A study by Barnes (2019) concluded that there exists an empirical environmental Kuznets curve (EKC) relationship between mismanaged plastic waste per capita and income per capita. However, this result needs careful interpretation. The study adopted data that used the World Bank database to compute mismanaged plastic waste amounts. Because data to compute them were not available for all countries, missing data were estimated by relating them to economic classification (i.e., income level). In other words, the data used for the analysis by Barnes simply assumed—without scientific validation—that mismanaged plastic waste amounts are related to economic classification (i.e., income level).