BPA exposure is mainly through:
Bisphenol A exposure in general population originates primarily from food contact materials. Polycarbonate bottles and epoxy resin linings of metal food cans contain polymerized BPA which hydrolyzes under heat, acidic food, repeated washing releasing monomer into contents. Ingestion after leaching represents dominant route leading to detectable urinary BPA in over ninety percent of individuals in biomonitoring surveys. Dermal contact, inhalation contribute minimally compared to dietary intake. Plastic containers and canned foods therefore constitute main source of chronic low-dose BPA endocrine disruptor exposure reaching fetus transplacentally during pregnancy causing developmental programming effects.
Ref: NCBI, Endocrine Disruptors Fact Sheet: BPA exposure plastic containers and food cans.