New York firefighters who responded to the 9/11 attacks at the World Trade Center are more likely to have cancer than their colleagues who were not exposed, a new study suggests. During the study, the researchers found 263 cases of cancer occurred compared with 238 expected from the general population. Among firefighters who did not work at the site, 135 cancers were diagnosed compared with 161 expected from the general population.

Besides causing cancer directly, working at the World Trade Center could also trigger chronic inflammation, through microbial infections, autoimmune diseases, or other inflammatory disorders, all of which are thought to contribute to causing cancer, the researchers said.

Rescue workers carry fatally injured New York City Fire Department chaplain, the Rev. Mychal Judge, from the wreckage of the World Trade Center in New York City early September 11, 2001. Chaplain was crushed to death by falling debris while giving a man last rites in the trade center. The twin towers collapsed on September 11 after being struck by jetliners

A New York City firefighter returns from battling building blazes near Vessey and Greenwich Streets after the World Trade Center collapse September 11, 2001. The World Trade Center collapsed after two planes crashed into them.

A New York City fireman calls for more rescue workers to make their way into the rubble of the World Trade Center September 15, 2001. [U.S. President George W. Bush said September 17, 2001 he wanted Osama bin Laden "dead or alive" for last week's attacks that left more than 5,000 people dead or missing while a jittery Wall Street reopened with the Dow Jones average suffering its largest point loss ever.

A September 14, 2001 file photo shows U.S. President George W. Bush talks to retired firefighter Bob Beckwith (R) from Ladder 117 at the scene of the World Trade Center disaster in New York. Bush, who was in office at the time of the Sept. 11 attacks and famously said he wanted Osama bin Laden dead or alive, said on Sunday the death of the al Qaeda leader was a "momentous achievement." "The fight against terror goes on, but tonight America has sent an unmistakable message: No matter how long it takes, justice will be done," Bush said in a statement

New York City firefighter Ron Parker of Ladder 84 rides the Miss Liberty ferry to the Statue of Liberty in New York harbor December 20, 2001. [Liberty Island was reopened to the public December for the first time since the September 11 attacks on the World Trade Center. The Statue of Liberty itself has not yet reopened to the public.]

Dressed as a firefighter, one-year-old Jose Antonio Castro holds a flag of the United States alongside Costa Rican honor guards during a ceremony on the first anniversary of the attacks on America, in San Jose, September 11, 2002. [Costa Ricans are showing their support abd solidarity for the Americans killed in the attacks at the World Trade Center in New York, the Pentagon in Washington and another airliner in the state of Pennsylvania. Some 3,000 lost their lives in the attacks.]

A note from the family of Scott A. Larsen is seen on the Wall of Honor at the Fallen Firefighters memorial in Colorado Springs, Colorado, September 21, 2002. Larsen was killed in the World Trade Center collapse. Four-hundred-twenty-five names were added to the wall in a ceremony today including the 343 killed in the September 1, 2001 disaster in New York.

Firefighter Darius Allman from Pittsburgh listens to a ceremony to mark the first year anniversary of the attack on the World Trade Center buildings in New York, on September 11, 2002. Mourners converged on the devastated site of the World Trade Center on Wednesday as New York City marked the painful anniversary of the September 11 attacks by honoring the thousands of victims and those who died in courageous efforts to save them.

Thousands of firefighters from all over the world view the firefighters who died in the World Trade Center Attacks on a jumbotron outside Madison Square Garden in New York October 12, 2002. [Firefighters from across the world filled Madison Square Garden and the surrounding blocks on Saturday to honor the 343 firefighters who died in the World Trade Center hijack attack last year. The year before this event was canceled due to the attack on the trade center, this year, an honor guard carried 356 flags, to also honor those firefighters who died in the line of duty in New York since mid-October 2000.]

A New York City firefighter hugs a woman as family members pay their respects to lost ones at the site of the 2001 World Trade Center attack, during a ceremony September 11, 2003. Bells rang across New York and moments of silence were observed to remember the 2,792 people killed at the World Trade Center on Sept. 11 ten years ago, when hijacked planes destroyed the 110-story twin towers. Thousands of victims' relatives, some holding flowers and portraits of their loved ones began arriving early in the morning at the site for the almost four-hour long solemn ceremony.

A girl holds up a picture of a fallen firefighter during a memorial for victims of the attacks September 11, 2003 in New York City. Bells rang across New York and moments of silence were observed on Thursday to remember the 2,792 people killed at the World Trade Center on Sept. 11 ten years ago, when hijacked planes destroyed the 110-story twin towers.

Anthony Taccetta, 10, right, holds a photo of his uncle, firefighter Lenny Ragaglia as he joins mourners gathering to remember those lost during the terrorist attacks on the World Trade Center at Ground Zero September 11, 2003. Ragaglia, who died in the attack, was with Engine 54

Pat Fulginiti (R) and his son Pat Jr. sit under a flag raised by the Cambridge, Massachusetts fire department in Cambridge, Massachusetts September 11, 2003. The flag, and the sign above it, remember the 343 firefighters who were among the 2792 people who died in the World Trade Center attacks ten years ago today.

A New York City Firefighter hugs his family in the pit as mourners pay their respects to lost ones of the World Trade Center attack during the 9/11 Commemoration Event 11 September 2003 at the World Trade Center. This year marks the tenth year anniversary of the attack on the site.

The coffin of Fire Fighter Michael Ragusa is driven on a fire truck from his funeral in New York on September 8, 2003. The service marks the final of the 343 members of the Fire Department of New York who died in the attacks on the World Trade Center. Ragusa had donated blood for typing by a bone-marrow donors program, and the vial of blood and a few personal effects were placed in the coffin since his body was one of the many never identified or recovered.

Michael Puzziferri, 52, commander of the Fire Department of New York's Battalion 27 in the Bronx, poses for a photo in New York August 16, 2006. The faces of people trapped behind windows high up in the World Trade Center just before it collapsed five years ago still haunt Michael Puzziferri but the image has only stiffened his resolve as a New York firefighter. Picture taken August 16, 2006.

Firefighters carry a casket containing the remains of Kiethroy Maynard, a firefighter killed in the World Trade Center attacks, in New York City June 11, 2005. Maynard's remains were among the last to be identified by the city before suspending their efforts this year.

U.S. President Barack Obama talks with firefighters as he visits the Engine 54 Ladder 4 New York Fire Department firehouse in Times Square in New York, May 5, 2011. The battalion lost 15 firefighters in the collapse of the World Trade Center buildings on 9/11.

Pictures honoring fire fighters Orio Palmer and Sean Tallon who were killed in the September 11, 2001 attacks, are placed in front of the site of the World Trade Center in New York March 9, 2006. Tallon's sister, Rosaleen, plans to hold a nightly vigil to protest the plans to build the World Trade Center Memorial underground.