As he worked on his thesis in public health two years ago, University of Miami master’s degree candidate Hansel Tookes spent hundreds of hours with fellow students prowling Miami-Dade’s most notorious sites for illegal drug use. They were counting needles.

At an abandoned condo site in downtown Miami, through a construction fence, Tookes counted a dozen or more used and potentially lethal needles scattered on the ground: “They were in among the construction debris.”

In subsequent interviews, 448 admitted injection-drug users in Miami confessed to throwing away a total of 9,845 needles in a single month – in public trash cans, on sidewalks, in parks, into sewers, down toilets. They shared or sold nearly 700 of them.

In all, 95 percent of those used needles — potentially infected with HIV, hepatitis or other blood diseases — were disposed of improperly.

In San Francisco, by contrast, only 13 percent of used needles are tossed away improperly, according to a study there. Why? That city has needle-exchange programs that let drug users swap used needles for clean ones without fear of arrest, say the public health officials who run the program.

Miami has no such programs. Florida law bans them.

Exposure to a used needle can be dangerous. Across the United States in 2009, injection-drug users accounted for 9 percent of new HIV infections, 15 percent of new hepatitis B infections and 44 percent of new hepatitis C infections.

“Many injection-drug users contract these viral infections through the sharing of contaminated syringes,” Tookes wrote in the resulting study, just published in the medical journal Drug and Alcohol Dependence. The article compared needle disposal in Miami to that in San Francisco. He noted that, although uncommon, non-drug users could be infected with viruses “through accidental needle-sticks from unsafely disposed contaminated syringes.”

Tookes, 30, is now a second-year medical student at the University of Miami Miller School of Medicine.

In San Francisco, which has had needle-exchange programs since 1988, health workers take in and dispose of used needles and distribute 2.4 million sterile ones a year. And a 2008 study indicated only 13 percent of used needles were disposed of improperly, says Alex Kral, director of urban health programs for San Francisco-based health research company RTI International.

Health officials there also use needle-exchange programs to create relationships with drug users to try to get them into treatment programs, Kral said.

“These people don’t easily come into contact with the system,” he said.

The programs seem to make a difference. In San Francisco, 12 percent of injection-drug users are HIV-positive; in Miami-Dade, it’s 23 percent, according to a 2009 study in the Journal of Urban Health.

But in Florida, needle-exchange programs are illegal. Florida Statute 893, on the books for over a decade, makes it a third-degree felony “to deliver, possess with intent to deliver or manufacture with intent to deliver drug paraphernalia, knowing, or under circumstances where one reasonably should know” that it would be used to inject, ingest or inhale an illegal substance.

As far back as 1992, opponents of needle exchanges — including former Florida Gov. Bob Martinez — have argued that the programs are potentially harmful. Martinez, who served as President George H.W. Bush’s “drug czar” from 1991 to 1993, said distributing needles "undercuts the credibility of society’s message that drug use is illegal and morally wrong."

More than 15 years of on-and-off attempts to amend the law “have passed legislative committees, but never passed the full Legislature,” says Tom Liberti, chief of the Florida Department of Health HIV/AIDS Bureau. Liberti would support needle-exchange programs on grounds they reduce disease. “They’ve been studied heavily around the country, and it’s a scientifically proven intervention to reduce the transmission of HIV and hepatitis,” he says.

The U.S. Centers for Disease Control and Prevention supports needle exchange programs, noting that studies have shown “syringe exchange programs do not encourage drug use or the recruitment of first-time drug users. They also can help injection-drug users stop using drugs by referrals to substance abuse treatment.”

In 1997, a study of 81 cities around the world concluded that in 29 cities with needle-exchange programs, HIV infections decreased by 5.8 percent per year while in 51 cities without exchanges they increased by 5.9 percent. The study was published in the British medical journal Lancet.

In Miami-Dade, the Health Department’s five clinics around the county will accept used needles without asking questions, said Samir Elmir, the department’s environmental health director. And he said the county’s solid waste department accepts used needles properly capped and put in sealed plastic milk jugs and into the trash. But he said the program is used mostly by diabetes patients who inject insulin. Few injecting drug users know about the programs, and might avoid such official contacts in any case because their drug use is illegal, he said. And, of course, there isn’t the motivation of receiving new needles in exchange.

Also, at least half of Miami-Dade illegal drug users are homeless, low-income or out of work entirely — not in a position to take advantage of such programs, says Lisa Metsch, professor of epidemiology and public health at the UM Medical School and academic advisor on Tookes’ study.

Needle-exchange programs have been politically charged for decades. The first programs were set up in San Francisco, New York and elsewhere in the 1980s, as the HIV/AIDS crisis was building. But in 1988, U.S. Sen. Jesse Helms, R-N.C., pushed through a ban on federal funding for such programs, arguing they encouraged drug use.

In 2009, a Democratic Congress with President Obama’s support rescinded the ban and permitted use of federal funds for exchange programs. But in 2011, the Republican-controlled House reinstated the ban.

AIDS-fighting groups were incensed: “Reinstatement of the ban on federal funding for syringe exchange is an anti-science, anti-public health action that undermines our country’s efforts to fight AIDS,” said Chris Collins, vice president of amFAR, the AIDS research foundation, in a press conference at the time.

The congressional ban on using federal funds does not bar states and local governments from using their own funds for exchange programs. And, with or without federal funding, more than 220 such programs in 32 states are distributing 30 million clean needles each year, according to the North American Syringe Exchange Network.

But federal funding is moot in Florida because of the state law banning drug paraphernalia.

“They’re not legal in Florida,” says Liberti. “No new attempts to change that have been made for a few years, and there’s no bill in the works to change it now.”