Open-air drug markets and opioid-related overdose deaths.

Place-based drug-related overdose studies rarely measure where drugs are sold directly, despite the potential policy value of identifying micro-areas where overdose prevention resources can be targeted. This study examines whether open-air drug-selling locations are associated with opioid-related overdose deaths on Chicago's Westside. I identified 86 open-air drug-selling locations through systematic field observation (May-December 2025). Opioid-related overdose deaths were drawn from the Cook County Medical Examiner's case archive and assigned to a monthly panel of 161 census block groups (January-December 2025; 1932 block group-months). Associations were estimated using Poisson regression with month fixed effects and census-tract fixed effects, with standard errors clustered by block group. Drug-selling locations were operationalized as (1) a count of observed drug-selling spots located within each block group, (2) a one-block spillover count, and (3) a distance-decay crowding score. Drug-selling locations were strongly positively associated with opioid-related overdose deaths across specifications: count of spots within each block group (IRR = 1.672, p < .001), one-block spillover count (IRR = 1.333, p < .001), and the crowding measure (IRR = 1.581, p < .001). Transit hubs and Chicago Police search warrants that resulted in the seizure of opioids were also positively associated with overdose deaths. The findings are supported by agglomeration theory, which predicts a larger number of buyers will be attracted to crowded market ecologies. The results can inform hyperlocal overdose prevention strategies, including targeted naloxone distribution, harm-reduction outreach, and linkage to treatment in areas where selling infrastructure is concentrated.