Public awareness and behaviors regarding plastic consumption, recycling, and microplastics among residents of Tehran, Iran

This cross-sectional study examined plastic consumption, recycling and littering behaviors, perceived plastic-related risks, and microplastic awareness among 300 Tehran residents aged 15–60 years. Participants were recruited through non-probability convenience and self-selection sampling using an online questionnaire distributed through Instagram, Telegram, and personal networks. Data were analyzed using Pearson’s χ², Mann–Whitney U, Kruskal–Wallis H, Dunn–Bonferroni post hoc, and Spearman correlation tests, as appropriate. Women reported greater intention to participate in waste segregation (χ²(4) = 12.733, p = .013, Cramer’s V = 0.206) and more positive feelings about environmental participation (χ²(4) = 14.554, p = .006, Cramer’s V = 0.220) than men. Microplastic awareness showed a weak positive association with educational attainment (Spearman’s ρ = 0.186, p = .001), and social networks were the preferred source of environmental information about plastic pollution and recycling (69.7%). A marked difference in perceived risks was observed: 53.7% selected the highest response category for plastic-related animal mortality, whereas only 3.4%, 11.6%, and 11.7% selected this category for cancer, hormonal disorders, and respiratory problems, respectively. Residential-area category was unrelated to most outcomes. However, plastic-bag consumption differed across housing-price categories (H(2) = 6.469, p = .039, ε² = 0.015), with higher consumption in middle- than upper-housing-price areas (adjusted p = .037). Among 296 disposable-mask users, 60.8% discarded masks with household waste, 29.1% with recyclable waste, and 10.1% through medical-waste channels; disposal methods did not differ significantly by gender, education, or residential-area category. These findings indicate uneven perceptions of ecological and potential human-health implications of plastics and support clear, evidence-based public communication about microplastics and appropriate waste disposal. Because the study relied on online convenience sampling and self-reported responses, the findings should not be generalized to all Tehran residents without caution.