Nationally representative data on urinary levels of BPA and its metabolites in the United States from the
2003–2004 to 2011–2012 National Health and Nutrition Examination Surveys (NHANES) were used to
estimate daily BPA intakes and examine temporal trends. Additionally, NHANES data on lifestyle/demographic/dietary
factors previously reported to be associated with BPA exposures were examined to
assess the resiliency of the reported associations (whether the association is maintained across the five
surveys). Finally, various approaches for addressing issues with the use of BPA concentration data from
spot urine samples were examined for their effect on trends and associations. Three approaches were
assessed here: (i) use of generic literature-based 24-h urine excretion volumes, (ii) use of creatinine
adjustments, and (iii) use of individual urine flow rate data from NHANES. Based on 2011–2012 NHANES
urinary BPA data and assumptions described in this paper, the median daily intake for the overall population
is approximately 25 ng/kg day; median intake estimates were approximately two to three orders
of magnitude below current health-based guidance values. Estimates of daily BPA intake have decreased
significantly compared to those from the 2003–2004 NHANES. Estimates of associations between
lifestyle/demographic/dietary factors and BPA exposure revealed inconsistencies related to both NHANES
survey year and the three approaches listed above; these results demonstrate the difficulties in interpreting
urinary BPA data, despite efforts to account for urine dilution and translation of spot sample data
to 24-h data. The results further underscore the importance of continued research on how to best utilize
urinary measures of environmental chemicals in exposure research. Until a consensus is achieved regarding
the best biomonitoring approaches for assessing exposures to short-lived chemicals using urine
samples, research on factors associated with BPA exposures should include – and report results from -
assessments using both volume-based urinary BPA and creatinine-adjusted urinary BPA data