Ocorrência de microplásticos em águas subterrâneas e riscos para consumo humano: do conhecimento global ao cenário do Sistema Aquífero Guarani

Abstract

Groundwater contributes approximately half of the global domestic water supply, yet the risks of microplastic (MP) contamination in this resource remain poorly understood. This study investigated the characteristics, occurrence, and ecological and human health risks associated with MPs in groundwater intended for human consumption, with emphasis on the Guarani Aquifer System (GAS) in Ribeirão Preto (SP, Brazil). A systematic review of 34 studies (2019–2025) revealed MP concentrations in global aquifers ranging from 0.0003 to 2103 particles/L, with predominance of particles <100 µm, fragments and fibers, and of the polymers polypropylene, polyethylene, and polystyrene. The application of integrated risk indices showed that 69% of the sites presented elevated PLI (Pollution Load Index) levels, 40% high polymeric risk H (Polymer Hazard Index), and 86% extreme PRI (Pollution Risk Index). The estimated daily intake of MPs based on quantity (EDIq) reached 140.2 particles/kg/day for children and 60.09 for adults, evidencing higher child vulnerability. Field investigations in two GAS recharge areas, namely Lagoas do Saibro and Recreio Internacional, revealed mean MP abundances of 20.02 and 7.03 particles/L, respectively, with predominance of fibers and transparent particles <100 µm. The higher concentration recorded at Lagoa do Saibro, compared to Lagoa Recreio, was associated with a 4.7-fold higher population density in the surrounding area of the former. Water samples from tubular wells presented abundances ranging from 0.61 to 3.19 particles/L, a mean of 12 particles/L in public drinking fountains, and 0.67 particles/L in bottled water. Polymeric analysis confirmed predominance of PP, PET, and PE, and the estimated daily intake values were higher for children (up to 2.04 particles/kg/day) than for adults (up to 0.53 particles/kg/day). The research concludes that microplastic (MP) contamination in supply aquifers is spatially heterogeneous, influenced by anthropogenic activities, hydrogeology, and land use. Integrated indices proved more effective than simple MP abundance assessment. Although treatment systems reduce MPs in most cases, sporadic increases indicate particle release from polymeric infrastructures. The study provides unprecedented evidence of MP contamination in groundwater within the Guarani Aquifer System (GAS) area, highlighting the need for standardized monitoring, integrated risk assessment, and protection of groundwater resources.