Home Podcasts THMG018 – Mercury Incidents

THMG018 – Mercury Incidents


In this episode, we cover a listener’s request for information on responding to incidents involving mercury.

Complete Show Notes

3:05 What is Mercury and Where Do We Find It?

  • Commonly known as quicksilver
  • One of only two elements on the periodic table that’s a liquid at room temperature (and the only metal to do so)
  • Alchemists considered mercury to be the first matter from which all metals were formed. They believed that different metals could be produced by varying the quality and quantity of sulfur contained within the mercury. The purest of these was gold, and mercury was used in attempts to transmute the base (or impure) metals into gold
  • Mercury is commonly found in thermometers, barometers, blood pressure cuffs, float switches, mercury switches, mercury relays, fluorescent lights, and HVAC gauges
  • You’ll also find it in older thermometers – they’re no longer manufactured in the U.S., but they’re still sold here (particularly in immigrant communities)

5:40 Chemical and Physical Properties of Mercury

  • Mercury’s boiling point is 629.88 degrees K (356.73 degrees C), which is the lowest of any metal; it’s freezing point is -37 degrees F (so don’t use it for a thermometer in cold storage)
  • It has a unique electron configuration where electrons fill up all of the available subshells – this configuration strongly resists electron removal, making it similar to the noble gasses
  • Mercury reacts with strong oxidizers (like nitric acid) and dissolves many other metals (like gold and silver) to form amalgams
  • Amalgams are alloys of metal (or mixtures of metal) – mercury can make this alloy with most metals
  • Inorganic mercury (in the form of mercuric nitrate) was commonly used in the production of felt for hats – workers who came into contact with vapors from this process often worked in confined areas, which was detrimental to their health
  • Elemental mercury isn’t combustible, but may be found in compounds that are flammable (or even explosive)
  • It reacts with acids, like nitric acid or any mineral acid
  • Slightly volatile at room temperature, but with a vapor pressure of only .002 millimeters – this is 12 times less volatile than water; significantly more volatile when heated
  • However, it releases a lot of vapor into the air – considering its toxicity, those small amounts of vapors can do a lot of damage over a long period of time
  • Elemental mercury is placarded as a Corrosive 8 – interestingly, though, many of the compounds containing mercury are classified as 6.1
  • Includes mercuric arsenate, mercuric chloride, mercuric nitrate, mercuric potassium cyanide, mercury acetate, and mercury-based pesticides (liquid versions of mercury pesticides are 3.1 if flammable)

15:00 Effects of Mercury on Humans

  • Water-soluble forms of mercury (like methyl mercury or mercuric chloride) are dangerous – these are the kinds of mercury we’re concerned with when we hear about contaminated fish
  • The addition of the methyl family group allows the mercury to be taken in through the digestive tract, making it an ingestion hazard
  • Case studies have shown effects such as tremors, impaired cognitive skills, and sleep disturbances in workers exposed to even low concentrations of mercury
  • Acute exposure (4-8 hours) can result in chest pain, dyspnea, cough, hemoptysis, impairment of pulmonary function, and interstitial pneumonitis
  • Like many chronic neurotoxins, the effects are much more profound on the young

17:05 Considerations When Metering Mercury

  • Mercury and most of its compounds are extremely toxic and should be handled with care – in cases of spills, there are specific cleaning procedures you have to use to avoid exposure and contain the spill
  • When mercury hits the floor, it shatters into thousands of little balls and doesn’t really stick to anything – the momentum of hitting the floor sends it rolling everywhere, so you’ll have to make a full search
  • Your responsibility is to mitigate property and life hazards by removing what you can get to
  • Mercury’s viscosity is similar to water, so if you see water, mercury could be there
  • Mercury beads can get in floor cracks and between cloth fibers – this shapes our operation, time, and the decisions we make
  • Our goal is to reduce the exposure until an environmental cleanup crew can get to the scene – especially true in business and industry

24:45 How We Meter Mercury

  • If you know mercury has spilled in an area, enter with caution – don’t step in the product and get it all through the scene
  • Always monitor both low and mid-range – meter low to find the vapors and mid-range since this is our breathing space

26:15 Mercury Cleanup

  • You don’t really need to meter during cleanup, unless you’re using a vacuum
  • The more you clean with the meter, the greater the chance of contamination with the meter – the meter is easy to decon, but the bag isn’t
  • When you’ve finished cleanup, do a quick sweep of breathing space – then, open the windows and vent mechanically (if possible)
  • Then, close the windows, search again, and compare your results – if your readings quickly get high, you’ll have to search out additional beads
  • If you’ve exhausted all of your options and are unable to locate the source, you may need to remove items or forbid reoccupation of an area until a cleanup crew shows up or it’s certified clean
  • Always monitor people and property – the best way to meter property is to place it in a bag and then meter the inside of the bag (works well for hands and feet, too)
  • If you get a hit on property, throw it away; if you get a hit on people, they need to be washed and then rechecked
  • Every area will have different regulations for the amounts of mercury that can be thrown away or recycled – check your local regulations

31:10 Choosing Your PPE

  • Use a Level B suit with full SCBA
  • Respiratory protection is a MUST – it can build up over the years, so always wear your masks
  • If your bunker gear is contaminated, it should be discarded – boots should be metered and decontaminated as well
  • Keep an eye out for mercury in the traps of houses, sinks, and toilets

34:40 Safety and Mercury

  • From NIOSH: “Elemental mercury is toxic primarily through the inhalation of mercury vapors. It is slowly absorbed through the skin, although it may cause skin and eye irritation. Elemental mercury droplets may be absorbed through eye contact. Ingestion is not an important route of acute exposure, as almost no elemental mercury is absorbed through the gastrointestinal tract”
  • NIOSH time weighted average (TWA) of mercury vapor is 0.05 mg/m3 (skin)
  • Milligrams is a measure of mass and m3 stands for meters cubed
  • NIOSH ceiling is 0.1 mg/m3 (skin)
  • OSHA PEL ceiling is 0.1 mg/m3
  • ACGIH TLV: 8-hour TWA is 0.025 mg/m3
  • NIOSH ILDH is 10 mg/m3

39:00 Decontamination and Removal Techniques

  • Decontamination – a solution of detergent and water (with a pH value between 8 and 10.5) should be used with soft brushes to remove contamination from your PPE
  • There are several different ways to dispose of mercury
  • Pumping
    • Two main types of pumps – handheld mechanical pumps and suction style pumps
    • Handheld mechanical pumps suck in the mercury and place it in a small container – cheap and easy to discard and don’t need to be plugged in, but using them for hours can be tiring
    • Suction style pumps put the product into a jar and has a hypodermic needle-like tip to get into small areas – great for really clean areas, but can clog easily if there’s dirt or small debris
  • Vacuuming
    • Similar to wet/dry vacuums, but also very different – since vapors are a major concern, these vacuums have layers of filters to remove vapors
    • They can clean large areas at once, but they also gas a lot and leave you with a lot of material to discard
  • Pipette
    • These do a great job, but they’re very time-consuming because each action requires you to move the pipette over a jar and release
  • Powdered amalgam
    • This also works well – all you have to do is sprinkle the powder (which grabs the mercury and holds it together) and sweep it up
    • Cons: the powder looks like mercury and is small enough to get into small areas
  • Duct tape
    • Wrap duct tape around your hand with the sticky side out and pat the ground – the mercury sticks to the tape

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