A probabilistic lifetime human exposure assessment for microplastics is essential for quantifying the magnitude, diversity and uncertainty of microplastic exposure. We review 134 studies on microplastic concentrations in nine intake sources, constituting 20 % of the human diet by mass. We simulate microplastic exposure in children and adults using probabilistic models for the gut passage that account uptake via dietary sources and inhalation, intestinal absorption and biliary excretion. To evaluate the potential chemical risk, we perform physiologically based pharmacokinetic modelling with and without chemical intake via microplastics. Microplastic median intake rates range from 553 to 883 #/capita/day and can accumulate up to 50100 #/capita ( 0.041 µg/capita) in the body at the end of 70 years. The contribution of microplastics to total chemical intake is negligible. In conclusion, there is a large variation in exposure and accumulation, and these estimates are subject to increase due to other unknown sources.