Illicit Drug Purity Varies with Distance from U.S.-Mexico Border
Distance to the border is more important for methamphetamine and heroin purity than for cocaine, according to study by UA College of Medicine researcher James Cunningham.

By Jean Spinelli, Arizona Health Sciences Center
Aug. 2, 2010


The purity of illicit drugs can differ sharply depending on where you live in the U.S., but there is little evidence as to why. This is a critical issue as higher drug purity is a risk factor for drug-related illness and overdose.

Researchers report Aug. 3 in the journal Addication that they have solved part of the puzzle: variation in drug purity across the U.S. depends substantially on distance from the U.S.-Mexico border.

An international research team led by James Cunningham, a Fulbright-Garcia Robles Scholar and social epidemiologist with the Department of Family and Community Medicine at the University of Arizona College of Medicine, used the Freedom of Information Act to obtain federal data on the purity of methamphetamine, heroin and cocaine seized throughout the U.S. from 1990-2004 – approximately 250,000 seizures.

They calculated the distance from the location of each seizure to the nearest major city (import portal) on the border and compared that distance to purity, adjusting for factors such as the size of the seizure.

The analysis found that the purity of all three drugs declined as distance from the border increased, though there were differences by drug type. Methamphetamine purity declined continuously with distance, with one exception: it jumped in the northeastern U.S. (more than 1,500 miles from the border) during 2000-04, probably because of methamphetamine imports from Quebec and Ontario, Canada, which began in the early 2000s.

Heroin purity declined through approximately 900 miles from the U.S.-Mexico border, but then began to increase with continued distance.

"The probable explanation here," Cunningham said, "is that while the nation's primary drug portal is the U.S.-Mexico border, there nevertheless are some significant drug import portals on the east coast as well, including New York City for heroin. As distance from the U.S.-Mexico border approaches another portal for a drug, purity stops declining and begins an about-face."

Cocaine also had a purity decrease, then increase, associated with distance from the border, but the association was substantially less pronounced. Cocaine's purity was generally the highest of the three drugs and varied the least with geography, suggesting that cocaine trafficking networks within the U.S. engage in relatively less "cutting," or dilution, of their product.

"Allowing for variance by drug type, it seems that traffickers increasingly cut their drugs – decrease purity – as distance from a portal increases, possibly to compensate for added transport costs," Cunningham said. "This is good news for communities farther from drug portals, as lower purity is desirable from a public health standpoint. But communities closer to a major portal, including communities near the U.S.-Mexico border, are left with greater risk for drugs of higher purity."

The title of the study is "Proximity to the U.S.-Mexico Border: A key to explaining geographic variation in U.S. methamphetamine, cocaine and heroin purity." Addication is an international scientific journal in continuous publication since 1884 and the top journal in the field of substance abuse.

In addition to Cunningham, study co-authors include Jane C. Maxwell, a senior research scientist with the Addiction Research Institute of the Center for Social Work Research at the University of Texas at Austin; Dr. Octavio Campollo, director of the Center of Studies on Alcoholism and Addictions at the Antiguo Hospital Civil in Universidad de Guadalajara, Mexico; Kathryn I. Cunningham, UA research assistant; Lon-Mu Liu, professor in the Public Economics Research Center at the College of Social Sciences at National Taiwan University in Taipei, Taiwan; and Hui-Lin Lin, a professor in the Department of Economics at the National Taiwan University in Taipei, Taiwan.

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Jean Spinelli

Arizona Health Sciences Center

520-626-2531

jspinell@u.arizona.edu