"It's not clear whether bismuth is a non-toxic shot alternative," says study co-author William Gough, a professor in the Department of Physical and Environmental Sciences at the University of Toronto at Scarborough. "Our final recommendation is to abandon bismuth and use steel shot until further research is completed."
Gough, along with graduate student Ruwan Jayasinghe and colleagues from McMaster and Queen's universities and the University of Waterloo, examined the background levels of bismuth and lead in the muscle and liver tissues of mallard ducks, northern pintails, green-winged teals, Canada geese and snow geese. The waterfowl samples were all provided by hunters from First Nations Cree communities in the western James Bay region, who eat the birds as part of their traditional diet.
Bismuth behaves in a ballistically similar way to lead and is cheaper than steel shot, making it the preferred alternative. But the researchers found what they believe are analytical errors in the original studies that justified the switch to bismuth as a non-toxic alternative to lead. Moreover, Gough and his colleagues found evidence of lead contamination resulting from bismuth use. Human and laboratory animal studies have suggested that excessive bismuth exposure may be linked to blood, liver, kidney and neural problems. Gough says that populations who rely on potentially contaminated food sources, such as First Nations people, may be at greatest risk.
The findings appear in the November issue of the journal Environmental Pollution.