Background: Heated Tobacco Products (HTPs) are electronic devices that typically heat tobacco to generate an aerosol that is inhaled. IQOS is a HTP manufactured by Philip Morris International (PMI), who also manufacture Marlboro cigarettes. IQOS is the most widely available HTP, available in over 45 countries globally, of which at least 20 are in Europe.  Harm perceptions of tobacco and nicotine products can influence their use and could be targeted by policies to change behaviour. IQOS was introduced to the UK in 2016, and there is little independent qualitative research on IQOS harm perceptions. This study explored the perceived health harms of IQOS to users and those exposed to the emissions, what shapes these perceptions, and what participants wanted to know about the harms of IQOS.

Methods: Qualitative interviews in London, UK, with 30 adult current and former IQOS users who currently smoked or quit smoking in the last 2 years.

Results: IQOS was perceived as less harmful than smoking but not risk-free, although there was great uncertainty. Influences on harm perceptions were consolidated into six themes: (1) dominance of manufacturer claims influenced perceptions that IQOS is less harmful than smoking to users and those around them, although mistrust of the tobacco industry heightened scepticism about harms; (2) limited independent and long-term research led to uncertainty about harms, although some participants trusted IQOS would not be marketed if it were very harmful. Participants wanted more independent and long-term studies into harm; (3) appearance of HEETS (tobacco sticks) packaging conveyed reduced harm because packets were 'pretty', without graphic/specific warnings, although written warnings conveyed some harm. Participants wanted more information on HEETS packets about harms; (4) process of heating and HEETS contents-heating, compared with burning, tobacco was perceived to produce fewer harmful chemicals, while tobacco, nicotine, and chemicals in HEETS were perceived to cause some harm. Participants wanted clarification about the harms of heating tobacco and HEETS ingredients; (5) improvements in physical health and personal appearance reduced perceptions of harm; (6) differences in sensory experiences (taste, sight, smell) when using IQOS over smoking reduced perceptions of harm, while 'black' deposits inside IQOS led to perceptions of some harm. Reduced volume and smell of IQOS emissions also reduced perceptions of harm to non-users exposed to the emissions.

Conclusions: IQOS was perceived as less harmful than smoking but not risk-free, although there was great uncertainty. Participants wanted clarification about IQOS harms from independent sources in accessible forms, specifically related to HEETS ingredients, heating tobacco, and emissions to others.