Thousands of tons of lead shot discharged every year during training by Olympic shooters pose a threat to birds and mammals and to water resources, said biologist Vernon Thomas of the University of Guelph in Ontario.
Thomas is co-author of a paper, "Banning the Use of Lead Shot: Options for the International Olympic Committee," published in the journal Environmental Policy and Law.
The Winter Olympic biathlon now under way in the Sochi Games is not the problem, he said, as lead shot is recovered and recycled from targets, and in the Summer games clay target shooting releases lead shot but the amount of lead discharged every four years is minimal.
The real problem stems from athletes training between the Olympic Games, he said, as each Olympic shooter discharges more than a ton of lead shot each year on and around practice shooting ranges.
"The real concern is the amount of shot released during the four-year interval by the many hopefuls in each country and the Olympic team members of each country who practice assiduously with over 1,000 shots per week," he said.
"This lead shot -- many tons -- is rarely recovered and poses real toxic risks to wildlife that may ingest it and to groundwater quality."
IOC officials could phase out the use of lead shot after the 2016 Olympics, Thomas said, with the result that all Olympic shooting and qualification events worldwide would have to use non-toxic steel shot.