Hongying Dai

Introduction: Blunts, combining tobacco and cannabis, fall into a regulatory gray area under United States federal and state laws. Blunt use is increasing among adults, yet limited evidence exists on how toxicant exposure among blunt users differ from that of non-blunt cigar users. Methods: We analyzed biospecimen data from 8332 adults in Wave 4 of the Population Assessment of Tobacco and Health Study. Weighted multivariable linear regression models compared urine biomarkers of exposure across five classes of harmful and potentially harmful constituents, along with a biomarker of oxidative stress between exclusive blunt users and exclusive non-blunt cigar users. Analyses were stratified by cigar type (traditional cigar, cigarillos, filtered cigar) and use frequency (some-day vs. daily). Results: Compared with non-blunt cigar users, blunt users exhibited higher geometric mean concentrations of volatile organic compounds (VOCs), including metabolites of acrylamide (AAMA: 129 vs. 64 ng/mg, P < 0.001) and acrylonitrile (CYMA: 31.7 vs. 7.8, P = 0.018), but lower lead (0.23 vs. 0.38 ng/mg, P < 0.029). Blunt use was associated with distinct toxicant exposure profiles that varied by frequency of use. Among some-day users, blunt use showed higher VOCs compared with non-blunt cigar use. Conversely, daily blunt users exhibited lower urinary nicotine metabolites, tobacco-specific nitrosamines, polycyclic aromatic hydrocarbons, and VOCs than daily non-blunt cigar users. Conclusions: These findings highlight the complexity of toxicant exposure associated with blunt use and underscore the need for future studies on health implications and regulatory approaches addressing concurrent tobacco and cannabis use. Implications: Blunt use is persistently rising among adults. This study provides important public health and regulatory implications. Blunt use represents a distinct and underregulated form of tobacco–cannabis co-use that exposes users to a unique toxicant profile, including elevated volatile organic compounds. The frequency-dependent exposure patterns observed suggest that blunt smoking behaviors, together with plausible variations in blunt product construction, substantially influence toxicant intake and associated disease risk. Targeted surveillance, consumer education, and evidence-based regulations are needed to address misconceptions about blunt safety and to mitigate long-term risks for cancer, cardiovascular disease, and respiratory illness.

Objective: Nicotine concentration is a key characteristic of modern e-cigarette products. This study aims to illuminate age-related differences and temporal trends in nicotine concentrations to help inform strategies to reduce nicotine-related public health risks. Methods: Data were drawn from the US Population Assessment of Tobacco and Health Study Wave 5 (December 2018–November 2019), Wave 6 (March–November 2021) and Wave 7 (January 2022–April 2023) and analysed in 2026. χ² tests and multivariable regressions were used to compare nicotine levels used in e-cigarettes (ie, unknown, 0%, 0.1–1.7%, 1.8–4.9%, 5.0%+) by age groups at Wave 7 and examine trends in nicotine concentrations for adults (18+) across Waves 5–7. Results: Among individuals currently using e-cigarettes at Wave 7 (n=3782), about 60.1% of those aged 12–14 and 51.2% of those aged 15–17 reported not knowing nicotine concentrations, and young adults aged 18–24 were the most likely to report using 5.0%+ (38.7% prevalence vs 24.4% of those aged 25–34, 14.6% of 35–54 and 4.3% of 55+). The proportion of adults responding ‘I don’t know’ increased from 15.8% at Wave 5 to 23.8% at Wave 7, especially among those aged 18–24 (13.9–26.0) and 25–34 (13.9–23.6%). The proportion of adults reporting 5.0%+ increased from 13.9% to 24.4%(p<0.0001), and those reporting 0.1–1.7% decreased from 49.2% to 35.4% (p<0.0001). Conclusions: Over half of youth using e-cigarettes were unaware of the nicotine concentration. High-concentration products have become increasingly prevalent, especially among young adults. Clearer nicotine concentration labelling on e-cigarette products and continued surveillance of nicotine levels are needed.

