1. Introduction
An emerging area of tobacco research is the environmental hazards of tobacco waste. For instance, cigarette butt debris remains an environmental issue, with trillions of cigarette butts being discarded inappropriately annually [1]. Tobacco waste is also a significant threat to aquatic ecosystems due to the leaching of contaminants, including nicotine, polycyclic aromatic hydrocarbons, and metals, into the environment [2,3]. Filters found in cigarettes are made from plastic cellulose acetate, a compound that is resistant to biodegradation and releases toxic plastic micro-fibers and nanoparticles that can transfer surface-bound metals and other organic contaminants into the environment [2,4]. In addition to the toxicity of cigarettes leaching into the environment, e-cigarettes, plastics, and other sharp elements of the containers pose an additional risk given the ubiquitous discarding of this waste in the environment [5]. In an effort to protect public health, the FDA attempted to ban JUUL in the United States (U.S.) because of evidence suggesting harmful chemicals such as chromium, iron, and lead leach from the JUUL pods themselves [6,7]. However, JUUL has yet to be removed from shelves following an appeal.
Inappropriately discarded tobacco waste extends beyond an environmental issue, as cigarettes themselves contain a host of chemicals, including acetaldehyde, arsenic, and benzene, which have been linked to deleterious health effects, including cancer, birth defects, and other health harms [2,8,9,10,11]. Cigarette filters are misconstrued to reduce or eliminate the toxic ingestion of tobacco chemicals, yet existing research suggests that since the addition of these filters, patterns of smoking have changed, with smokers taking deeper inhalations, as well as increases in lung adenocarcinomas [12,13]. Moreover, the accidental ingestion of cigarette butts is especially concerning due to the chemical poisoning risk among children and animals, which may result in nausea and vomiting or other extensive neurological issues [14].
One ongoing strategy to raise public health awareness about these pressing issues has been engaging the public in tobacco waste clean-up. However, there remains a scarcity of studies evaluating the usability of TPW methods for public participation. Examining clean-up methods from the lens of citizen science and usability is important, particularly as citizen science approaches have been shown to have positive impacts on the participants [15,16,17]. We describe a citizen-scientist approach that evaluates the operational usability of two protocols used to collect and categorize tobacco waste as part of a TPW clean-up project that took place in two cities in California’s San Joaquin Valley (SJV). The findings of this study are significant for communities who wish to lessen the impact of tobacco waste on the environment and for scientists interested in utilizing a community-centered approach to tobacco waste collection.
Citizen Scientist Approach
The public (citizen, hereafter) can play a key role in generating new scientific knowledge, a process commonly known as citizen science projects. Citizen science involves the non-professional public’s collaboration in the scientific process with academic and professional scientists [18]. Citizen science projects are popular in areas that address environmental and health disparities [19]. Some well-known citizen scientist projects include wildlife counts [20], astronomy assessments [21], plastic pollution [22], marine litter [23], and other biological and ecological sample collections [24]. The advantage of this approach is that citizens can identify, collect, analyze, and utilize data that are meaningful and relevant to them. Empirical research suggests that citizen involvement in science can impact how people perceive scientists, their community, and themselves. For example, community members participating in citizen science projects have improved their scientific inquiry skills [15], developed a sense of environmental agency [17], and adopted a “science identity” [16]. Engaging young adults as citizen scientists can help prepare the next generation of researchers and promote tobacco cessation and environmental engagement [25,26].
TPW projects share similar characteristics with existing citizen scientist projects; they are designed to be non-labor intensive and take place in local environments such as residential neighborhoods. Indeed, TPW assessments have recruited volunteers, particularly among youth coalitions who seek to determine the impact of tobacco waste on their environment in order to advocate for tobacco control policies [27]. However, the primary goal of these assessments is to clean up the area of all waste, not just TPW.
Using a citizen scientist approach is particularly helpful in areas such as the SJV, an area where rates of tobacco use are consistently higher (16%) than the rest of the state (12%) [28] and where roughly a quarter of the residents are impoverished [29]. In 2022–2023, approximately 84% of all University of California (UC) Merced undergraduate students received financial aid, many of whom have also been lifelong residents of the SJV and are highly connected in the Nicotine and Cannabis Policy Center (NCPC)/UC Merced catchment area [30]. In this regard, feasible TPW collection methods that are usable and acceptable can generate empirical data to estimate the impact of TPW, potentially resulting in enhanced evidence dissemination and community-based response for low-resourced regions like the SJV.
