BACKGROUND: There is a lack of research examining what prevents people who smoke heroin from transitioning to regular injection. This qualitative study aims to improve understanding of environmental influences preventing people who smoke heroin from transitioning to regular injection.

METHODS: In-depth, semi-structured interviews (n = 15) were conducted with people who currently smoked heroin but never injected (n = 10) and those who injected on a few occasions but did not transition to regular injection (n = 5) in Northern Ireland. Multiple recruitment strategies were utilized to generate a community-based sample. Interviews were thematically analysed.

MAIN FINDINGS: Participants identified two main, interconnected influences preventing transition to injecting heroin. Firstly, resistance towards injecting was rooted in micro level perceptions of risks primarily arising from meso level social interactions with people who inject drugs and, to a lesser extent, harm reduction agencies. Secondly, participants identified meso and macro environments defined as changing social contexts and normative beliefs surrounding the acceptability of injecting within their drug-using social networks, facilitated by expanding heron markets, negative interactions with people who inject drugs and new groups of people choosing to smoke heroin due to perceptions of injection risks.

CONCLUSIONS: Findings illuminate environmental influences surrounding and shaping drug consumption practices. Harm reduction strategies should develop and implement safer smoking rooms, community and peer interventions, and improve accessibility to opioid substitution therapy and low threshold outreach services to prevent transitioning to regular heroin injecting.