There were nine included studies, three of which focused on e-cigarettes (Table 2) and six on NRT (Table 3). We did not identify any qualitative studies of smokeless tobacco use that had a focus on distinct SES categories. Almost all these studies came from the UK, with just one study (reported in three articles) from elsewhere (Australia). The relatively small number of included studies was surprising, due to the large field of qualitative literature on smoking and disadvantaged communities [22, 42] . Many studies identified in the original search were not included on the basis that they did not contain references to NCNP or were focussed on some other aspect of disadvantage that was not SES. The small sub-set of studies highlights the lack of direct and sustained engagement with low SES groups and NCNP.
The NRT and e-cigarette studies were coded independently of each other given the difference in the length of time these products have been available and their different modes of use. The ultimate lines-of-argument for each NCNP were relatively similar with many themes occurring in both strands of analyses and being straightforwardly translated into each other. For this reason we have largely considered NRT and e-cigarettes together when the lines-of-argument for each NCNP were similar. We categorised our final identified lines-of-argument into three overall views on the prospects of NCNP for harm reduction: ‘pessimistic’, ‘optimistic’ and ‘uncertain’ (Table 4). Full details of the coding process can be found in the Supplementary File. Pessimistic results, which reflected a general lack of enthusiasm or perceived ability to use NCNP to replace smoking were the most common results and so are discussed first. Optimistic findings and ‘uncertain’ findings which reflected uncertainty and indecision, especially in terms of NCNP potential for harm reduction or cessation were less common. However, there were significantly more optimistic findings relating to e-cigarettes which appeared to reflect different modes of use and understandings of relative harm. As the most common, the pessimistic views are presented first, followed by the optimistic and finally the uncertain.
Social, cultural and economic circumstances of low SES smokers not conducive to NCNP uptake. Social and cultural circumstances in which smoking was perceived as a normal, inevitable and even necessary part of everyday life were a feature of most studies. Stress was commonly mentioned as a reason for postponing cessation or reduction plans, and participants indicated the feeling that continued smoking was almost inevitable:
Because […] there’s a wee bit too much stress in my life at the moment that I had to go back on the cigarettes. (Female, 47, smoker) (Rooke et al: e63 )
I gave it away and then 7th of July last year, went off for four months and then me nerves played up on me so I went back on. (Male, smoker) (Bryant et al: 4 )
Female participants frequently described prioritising family caretaking over their own wellbeing, leaving little time for self-care such as smoking reduction. Additionally, Thirlway (2016) noted that e-cigarette use in a working class area in north-east England appeared to be dominated by young men who were attracted to the novelty and gadgetry of the devices. She found young women reluctant to visit specialist ‘vape’ shops where men seemed to congregate.
The idea of a working class hedonism was also evident throughout Thirlway’s  study, e.g. “them at Greendale [middle class area] haven’t enjoyed themselves the way us lot have – I’ve no regrets” (p. 110, male, 47, smoker) . Thirlway observes that other young men in her study felt vaping did not fit with a ‘hedonistic’ masculinity that valued carefree consumption. Hence, there were variations in local responses to, and views of, e-cigarettes both between men and women and among men.
Both Atkinson et al  and Wiltshire et al  noted that participants rarely encountered situations of enforced temporary abstinence at home or work due to unemployment . For example a male (smoker) participant in Wiltshire et al said of him and his partner: “[We’re] not comfortable living here... I’m unemployed... Stress levels have been very high [and] we have noticed we smoke a lot more” (p. 299). Atkinson et al and Wiltshire et al both suggest that encountering such restrictions is more common for more affluent individuals in higher grades of employment, and for whom smoking reduction and cessation then becomes expected and normalised.
The perceived high price of NCNP, along with a concern about not getting value for money if they turned out not to help smoking cessation or reduction, recurred throughout most of the studies. Financial concerns were particularly highlighted by participants in Thirlway’s  study:
Although £10 would buy a starter tank and e-liquid, smokers like Martin could get a week's worth of illicit rolling tobacco for the same money and could not risk such a large outlay on something that might not ‘work’ for him (p. 108).
Furthermore, Thirlway noted that people were likely to revert to cigarettes when their e-cigarette broke, rather than seek a replacement. Similarly, Wiltshire et al  and Roddy et al  found that cigarettes were easily obtainable through informal networks when money was tight, suggesting that the financial disincentive to smoke was not as great as might be expected in a context of high tobacco taxation.
