(Sioux Falls, SD) — Sioux Falls city leaders and the Great Plains Zoo are explaining their decision to close the Delbridge Museum of Natural History. Mayor Paul TenHaken spoke at the Tuesday morning press conference, citing detectable arsenic levels as the problem. The mayor said even if someone showed up with a donation to build glass enclosures for the exhibits or an offer to move and display them somewhere else, the existing risk to the city would still probably be too great. Zoo president Becky Dewitz said that a detectable level of this carcinogen was found in nearly 80-percent of specimens at the museum. The city can’t sell the items at auction or sell them because of federal regulations the city has to follow. A presentation is planned for the city’s informational meeting on September 5th, and the council is expected to consider surplus and decommission later in the month.