To better understand the sociological, ecological, and biological impact of inappropriately discarded tobacco waste, California researchers have developed two tobacco debris protocols to examine TPW in the environment. Protocol A, developed by researchers at San Diego State University (SDSU), is designed to map TPW based on neighborhood surveys, develop predictive models of TPW based on socioeconomic and other factors, and disseminate findings to help eliminate TPW with communities [31,32,33]. Protocol B, designed by researchers at UC Merced and UC Santa Barbara, assesses the ecosystemic effects of inappropriately discarded TPW in protected areas (e.g., parks and nature preserves) [34,35]. This study assesses the operational usability and acceptability [36]—considering ease, time, and data collection processes—of each protocol. Findings are discussed in terms of (1) how well these protocols worked among citizen scientists in the SJV and (2) the level of engagement of the citizen scientists with each protocol.
2. Materials and Methods
We engaged nine citizen scientists (also referred to as “volunteers”), who were young adult undergraduate students actively residing in the SJV. These students were part of the NCPC Tobacco Endgame Internship at UC Merced and the Smoke and Vape Free Scholars Initiative at California State University, Stanislaus (CSU Stanislaus). Participants joined the project voluntarily, ensuring that they had a personal interest in the research’s objectives. Five citizen scientists along with the research team (AAT, MMJ, JRDG, MWB, AVS) were present at the Merced site. Seven citizen scientists along with three members of the research team (AAT, MMJ, JRDG) were present at the Turlock site. Three of the citizen scientists were present at both locations.
2.1. Area Selection
Lead investigators (AVS, JRDG) selected two sites within the cities of Merced, California, and Turlock, California. Investigators chose these sites because of their personal knowledge of the area, strategically selecting lower-income residential neighborhoods where tobacco waste was known to be present. Data were collected in Merced in December 2022 and data in Turlock were collected in February 2023. After arriving at both sites, lead investigators surveyed the area to determine the specific sidewalk citizen scientists would assess. In Merced, the area of interest was located directly across the street from a small park and single-family homes and was on the side of a speedway racetrack (see Figure 1). In Turlock, the area of investigation was on the side of a children’s park and was directly across the street from single-family homes and close to train tracks (see Figure 2).
While the citizen scientists were provided with data collection materials and instructions, one lead investigator (JRDG) used the mobile application Survey123 [37] to map geo-point locations (i.e., the path of the city block). Sites for Protocol A and B spanned one residential side of a sidewalk (corner to corner) on one city block (see Figure 1 and Figure 2). After receiving training on both protocols, citizen scientists were given specific geographic boundaries of the sidewalk so that each pair had an equidistant area of the sidewalk for which they were responsible for assessing all TPW.
2.2. TPW Collection Protocols
At each site, the research team utilized two distinct TPW collection protocols, labeled Protocol A (SDSU methodology) and Protocol B (UC Merced/UC Santa Barbara methodology). For the purposes of this study, we adapted aspects of Protocol A to accommodate the requirements and limitations of our research team. Originally, Protocol A involved collecting TPW after data were recorded. However, for this study, we instructed citizen scientists not to collect the TPW post-recording, ensuring the waste remained for the subsequent data collection using Protocol B. Below, we detail the methodologies, tasks, and materials involved in each protocol.
Protocol A. Five citizen scientists and members of the research team were paired up and given their geographic boundaries for data collection, as well as a 20-inch hoop (see Figure 3). One person from each pair placed the hoop on the ground that contained any visible TPW. Using Survey123 on their personal smartphones, the other partner marked their geo-location, recorded the type (see Figure 4) and amount of TPW within the hoop, recorded a brief site description (i.e., surrounding infrastructure), and took a picture of the hoop. After this submission, the pair left the waste as it was found and moved onto the next piece(s) of visible TPW within their section and repeated these steps until there was no more visible TPW to record in their section.
Materials. All citizen scientists were provided with latex gloves, and each pair shared a 20-inch hoop. Citizen scientists were provided print-out images of classifications for points of interest (e.g., single family residence, retail store, etc.; see Supplementary Material S1) and were shown images of types of tobacco products (e.g., cigarette butt, e-cigarette waste, etc.) using online images. One person in each pair used their personal smartphone to record data. As we modified Protocol A from its original form and instructed the team not to pick up TPW after recording, citizen scientists were not provided with pickers for waste collection.
