Area Income, School Instruction, and Adolescents' Zero Waste Knowledge, Access, and Beliefs

Abstract

Background. California mandates organic waste diversion, but participation depends on infrastructure and instruction that may be unevenly distributed. Whether socioeconomic disparities in adolescent zero waste engagement reflect unequal access, unequal knowledge, or unequal conviction has not been established.Methods. A cross-sectional survey of 218 middle and high school students across 15 San Francisco Bay Area schools (March–May 2026) measured zero waste knowledge, home and school access to sorting infrastructure, sustainability beliefs, self-reported behaviors, and perceived barriers. Residential ZIP codes were linked to median ZIP-code income (n = 207 matched). Analyses comprised Mann–Whitney comparisons and Spearman correlations with Benjamini–Hochberg correction and bootstrap confidence intervals, intraclass correlations by school, hierarchical regression, a mixed-effects model, and an exploratory mediation. Results. Median area income was positively associated with familiarity with the term "zero waste" (ρ = .26, 95% CI [.12, .38], p₍adj₎ = .002), waste-reduction habits (ρ = .19, p₍adj₎ = .031), composting frequency (ρ = .18, p₍adj₎ = .031), and home compost access (ρ = .17, p₍adj₎ = .042), but not with practical composting knowledge (ρ = .11, p₍adj₎ = .257), sorting confidence (ρ = .03), or either belief item (ρ = −.06 and −.08, both n.s.). Income added a small unique increment to composting frequency over demographic covariates (ΔR² = .025, p = .020) but none to knowledge (ΔR²