With increasing volumes of pharmaceuticals being prescribed, it is important we limit the number of medicines disposed incorrectly by ensuring people dispose of their medicines in appropriate, environmentally safe methods, preventing future environmental harm [
49]. Using a nationally representative UK sample, in this paper we have (i) described patterns of medicines waste usage, storage and disposal practices; explored the relationship between type of medicine preparation and choice of disposal method; and (iii) examined a set of predictors of self-reported medicines disposal behaviour.
Patterns of medicine waste disposal practices
Consistent with UK data collected in 2003 [
11] almost all participants (
n = 641, 97%) in this work reported having medicines in their house with two-thirds having a mix of prescription and OTC medications. In the present work and that of Bound and Voulvoulis, 9% of the respective sample sizes reported obtaining only prescription medicines and it is important this should not mask the fact that more pharmaceuticals are being prescribed per person (polypharmacy) to a greater absolute number of people [
50].
In the present study, the bin was the most common disposal route for unused pharmaceuticals. The percentage of bin disposal was lower in this work (
n = 426, 48%) than reported in earlier UK research (i.e. 65%) [
11]. Yet, whilst a reduction in general waste disposal suggests a positive trend, disposal via toilets and sinks increased (i.e.
n = 230, 25%) when compared with data from 2003 (12%) [
11]. It is unclear why liquid disposal appears to have increased relative to bin disposal but one reason may be the increase in recycling.
In the present work, return rates to pharmacies were 27% (
n = 242) compared to 22% in 2003. General waste and sink/toilet disposal are also much lower than reported in research conducted in other countries such as Sweden, where increasing numbers of the population are worried about the impact of pharmaceuticals [
51]. This has been linked to increased awareness of the issue stemming from information campaigns [
51]. Thus, a plausible explanation may be that the UK has not yet had any high profile, national campaigns relating to medicine waste disposal and over half of the study sample reported not seeing any information on how to dispose of unused medicines.
Most of the sample disposed of medicines in multiple locations. It is important to understand the reasons guiding these behaviours as the aim of any intervention will be to decrease the frequency of disposing medicine into the bin, toilet and sink. It is also important to consider ways in which shifting to increased pharmacy disposal requires different strategies than to switch from inappropriate disposal to a completely—and certainly more effortful – disposal location.
Relationship between the preparation type of medicine and choice of disposal
Our work represents the first UK investigation of the relationship between preparation type of pharmaceutical waste and disposal destination. Here, there were clear regularities: liquids tend to be disposed in sink or toilet and solids, creams and ointments in general waste. The broad relationship between medicine type was similar to results from a New Zealand study [
12] in respect of disposal to general waste for solids (UK:
n = 317, 54% vs NZ:
n = 229, 51%) and ointments (UK:
n = 426, 76% vs NZ:
n = 361, 80%). However, our results showed a lower percentage of liquids disposal in sinks/toilets (UK:
n = 226, 38% vs NZ:
n = 249, 55%). Globally, the pattern of disposing liquids into waste water is similar with a review of international surveys concluding respondents were 2–5 times more likely to flush a liquid than solid [
23]. These practices are in line with general disposal practices where solid household waste is disposed of via bin and where the toilet or sink is the most obvious receptacle for liquid waste. Rates of liquid disposal have more than doubled since Bound and Voulvoulis [
11] and although not examined in the present work, one reason could be increased recycling whereby people are more likely to pour away liquid medication in order to recycle bottles/containers. When recycling was less common, more unused medicine bottles may have been discarded in the bin. The route to natural waterways and environment is more direct through flushing than via general waste and landfill. Boehringer [
52] deemed it to be more harmful suggesting a prudent approach would be to focus strategies on reducing exposure at this destination by raising awareness of the environmental dangers of this route and including take back advice on liquid containers and bottles. In Sweden, pharmacies supply transparent bags with informational text on where unused medicines should be placed which enables households to correct handling [
51].
