SIOUX FALLS, S.D. (KELO) — There’s a good chance that taxidermy mounts made before 1980 contain arsenic, based on the materials used to preserve the animals.

Most of the roughly 150 mounts at the closed Delbridge Natural History Museum at the Great Plains Zoo have tested positive for arsenic, city officials said during a Tuesday news conference about the collection. Zoo and city officials decided to close the museum on Aug. 17 after learning the results from recent tests.

Arsenic has been detected in other taxidermy mounts in the U.S. and Europe. Arsenic is linked to cancer, cardiovascular disease and other illnesses.

Arsenic is often the general term for the chemical but it is mainly found in two forms, inorganic and organic.

Inorganic arsenic is a known human carcinogen, according to a 2015 report about Managing Arsenic and Asbestos by Birmingham Museums of the United Kingdom.

Inorganic arsenic is a compound that does not contain carbon and is highly toxic, according to the McGill Office for Science and Society of Canada.

Organic arsenic is attached to carbon.

Inorganic arsenic is generally more toxic than organic arsenic, according to the Centers for Disease Control (CDC).

The toxicity of the arsenic used in taxidermy is what has raised concerns about collections with animals before 1980.

Arsenic in museums has been the subject of multiple research and topic discussions since at least 1996.

The American Alliance of Museums is hosting a webinar called Arsenic and Collections on Sept. 6.

Even mounts in the National Park Service have been tested for arsenic.

The NPS recommends testing taxidermy mounts for arsenic. “NPS staff should treat all natural history specimens prepared before 1980 as if they may contain arsenic or other toxic compounds unless the specimens are confirmed to be safe,” the NPS said in its September 2000 Conserve O Gram bulletin.

Visitors to natural history museums or similar may still see taxidermy mounts. Some of those could be pre-1980 while others were assembled later when arsenic was not used in taxidermy.

How museums have handled arsenic-contaminated mounts is similar, but still varied.

Many have placed displays out of the reach of the public; others have enclosed them in glass or removed contaminated mounts.

“Fully encasing the taxidermic object in a sealed display case can be a good way to protect staff and visitors. This would help reduce the amount of arsenic that might become airborne if the item must be moved and would also eliminate the need to touch the artifact directly,” said an August 2020 article by the Indiana Historical Society.

“From our research, the best practice is once you detect arsenic, you remove the specimen, wrap it in plastic and remove from exhibit. Or you put them in glass. With 80% positive for arsenic and the lack of glass, we really had no other choice at that point in time,” Great Plains Zoo Chief Executive Officer and President Becky Dewitz said at a Tuesday news conference on the Delbridge collection and Aug. 17 closure.

A March 2020 post from Cardiff University discussed how the public should approach taxidermy mounts.

“The trace amounts of chemical you will be exposed to through minimal, sporadic, handling of taxidermy are unlikely to cause any health issue. So, the risk of a one-off handling is small, but still present, and therefore is not advised,” an official with Cardiff University said in a March 2020 post about arsenic contamination.

“Under no circumstances should any taxidermy mount be used for ‘hands-on’ demonstrations for children or adults before it has been tested for the presence of arsenic, the NPS said in its handbook.

“Any exhibited specimens from this period (pre-1980) should be enclosed in an exhibit case,” NPS said in 2000.

The Collections Trust of Norfolk Museums and Archeology Services and SHARE Museums East also advises that when arsenic or similar hazardous material is identified in a collection to “make sure that no potentially hazardous objects are accessible to the public in open displays, handling collections or school boxes.”

Multiple research reports and guidelines recommend regular testing for arsenic because the chemical can migrate.

The NPS, for example, recommended in 2000 testing every two to three years.

The GPZ said in an email to KELOLAND News that “Neither the zoo nor the city has records of any previous chemical testing on the Delbridge Museum of Natural History.”

The GPZ CEO Becky Dewitz started as CEO and president in October 2020. Sioux Falls attorney C.J. Delbridge bought the collection in 1981 and donated it to the city to establish the Delbridge Museum of Natural History in 1984.

The mounts were tested this summer at GPZ. The graph below shows some of the variations in arsenic levels.

The NPS said in 2000 if health and safety procedures are followed any encounter the staff has with arsenic would not be harmful. The roughly 1,500 page NPS Museum Handbook section on Museum Collections has details on handling mounts and displays with arsenic.

Decontamination of arsenic mounts and items has been used by museums.

The U.S. Department of Interior said it is possible for items to sometimes be decontaminated of hazardous material. Still, “Even if detoxification methods are applied, 100% removal of a contaminant is not likely, the DOI said in the 2006 report.

“A High-Efficiency Particulate Air (HEPA) vacuum could be used to absorb at least part of the arsenic powder on the specimen (Knapp 2000). This method may have restricted application in taxidermy because arsenic or arsenical soap was usually applied as a paste on the inner side of the specimen skin, said a report titled “Arsenic in Taxidermy Collections: History, Detection, and Management” by Fernando Marte, Amandine Pe’ Quignot and David W. Von Endt, for the Smithsonian Center for Materials Research and Education.

A 1996 report called “The Merckoquant 10026 Arsenic Test for Natural History Collections” said partial removal of arsenic is possible by vacuuming the artifact.

Research has explored the different tests for arsenic in museum displays.

For example, three tests were conducted and compared for the research report “Arsenic in Taxidermy Collections: History, Detection, and Management” by Fernando Marte, Amandine Pe’ Quignot and David W. Von Endt, for the Smithsonian Center for Materials Research and Education.

Researchers for the Smithsonian Center tested Weber’s test and the arsenic paper test from Macherey-Nagel. The researchers concluded that Weber’s test and the arsenic paper test “are positive at 200 ppm concentration of arsenic, as there is a strong black/brown coloration. The reaction still clearly appears at 100 ppm for both tests, and two tests still react at 20 ppm. Both tests are very sensitive and are suitable for arsenic detection.”

These specimens should be stored separately whenever possible. Objects that are
contaminated with arsenic should not be exhibited without appropriate conditions
and/or decontamination to reduce the risk of exposure.

A High-Efficiency Particulate Air (HEPA) vacuum could be used to absorb at least part of the arsenic powder on the specimen (Knapp 2000). This method may have restricted application in taxidermy because arsenic or arsenical soap was usually applied as a paste on the inner side of the specimen skin.