An analysis of museum artifacts returned to California's Hoopa tribe through a federal repatriation act reveals traces of mercury and various pesticides, including DDT. Such chemicals — commonly applied in the past by museums to defend their collections against pests — could pose a risk to tribal members who may wear the objects during religious ceremonies, as well as to museum workers who handle the artifacts.
Of the 17 artifacts studied, seven had a mercury level of more than 1 percent by weight, and one object had a level of more than 16 percent. Naphthalene and DDT were also found frequently throughout the samples.
The research is reported in the March 15 print edition of Environmental Science & Technology, a peer-reviewed journal of the American Chemical Society, the world's largest scientific society.
The Native American Graves Protection and Repatriation Act (NAGPRA) of 1990 allows federally recognized tribes to request that museums return objects taken from their ancestors.
"Many Native Americans are now requesting that objects be returned to them under NAGPRA, and it is highly likely that these objects will be returned without any prior testing," says Peter Palmer, Ph.D., a professor of chemistry at San Francisco State University and lead author of the paper.
Determining the potential threat to human health is a complicated issue, Palmer acknowledges. "We don't know the risks, we don't know the exposures, and hence more work needs to be done." There is currently no straightforward method to decontaminate the objects without damaging them, so until more study is done, Palmer suggests that the artifacts not be worn.
Museums have long used chemicals to protect valuable objects from rodents, insects and microorganisms. The earliest agents were various forms of arsenic and mercury salts, but as technology evolved, curators began using organic pesticides like DDT. Over the years, some pieces may have been treated with several applications of a variety of pesticides.
Many of these chemicals are now known to be dangerous and are no longer used in museums, but residues remain in trace quantities. "This problem is only now beginning to receive the attention it deserves," Palmer says. "Museum workers are at risk, as would be anyone who handles such objects that are contaminated."
The objects in this study were taken from the Hoopa, or Hupa, tribe in 1904 and kept at the Peabody Museum at Harvard University for most of the 20th century. In 1997, after three years of negotiation, 17 items were returned to the tribe, along with a letter saying the objects may be contaminated with a variety of pesticides used in the museum over the years.
A curator at the Hoopa Tribal Museum arranged for chemical analysis of the objects, which include headbands, feathers, baskets, necklaces and other ceremonial artifacts. The tribe collaborated with chemists and anthropologists at San Francisco State University to perform the study.
In addition to mercury and arsenic, the researchers targeted six pesticides that were used widely by museums in the past: p-dichlorobenzene, naphthalene, thymol, lindane, dieldrin and DDT.
Seven of the items had mercury in levels greater than 1 percent (based on the weight of the sample), and one set of eagle feathers had a mercury level of more than 16 percent. Naphthalene was detected most frequently on the artifacts, with DDT and mercury coming in second and third. Neither arsenic nor dieldrin was found on any of the objects.
Although further study is needed, Palmer and his colleagues say people should be aware and take measures to minimize exposure: "These results indicate that Hoopa tribal members should not wear these objects in religious ceremonies, proper precautions should be followed when dealing with potentially contaminated objects, and more serious consideration should be given to this issue at a national level."
Materials provided by American Chemical Society. Note: Content may be edited for style and length.
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