FDNY firefighters carry the casket of firefighter Jack McCauley at...

FDNY firefighters carry the casket of firefighter Jack McCauley at his funeral in Nesconset on June 2. McCauley died May 28 from 9/11-related illnesses. Credit: James Carbone

In the first half of next year, if not sooner, we'll likely hit a grim milestone.

By then, FDNY firefighters who succumbed to illnesses related to the toxic dust that emanated from Ground Zero in the days, weeks and months after the Sept. 11, 2001 terrorist attacks could outnumber the firefighters who died on that horrific day.

On the day of the attacks, 343 firefighters were killed. In the 21 years since, an additional 287 FDNY members have lost their lives due to related illnesses. Those who have died or are gravely ill are men and women who spent that day trying to save lives, running into the towers, helping others even as hazardous debris rained down. They then spent months digging through and cleaning up a pile of horror, as poisonous particles filled the air and their lungs.

As the years pass, they are dying with increasing frequency. Within four days at the end of May, we lost four heroes — Vincent Mandala, Michael Verzi, Robert Reynolds and Jack McCauley, all to 9/11-related illnesses.

McCauley, 65, hailed from Ronkonkoma. Like many of his peers, he left behind a wife, children and grandchildren — a family who welcomed him home after he survived the World Trade Center collapse, only to lose him to a cancer that stemmed from it.

The four latest deaths came as New York marked the 20th anniversary of the end of the recovery efforts, the day when first responders carried one final stretcher, holding a folded American flag, out of Ground Zero.

Even though we worried about the air then, we couldn't have known how many more American flags would drape the coffins of first responders, or be folded and given to loved ones, in the years that would follow. We still don't know. But each image, like each blaring of the bagpipes, reminds us that the tragedy of 9/11 didn't end on 9/11. Thousands of first responders, and others who lived or worked in lower Manhattan, still are struggling to breathe or have been diagnosed with other 9/11-related sicknesses. And we still don't know enough about the potential impact on the children who were school-aged or younger in 2001, who've now begun adulthood and might not yet know whether they, too, will fall ill.

And we couldn't have known that an ugly and disheartening political fight would ensue as lawmakers in Washington refused for years to provide adequate funds for health care and compensation for 9/11 first responders and other victims. Even today, that fight continues, as a deficit in the World Trade Center health care program looms. That could mean cuts to the number of people accepted into the health program if the funding shortfall isn't corrected. New York lawmakers introduced a bill to make that fix last year. Our first responders are still waiting for its passage.

It's easy to remember every Sept. 11, to listen to the tolling bell, to talk about where we were and whom we lost, to mourn as the towering blue lights rise from the memorial. But during the rest of the year, it also can be easy to lose sight of the awful toll that day continues to take, the losses that continue to mount, the families who continue to grieve, the first responders who continue to battle.

They will continue to die. And we must continue to remember and honor them.

Columnist Randi F. Marshall's opinions are her own.