Bisphenol A: A Scientific Evaluation

Michael A. Kamrin, PhD

In This Article

What Is the Magnitude of BPA Exposure?

To determine whether ingestion of BPA by infants (as well as by adults and children) is a significant public health threat, the first step is to assess the amount of dietary BPA exposure. Although direct measurements of this exposure value would be ideal, they are not widely available, and so a variety of indirect approaches have been employed.[2] Exposure values may be based on:

  • The results of studies of the migration of BPA into food and drink from polycarbonate bottles or food and beverage cans;

  • Measurements of actual levels of BPA in canned goods; and/or

  • Estimates of the amount of each type of food or drink consumed.

The results from the migration studies, measurements of BPA in food and drink, and estimates of food and drink consumption are then combined as appropriate for different age groups. The calculations are performed with assumptions that are designed to produce an exposure level that is significantly higher than would be calculated with the best science. For example, it is assumed that harsh laboratory methods of inducing migration of BPA into food and beverages reflect realistic migration values, and that the highest migration values and infant food- and drink-consumption numbers are the most appropriate to use in the calculations. Exaggerated exposure estimates are commonly used by regulators to encourage risk-management measures; they include significant margins of safety, and thus err on the side of protectiveness.

The European Commission Scientific Committee on Food took this approach in estimating human exposure to BPA in its 2002 report.[2] Its conclusion was that, with these assumptions, the daily intake of BPA by infants is about 1.6 mcg/kg bw/day. A similar approach calculated that children of 4-6 years of age consume approximately 1.2 mcg BPA/kg bw/day and adults consume about .4 mcg BPA/kg bw/day.

Another approach to evaluating exposure is to measure levels of BPA and/or its metabolic products in human urine, and to combine this with information on the metabolism of BPA in humans. Knowing how much BPA and its metabolic products are found in urine and how much BPA is converted to its metabolic products before being excreted makes it possible to calculate the amount ingested. A number of studies of urine levels in adults have been conducted,[3,4] and the results indicate that BPA intake in this population ranges from about .002 to .3 mcg/kg bw/day, with the median being much closer to the low value. The wide range of results reflects significant person-to-person variability, and close examination of the data from some of these studies also reveals that intakes vary significantly from day to day, especially in individuals having higher intakes.

A last approach, represented by just 1 study conducted by Wilson and coworkers,[5] is to make actual measurements of BPA levels in food, liquid, and the environment for a specific population, and to combine these measurements with estimates of ingestion and inhalation amounts for this population to calculate the total exposure. This was done for a group of children aged 2-5 years, and measurements were made both in the home and at the day care facility they attended. On the basis of the combination of exposures, the median intake of BPA was calculated to be about .04 mcg/kg bw/day and the value for the child with the highest exposure to BPA was .07 mcg/kg bw/day.

Taken together, the results of these different approaches to evaluating exposure reveal fairly consistent estimates of daily intakes of BPA by both children and adults. Although there is variation from individual to individual and over time, it appears that the best estimates of BPA ingestion range from about .001 to .1 mcg/kg bw/day. Reports of higher exposure estimates are based on studies that rely heavily on assumptions about consumption behavior and laboratory simulations of migration rather than direct measurements of body fluids or levels in food and drink ingested.

Although the evidence is limited, available data suggest that exposure amounts per body weight of adults and young children are similar. In addition, they indicate that the difference in BPA exposure per body weight between infants and young children is small.


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