Anemona Hartocollis / New York Times News Service

NEW YORK — About five years ago, Patricia Workman’s bones started breaking, and she was found to have multiple myeloma, a cancer of the bone marrow. At the same time, her skin cancer started to proliferate, leaving her face so scarred that she needed reconstructive surgery.

Workman and others who believe their cancers were caused by toxic substances released by the fall of the World Trade Center are due to learn this week whether they may be treated and compensated from a $4.3 billion fund set aside by Congress.

An advisory committee in March found justification for covering 14 broad categories of cancer, raising expectations that the fund would cover at least some of them. But such a decision would create a logistical quagmire, advocates for patients and government officials conceded, and could strain the fund’s resources.

“Depending on the numbers of cancers and the criteria for those cancers, we would certainly be getting more and different claims than we were receiving previously,” said Sheila Birnbaum, the special master overseeing the Sept. 11 Victim Compensation Fund.

The advisory committee found some evidence linking Sept. 11 to increased rates of cancer, but existing studies are far from conclusive. And since there is probably no way to distinguish those who developed cancer from ground zero from those who might have developed it anyway, anyone who can prove sustained exposure could potentially be eligible for payment.

“There’s tens of thousands of people that are potentially eligible, so how do you sort through that?” said Dr. James Melius, administrator of the New York State Laborers’ Health and Safety Trust Fund, who has closely monitored the research. “Will it be everybody with lung cancer in Lower Manhattan who was there around Sept. 11?”

After heavy lobbying by the Bloomberg administration, Congress in 2010 approved the James Zadroga 9/11 Health and Compensation Act, named after a police officer who died years after working at ground zero. It allocated $2.8 billion for compensation for those sickened by World Trade Center dust, smoke and fumes, or their survivors. It also set aside $1.5 billion for treatment and monitoring.

Dr. John Howard, director of the National Institute for Occupational Safety and Health, is expected to rule by Saturday on whether to accept the advisory committee’s recommendation. If he does, no one knows for sure how many more people will become eligible for the fund.

So far, more than 5,000 people have registered for the fund, but fewer than 400 of them have actually submitted claims, according to Birnbaum, the special master. Many, she presumes, are still gathering documentation to prove they meet the eligibility rules.

Federal officials have estimated that up to 35,000 people could ultimately sign up, even without cancer’s inclusion.

The committee made its recommendations primarily by correlating substances found in the dust, smoke and fumes at ground zero with the types of cancer they are known to cause.

The panel used reviews of evidence on carcinogenic substances from the International Agency for Research on Cancer in Lyon, France, part of the World Health Organization, and from the National Toxicology Program, under the Department of Health and Human Services..