Nowhere on earth has the power to inspire awe and wonder in the endless outcomes of evolution than a natural history museum. It’s a bold claim, but where else can you find over 500m years of biodiversity? 

In a good museum, visitors can literally walk around open mouthed in astonishment at seeing the biggest animals that ever lived – whales and dinosaurs – and specimens showing extraordinary biological processes, like how a two-metre tall kangaroo is born the size of a jelly bean.

But lurking within these wondrous collections are chemical legacies of the ways they were prepared and preserved that can make museums a risky place to work. Here are four of them…

1. Arsenic

One of the main challenges of caring for a biological collection is that everything is edible, and we have to work hard to ensure that insect pests like clothes moths, carpet beetles and silverfish don’t nibble our specimens out of existence. Unchecked, they can turn invaluable objects into dust. When it comes to taxidermy and skins, the practice until recently was to coat the inside of the skins with arsenic soap or other poisons such as heavy metals or even strychnine and cyanide. 

 

A taxidermy ocelot at the University Museum of Zoology. Image: University of Cambridge/Chris Green

While these are extremely effective at killing pests, they have the potential to make us very ill. If a specimen is old but looks in good condition, it’s likely to have been treated in this way. Short story: don’t stroke a museum skin unless you know for sure it’s poison-free.

2. Formalin

Another mainstay of museum collections is animals preserved in jars of fluid. The first step in preparing these specimens is called ‘fixation’, which keeps the animal in suspended animation by halting the decomposition process at a cellular level, causing cross-links between molecules (including DNA). Formalin is a solution of the toxic and carcinogenic gas formaldehyde.

 

Preserved fish collected by Charles Darwin on the voyage of the Beagle at the University Museum of Zoology. Image: University of Cambridge/Chris Green

3. Alcohol preservative

The second step in preparing fluid specimens is to store them permanently in a preservative, and the most common is a solution of ethanol. Vodka, gin, rum, brandy etc. are all solutions of alcohol, and indeed sailors on historic voyages of discovery would find that the naturalist on board had commandeered their booze rations to preserve an important specimen. 

Today, we tend to use stronger solutions of ethanol – at 70% – as it is more effective. Ethanol is obviously consumable, so why is this in a list of dangers? The ethanol museums use is called industrial methylated spirits, or denatured alcohol: it has a tiny bit of methanol added. 

The toxic methanol has no beneficial properties for preservation – it’s there simply to stop museum workers from drinking it (and means that it isn’t subject to the high tax rates of alcoholic drinks).

4. Radioactivity

Geological collections come with a whole different suite of hazards. Many minerals are inherently poisonous, or can break down in museum conditions to release toxic gasses. Others are naturally radioactive. If you’ve got a lump of uranium ore in your collection, that’s a pretty obvious risk, but there are also certain locations that a lot of fossils come from that have relatively high levels of radiation. 

 

Museums have to be careful about how these are stored as once we lock these fossils up in a museum drawer or cabinet, the concentration of radioactivity in that sealed environment builds up over time, releasing a dangerous cloud once the drawer is eventually opened.

I should say that museums are pretty clued up on managing these risks, and there is no danger to the visiting public. Just don’t lick anything.