The rates for pharmacy disposal are higher in the UK than in New Zealand both for liquids (UK:
n = 170, 28% vs NZ:
n = 79, 17%) and solids (UK:
n = 236, 40% vs NZ:
n = 110, 24%). Our data suggest a higher likelihood of returning a medicine to a pharmacy if it is solid rather than liquid or creams/ointments. Global surveys which have collected data on medicine preparation and disposal have focused on general waste or toilet/sink disposal rather than pharmacy disposal limiting international comparison. Many countries have no standard medicine disposal protocols or procedures for pharmacies to accept unused medicines [
16,
23] which may be one reason for why comparison of pharmacy take-back by country is limited. Current European legislation obligates member states to implement appropriate collection schemes for unused medicines [
53,
54] but in some member states there is little information to demonstrate any collections systems exist [
55]. It is important that a policy for medicine collection is financed properly and clearly outlines the responsibilities of each organisation. The legislation in Lithuania, for example, states the government are responsible for financing but the roles are unclear which means in practice, pharmacies pay for disposal of collected medicines and are, therefore, less likely to accept them [
23].
The role of multiple variables in predicting self-reported medicines disposal behaviour
Several variables had a unique role in predicting previous disposal behaviour. The results of the regression analyses supported our hypothesis (H1) and past work (e.g., [
12,
18]) that age would negatively predict a person’s waste bin disposal. In contrast to previous work [
19,
21,
56] and our hypothesis (H2), age was not a positive predictor of returning unused medicines to a pharmacy. Yet, age was a positive predictor of sink/toilet disposal [
19]. It may be older people express a guardian role around family and are more inclined to flush medicines for safety reasons.
Contrary to Hypothesis 3, Owens and Anand [
18] findings that demonstrated females have greater sink/toilet disposal were not supported in the final model. SES was not a significant predictor of correct disposal. The hypothesis of presence of children predicting more frequent sink/toilet disposal (H4) was supported. Presence of children was also a positive predictor of bin disposal and a negative predictor of correct disposal, suggesting households with children disposed less appropriately than households without. Here, it may be that people with children are more likely to flush and dispose in bins for reasons of child safety. It may also be that those with children perceive themselves to have less time available to them. In this regard, Foon [
25] reported that perceived busyness had a negative effect on intention to properly dispose medicines.
In support of Hypotheses 5 and 6 both received Information on correct disposal and awareness that medicines can be safely disposed at a pharmacy were positive predictors of correct disposal. Similarly, both variables were positive predictors of returning medicines to a pharmacy and not disposing in the bin, although interestingly they were not associated with lower disposal in sinks/toilets. Such findings may suggest awareness of incorrect disposal is limited to disposal in the bin and sink/toilets may not be seen as incorrect or harmful. Campaigns that carry a particular emphasis on avoiding water pollutions via the sink/toilet in addition to encouraging safe pharmacy returns would help to address this and we discuss the role of information campaigns below.
Convenience (H7) was included as a positive predictor of correct disposal but was not significant in the final model. Convenience of getting to a pharmacy was rated highly (M = 4.95 from 7) which is likely due to widespread availability of pharmacies. However, it may be that other convenience factors such as ease of medicine storage (before disposal), remembering to dispose and having time to dispose may be more important to disposal destination than convenience of getting to a pharmacy.
The probability variable in the present work captures assessments of the likelihood of good disposal practices by others in the neighbourhood. Probability of good disposal by others positively predicted overall good disposal behaviour (H8) and was also a negative predictor of bin disposal. It is interesting to reflect on this alongside the profile of results for the subjective norm variable which refers to the idea that important people would approve of and support good medicines disposal behaviours. This was not a significant independent predictor of disposal behavior—this was also the case in the study by Foon et al., [
25] where intention was the outcome variable. The difference may reside in the question wording with probability questioning a person’s likelihood of inappropriate disposal and SN questioning people’s belief about approval of returning medicines to a pharmacy in the next 6 months; disposing inappropriately is likely seen as more disapproving than not returning medicines to a pharmacy. Additionally, disposing of medicines is often an infrequent behaviour and may not be necessary in the next 6 months. For instance, when asked in Sweden, a country known for its high rates of pharmacy return, what people did with unused drugs, more than half the respondents replied they were stored in the cupboard [
51]. Future studies may want to adapt this question by removing reference to a timeline for the behaviour to occur.
Contrary to H8, affect did not predict the overall disposal measure or disposal to the pharmacy but was a negative predictor for the bin and a positive predictor for disposal in sink/toilet indicating those more fearful and anxious of inappropriate disposal were also those reporting less frequent disposal in bin and more frequent disposal in sink/toilet. One possibility here relates to the explanation proposed in relation to the children variable. It may be that for some the notion of inappropriate disposal relates to safety—and anxiety and concern about this necessitates immediate and self-evident removal of that potentially dangerous substance. This is achieved through disposal in the sink or toilet more easily than in the bin or via the pharmacy both of which likely require the substance to be present in the house for a more extended period.
