The prevalence of opioid use in New York City has been documented. I aim to explore the prevalence of fentanyl in NYC heroin using rapid test-strips. Prevalence will also be described among distinct brands in New York City black-markets.

Fentanyl presence will be explored in already used and empty heroin bags. Residual amounts will be tested, which may not be visibly present to the naked eye. The study will impact health policy and help inform interventions for fentanyl overdose.