From producer attribution to governance: Quantifying responsibility concentration in marine plastic pollution

Abstract

Extended Producer Responsibility (EPR) requires quantitative tools to identify responsibility concentration and prioritize interventions. This study introduces an inequality-based framework combining Lorenz curves, Gini coefficients, and concentration ratios to assess producer responsibility in marine plastic pollution. We analyzed 232 producer-attributable items from 830 macrolitter items collected on Isla Arena, an uninhabited Colombian Caribbean island, identifying 48 producers, 72 brands, and 95 products. A Corporate Environmental Impact (CEI) index assessed whether abundance-based dominance corresponded to potential environmental impact. Producer responsibility was highly concentrated (Gini = 0.690; bootstrap 95% CI: 0.629–0.698), with the five and ten leading producers accounting for 65.5% and 80.6% of attributable litter, respectively. Beverage companies dominated, while Pony Malta alone represented 27.2% of attributable items. Impact-based inequality was nearly identical (Gini = 0.692). Sensitivity analysis addressing the 72.0% unattributed fraction showed that category-specific attribution corrections increased inequality (Gini = 0.714), supporting the robustness of observed concentration. These findings establish responsibility inequality as a measurable property of pollution assemblages and provide a transferable framework for targeting EPR interventions, assessing governance feasibility, and monitoring corporate environmental performance across pollution systems.