she went to the hospital. This tragedy perfectly reflects how dangerous is mercury and all of its compounds.
As a result of this accident, international safety standards for gloves and other protective equipment needed when handling this element were revised. Moreover, a movement to eliminate the use and production of this deadly mercury form began shortly after the professor’s death.
Even though this is an extreme case, caused by the deadliest mercury form, liquid mercury is still extremely toxic and should always be handled with caution.
Another liquid mercury tragedy happened in Iraq, between 1971 and 1972, when this country saw a major epidemic. Back then, 6,530 people were hospitalized and about 500 lost their lives because of this metal. Other cases of mass poisoning have also been registered in Japan and Canada, most of them involving methyl mercury from consumption of fish from contaminated waters.
In fact, most people are exposed to mercury by eating fish containing mercury. How is this possible, though? Here is how this element accumulates at the highest levels of the food chain and eventually becomes concentrated in fish:
- Methyl mercury in the water and sediment is taking up by tiny animals and plants called plankton.
- Minnows and juvenile fish consume large plankton quantities over time.
- Larger predatory fish eat large quantities of smaller fish, therefore accumulating methyl mercury in their tissues.
- Fish are caught and eaten by animals and humans, who slowly start to accumulate methyl mercury in their tissues.
The larger and older the fish, the higher the chances of having high methyl mercury levels in their bodies. Unfortunately, there is no way of cleaning or cooking the fish in order to reduce the amount of mercury in a meal, which is why people should be particularly careful when it comes to this matter.