Protocol B. Seven citizen scientists and members of the research team were paired up and returned to their geographic areas for data collection. Each pair of citizen scientists was instructed to set a ten-minute timer and collect all visible TPW in their section. Once their timers went off, the pairs’ search immediately ended. Citizen scientists then sorted, counted, and described the TPW found in their section (see Supplementary Material S2). After all waste was counted, each pair took a picture of their accumulated waste, recorded their geolocation, and submitted their counts via a personal smartphone into Survey123. The survey included a section for site description where citizen scientists were asked to describe the general area, surrounding infrastructure (i.e., garbage cans, drain, etc.), and their starting and ending geolocation.
Materials. All citizen scientists were provided with latex gloves, pickers, and cups to collect TPW. Citizen scientists were provided a print-out survey data sheet to record the types of tobacco products they found (e.g., “fresher/older” cigarette butts, e-cigarette waste, etc.) and were asked to record a brief site description (see Supplementary Material S2). Citizen scientists or members of the research team used their personal smartphones to record information.
2.3. Training
On each day of data collection, citizen scientists received comprehensive on-site training from members of the research team (JRDG, MWB, AAT), focusing on the study’s aims and significance, ensuring that all participants were informed of the goals and the role they would play in advancing tobacco control through environmental health research. Initially, they were trained on Protocol A and provided relevant handouts for the various classifications they would need to identify (i.e., type of tobacco product waste, type of building structure, etc.) along with necessary materials (e.g., gloves, hoops) [31]. Citizen scientists then completed data collection using Protocol A.
Following the completion of data collection with Protocol A, citizen scientists underwent a second training session for Protocol B. They also received a survey sheet [34] and other necessary materials for data collection (e.g., gloves, disposable cups, pickers). After training for Protocol B concluded, they began collecting data using this methodology.
In Merced, citizen scientists were either paired with or directly overseen by lead investigators (AVS, JRDG) to ensure they understood and followed protocol. In Turlock, citizen scientists who participated in data collection in Merced (n = 3) were paired with citizen scientists who had not yet participated if they could not be paired with a lead investigator. This was performed to foster peer-to-peer learning and ensure consistency across different data collection and locations.
2.4. Debriefing Interview Sessions
A member of the research team (MMJ) conducted brief semi-structured interviews with three citizen scientist volunteers on-site immediately after they completed both protocols. These interviews, lasting 5 to 10 min, focused on assessing the operational usability and acceptability of the protocols. Specifically, they explored the volunteers’ motivation for participating, their impressions of using both protocols, aspects of the data collection process that worked well or could be improved, and how the activity influenced their views on their communities.
3. Results
There were slight differences in the amount of time it took to collect data using Protocols A and B at both site locations. In Merced, Protocol A took approximately 37 min to complete (vs. Protocol B ~ 10 min). In Turlock, Protocol A took approximately 29 min to complete (vs. Protocol B ~ 10 min). Citizen scientists were able to complete Protocol A in Turlock at a faster speed because at least one person in each pair was present in Merced and had prior experience collecting data using Protocol A (i.e., once they collected data using Protocol A, it became easier for them when using this method again).
3.1. Counts
Both Protocols A and B returned comparable counts of TPW in both Merced and Turlock; however, the classification of TPW within these protocols are slightly different from one another (e.g., Protocol B separates “fresher” cigarette butts vs. “older” cigarette butts, etc.). In the city of Merced, Protocol A returned 76 pieces of TPW, and Protocol B returned 78 pieces of TPW (see Table 1). In the city of Turlock, Protocol A returned 78 pieces of TPW, and Protocol B returned 77 pieces of TPW (see Table 1).
Imaging of Tobacco Product Waste. TPW visualization varied between Protocols A and B. Protocol A required photographing each piece of TPW in situ (see Figure 5 and Figure 6). Using this protocol, citizen scientists recorded the immediate surrounding environment of each piece of TPW (e.g., surrounded by leaves, etc.) and denoted where waste was found (e.g., inside of sidewalk vs. gutter) along with how much waste was found within the hoop.
In contrast, Protocol B photographed all pieces of TPW found within a pair’s geographical restrictions using one photo (see Figure 7 and Figure 8). This protocol highlighted the amount and type of waste found within a given area rather than describing the immediate surrounding environment in which it was found.