Background: Maternal tobacco use during pregnancy poses a public health concern. Longitudinal assessment of maternal smoking cessation’s association with late childhood neurocognitive development is limited.Methods: This cohort study included children aged 9-10 years at baseline (October 2016-October 2018) and 11-12 years at follow up (August 2018-January 2021) across 21 U.S. sites in the Adolescent Brain Cognitive Development study. We used multivariate regression to assess relationships between cessation of maternal tobacco use at knowledge of pregnancy versus continued use and neurocognition as measured by the National Institutes of Health Toolbox Cognition Battery, as well as morphometric brain measures from structural magnetic resonance imaging.Results: Among 11,448 children at Wave 1, 1,625 (weighted: 16.1%) had prenatal tobacco exposure, with 1005 (59.9%) of mothers quitting and 620 (40.1%) continuing after pregnancy awareness. Children whose mothers continued smoking consistently exhibited lower scores in picture vocabulary (Wave 1: b[SE]=-1.1[0.4], p=0.01; Wave 2: b[SE]=-1.3[0.6] p=0.03) and crystallized cognition (Wave 1: b[SE]=-1.4[0.4], p=0.001; Wave 2: b[SE]=-1.5[0.6], p=0.02) and lower subcortical volumes in the left ventral diencephalon (Wave 1: b[SE]=-35.5[17.7], p=0.04; Wave 2: b[SE]=-46.8[23.1], p=0.04), right ventral diencephalon (Wave 2: b[SE]=-56.4[21.9], p=0.01), left pallidum (Wave 2: b[SE]=-34.4[15.7], p=0.03), and right nucleus accumbens (Wave 2: b[SE]=-20.2[6.4], p=0.002). About 25% of the association between extended prenatal tobacco exposure and crystallized cognition was mediated by left and right ventral diencephalon volume. (p<.0001).Conclusion: Maternal tobacco cessation during pregnancy was associated with fewer deficits in neurocognition and morphology during late childhood, indicating the importance of early cessation interventions.

Background ZYN brand and non-tobacco-flavoured products capture most of the US nicotine pouch market. Evidence of which nicotine pouch flavours and brands US youth use is critical for informing youth regulatory protections, but currently lacking. Methods We analysed data from adolescents reporting lifetime nicotine pouch use in the 2025 Monitoring the Future study, a nationally representative, in-school, cross-sectional annual survey of US 8th-grade, 10th-grade and 12th-grade students. Prevalences of nicotine pouch flavours and brands adolescents reported using most often were estimated in the overall sample and stratified by demographic characteristics and past-30-day pouch use patterns. Results Among 472 youth who used nicotine pouches in their lifetime, 97.0% (95% CI 94.6% to 98.4%) reported using nicotine pouches with a non-tobacco flavour most often; non-tobacco flavoured pouch use prevalence exceeded 93% across all demographic and past-30-day pouch use-frequency categories studied. Mint was the most commonly reported flavour used (58.6%), followed by fruit (16.0%); use of original/unflavoured pouches was rare (3.0%). ZYN was the most common brand used, reported by 79.7% (95% CI 74.1% to 84.4%) of youth. Use prevalence of ZYN versus other pouch brands was lower among non-Hispanic Black versus non-Hispanic White, but did not vary by sex, grade, population density or pouch use frequency. Conclusions Among US adolescents reporting lifetime use of nicotine pouches in 2025, use of non-tobacco flavoured pouch products was nearly universal and ZYN was the predominant brand used. Prioritising regulatory policies on flavoured pouches, especially ZYN brand products, merits consideration to reduce youth nicotine pouch use.

Objective: E-cigarette nicotine concentration level is critical to tobacco regulation. This study seeks to examine whether nicotine level is associated with transitions in tobacco use status such as exclusive cigarette, exclusive electronic (e-)cigarette, dual and no use. Methods: Using a large, nationally representative cohort from the Population Assessment of Tobacco and Health (PATH) study in the USA, we compared changes in the prevalence of tobacco use status at 1-year follow-up (Wave 7) based on level of e-cigarette nicotine exposure at baseline (Wave 6). Self-reported nicotine concentration was categorised into high (5.0% or more), moderate (1.8–4.9%), low (0.1–1.7%), 0% and ‘I don’t know’. Results: Among those using e-cigarettes at baseline, those using products containing nicotine (≥0.1%) were more likely to continue exclusive e-cigarette use at follow-up than those using 0% or unknown nicotine content. Among those reporting dual use at baseline, nearly half continued dual use at follow-up regardless of nicotine concentration. However, those using higher nicotine concentrations (≥1.8%) were more likely to either switch to exclusive e-cigarettes or quit entirely indicating greater harm reduction than those using low-nicotine or no-nicotine products. In contrast, nearly half with baseline dual use and 0% nicotine transitioned to exclusive cigarette smoking. Conclusion: These findings highlight the complex relationship between e-cigarette nicotine concentration and tobacco use transitions. Regulatory and public health approaches may benefit from balancing the potential harm reduction role of nicotine-containing e-cigarettes for adults who smoke with concerns regarding sustained nicotine dependence and long-term e-cigarette use.

