Poisoning by a mercury thermometer

aka Toxicology Conundrum 002

Your next patient is an 80 year old man suffering from Alzheimer’s dementia. He was brought into the ED by his wife and daughter who are his care-givers. He had a recent catheter-associated urinary tract infection and his daughter was checking his temperature orally with a mercury thermometer 30 minutes previously. Unfortunately he bit down on the thermometer. The thermometer broke and some mercury spilled onto the floor. The daughter believes that the amount spilled is less than 1 mL. The patient is asymptomatic.

Questions

1. What is the risk assessment for the patient in this case?


The patient’s mercury exposure is benign.

Accidental oral or skin exposure to elemental mercury does not need medical assessment unless the patient is symptomatic. Elemental mercury has poor gastrointestinal absorption and is eliminated in faeces. The volume of mercury in a thermometer is very small.

However – other factors to consider:

Increased absorption of elemental mercury may occur if the patient has an abnormal gastrointestinal mucosa, or delayed faecal elimination due to an ileus or a gastrointestinal perforation. There have been reports of mercury getting trapped in the appendix, but in the absence of appendicitis or features of toxicity no intervention is required.

Vomiting of orally ingested elemental mercury may lead to aspiration. This is higher risk as aerosolized or vaporized elemental mercury is well absorbed from the respiratory tract.

2. Describe the investigations and management required for the patient.

Decontamination:

  1. Remove contaminated clothing and discard in sealed plastic double-bag (do not put in a washing machine or dryer as they will become contaminated).
  2. Removal of mercury from the skin – remove all jewelry (mercury forms a gold amalgam) and wash with soap and water.

Assess for traumatic injury to the mouth from broken glass.

Assuming there is no injury, no further investigation or management is required.

X-ray may reveal mercury…

mercury poisoning

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3. What is the risk assessment for the care-givers who live with the patient?

If the elemental mercury is not adequately cleaned up there is the possibility of ongoing vaporization. However the volume of mercury in a household thermometer is so small that the risk of chronic mercury toxicity due to inhalation is probably negligible.

4. How should the spilled mercury be cleaned up?

In Australia, the Local Government Environmental Health Officer can be contacted for advice about cleaning up spilled mercury. Amounts of elemental mercury greater than ~ 2 teaspoons should be dealt with by professionals.

Clean up advice:

  • Clear the room of people and pets.
  • Open windows and doors to ventilate the room.
  • Turn off heating or cooling.
  • Clean up as thoroughly as possible as ongoing release of vapour is a risk.
  • The cleaner should remove jewelry (forms gold amalgam).
  • Ideally remove and discard contaminated carpet or tiles.
  • Suck up droplets with an eye dropper or similar device.
  • Avoid brooms (breaks up droplets).
  • Avoid vacuums (agitation and heating promotes vaporization) – if a vacuum cleaner has been used the tubing, filter and bag will need to be replaced. It is best discarded or decontaminated by a professional.
  • Treat the remaining mercury (e.g. in cracks between tiles or on carpet) with a calcium polysulfide slurry (mix 1 part lime with 1 part powdered sulfur in water), leave overnight, and then vacuum.
  • Place any residue in a sealed plastic bag and discard as per local authority requirements.

References

  • Murray L, Daly FFS, Little M, and Cadogan M. Chapter 3.44 Mercury; in Toxicology Handbook, Elsevier Australia, 2007. [Google Book Preview]
  • Caravati EM, Erdman AR, Christianson G, et al. Elemental mercury exposure: an evidence-based consensus guideline for out-of-hospital management. Clinical Toxicology 2008 46(1):1-21. [Pubmed]
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