3.2. Debriefing Interviews
Overall, the interview sessions resulted in several key themes: training was associated with enhanced confidence and capability; citizen scientists suggested improvements including more structured protocols and increased volunteer collaboration among volunteers; participation led to increased environmental awareness and provided insights into community behaviors, hence the greater appreciation for the benefits of civic engagement; and investigating TPW deepened participants’ connections to their community and environmental health concerns.
Volunteer participants offered practical suggestions to enhance the data collection protocols, such as the need for additional volunteers to ensure thorough coverage and enhanced markers to delineate data collection areas more clearly. Moreover, they reported having positive experiences with carrying out tasks independently. For example, one citizen scientist highlighted how the training session was helpful to build their confidence, stating the following:
I really liked getting practice and being able to go out and do it ourselves. So we got to be shown on the phone, how the GPS coordinates work, pretty much how to do things ourselves and get the confidence to do it.
(Psychology Major, UC Merced Senior, Merced site)
Citizen scientists also offered suggestions to improve the overall usability of the protocols. For example, some mentioned how more volunteers on site would allow for more thorough data collection, as follows:
It would be nice if we had more eyes. We missed a few butts here and there. And so in [Protocol A], we missed a few.
(Psychology Major, UC Merced Senior, Merced site)
Furthermore, the same citizen scientists recommended specific tools to aid in data collection, such as markers or boundaries:
[I]t would be helpful to have specific markers, like a flag, to be able to say, we are starting over here and then for enough communication between teams to be able to say ‘okay we covered this area,’ so that we’re not going over the same area.’ This would be important to do if you were going to survey a whole park.
(Psychology Major, UC Merced Senior, Merced site)
Other volunteers mentioned the importance of considering environmental conditions when carrying out fieldwork. For example, providing better materials to better identify waste and pick up hazardous litter, as follows:
I think it could be improved if we had some more tools to pick through the leaves. So maybe some rakes, pickers, something like that. The hoop [Protocol A] takes a lot of time, taking a picture, setting it down. Another thing would be to just make sure that we clean up all the trash in the area, and maybe we bring more correct equipment, to pick up things like glass. I think the community is a lot more receptive to you digging around their back yards, if you’re physically helping.
(Public Health Major, CSU Stanislaus, Merced site)
Citizen scientists described their personal heightened awareness of TPW in their environments following their involvement in the project:
Ever since we did the first activity, I started noticing the ground more, like ‘oh there’s a cigarette butt.’ Because we don’t know how long they’ve been there. They could have been there for weeks or years. It was also surprising the amount of cigarette butts we were able to find. I wasn’t expecting so much. I feel like we’re helping with the litter.
(Psychology Major, CSU Stanislaus Senior, Merced site)
Another citizen scientist remarked that the activity encouraged her to share knowledge about TPW with her friends on campus:
Just the first practice run, I started noticing the waste around my city, like if I was going to the bank. So I was able to take that information to the people I’m around, and let them know.
(Psychology Major, UC Merced Senior, Merced site)
Another student mentioned how the waste revealed socioeconomic patterns in behaviors of the residents, which was something that she had never thought about before:
I didn’t think about what people are using, and what area, and why, and what their income level is around here…it made me think what people are doing in different areas and how the waste can tell us about their behaviors.
(Psychology Major, UC Merced Senior, Merced site)
Citizen scientists provided valuable suggestions for enhancing future TPW collection protocols, such as the use of better materials to facilitate sorting through waste. Additionally, they reported that their overall experience was not only impactful but also provided significant insights into their learning, particularly in terms of engaging more with community and environmental health issues.
4. Discussion
This study is among the first to assess the operational usability of two unique TPW collection protocols engaging citizen scientists. Our findings present a model for how citizen scientists can study the environmental impact of TPW and participate in tobacco control research more generally. This project also underscores novel approaches in environmental and health sciences, demonstrating a significant potential of integrating citizen scientists in tobacco control research and innovative approaches in environmental health science.
