A five-year Taconite Workers Health Study indicates the more Minnesota workers spent on the job, the more likely they developed a rare and deadly lung cancer. Taconite, a hard, banded, low-grade ore, is mostly used in the iron and steel industry. The University of Minnesota research was designed to address the debilitating and deadly lung diseases by the needle-like fibers in commercial asbestos and dust from taconite ore. The study found each year a worker spent in the taconite industry, his risk of being stricken by mesothelioma increased by 3 percent, the Minneapolis Star Tribune reported. However, the $5 million study did not provide complete answer to the question that has been confronting miners and their families for decades -- did taconite dust exposure bear some blame for the lung illnesses? The researchers said at this point their research shows a possible link, but not a certain one. \"Working longer times in the taconite industry does have risk associated with it -- that is an important finding,\" study leader Dr. Jeffrey Mandel, a physician and epidemiologist, said. Craig Pagel, executive director of the Minnesota Iron Ore Association, said industry officials would study the results in depth before commenting. The link between taconite and lung disease has been an Iron Range question for decades after needle-like fibers were discovered in Lake Superior and traced to the dumping of taconite waste rock 40 years ago. The researchers found 80 miners, all men, died of mesothelioma -- a rate nearly three times higher than the rest of the state\'s population. Commercial asbestos was once used widely in the taconite industry for insulation and other purposes and remains a prime suspect in the Iron Range cases, the researchers said.