Supplies of highly potent Afghan heroin in the United States are growing so fast that the pure white powder is rapidly overtaking lower-quality Mexican heroin, prompting fears of increased addiction and overdoses.

Heroin-related deaths in Los Angeles County soared from 137 in 2002 to 239 in 2005, a jump of nearly 75% in three years, a period when other factors contributing to overdose deaths remained unchanged, experts said. The jump in deaths was especially prevalent among users older than 40, who lack the resilience to recover from an overdose of unexpectedly strong heroin, according to a study by the county's Office of Health Assessment and Epidemiology.

"The rise of heroin from Afghanistan is our biggest rising threat in the fight against narcotics," said Orange County sheriff's spokesman Jim Amormino. "We are seeing more seizures and more overdoses."

According to a Drug Enforcement Administration report obtained by The Times, Afghanistan's poppy fields have become the fastest-growing source of heroin in the United States. Its share of the U.S. market doubled from 7% in 2001, the year U.S. forces overthrew the Taliban, to 14% in 2004, the latest year studied. Another DEA report, released in October, said the 14% actually could be significantly higher.

Poppy production in Afghanistan jumped significantly after the 2001 U.S. invasion destabilized an already shaky economy, leading farmers to turn to the opium market to survive.

Not only is more heroin being produced from Afghan poppies coming into the United States, it is also the purest in the world, according to the DEA's National Drug Intelligence Center.

Despite the agency's own reports, a DEA spokesman denied that more heroin was reaching the United States from Afghanistan. "We are NOT seeing a nationwide spike in Afghanistan-based heroin," Garrison K. Courtney wrote in an e-mail to The Times.

He said in an interview that the report that showed the growth of Afghanistan's U.S. market share was one of many sources the agency used to evaluate drug trends. He refused to provide a copy of DEA reports that could provide an explanation.

The agency declined to give The Times the report on the doubling of Afghan heroin into the U.S. A copy was provided by the office of U.S. Sen. Dianne Feinstein (D-Calif.), a member of the Senate Caucus on International Narcotics Control.

[...]

Antonio Maria Costa, executive director of the U.N. Office on Drugs and Crime, warned world health authorities in October of the increase in Afghan heroin.

"This, in turn, is likely to prompt a substantial increase in the number of deaths by overdose, as addicts are not used to injecting doses containing such high concentrations of the drug," he said.

[...]

The Department of Homeland Security also has found evidence of increasing Afghan heroin in this country. The agency reported skyrocketing numbers of seizures of heroin arriving at U.S. airports and seaports from India, not a significant heroin-producing country but a major transshipment point for Afghan drugs.