dr. david prazan authored a study just published in a medical journal suggesting that something may may change this debate. answering the question that many believed would never been answered. that firefighters working ground zero are, in fact, at increased risk for cancer. >> we found a 19% increase in all cancers in our exposed firefighters as compared to our non-exposed firefighters. >> 19% increase in cancer rates. that's a significant increase. >> a significant increase. we excluded cancers that might have been diagnosed early. we still see this 19% increase when we put those cancers back in. we see a 32% increase. >> before dr. prezant's study was released, the study of health found no link between cancer and dust. his study may change that standing. >> does this change anything for the first responders or rescue workers? >> whether we can say that cancer is increased in other responders or other residents, we have no idea. this is a study about firefighters. their exposure is unique. 85% of the exposed were present in the first 48 hours of the collapse when the exposure was massive. tha