Every conversation about San Francisco's homeless problem needs to include an understanding of the growing injection drug problem that's affecting not only our city, but many around the nation in recent years. Addiction, and in particular heroin addiction, is largely responsible for a hefty percentage of the root causes of homelessness here, and the Chronicle's Heather Knight recently sat down with Dr. Barry Zevin, the medical director of San Francisco's Homeless Outreach Team to understand this better. Zevin has done over two decades of work with the City's Department of Health, and he's therefore a font of information about the drug epidemic that plagues much of our local homeless population.

Zevin and his team treat approximately 1,000 homeless people annually, 75 percent of whom are addicted to heroin. And the number of heroin users seeking treatment in San Francisco has been on the rise for at least three years, with a 15 percent uptick between 2014 and 2015 alone.

First things first — let's get the terminology straight. According to the 55-year-old Bernal Heights doctor, "injection drugs" is actually the preferred term over "intravenous drugs" these days, given that many users no longer have functioning veins they're injecting the drugs into.

"People might be using heroin for 20 years, and the really pleasant part of it might have been the first few months and then another 19½ years is a kind of misery," explained Zevin.

Zevin also talks about something you've likely heard about, or seen a recent documentary about on HBO: The nation has the over-prescription of opioid painkillers to blame for the current heroin epidemic, as drug cartels began selling cheap heroin in the US in recent years, with many of the buyers being opioid addicts who couldn't afford prescription pills anymore.

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Zevin credits the recently rapid construction growth and development within the city as one of the main reasons that heroin use is taking place so blatantly out in the open. Drug users used to have empty lots and abandoned buildings in which to hide and use. San Francisco real estate is too valuable to be left empty these days, and those heroin users have no choice but to spill out onto the streets.

Further, Zevin notes that around San Francisco's Civic Center, one sees a lot of use of both heroin and methamphetamine, which he calls "a relatively unusual combination of drugs" compared to other city centers around the country. "Drug use is very local," he says, adding that around the Tenderloin more people may be using meth as a way to stay awake at night and avoid rousting by police.

In 2016, we heard about the huge uptick in the use of the overdose-antidote drug naloxone by police and first-responders on the streets of SF, in response to the growing heroin epidemic, and this means that potentially hundreds of heroin users' lives have been saved — though their burden on the city's emergency services continues.

As one might imagine, Zevin is a proponent of safe injection sites (a concept that's receiving a new push via the Board of Supervisors, as we discussed here last week.) "So yeah, someplace different — clean, safer, with services that come with it and entry into treatment — I am definitely supportive of."

Knight's whole Q&A with Zevin is worth your eyeballs.

Related: City Drug-Injection Sites Endorsed By Department Of Public Health Director