Some experts have mischaracterized smoking fentanyl as “safer” than injecting, seeking to reduce risks among users. Narrowly considered, the statement is accurate, as inhalation avoids needle-sharing, reducing risks for HIV, hepatitis C, bacteremia, abscess formation, and infective endocarditis among users. However, there’s no clinical-trial–level evidence (randomized trials with real patients) showing smoking illicit fentanyl is safer than injecting it. It isn’t, and that conclusion is unsupported by toxicology, environmental exposure science, or emerging data. Smoking fentanyl also may facilitate speedballing, as with methamphetamine plus fentanyl. Smoking fentanyl is akin to injection without a needle, but in addition to this, smoking creates environmental contamination and major exposure risks. Evidence from tobacco, cannabis, methamphetamine, and household opioid-smoking indicates such risks exist, not only to users, but also to anyone living in or frequenting the same environment. Secondhand tobacco smoke is firmly established as a cause of cardiovascular disease, lung cancer, asthma exacerbations, adverse pregnancy outcomes, and sudden infant death syndrome. More recently, “third-hand” smoke—residual nicotine and combustion byproducts persisting on walls, carpets, clothing, and dust—is recognized as …