Asadullah shivers, but not on account of the icy Kabul morning. Frowning intently, he unwinds his orange turban, knots it in a ligature around his right biceps, and starts pumping his arm. He stops to examine the crook, where a blue tattoo of a girl's face is pocked with ugly black scabs. But Asadullah, 27, cannot raise a vein.
Taking a syringe loaded with heroin from his nine-year-old nephew, Asadullah starts stabbing into the scabs, feeling for a vein.
Then, he unties the ligature, and knots it around his left arm.
"It's too difficult," he hisses. "I hardly have any veins left."
Asadullah's left arm is equally damaged. Swapping the ligature, he takes 40 minutes to strike a vein. As the heroin slides into him, he sighs, and slumps back against the mud wall. The pretty tattooed face is now invisible beneath a pool of blood.
Asadullah is what many of Afghanistan's opium farmers deny the existence of: an Afghan heroin addict. Nor is he alone: 90 percent of Afghan opium remains in the region, according to a recent CIA report. Iran has an estimated 2 million opium and heroin addicts. Afghanistan could suddenly have 1 million, the report suggests, mainly among the 3 million refugees who have returned from Iran and Pakistan over the past two years since the fall of the Taliban.
"Historically, Afghanistan never had a drug problem. This is something new," said Adam Boulakos, the deputy chief of the UN Office on Drugs and Crime in Kabul.
"Among returning refugees especially, we're seeing a massive increase in drug addiction," he said.
Asadullah's story is in many ways typical. He began taking heroin eight years ago, shortly after fleeing to Iran.
"It's hard being in a foreign place: so many of my family were missing, and the Iranians didn't really want us," said Asadullah, now lucid after his fix.
"There were dealers everywhere, even the police used to bring drugs to our camp. It was a way of forgetting our sorrows," he said.
Despite their troubles, many Afghan refugees prospered in Iran, working on construction sites to fund their new habits.
"Almost all the builders in Iran are Afghan, and most take heroin," Asadullah said.
Since he returned to Afghanistan three months ago, life has been hard. He has no job, and only around US$60 saved up to sustain his US$6 -- or half a gram -- a day habit.
"And there's another problem," Asadullah said. "Iran was like living in a different world; but here my family's friends can see what I've become, and that brings us shame. I'll never be able to marry while I'm on heroin."
As local demand soars, so Afghanistan's drug industry is adapting, by processing records amounts of heroin.
"Again, historically almost all Afghan opium was processed into heroin in neighboring countries," Boulakos said. "But we're now seeing signs of a significant increase in heroin processed here."
Around a dozen heroin factories were dismantled near the Pakistan border after the harvest of this year's opium crop -- the second biggest to date -- according to Afghan police sources. But with Afghanistan's new government still barely functioning outside Kabul and corruption endemic, no Afghan has yet been convicted on drug charges.
During the harvest, according to diplomats in Kabul, the then police chief of northern Badhakshan province maintained a heroin factory in his garden.