NEW YORK (CBSNewYork) – The longer rescue workers were at Ground Zero, the more likely they are to have an autoimmune disease, according to a new study.

The study found the risk jumped 13 percent for each month at the site.

Michael Crane was not involved in the research, but heads the World Trade Center Health Program at Mount Sinai Medical Center.

“Very important, because it shows us that even lower dose exposure later on to the dust maybe very, very important,” he told WCBS 880’s Peter Haskell.

Crane said what’s striking is that most of the patients are men.

“These autoimmune conditions tend to be more commonly seen in females,” he said.

The often debilitating illnesses include rheumatoid arthritis and lupus.