While museums have long been aware of the pesticide problem, tribes only discovered it as they began to reclaim artifacts under NAGPRA. Objects often arrived with lists of the frightening chemicals they might contain, from neurotoxic and lung-damaging mercury to carcinogenic arsenic; accompanying notes often warned against skin contact.

Soon after NAGPRA passed, for example, northern Arizona's Hopi won back a handful of sacred items, such as prayer sticks. Some were returned to individual families and others placed in grain storage devices to ensure a bountiful harvest. But testing later revealed that most were dangerously high in arsenic. The tribe issued a moratorium on repatriations, which remains in place today. "We only pursue something if we know it's clean," says Leigh Kuwanwisiwma, director of the Hopi Cultural Preservation Office, noting that this experience is common among tribes. "It's a huge obstacle to the full implementation of NAGPRA." And NAGPRA is already a long, disillusioning bureaucratic process: It took three years of negotiating for the Hoopa to obtain just 17 of the 52 relics they requested from the Peabody, and hundreds more are scattered among museums across the country, from a red deer skin in a Smithsonian storage room in Maryland to a stockpile of artifacts in a UC Berkeley warehouse. "I'm always asked by the council to go after more items," the Hoopa Tribe's Jackson says, "but I just keep telling them, 'Do you want to give me a toxic work environment?' "

Some larger museums and universities, such as San Francisco State, use federal funds to screen for pesticides and alert tribes to the dangers items might pose before they're returned. But even San Francisco State has pesticide troubles: In 2001, an environmental consulting firm found that the school's archaeological collection had left dangerous amounts of mercury in the anthropology department and museum.

Though a number of safety measures were implemented, in January the university's Old Science Building – which houses the museum and many anthropology labs – was shut down partly because of high levels of mercury and arsenic. University officials say the contamination emanated from broken thermometers, but researchers determined that archaeological collections were also likely to blame. More than 2,000 students and professors were displaced. One room, with mercury vapors 14 times higher than state safety limits, was padlocked shut and a Hazmat suit and respirator required for entry.

The building was emptied of artifacts and deep-cleaned.

There are some fairly effective methods for removing pesticides from artifacts without harming them, though they're all costly: Certain bacteria can draw out mercury by converting it into gas, lipolic acid removes arsenic from wool and feathers, and liquid carbon dioxide can flush synthetic pesticides from fragile materials. Now, though, the Arizona State Museum in Tucson is studying a new technique that uses water, with its pH adjusted using basic and acidic chemicals, to draw out specific heavy metals.

"It isn't simply, 'Wash it for three minutes and hang dry,' " says Nancy Odegaard, the museum's preservation division head, who is overseeing the effort, "but it also doesn't require an extensive amount of equipment." If it succeeds, tribes could easily clean certain items using little more than a faucet, latex gloves and a mask. The research is preliminary, but Odegaard hopes it encourages tribes to again aggressively pursue their sacred artifacts.

Carpenter, of the Hoopa cultural committee, hopes to soon retrieve more of the tribe's long-lost treasures. Each artifact remains an "old friend," even with mercury and arsenic present, he explains. "I wouldn't wear them, but our ancestors' spirits are in them. We're bringing their spirits home."

"They belong here," adds elder Walter Lara of the Yurok Tribe, whose reservation is just north of Hoopa and has similar traditions. Last year, Lara was discussing the return of another artifact housed at a Denver museum when he noticed a display containing a Hoopa white deerskin dress – one of the tribe's most sacred items.

When he sang to the dress, he says, it started moving. "I believe the spirit of that dress heard me and wanted to dance."