Chapter 16 - Occurrence, human exposure pathways, and health risks of (micro)plastics

Abstract

An increasing body of evidence exists on (micro)plastics in various environmental systems. Yet limited comprehensive reviews exist on the human health effects of (micro)plastics and their chemical additives, and the potential human exposure routes in low-income and developed countries. Here, evidence is examined to address three objectives: (1) to summarize the occurrence of (micro)plastics and their additives in environmental media relevant to human exposure, (2) to discuss the multiple human exposure pathways to (micro)plastics and chemical additives, and (3) to discuss potential and confirmed cases of human health risks of (micro)plastics and their additives. Evidence shows that (micro)plastics and their chemical additives occur in various environmental media including soils, aquatic systems, biota, human foods (e.g., fish, honey, table salt), and airborne particulates in occupational and non-occupational settings. This points to the potential transfer of (micro)plastics and chemical additives into the human food chain and the human body. Occupational and non-occupational human exposure to (micro)plastics and chemical additives occurs through: (1) ingestion of contaminated foods and water, (2) inhalation of air-borne (micro)plastics, and (3) dermal or skin intake (contact exposure). (Micro)plastics pose multiple potential human health risks, including: (1) cell and DNA damage through oxidative stress, (2) inflammation, (3) lung/respiratory disorders, and (4) compromised immunity. Human health risks of chemical additives including endocrine disruptors are also documented. However, besides a few empirical studies, the bulk of the evidence remains largely inferential, and the reasons accounting for this are discussed. Future directions and perspectives on human health risks of MPs are summarized, including: (1) quantitative evidence linking human exposure risks to specific health outcomes, (2) human health risks in low-income countries, (3) human health risks arising from the interactions of (micro)plastics and chemical additives, and other human health stressors, and (4) long-term and inter-generational health risks.