Human Microplastics Exposure and Potential Health Risks to Target Organs by Different Routes: A Review

Microplastics in the environment enter the human body through diet, drinking water, and air inhalation. The widespread detection of microplastics in several human tissues was conducted. However, limited knowledge exists on the number of microplastics that can be ingested by humans and the potential adverse effects on various organs. To address these issues, we reviewed the types and abundance of microplastics through different pathways and summarized the average annual intake in humans. An adult can ingest about (4.88–5.77) × 105 microplastics/year through the dietary route [including salt (5.00–7.00) × 103, fish (0.50–1.20)×104, fruits (4.48–4.62) × 105, and vegetables (2.96–9.55)×104]. The amount of microplastics ingested via drinking water route was approximately (0.22–1.2)×106 microplastics/year. Inhalation of microplastics via atmospheric environment was nearly (0.21–2.51) × 106 microplastics/year [including indoor (0.16–2.30) × 106 and outdoor (0.46–2.10)×105]. In conclusion, we found that the human body ingests microplastics most through inhalation, followed by drinking water and diet. We also summarized the types and abundance of microplastics that were enriched in different organs after microplastics entered the human body. Microplastics entering the body would cross the barrier into the target effector organs and cause adverse health effects, mainly including induction of intracellular oxidative stress, genotoxicity, reproductive toxicity, and inflammatory responses. In conclusion, exposure to microplastics can cause many adverse effects on the health of the organism. Thus, an increased awareness of the crisis, urgent discussion, and practical actions are needed to mitigate microplastics contaminants in the environment.