This is problematic because acute animal exposure studies are used to estimate daily human exposure to BPA , and no studies that had examined BPA pharmacokinetics in animal models had followed continuous low-level exposures .
However , the experts noted that 1 ) BPA is not persistent in the environment or in humans , 2 ) biomonitoring surveys indicate that exposure is continuous , 3 ) it is hard to use acute animal exposure studies to estimate daily human exposure to BPA , and 4 ) no studies that had examined BPA pharmacokinetics in animal models had followed continuous low level exposures .