ASK ELi: Can Mercury Hurt?

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Friday, February 20, 2015, 9:36 am
By: 
Aron Sousa, M.D.

Editor's note: This week's "Ask ELi" connects to our ongoing series, The Mercurial Trail, which traces what happened during and after about 1 to 1.5 pounds of mercury were spilled at the East Lansing Wastewater Treatment Plant in November 2013. This column addresses a question we've been getting in response to the series.

The question asked of ELi this week is: Could 1.5 pounds of mercury hurt a person?

As with so much of life, the answer is, it depends. It depends on the person's relationship with the mercury. At the least a person can be pretty sure that she or he will be more afraid of the mercury than mercury is afraid of them. 

Mercury in a well-maintained manometer (pressure gauge) or barometer (atmospheric pressure gauge) or thermometer or thermostat is not dangerous. The mercury will sit in a well-maintained device for decades and won't cause harm. Many doctor’s offices have wall mounted mercury sphygmomanometers (blood pressure gauges) that date back to the 1950’s, 1960’s, and 1970's, and the mercury in those devices is not hurting anyone.

Mercury on the lam is more dangerous. Like most things unfettered, mercury on the run is more likely to cause trouble.

Beads of mercury themselves are not very dangerous at room temperature. The liquid metal form of mercury is not well absorbed if eaten and at room temperature, the beads of mercury give off very little vapor. That’s why beads of mercury were still in the wastewater plant and the city truck when the health department was called four months after the spill.

The health risk in places like the wastewater treatment plant is small amounts of uncorralled mercury accidently ending up somewhere hot where it would vaporize. It does not take much mercury to contaminate a lot of space.

Many of us have played with beads of mercury on a tabletop, and can picture a bb-sized bead of mercury, so I’ll use that as an example. If all of the mercury in a bb-sized (4.5mm) bead of mercury was vaporized, that bead contains enough mercury (about 0.65 grams) to contaminate all of the air in 380 houses (2000 square foot, one story houses) to the MIOSHA safety cut-off of less than 3 micrograms (0.003mg) of mercury per cubic meter of air.

That same bead could contaminate 23 houses to the MIOSHA cut-off level recommending inspectors “Evacuate occupants. Do not enter” (more than 50 micrograms (0.05mg) mercury/cubic meter).

Clearly, this example is a bit extreme. It is not really possible to get all of the mercury in bb-sized bead vaporized and distributed to all of those houses. But if beads of mercury can find their way from a building to a truck, as happened at the wastewater plant, then the mercury can find its way to a boiler room, or heating vent, or steam pipe, where it may be hot enough to vaporize mercury fast enough to contaminate a local area.

Nearly all mercury vapor poisoning comes from occupational exposures, and those tend to be long-term exposures from heating or vaporizing mercury over long periods of time.

It’s not possible to say what the risk from this mercury spill has been or will be, because the cleanup did not collect all of the mercury. But, a pound and half of mercury is more than enough to hurt someone.

 

Aron Sousa, M.D., is a board-certified internist and Senior Associate Dean for Academic Affairs at MSU's College of Human Medicine. (Disclosure: He is also the spouse of Alice Dreger, who has been reporting The Mercurial Trail.)

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