Introduction: Exposure to tobacco content on social media is associated with adolescent susceptibility to tobacco product initiation. This study examines the prevalence of adolesecent exposure to nicotine pouch content on social media and characteristics of those exposed. Methods: Data came from US Population Assessment of Tobacco and Health Wave 7 participants aged 12-17 (January 2022–April 2023). Past-week exposure to nicotine pouch content on social media was estimated overall and by demographic, behavioral, and tobacco use characteristics using weighted percentages and covariate-adjusted logistic regression. Results: Among 10 650 respondents, 1.9% reported past-week exposure to nicotine pouch content on social media. Exposure prevalence varied by platform used most often (Snapchat [4.1%], TikTok [2.6%], Instagram [2.0%], YouTube [1.2%]) and was curvilinearly associated with time spent using social media (inverted U). Exposure was more common among adolescents who had ever used nicotine pouches versus never (adjusted odds ratio [AOR] = 3.1[95% CI: 1.4-7.0]) and those with high versus no externalizing problems (AOR [95% CI] = 1.9[1.1-3.5]). Hispanic adolescents had lower exposure prevalence than non-Hispanic White respondents (AOR [95% CI] = 0.6 [0.4-1.0]). Conclusions: Past-week exposure to nicotine pouch content on social media was not merely the result of time spent on social media, but was associated with race and ethnicity, social media platform, and externalizing behaviors. Longitudinal data and further questioning are needed to identify why some adolescent groups have greater exposure to nicotine pouch content and to understand long-term consequences. Implications: Past-week exposure to nicotine pouch content on social media was not merely a function of time spent on social media, but was associated with race and ethnicity, social media platform, and externalizing behaviors.

Introduction: Nicotine concentration level, a key characteristic of modern e-cigarettes, may affect dependence risk. This study examined whether e-cigarette nicotine concentration is associated with dependence on e-cigarettes and/or combustible tobacco. Methods: We conducted a cross-sectional analysis using data from adult Wave 7 (2022-2023) of the Population Assessment of Tobacco and Health study, which surveys individuals aged 18+ in the United States. Self-reported nicotine concentration was grouped as high (5.0%+), moderate (1.8%–4.9%), low (0.1%–1.7%), 0%, and “I don’t know.” Separate regressions tested associations between nicotine levels and symptoms of dependence on e-cigarettes (e-cigarette nicotine dependence [ETD], range 0–32) derived from Wisconsin Inventory of Smoking Dependence Motives, Nicotine Dependence Syndrome Scale, and Diagnostic and Statistical Manual criteria, for individuals reporting exclusive e-cigarette use or dual (e-cigarette+cigarette) use, and symptoms of dependence on combustible tobacco (tobacco dependence, range 0–32) for dual use. Results: Among 2246 respondents with exclusive e-cigarette use and 896 with dual use, 24.4% reported using e-cigarettes with high nicotine levels, 11.1% moderate, 36.4% low, 4.3% with 0%, and 23.8% responded “I don’t know.” For exclusive e-cigarette use, individuals with 0% nicotine had the lowest average ETD (8.5), while 5.0+% had the highest (17.0). For dual use, ETD was likewise highest with 5.0+% nicotine (14.2) and lowest with 0% nicotine (4.5); tobacco dependence was highest with 0.1%–1.7% nicotine (16.7) and lowest with 5.0+% (10.2), though not statistically significant after adjusting for covariates. Conclusions: E-cigarette nicotine concentration was associated with nicotine dependence, suggesting that product nicotine levels may play an important role in addiction risk. Implications: E-cigarette dependence increased with increased nicotine concentration among individuals using exclusive e-cigarettes and dual cigarettes+e-cigarettes, suggesting that product nicotine levels may play an important role in addiction risk. Policies are needed to regulate nicotine concentration in e-cigarettes. Clear and full disclosures and warnings about the nicotine concentration in e-cigarettes are needed.

Background: On 17 June 2025, the U.S. Food and Drug Administration (FDA) filed a scientific review for modified risk tobacco product (MRTP) applications from Swedish Match USA for 20 ZYN oral nicotine pouches. This study aims to provide a timely test of the MRTP claim to inform the FDA’s decision-making, by examining the effects of the claim on risk and benefit perceptions, intentions to use ZYN to cut down on cigarettes and intentions to switch completely from cigarettes to ZYN among adults who are currently smoking cigarettes. The study also examined how nicotine strength and label impact ZYN perceptions and intentions. Methods: We recruited 485 adults who were currently smoking cigarettes and conducted a 2 (MRTP claim: present, absent) by 2 (nicotine strength: 3 mg, 6 mg) by 2 (nicotine label: ‘tobacco-free nicotine’, ‘nicotine’) between-subjects experiment with a control condition. Multivariate analyses and logistic regressions examined the impact of the MRTP claim on risk and benefit perceptions, relative risk perceptions and use and complete switch intentions of ZYN, as well as the impact of nicotine strength and nicotine label on perceptions and intentions. Results: MRTP claim led to higher benefit perceptions of ZYN and greater odds of perceiving ZYN as less harmful than cigarettes. ZYN with 3 mg nicotine and the ‘tobacco-free nicotine’ label were associated with greater odds of perceiving ZYN as less harmful. Ethnicity and ZYN use status moderated the impact of message features. The impact of each message feature on use and complete switch intentions was non-significant. Conclusions: The proposed MRTP claim may have limited effectiveness in nudging switching from cigarettes to ZYN among adults who currently smoke. More education is needed to better inform people of ZYN health harm and nicotine risks.