Using Protocol A, volunteers could observe the context surrounding each piece of TPW and record the waste in its natural environment via photographs, which facilitates reassessment. Regarding usability, citizen scientists noted that this protocol was more taxing (compared to Protocol B) as it required them to bend down to place the hoop on the ground whenever they saw a piece of waste, record information on the contents within the hoop, and repeat this process until all of the waste in their section had been recorded. Citizen scientists also noted that when TPW was found in the gutter with some water, they had to work at a faster pace to capture an image and denote the surrounding environment of the waste before it could flow into the drain at the end of the street. During the timeframe of our demonstration project, water sources were not verified or considered relevant, as there had been no rainfall in the seven days preceding data collection. Additionally, under Protocol A, citizen scientists also had to communicate with other pairs to ensure that data were not double-counted. In this regard, citizen scientists suggested providing physical markers or boundaries to ensure data are not recorded twice. That said, Protocol A appeared to be acceptable since the volunteers appreciated how the hoop and unlimited time allowed them to focus on their designated area to find and record waste. Without a time restriction, citizen scientists could spend time searching for hidden or disguised TPW.
In contrast, the usability of protocol B was observable. This protocol required less physical exertion from our citizen scientists. Setting a 10-min timer seemed to be a sufficient amount of time to locate and pick up visible TPW. Additionally, Protocol B allowed citizen scientists to pick up waste that they were not necessarily sure was tobacco-related and could sort it after their timer had elapsed. Specifically, when the outer paper of a cigarette degrades, the filter may initially resemble a material similar to cotton or cloth (see left side of Figure 7). Once citizen scientists were shown what a disintegrated cigarette can look like in the training sessions, they were able to identify TPW more accurately.
The debriefing sessions revealed that citizen scientists (comprising nine undergraduate university student volunteers in this case) became more aware of their environment after data collection. Most notably, this activity shaped the volunteers’ research in future coursework. The citizen scientists on the project (students from CSU Stanislaus) developed an independent research project on the topic of environmental risks of TPW. They conducted a survey of staff, faculty, and students and tested the level of knowledge about the hazards of TPW on the environment. The citizen scientists stated that they would not have chosen this research topic without their involvement in the TPW project. Consequently, allowing citizen scientists to have agency and input on the process while following up with a subsequent activity of their choosing (e.g., research, community action, letter to the editor, etc.) sustained the project for much longer than we anticipated. The long-term impact of this activity on citizen scientists remains an emerging area of research. From the debrief interviews, volunteers stated that they had never done anything like this before and that this was the first time they had participated in scientific data collection. They stated how the activity caused them to notice more TPW on the ground in their everyday lives. These findings are consistent with previous research on how a citizen science approach to data collection can raise awareness about environmental and health risks in their own communities, potentially encouraging future action [38].
Some limitations should be acknowledged. Firstly, this project lacked a rigorous experimental design. We did not develop controls, randomization, blinding, or pre-post testing, which creates limitations in the generalizability of some of our findings. Instead, the goal of this project was to demonstrate how TPW could be collected and categorized in a standardized way using two different protocols and gather input on the usability and acceptability of the TPW collection protocols. In the future, we aim to assess the collection protocols with citizen scientists across a wider age range (including adolescents), conduct pre-post quantitative evaluations and interviews, and establish the efficacy of both protocols, enhancing the generalizability of our findings. Secondly, both debris survey protocols were tested only in low-income residential areas of Merced and Turlock, where lead investigators (AVS, JRDG) were familiar with the general area. While our TPW counts were comparable to city values found in previous efforts assessing cigarette butt counts [39], we plan on testing the methodologies in different geographic regions (e.g., commercial areas, higher income residential areas) to determine whether findings remain reliable. Furthermore, we will incorporate a more systematic approach to choosing sites, guided by objective criteria such as rurality vs. urbanity and known prevalence rates of tobacco use or demographic data to ensure a representative sample of sites. Thirdly, although we were not necessarily interested in determining the count efficacy of these two TPW protocols, it is possible that citizen scientists experienced practice effects in finding waste in Protocol B, given they had just completed taking photographs of each piece for Protocol A. As such, we do not recommend comparing the efficacy of these two protocols using our TPW counts. We plan on mitigating this issue in the future by switching the sections of the block that citizen scientists are assigned between Protocols A and B to eliminate practice effects or by calculating TPW per minute to compare areas that may have high and low use rates of tobacco products. Finally, the weather and time of season were also an issue for some volunteers. Data were collected during the fall season with many leaves on the ground and gutters, and citizen scientists found this challenging. We anticipate training future volunteers on how to sift through other debris to record any hidden TPW.
