Dressed in forest-green scrubs, Dr. Hansel Tookes spends his lunch break searching for used syringes around an Overtown overpass.

Tookes’ eyes scan the weeds beside the sidewalk. He glosses over condom wrappers and shattered beer bottles, then hones in on one tiny orange cap from the tip of a syringe. It’s the size of a thumbnail. “Cap!” he hollers. He leans in, pressing his face against a dilapidated fence meant to keep people on the sidewalk. He waves his finger from left to right, kind of like a metal detector, until he spots it: the skinny glass body with a shiny, sharp hypodermic pointing out of the grass.

“Where there’s a cap, there’s a needle,” he explains. “They take off the cap, inject, and toss the needle. It’s not like they’re putting these back in their pockets.”

Tookes takes three steps forward and spots another cap and then a needle peeking out from under a piece of cardboard. Less than a foot away, he sees a third needle with the orange cap still on it. Under the overpass, he points out nine more. Some of them are capped, others aren’t. Some are broken, with the plunger ripped out.

He emerges into the daylight and stops at the red fence bordering Frederick Douglass Elementary School. Just outside the fence, a shriveled can of Diet Coke lies in the grass. “That’s what they use to cook in,” he says. An uncapped needle rests six inches away. Tookes continues his search. He spots two more that are capped. “Whatever you do, don’t touch them,” he warns.

Then he stops suddenly. He wedges his arm through the fence and points to a hypodermic lying five feet inside on school grounds. The tip is peeking out of the grass in the courtyard. “That’s pretty shocking,” he says.

In 13 minutes, the tall, bearded 34-year-old medical resident spots 16 syringes. “This is morally reprehensible,” he says, shaking his head.

Tookes is Miami’s needle crusader. For years, he has fought for addicts — kids who are threatened by the random, potentially hazardous metal strewn throughout their neighborhood — and for needle exchanges.

He grew up in Connecticut but moved to South Florida when he was a teenager. Back then, he volunteered at a homeless shelter with his grandmother, a nurse with Veteran Affairs. That’s when he realized he wanted to go to medical school and really help people. After graduating biology from Yale in 2003 and completing a master’s in public health at the University of Miami in 2009, he began working at a Miami-Dade Health Department clinic where sexually transmitted and intravenous diseases are treated. He graduated from UM’s medical school in 2014. Now, as a medical resident, he works with patients, many of whom are battling HIV and hepatitis C.

Miami-Dade County has the highest rate of HIV infection in the nation. Broward County is second. The Centers for Disease Control and Prevention determined last month that heroin use has increased significantly across all demographic areas.

Tookes’ colleagues call his ability “syringe radar.” He says he acquired it in 2009, when he and a team of public health workers scoured 800 blocks in Miami, counting syringes. They tallied thousands in Overtown and Liberty City as well as ritzy neighborhoods such as Coral Gables and Brickell. Through interviews, they discovered that 95 percent of injection drug users dump their needles into the street after use. “There wasn’t one day we went out and didn’t find a needle,” Tookes recalls.

In the years that followed, he kept looking. He just couldn’t help himself. “My eyes just scan when I walk through the city,” he says. “It’s basically a color association I have. The caps are orange and stand out on the ground. So I’m always scanning for orange.”

Tookes estimates he has found at least 500 syringes in Miami in the past few years. And that’s not including the photos his friends send him when they spot them. He shrugs. “At this point, I’ve seen so many it’s hard to put a number on it.”

Most people don’t notice all the dirty needles around Miami. But it’s a health hazard for anybody who might step on one. If the person who used the needle was infected with a disease, it could be transmitted. And addicts desperate for a needle pick used ones off the ground.

The study found that the number of needles on the street in Miami is higher than in San Francisco. Tookes believes this difference is due to that city’s exchange program, in which volunteers and others provide syringes without charge to addicts. State law prohibits this practice in Florida.

“The research is out there. Needle-exchange programs like the ones in San Francisco work,” he says. “And it’s so much more than getting a clean needle; there are people working there who will examine any abscesses and make sure they aren’t infected. It prevents these common infections from getting worse.”

Then Tookes explains he has spent the past three legislative sessions lobbying for passage of a bill that would allow a needle-exchange program in Miami. “I really don’t understand why this legislation won’t go through. We published a cost-analysis study this year — and found it would save Jackson $11.4 million.”

After his stroll through Overtown, Tookes runs into 32-year-old Kelly Rall under an overpass on 14th Street. She sits on a slab of cardboard while hugging her bony knees. She stretches out her arms to reveal a trail of healed pricks from when she was a drug user. She says she injected heroin for more than ten years but has been clean for the past two.

As a recovering addict, Rall says Miami would benefit from an exchange program. She considers herself “lucky” because she has diabetes, so she can pick up clean needles from a clinic.

“I think in the long run, it becomes a medical problem,” she says. “Nobody wants to use a dirty needle, but it’s not a choice.”

After a few minutes, Tookes realizes he has to return to his patients. He shakes Rall’s hand. She nods and smiles at him. “Really, thank you so much,” she tells him.

A little later, six fifth-graders from Frederick Douglass Elementary ride their bikes down 14th Street. They abandon them on the sidewalk and climb over the fence. They’ve all seen needles on the ground before. “One time, near Biscayne, I saw some bleeding guy stick one needle into a tree,” a smiling 10-year-old boy remembers.

“What happens if I step on one?” a 9-year-old girl asks, leaning on her handlebars. “If I start bleeding, do I put a Band-Aid on it?”

