"In the early 1990s, about 40 percent of IDUs in New York City were HIV-infected, while only about four percent of IDUs in Los Angeles were infected with HIV. Yet in both cities, about 25 percent of gay men were HIV-infected. The solution to this discrepancy is found in the distribution and use of black tar heroin and is due to its unique chemical properties," said the study's lead author, Daniel H. Ciccarone, MD, MPH, assistant professor in the UCSF departments of family and community medicine and of anthropology, history and social medicine.
The study, published in the December 2003 issue of Substance Use & Misuse, examined data from the Drug Enforcement Agency (DEA) on the predominant types of heroin used in 20 US cities from 1990 to 1993. This data was compared with estimates published in the American Journal of Public Health in 1996 of the percentages of both IDUs and gay men infected with HIV in the same cities during the same time frame.
In cities west of the Mississippi, black tar heroin - a dark, gummy, resinous substance from Mexico - is the type of heroin predominately available. On the East Coast, white and light brown powder heroin from South Asia and South America is the type predominately available. Study findings showed the percentage of IDUs infected with HIV was sharply lower in cities where black tar heroin use predominated compared to cities where powder heroin use predominated, a pattern that was not mirrored in the percentages of HIV-infected gay men.
Using ethnographic, clinical, epidemiological, and laboratory data, researchers determined that black tar use by IDUs could lead to less HIV transmission. First, before injecting black tar heroin, it must be heated to about 165 degrees F, according to research done elsewhere. This temperature is sufficient for killing the HIV virus, which limits the likelihood of HIV transmission through sharing of drug preparation paraphernalia, according to the UCSF researchers.
In addition, black tar heroin clogs syringes, they note. Frequent rinsing and flushing is required, reducing the amount of residual blood and HIV virus present.
"In California, injectors are constantly complaining that their needles clog. They almost always rinse their syringes immediately after shooting up in order to keep them from jamming. The grounds of shooting encampments and the walls of shooting galleries are wet from the water that they squirt through their used needles. This is not the case in New York, where white powder heroin does not 'gum up' needles. Laboratory studies have shown that rinsing syringes copiously with water works well to clean out HIV," said the study's co-author, Philippe Bourgois, PhD, professor and chair of the UCSF Department of Anthropology, History, and Social Medicine.
Moreover, using gummy black tar heroin ruins syringes, leading to increased turnover of syringes. "Black tar injectors rarely report using a single syringe more than five times, while powder heroin users claim many more uses out of their syringes," said Ciccarone.
The study also noted that injecting black tar heroin leads rapidly to venous sclerosis - a condition that results in the loss of veins for injection sites. Thus, black tar heroin users are much quicker to move to subcutaneous and intramuscular injecting. Studies have shown that these are not as efficient as venous injection for transmitting HIV.
"We believe that we have solved this longstanding epidemiological puzzle thanks to multidisciplinary science and data from the DEA on the types and distribution patterns of heroin. This data is valuable to public health authorities. Consider that if powder heroin were to become more widely available on the West Coast, public health agencies would need to prepare for the possibility that currently successful interventions to prevent HIV transmission among IDUs may lose much of their effectiveness," said Ciccarone.
"Likewise, while black tar heroin use becoming predominate on the East Coast may positively affect HIV transmission rates among IDUs, public health officials will need to be aware in order to prepare for the different risks associated with its use. The increased intramuscular injecting associated with black tar heroin use leads to higher rates of abscesses, wound botulism, tetanus, gas gangrene, and necrotizing fasciitis. In fact, soft tissue infections are the number one medical/surgical admission at San Francisco General Hospital," said Ciccarone.
Funding for this study was provided by the National Institute on Drug Abuse.