(CNN) -- John Meyers remembers standing at ground zero, feeling like a small speck amid mountains of debris.
"Everything was pulverized," said Meyers, a former New York police officer and first-responder who provided security after the September 11 terror attacks. "It was nothing but dust."
For 20 days, during 14-hour shifts, Meyers breathed in countless chemicals; he even ate meals on site as the dust hovered.
Most of that time, he did not wear a mask. In retrospect, he said, "We were ingesting whole buildings."
Less than four years later, at age 46, Meyers was diagnosed with stage IV oropharyngeal cancer. One tumor had formed in Meyers' throat and two on his lymph nodes. An ultrasound later revealed another tumor near his collarbone.
John Meyers was a first-responder with the New York police in September 2001.
"All four were malignant," said Meyers, who choked up as he recalled being diagnosed. "I asked, 'What's my chances?' No one could give me an answer."
According to the most recent data from the World Trade Center Health Program, there are nearly 3,000 cases of cancer among firefighters, police officers, contractors and civilians who worked or lived near the site of the attacks.
A growing number are being diagnosed with oropharyngeal cancer, but some -- including Meyers -- are being denied insurance coverage because their cancers were diagnosed too soon after 9/11.