The original laboratory study found up to 44 percent mortality among monarch larvae that consumed milkweed leaves—their exclusive food source—that had been dusted with transgenic pollen.
But after two years of research, teams in Canada and the United States have declared the transgenic pollen's effects in nature negligible to the butterflies.
Only one type of the genetically modified corn, known as Bt-176, was found to pose a threat in concentrations low enough to be found outside of the laboratory, and this unpopular variety is expected to be phased out in the United States by 2003.
Sears pointed out that he has witnessed more damage to the butterfly population through "road kill" while driving along country roads than he did in his experiments.
"Useful Uproar"
While this recent research contradicts earlier findings of risk to the butterflies, Sears said the uproar caused by the original study was useful in forcing the Environmental Protection Agency in the United States and the Canadian Food Inspection Agency to evaluate their procedures for approving such organisms.
"The healthy part of the whole thing is we now have a new view how to manage new technology like this," he said.
Nadege Adam of the Council of Canadians said the recent findings raise questions about the type of research being done before products get to market. "It may be completely safe," she said. "Our problem is that we don't know and we're not going to be guinea pigs."
Results of the studies were to be published in the U.S. scientific journal Proceedings of the National Academy of Science in early October. The release of the findings was stepped up, however, because the EPA is undergoing a five-year mandatory review of corporate applications to continue producing the product, and this research has been cited in the applications. The deadline for that process is the end of September.
While Canada does not have a similar mandated review process, Sears said the Canadian Food Inspection Agency is likely to keep a close eye on proceedings in the United States.
"I think you have to rely on these agencies, elected or appointed, to evaluate the evidence that's available," Sears said. He noted that research done before the initial approval process concluded that the risk to non-target species was small.
The recent studies were funded primarily by the United States Department of Agriculture and the Canadian Food Inspection Agency.
Copyright 2001 The Canadian Press
