FILE - In this Oct. 11, 2001 file photo, firefighters make their way over the ruins of the World Trade Center through clouds of smoke at ground zero in New York. A decade’s worth of study has answered only a handful of questions about the hundreds of health conditions believed to be related to the tons of gray dust that fell on the city when the trade center collapsed, from post-traumatic stress disorder, asthma and respiratory illness to vitamin deficiencies, strange rashes and cancer. .(AP Photo/Stan Honda, Pool)

Associated Press
FILE - In this Oct. 11, 2001 file photo, firefighters make their way over the ruins of the World Trade Center through clouds of smoke at ground zero in New York. A decade’s worth of study has answered only a handful of questions about the hundreds of health conditions believed to be related to the tons of gray dust that fell on the city when the trade center collapsed, from post-traumatic stress disorder, asthma and respiratory illness to vitamin deficiencies, strange rashes and cancer. .(AP Photo/Stan Honda, Pool)
FILE - In this Oct. 11, 2001 file photo, firefighters make their way over the ruins of the World Trade Center through clouds of smoke at ground zero in New York. A decade’s worth of study has answered only a handful of questions about the hundreds of health conditions believed to be related to the tons of gray dust that fell on the city when the trade center collapsed, from post-traumatic stress disorder, asthma and respiratory illness to vitamin deficiencies, strange rashes and cancer. .(AP Photo/Stan Honda, Pool)