• Johnny Walker was working for the NYPD on
  • Scientists studying 9/11 survivors say
  • Walker had his family's DNA mixed into red tattoo ink used on his arm to keep them close during treatment.
  • The DNA extraction technique was developed by a company called

Retired NYPD officer Johnny Walker is living with the toxic effects of responding to the World Trade Center attack on 9/11.

As a result of the time he spent in the dangerously dusty air that circulated "on the pile" after the twin towers fell, Walker said, he's now dealing with stage 4 colon cancer, the most advanced kind. He spent three full days at Ground Zero, helping with the recovery, cleaning up rubble, filling buckets, and even inadvertently digging out body parts, as he told Men's Health earlier this year.

Yet Walker maintains a wry sense of humor about his condition.

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Many 9/11 rescue workers and survivors are plagued by tumors. According to the federal World Trade Center Health Program count, more than 9,000 firefighters, cops, office workers, and children who were living in or working around downtown Manhattan have high rates of many kinds of cancer. An estimated 420 9/11 survivors with cancer have died.

This group has higher rates of roughly70 types of cancer,cervical, colon, and lung cancers There have even been 15 cases of breast cancer in men, as the New York Post reported. Many of these cancer cases are likely because these workers and survivors breathed in air contaminated with asbestos, lead, mercury and other toxic substances in the days and weeks following the attack.

The bulk of the cancer cases, more than 7,500, are in first responders like Walker. His cancer has spread outside of his colon, and he has lymph node tumors pressing on internal organs near his digestive tract and pelvis. Sometimes, when he's undergoing chemotherapy treatment, he likes to feel the support of his wife, kids, or a close friend.

That's when he touches a cluster of red inked tattoos on his left arm.

The ink on Walker's arm is infused with a powder that contains his loved ones' genetic material. The powder, called Everence, is essentially a bunch of tiny, plastic containers that hold individual DNA strands. Each of the plastic enclosures is about one-tenth the size of a human hair.

Putting your people in a tattoo

When a colleague told Walker about the possibility of putting genetic material into tattoos, he wasn't immediately enthusiastic about it.

But after he thought about the idea a little more, Walker decided he wanted to be able to take his family with him wherever he went from now on.

Ts made from a polymer called PMMA (poly-methyl methacrylate), which you might know better in its acrylic glass form, Plexiglas. Each grain of the powder acts as a tiny plastic container that holds one strand of extracted DNA, ash, or hair. The coating is sterile and won't erode over time, so it sits under a person's skin forever.

t’s a medical-grade material that is being used all over the world for many therapeutic applications," Mathiowitz said in a video on Everence's site.