Testing for Safety: Heavy Metals and Pesticides in Museum Collections

Are there hidden dangers in your museum collection?  When it comes to health and safety sometimes you can’t even see the most dangerous elements.  Did you know that from the 1700’s to the 1970’s heavy metals, such as arsenic and mercury, were used in museums as active pesticides to protect their artifacts, especially those made from organic materials?  Organic materials are those which were originally living such as textiles, baskets, leather, and other materials very commonly found in Native American collections.   As we always say, every material on earth will eventually return to dust, but organic materials are much more susceptible to this deterioration and are therefore in greater need of protection from environmental factors especially insect damage.

Cheryl Podsiki testing beads on a bandolier bag

                The practice of treating collections with heavy metal pesticides was extremely common in the United States, Canada and Europe.  Arsenic (in many forms such as arsenic trichloride, orthoarsenic acid, potassium arsenate) and mercuric chloride could be applied in many manners.  It could be used as a powder, as a soap, or as a solution.  It could be rubbed, brushed, sprayed or sprinkled on.  This practice was extremely successful.  Bugs and pests stayed clear of artifacts that had been treated with this type of material.  These pesticides remnants on artifacts today remain potent and extremely hazardous to all bugs, pests, and not surprisingly to museum employees and community members who have contact with the artifacts.  As a rule of thumb, I consider any ethnographic or Native American artifact older than 100 years that is in extremely good condition with very little pest damage highly suspicious for dangerous pesticide content.

XRF computer display with turtle shell mask

                How can you detect pesticide residues on your collection?  I carefully examine any older artifact that I find in suspiciously good condition.  Loose white powders found on the surface of the artifact or in the storage materials can raise red flags.  At the Ah-Tah-Thi-Ki Museum we were lucky enough to have Cheryl  Podsiki, a Conservator  from New York State who specializes in Contaminated Objects, come to test 29 of our objects as a short survey into the pesticide presence at the museum.  Cheryl works with a hand held X-ray fluorescence (XRF) Elemental analyzer called a Tracer III-V made by Bruker-AXS .  The XRF machine uses a completely non-invasive and non-destructive technique that bounces x-rays off of the surface of an artifact in order to identify the organic elemental content of the surface of the artifact.  Twenty eight of the artifacts chosen for the sample testing were selected from the Speck Collection, while the last one was a bandolier bag that is going into an upcoming exhibition at the museum.  Frank G. Speck, who was the originally collector of these objects was a professor at the University of Pennsylvania.  It is known that the UPenn Museum used arsenic as a pesticide during the years at the beginning of the 20th century when the Speck Collection was stored in their facility.  Only one of the twenty nine artifacts selected for this study clearly had arsenic applied as a pesticide.  The feathers on this blow dart are in extremely good condition without any insect damage present, so the visual evaluation corresponds to the scientific results.

                My favorite moment during the testing with Cheryl was when we examined our lab mascot, Vlad the Bear.  Vlad is a stuffed Maine bear that lives in the conservation lab.  Since he is from the state of Maine, he does not fall under the mission of our museum and is not an accessioned artifact.  We keep him in front of the observation hallway window to entertain the school children that come through the hallway.  Taxidermy animals are also very likely to contain heavy metal pesticides.  In fact, these pesticides were used inside the stuffing of the animals as late as the 1970s, so be careful with those stuffed dear heads in your dens!  For the most part Vlad tested negative for heavy metals, but one small spot on his paw where the skin is very thin tested faintly positive for mercury.  It is likely that there is mercury inside his stuffing, but as long as he stays in good condition with proper handling he is safe to stay in the lab.

XRF testing of Vlad the bear.

                What can you so about pesticide content within your collection?  Sadly, the answer is very little.  There are no common treatments for the removal of pesticides from museum artifacts, although conservation scientists across the world are currently researching methods.  At this point we vacuum the surface of pesticide containing artifacts with a HEPA filter vacuum to remove any loose powders, seal the artifact in a bag to prevent cross contamination between artifacts, and clearly label all records and the artifact storage itself.  Keep in mind that you need to ingest the pesticides for them to cause major damage.  If safe handling and storage practices are followed, you should not be at risk from pesticides within your collection.

Corey Smith, Conservator, Ah-Tah-Thi-Ki Museum


One thought on “Testing for Safety: Heavy Metals and Pesticides in Museum Collections”

  1. I interned in the Conservation lab of Harvard’s Peabody Museum and this is a huge problem…so many nasty chemicals were used in the past that make handling artifacts potentially dangerous. It was always a struggle to keep visitors mindful of the dangers.
    Great post!

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