NCNP do not carry enough ‘relative advantage’ over smoking or other harm reduction products. When discussing NRT, many of the participants explained that NRT had an unpleasant taste, or was not felt to work as intended. Additionally, some participants enjoyed smoking and were unconcerned about continued smoking.
I know it’s bad for me and everything like that, but I do enjoy it. (Female, smoker) (Wiltshire et al: 297 )
I just like fags. I just like the taste of fag. (Male, 20, smoker) (Rooke et al: 063 )
While NRT represented a complete break from smoking actions that did not fit in with a stress relief ritual, e-cigarettes were sometimes experienced as more unsettling due to their similarity to smoking. Participants noted that switching to an e-cigarette did not feel like quitting and that the similarities could potentially lead to continued nicotine addiction or relapse in smoking:
I don’t feel like I’ve stopped smoking, I just feel like I smoke them instead. (Female, 47, ex-smoker) (Rooke et al: e63 )
It’s not getting rid of the habit. [...] I’m still trying to persuade my husband to go on [nicotine replacement] patches, because I’m like, honestly, you’ve got to stop with that part of it [simulating smoking action]. (Female, 40, smoker) (Rowa-Dewar et al: 18 )
Likewise, Thirlway  found that some people regarded addiction as the primary ‘deviance’ and reflected that e-cigarettes did little to improve this given the continuation of nicotine use.
Lack of clear information about relative harm of NCNP. Finally, many of the studies reported uncertainty about the relative harms of NCNP, often centring on the continuation of nicotine consumption and becoming addicted to something new.
I kind of understand it [NRT] … but then on the other side of it I think because it’s nicotine replacement so how is it gunna help you stop if it’s still giving you the nicotine. (Female, 25-34, smoker) (Atkinson et al 2013: 4 )
Studies of e-cigarettes also found some participants to be unsure about the health risks of e-cigarettes.:
I don’t trust the electronic cigarettes, I just...I don’t think there’s been enough research on them. (Male, 39, smoker) (Rowa-Dewar et al: 17 )
Some of the participants in Rooke et al  were particularly distrustful of e-cigarettes that were not sold through official retailers such as Boots, citing unknown and possibly dangerous ingredients. Atkinson et al suggested that the negative effects of environmental tobacco smoke had come to be underestimated due to a lack of knowledge, and contributed to lack of uptake of NRT in the homes of those smokers with children.
Despite a general lack of enthusiasm for all forms of NCNP across the nine studies, there were more positive attitudes to e-cigarettes, captured particularly through the ethnographic encounters in Thirlway’s study . In contrast to e-cigarettes not fitting with a ‘hedonistic’ identity, their novelty technology could be an attractive point for some young men who used the devices to develop a ‘vaper’ identity through expertise and owning the latest equipment:
When last I saw Adam (30, smoker), he was very proud of his latest, fourth-generation e-cigarette with wireless connectivity, and he told me that several of his friends had followed his example. (Thirlway: 108 )
By examining the everyday tactics of buying and using e-cigarettes in a working class community, Thirlway discovered that some smokers used the ‘informal e-cigarette economy’ to avoid higher prices and so resist the more middle-class lifestyle and hobbyist approaches to e-cigarette use. These working class vapers were able to cast their use as functional rather than recreational and so “demonstrate moral worth in relation to the moral problems of addiction and expenditure on the self” (p. 111).
This evidence of a thriving informal economy in Thirlway’s paper indicates the importance of community-led distribution and exchange mechanisms for e-cigarettes and associated items such as e-liquids, which is unlikely to be a feature of NRT use. Aspects of Rooke et al’s study  refute this, indicating that smokers prefer ‘trustworthy’ high street retailers and avoid informal retail sources. These differences may be explained in part by the recruitment methods in the two studies. Many of the participants in Rooke et al were recruited through smoking cessation groups and so may have been predisposed to e-cigarette products that followed licensed NRT in being ‘official’ and endorsed by reputable retailers. In contrast, Thirlway’s participants were approached through general community settings and so not necessarily interested in cessation.
Gender dynamics were further evident in Thirlway’s  study as men with serious health problems were able to enrol e-cigarette use in “local constructions of masculinity” through being a “badge of moral intent” (p. 110) to take responsibility to improve health outcomes. Despite this intent, Thirlway observed these men continuing to smoke, or at least being in possession of smoking paraphernalia, and was unsure whether their vaping went beyond a marker of moral identity to signify significant behaviour change.