A positive association between Knowledge and correct disposal (H9) was not found. The disjoint between environmental risk-knowledge and behaviour is apparent in other studies [
19,
57] which have found those with good knowledge of harmful effect of medications on the environment still practice incorrect disposal. It may be that individuals who consider themselves knowledgeable on the environmental risk do not believe it is sufficiently risky enough for them to change behaviour.
Although attitude was a significant predictor of
intention to dispose in the study by Foon et al. [
25], it was not positively associated with correct behaviour (H10). Those that were more negative about returning medicines to the pharmacy over the following 6 months were those that were more likely to have had higher frequency correct disposal in the previous 6 months. This may be due to disposal frequency with those who have already returned medicines considering a repeat disposal over the next 6 months as useless and unwise.
The potential disjuncture between attitude and performance of the behaviour was also evident in relation to the PBC variable which was not positively associated with correct behaviour (H11). Indeed, there is little evidence for the direct effect of PBC on
behaviour [
58]; having control over the performance of a behaviour may be unrelated to its occurrence [
59]. This was evidently the case here, and notably so given the mean of PBC was high.
Intention to return in the next 6 months was positively associated with past behaviour. This fits with previous theories that experience increases the accessibility of intention [
60]. Sheeran et al. [
61] found greater experience enhances predictive validity up to a point; thereafter increased experience was associated with weaker prediction of intention. The relative infrequency of medicine waste recycling makes it more likely to follow the intention stability perspective rather than become habitual thereby reducing intention–behaviour consistency.
Study limitations
The cross-sectional nature of the study limits determination of causality between variables in the model, for example, it is not possible to establish whether higher awareness to dispose at pharmacies resulted from previous disposal or was the cause of that disposal. The sole use of a questionnaire introduces possible common-method variance and further exploration of the determinants of medicines waste would benefit from triangulation with other data sources. Additionally, remembering infrequent yet possibly unremarkable events poses particular challenges to self-reports of recall of disposal frequency, type, and destination [
62]. Finally, we have sought to set this research in the context of other studies in the area and particularly in relation to previous UK research [
30]. Overall, however, the literature is relatively sparce and available comparisons are in different cultural settings sometimes with different disposal options and policies.
Future research
To address limitations inherent in cross-sectional study designs, future work may want to consider a longitudinal approach. Moving beyond self-report data is essential if we are to evaluate a campaign on medicines returns. Here, having a clear baseline understanding of what medicine is returned to a pharmacy, taking account of population and seasonality is required. In establishing these baseline parameters and informing the design of a campaign, it would also be useful to understand why specific medicines are being returned with medicine data at the point of return also ensuring greater accuracy of measurement type and count.
This study is the first to allow characterisation of the way in which people’s disposal strategies can vary—most people in this study had disposed of medicines waste in at least two different locations. We suggest that future research continues to recognise this and seeks to further understand the circumstances that lead to disposal to the different destinations. We have suggested one determinant of this is type of medicine but given variability in the disposal destinations of a single medication preparation type (e.g., liquids), a clearer understanding of this is required.
It may also be important to consider how people’s mental models of disposing of medicines waste relates to more general—much more established—models of recycling behaviour. This might usefully explore, for example, whether unused liquid medicine is disposed of in the sink or toilet to recycle the plastic or glass bottle.
Research in this area should ultimately inform strategies to change medicines disposal behaviours. We have noted the value of increasing awareness of the options for safe disposal of medicines waste but a more tailored analysis of the capability, opportunity and motivation people have to return medicines to the pharmacy is required in order to design and target appropriate interventions [
63] that will be effective in reducing the amount of medicines waste in the environment. This might, for example, involve reminders about disposal at point of dispensing, and on packaging, developing ways of ensuring pharmacy disposal processes are frictionless. Official disposal options in some countries are not via the pharmacy—situating official disposal options in other places may assist in increasing visibility and legitimacy of correct medicines waste practices.
Of course, addressing the issue of medicines waste disposal is only one side of the equation. It is also vital to develop and prioritise pharmaceuticals that have less impact on the environment as well as to avoid unnecessary prescriptions. Social prescribing is an initiative increasingly embedded in primary care in the UK that may have a role in contributing to this [
64].