5. Conclusions
Inappropriately discarded tobacco waste continues to endanger environmental health. Our study suggests that while both data collection protocols provide information regarding locating and identifying the environment(s) in which TPW is found, Protocol B provides a more usable and acceptable approach for citizen scientists compared to Protocol A. The positive impact of this engagement is evident as citizen scientists reported a greater understanding of the impact of TPW in the environment and the broader societal implications of TPW waste within their communities. Utilizing a citizen science approach is one way to involve community members in the TPW research process to build capacity for change, motivate tobacco control efforts, and increase awareness of environmental health issues. Future initiatives should continue to explore and enhance engagement strategies in environmental health to maximize these benefits, particularly engaging citizen scientists as both contributors to and beneficiaries of environmentally-based tobacco control endeavors. Highlighting where, how much, and what kind of tobacco waste is found in local communities can foster efforts in passing stringent public health policies to protect our community and environmental health.
Conceptualization, J.R.D.-G., M.W.B. and A.V.S.; Data curation, A.A.T., M.M.J., J.R.D.-G., M.W.B. and A.V.S.; Formal analysis, A.A.T., M.M.J. and J.R.D.-G.; Funding acquisition, A.V.S. and J.R.D.-G.; Investigation, A.A.T., M.M.J., J.R.D.-G., M.W.B. and A.V.S.; Methodology, J.R.D.-G. and M.W.B.; Project administration, A.A.T., M.W.B. and A.V.S.; Resources, A.V.S.; Software, J.R.D.-G.; Supervision, A.D., M.W.B. and A.V.S.; Writing—original draft, A.A.T. and M.M.J.; Writing—review and editing, A.D., M.M.J., J.R.D.-G., M.W.B. and A.V.S. All authors have read and agreed to the published version of the manuscript.
Not applicable.
Not applicable.
Data can be made available on request.
We thank the citizen scientists from the 2021–2022 Smoke and Vape Free Scholars Initiative Program (Lara Al-Jaser, Monica Montenegro, Asha Nair, Gianna Nunes, and Jacqueline Villasenor-Ramirez; CSU Stanislaus) and the Nicotine and Cannabis Policy Center’s (NCPC) Tobacco Endgame (Mary Garcia, Alondra Mercado, Hargun Sethi, and Karina Vasquez; UC Merced) for their time and effort in helping us with this project. Also, we thank Alexander Mellor, NCPC Head of Operations, who led field organization and scheduling. The views expressed in this report are those of the authors and do not reflect the position of the citizen scientists and staff.
The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.
The following abbreviations are used in this manuscript:
| TPW | Tobacco Product Waste |
| SDSU | San Diego State University |
| NCPC | Nicotine and Cannabis Policy Center |
| SJV | San Joaquin Valley |
Footnotes
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.
Tobacco product waste count by residential area and protocol.
| City of Merced | City of Turlock | |
|---|---|---|
| Protocol A | ||
| Cigarette Butts | 58 | 59 |
| Tobacco Products | 17 | 19 |
| E-cigarettes or Vapes | 0 | 0 |
| Cannabis Waste Products | 0 | 0 |
| Dual Use Products | 1 | 0 |
| Total | 76 | 78 |
| Protocol B | ||
| “Fresher” cigarette butt | 60 | 61 |
| “Older” cigarette butt | 17 | 13 |
| Hand-rolled tobacco or cannabis paper/“butts” (no filter) | 0 | 0 |
| Cigars/Blunts | 0 | 0 |
| E-cigarette and Cannabis Vape Product Waste (i.e., heat-not-burn products, pens, pods) | 0 | 0 |
| Other Litter (e.g., cigarillo tips, lighter, smokeless pouches, packaging/wrappers) | 1 | 3 |
| Total | 78 | 77 |
Supplementary Materials
The following supporting information can be downloaded at
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Details
; Durazo, Arturo 2
; Jordan, Meggan M 3
; Díaz-Garayúa, José R 3 ; Beutel, Marc W 4
; Song, Anna V 5
1 Center for Tobacco Control Research and Education, University of California, San Francisco, CA 94117, USA;
2 Nicotine and Cannabis Policy Center, Health Sciences Research Institute, University of California, Merced, CA 95343, USA;
3 College of the Arts, Humanities & Social Sciences, California State University, Stanislaus, Turlock, CA 95382, USA;
4 Environmental Systems Graduate Group, School of Engineering, University of California, Merced, CA 95343, USA;
5 Nicotine and Cannabis Policy Center, Health Sciences Research Institute, University of California, Merced, CA 95343, USA;