title: Proximity to the US-Mexico border: a key to explaining geographic variation in US methamphetamine, cocaine and heroin purity.
abstract: OBJECTIVE
  Although illicit drug purity is a widely discussed health risk, research explaining its geographic variation within a country is rare. This study examines whether proximity to the US-Mexico border, the United States' primary drug import portal, is associated with geographic variation in US methamphetamine, heroin and cocaine purity.
  
  
  METHODS
  Distances (proximity) between the US-Mexico border and locations of methamphetamine, cocaine and heroin seizures/acquisitions (n = 239,070) recorded in STRIDE (System to Retrieve Information from Drug Evidence) were calculated for the period of 1990-2004. The association of drug purity with these distances and other variables, including time and seizure/acquisition size, was examined using hierarchical multivariate linear modeling (HMLM).
  
  
  METHODS
  Coterminous United States.
  
  
  RESULTS
  Methamphetamine, cocaine and heroin purity generally decreased with distance from the US-Mexico border. Heroin purity, however, after initially declining with distance, turned upwards-a U-shaped association. During 2000-04, methamphetamine purity also had a U-shaped association with distance. For each of the three drugs, temporal changes in the purity of small acquisitions (<10 g) were typically more dynamic in areas closer to the US-Mexico border.
  
  
  CONCLUSIONS
  Geographic variance in methamphetamine, cocaine and heroin purity throughout the coterminous United States was associated with US-Mexico border proximity. The U-shaped associations between border-distance and purity for heroin and methamphetamine may be due to imports of those drugs via the eastern United States and southeast Canada, respectively. That said, areas closer to the US-Mexico border generally had relatively high illicit drug purity, as well as more dynamic change in the purity of small ('retail level') drug amounts.
authors.affiliation: Department of Family and Community Medicine, The University of Arizona, Tucson, AZ 85719, USA. jkcunnin@email.arizona.edu
authors.forename: James K
authors.initials: JK
authors.lastname: Cunningham
authors.forename: Jane Carlisle
authors.initials: JC
authors.lastname: Maxwell
authors.forename: Octavio
authors.initials: O
authors.lastname: Campollo
authors.forename: Kathryn I
authors.initials: KI
authors.lastname: Cunningham
authors.forename: Lon-Mu
authors.initials: LM
authors.lastname: Liu
authors.forename: Hui-Lin
authors.initials: HL
authors.lastname: Lin
mesh_terms: D003042:Cocaine / Q000737:chemistry* / Q000600:supply & distribution; D003132:Commerce / Q000331:legislation & jurisprudence / Q000706:statistics & numerical data; D003627:Data Interpretation, Statistical; D004339:Drug Compounding; D004340:Drug Contamination / Q000706:statistics & numerical data*; D004335:Drug and Narcotic Control / Q000331:legislation & jurisprudence / Q000706:statistics & numerical data*; D003932:Heroin / Q000737:chemistry* / Q000600:supply & distribution; D006801:Humans; D016247:Information Storage and Retrieval; D016014:Linear Models; D008694:Methamphetamine / Q000737:chemistry* / Q000600:supply & distribution; D008800:Mexico; D015233:Models, Statistical; D013997:Time Factors; D014481:United States
chemical_list: D008694:Methamphetamine; D003932:Heroin; D003042:Cocaine