Detecting Emerging Drugs in LA County Overdose Deaths

Wed, 09 Sep 2026 00:00:00 -0700

The drug supply behind overdose deaths keeps changing: para-fluorofentanyl, bromazolam, carfentanil, xylazine. Death records usually can’t keep up. In Los Angeles County, the modeling panel carries just 8 coded substance flags and lumps everything else into “Others.” The medical examiner’s free-text cause-of-death narratives are far richer, and this project uses them to answer a simple question: which substances are emerging, and where?

Extraction. A lexicon of 4,089 aliases mapped to 3,127 canonical substances, built from the DEA NFLIS catalog plus curated misspellings and metabolite rollups, turns 8 coded columns into 219 distinct substances at 99.8% decedent coverage.
Detection. An empirical-Bayes (gamma-Poisson) shrinkage ranking flags substances whose share of deaths is rising. It combines case-weighting, dual-gate normalization, and a closed-form spatial-clustering term, alongside a tree-temporal scan over the pharmacological hierarchy. After prototyping more than 20 detector variants, the final design reaches 0.85 precision.
Validation. Every variant is back-tested quarter by quarter using only the data available at the time, and scored against hand-curated emergence timelines and synthetic Monte Carlo profiles with known ground truth.
Characterization. Spatial and space-time scans show whether a flagged substance is concentrated geographically, and polysubstance analysis separates substances that cause deaths from ones that are merely present.

Known emerging substances in LA County. Yellow bands mark the quarters the detector was in alarm; dotted lines mark the first recorded LA death. para-Fluorofentanyl was flagged one quarter after its first death, while xylazine, with only 10 deaths, never crossed the threshold.

spatial statistics | Fabrice Harel-Canada

Detecting Emerging Drugs in LA County Overdose Deaths