Don't Drop That Thermometer

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Despite the advent of digital thermometers, there are still plenty of mercury-filled ones around. It's not the shiny silver metal that's dangerous when a thermometer breaks, but rather the vapour from the mercury. The erratic behaviour of English hatters was due to their exposure to the hot mercury compounds used in treating rabbit fur. This may have inspired the "Mad Hatter" character in 'Alice in Wonderland.'

If you break a mercury thermometer, don't run for the vacuum cleaner. Vacuuming a mercury spill breaks the liquid metal into tiny droplets. Then the vacuum exhausts mercury vapour into the air.

As undesirable as it is to breathe mercury vapour, the most serious problems arise when mercury is combined in certain carbon compounds. We first realized this danger in the 1950s from some cases in Japan. In the fishing village of Minamata, cats who had been eating fish began to stagger and collapse. Local industry had been discharging used mercury into the ocean. Since mercury is not soluble in water, they thought it would just sit there harmlessly. But time and micro-organisms converted the shiny elemental mercury into a soluble form, in a highly toxic substance called dimethyl mercury.

So next time you break a mercury thermometer, get the spill into a plastic bag and take it to a toxic waste disposal centre.