Lifetime exposure to microplastics: From consumption to distribution in the body

Microplastics are an emerging environmental contaminant, but human exposure levels throughout life and across different age groups remain largely unknown. They enter the human body mainly via ingestion and inhalation. This review estimates the lifetime intake, excretion, and accumulation of microplastics for an average individual across the lifespan, encompassing infants, children, adolescents, adults, and the elderly. The intake is analysed based on the number of microplastics in the consumed liquids, food, air, and plastic containers. An individual ingests about 223.7 million microplastics in their lifetime (range 95 – 5348 million), with about 59% accumulating in the body and 41% being excreted through urine and feces. During the age period of two years, infants ingest microplastics mainly through breast milk and feeding bottles, while other age groups mainly intake microplastics through edible oil, fruits, and air. The lifetime intake of microplastics increases with age from infancy to adulthood due to prolonged exposure. The percentage of total lifetime microplastic accumulation is distributed across age groups as follows: infants (3.7%), children (4.9%), adolescents (11.0%), adults (53.9%), and the elderly (26.5%). Within the body, microplastics are distributed and accumulated across various organs. The highest concentration is found in ovarian follicular fluid (2191 microplastic particles) of females. The current strengths, limitations due to limited imaging techniques and the lack of standard protocols, and considerations for future assessments of microplastics exposure to humans are also discussed. Urgent interventions are needed to address this emerging threat.