In contrast to findings suggesting NCNP were too expensive [23, 45, 46], Rowa-Dewar et al  found one instance of e-cigarette use being described as saving money for a couple compared to smoking. Also in contrast to pessimistic findings in the papers about the embodied similarities of smoking and vaping impeding use, Rooke et al  and Rowa-Dewar et al , both found that the embodied similarities between vaping and smoking could also be a positive. For one of Rooke et al’s  participants:
They’re more satisfying. Much more satisfying. I think because, see when you take a puff, it actually feels like, you used to get that kind of hit off a cigarette when you took a puff off the cigarette, you get that sensation from the e-cig. (Female, 42, ex-smoker) (p. e62)
Further contrasting aspects within included studies were that Rooke et al and Rowa-Dewar et al found some participants to be well informed about the relative harm of vaping compared to smoking, so suggested that e-cigarettes carried a clear relative advantage and were generally healthier than smoking:
You’re still smoking nicotine, but you’re not smoking tar and you’re not making your lungs… you’re not making your lungs get covered in tar. (Male, 20, smoker) (Rooke et al: e63 )
NCNP useful for smoking reduction but not necessarily smoking cessation. Both the e-cigarette and NRT studies reported that the products could be useful for smoking reduction but not necessarily for complete cessation:
I’d go on the patches … and the inhaler … Then I’d cut down slowly as much as I could. (Female, 35-44, smoker) (Atkinson et al: 5 )
I’m going to buy one of they new electronic fags […] Because a few of my friends have got them, and they do work, do you know what I mean. It’s like you can have a morning fag, and like a night time fag, but that helps you through the day if you’re out, [...] so I’m going to get one of them. (Female, 28, smoker) (Rowa-Dewar et al: 15 )
There were some differences between NRT and e-cigarettes when it came to potential harm reduction beliefs. Both Rooke et al  and Thirlway  noted participants regarded NRT as more obviously a cessation aid than e-cigarettes, as vaping had connotations of recreation. This was reflected in Atkinson et al’s  study, which found that NRT was considered a cessation aid and medicinal product. The participants in Atkinson et al were generally negative about the potential for NRT to assist in temporary abstinence in the home. They felt that anything short of complete abstinence was not effective and using NRT while still smoking was ‘cheating’:
Well, I wouldn’t see much point in that [using NRT for temporary abstinence] to be honest if I was, if I was going to stop smoking, if I was going to use something like that I’d want to stop smoking completely, not just in the house. You know, because that way I wouldn’t be cheating going outside for a cigarette. (Female, 16-24, smoker) (p. 5)
One participant in Atkinson et al’s study did successfully use NRT for temporary abstinence in home, but the authors note that this was contrary to the prevailing experience of other participants. Despite these beliefs, many of the participants in Atkinson et al still indicated that they would try NRT sometime in the future. The participants in Rowa-Dewar et al’s  study of parents who smoke were more optimistic about the potential of e-cigarettes for temporary abstinence in the home:
Handy for you to cut down, because you can use that between … I smoke it in the house. (Female, 28, smoker) (p. 16)
NCNP alone have limited potential for smoking harm reduction. A common theme among all the studies was that NCNP would not work unless people had motivation to quit smoking in the first place. Willpower was frequently mentioned as a more important resource for quitting than NCNP to the extent that some participants dismissed the value of NCNPs altogether:
While ‘patches’ might be used to initially stop smoking, like many interviewees, F35 felt that without ‘the willpower I don’t think they’re going to help you’. (Female, smoker) (Wiltshire et al: 299 )
I just don’t see the point. If you’re going to stop, use your willpower, don’t use some silly electronic device. (Female, 36, smoker) (Rowa-Dewar et al: 17 )
E-cigarettes seen as a gateway or relapse to smoking. In Rooke et al  the authors collected the views of ex and current smokers and found that opinions on e-cigarettes depended on a smoker’s current attitude to smoking. They found that recent ex-smokers felt e-cigarettes could be a ‘slippery slope’ back to smoking due to the similar embodied actions. Smokers in the study were somewhat split in their opinions of e-cigarettes. Some saw the devices as replacements o for cigarettes while others felt they were undesirable and preferred to continue smoking.