Knowing the Dangers

The Mad Hatter in Lewis Carroll’s Alice in Wonderland is a caricature of hat makers who cured felt in pools of mercury, leading to symptoms such as emotional instability like that displayed by the character in the book. Unlike hat makers of that time period, lab managers today know how dangerous mercury can be and that proper safety measures must always be taken when working with equipment or compounds that may contain this substance.

Being aware of the way mercury enters the system and what it can do is a good first step to lab managers in keeping themselves and their workers safe from this element.

How Mercury Poisoning Occurs

When you work in an environment contaminated with mercury, you quickly absorb the toxic metal. All forms of mercury are toxic. Mercury poisoning can result from inhalation, ingestion, and injection or absorption through the skin.

Elemental mercury poses a health hazard because it is volatile. Elemental mercury, as a vapor, penetrates the central nervous system, where it is ionized and trapped, attributing to its extreme toxic effects. Elemental mercury is not well absorbed by the gastrointestinal tract; therefore, when ingested, it is only mildly toxic.

Mercury metal and mercury compounds are highly hazardous if inhaled or if they remain on the skin for more than a short period of time. Dimethyl mercury rapidly penetrates intact skin. Depending on the type of mercury and dose, symptoms may appear relatively quickly or take a number of years to show up.

Listed below are various forms of mercury and their effects and hazards:

Mercury vapor (i.e., elemental mercury) is readily absorbed through inhalation and can also pass through intact skin. After absorption, elemental mercury is carried by the blood to the central nervous system where it is oxidized. The oxidation product is what causes injury. Persons heavily exposed to elemental mercury will develop worsening tremors of the hands, shyness, insomnia, and emotional instability. Mercury vapors can reach very high levels when the liquid is heated. Such levels will cause adverse effects in humans almost immediately if workplace controls are inadequate. Some equipment, such as thermometers, vacuum pumps, manometer, and sphygmomanometers, may contain mercury.

  • Mercury salts (e.g., mercuric nitrate) are highly toxic and corrosive. They accumulate mostly in the kidney, causing renal damage.
  • Organo-mercury compounds attack the nervous system, causing tremors, impaired vision and hearing, and paralysis. These compounds may also cause birth defects. The effects from exposure to excessive levels of airborne mercury or skin contact with mercury compounds may not be noticeable for months or years.
  • Mercury fulminate, Hg(ONC)2, is a detonator used in explosives.
  • Mercury(II) oxide is an oxidizer. It can cause organic materials to start burning in the same manner as any strong oxidizer.
  • Dimethyl mercury, an extremely toxic material, is a colorless, sweet-smelling liquid. It is a severe fire hazard, with a flash point of -4°C. This material rapidly penetrates the skin, resulting in severe exposure from very minor quantities, which can be fatal. Extreme caution is required when working with this material and when selecting personal protective equipment (PPE).