Joseph Zadroga, father of the late first-responder James Zadroga, said the government should have been aware of the dangers at the World Trade Center site.
ZADROGA: This was just like Chernobyl, in Russia, where they had the Russians take wheelbarrows and dump it down into the nuclear reactor to stop the fire.
REPORTER: But, Doctor Joan Reibman of the World Trade Center Environmental Health Center said it's hard to determine which ailments are related to 9/11.
She said medical professionals have to look at when someone was working or living near the site and when their symptoms first occurred.
REIBMAN: And also, look at that in the context of what we're seeing in the other programs - in the Fire Department, in the responders, as well as in our program - to try to understand when certain symptoms are related. But there's an awful lot we still don't know.
REPORTER: Speakers also called for comprehensive healthcare services...and better research into 9/11-related illnesses.
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