WASHINGTON -- The grim uncertainty facing the men and women who toiled among the wreckage of the World Trade Center hit home once again Thursday with the revelation that some 20 cancers may be added to the list of diseases caused by the terrorist attacks.

That possibility is contained in a draft report set to be discussed next week that recommends adding cancers that attack organs -- such as the esophagus, stomach, colon, liver, skin, lungs, kidneys and others -- to the ailments covered by the James Zadroga 9/11 Health and Compensation Act.

Also released Thursday were the email discussions of members of the scientific and technical advisory committee that was weighing which cancers are likely to be the result of service at Ground Zero.

They starkly illuminate the difficulty in assessing such contentious decisions, even as they make clear the unprecedented catastrophe that has left thousands of responders at risk for the rest of their lives.

"The collapse of massive skyscrapers and the resulting pulverization of their substance and contents, the uncontrolled combustion for many months (that among other toxics, emitted the largest ever recorded releases of dioxins), the range and intensity of exposures that occurred in the morning of 9/11, and also those that occurred for weeks, months and in the case of indoor environments, for years," wrote Kimberly Flynn, co-chair of the WTC Survivors Steering Committee, in one exchange discussing whether prostate cancer should be included.

"We know that responders and survivors were exposed simultaneously to complex mixtures, including multiple carcinogens, which have the potential to act synergistically," she wrote. "And most people were not wearing [personal protective equipment] when they were exposed."

By most estimates, there were some 72 different carcinogens that people in the area were exposed to, perhaps all at once, including asbestos, PCBs, dioxin, cadmium, mercury and arsenic.

"The materials posted today on the NIOSH website show that we are making real progress in adding coverage for cancers under the Zadroga Act," said a statement by the act's first sponsors, Reps. Carolyn Maloney (D-N.Y.), Jerrold Nadler (D-N.Y.) and Peter King (R-N.Y.).

“Our heroes are sick and literally dying from cancers obtained by breathing the toxins at Ground Zero," said Sens. Chuck Schumer (D-N.Y.) and Kirsten Gillibrand (D-N.Y), also in a statement. "For too many first responders and community survivors, this program could be the difference between life and death. It is time to provide the care these heroes deserve, and we will not rest until cancer is included on the list of eligible diseases for treatment and compensation by the 9/11 health bill.”

Including cancer would be a major victory for 9/11 survivors, especially since as many become sick and unable to work, they often lose insurance. Even with insurance, cancer is extremely expensive to treat. Having the ailment covered guarantees care.

But it also likely means that the $1.5 billion set aside for treatment in the Zadroga law will run out sooner rather than later. It also means that when the funding runs out with the five-year expiration of the bill, Congress will have to pass a new measure -- which is not a guarantee as the emotions inspired by 9/11 drift further into the past.

John Feal, a 9/11 responder and advocate, pledged to start that fight as soon as it's clear that it's needed.

"We have enough money to start, but we're not going to know what the full picture is until cancer is covered for awhile," said Feal, who runs the Fealgood Foundation, with a list of 305 9/11 responders who have died from cancer.

"When we know what the situation is, then we'll have to go back to D.C," Feal said.

The 9/11 scientific and technical advisory committee will meet March 28 and April 2 before making its final recommendation.

It is then up to officials in the Department of Health and Human Services to decide which cancers ultimately are covered.

"I never knew anybody with brain cancer before 9/11. Now I know of over 40," Feal said. "I'm confident at least some of these cancers will be added. But listen, nobody ever thought we would get this bill passed. We put pressure on them to get the bill passed, and if we have to, we'll put pressure on them to get cancer added. This is about people's lives."

Michael McAuliff covers politics and Congress for The Huffington Post, and recently had the World Trade Center dust he collected on 9/11 analyzed. Talk to him on Facebook.