FDA Research on BPA

A scientifically accepted way to measure exposure to BPA, from all sources, is through biomonitoring studies. These studies measure levels of chemicals in human tissues or fluids such as blood or urine. Because BPA is rapidly eliminated from the body in urine, biomonitoring studies typically measure levels of BPA in urine.

The U.S. Centers for Disease Control and Prevention (CDC) conducts large-scale biomonitoring studies on BPA, and many other chemicals, as part of a long-standing program known as the National Health and Nutrition Examination Survey (NHANES). In 2014, CDC released the 5th biennial set of BPA biomonitoring data from urine samples collected in 2011-2012. The NHANES biomonitoring studies assess exposure to BPA across the U.S. population (age 6 years and above).

The Canadian government conducts similar biomonitoring studies and recently released a study on exposure to BPA in pregnant women. This data is from the Maternal-Infant Research on Environmental Chemicals (MIREC) project, which is sponsored by Health Canada and other Canadian government agencies. The urine samples were collected in 2008-2011.

These data show that typical exposure to BPA (50th percentile values) is hundreds of times below Health Canada’s safe intake limit. Even the 95th percentile values are approximately 100 times or more below the limit. The large margin of safety between the biomonitoring values and the safe intake limit clearly indicates that the U.S. population and pregnant women in Canada are not at risk from real-life exposures to BPA.

The potential for any substance to cause toxicity is substantially impacted by its pharmacokinetic properties. Pharmacokinetic data describe how a substance is absorbed into the body, how it’s distributed and in what form, how long it lasts in the body, and how it’s eliminated. Building on earlier studies, FDA has conducted a series of in-depth pharmacokinetic studies in rodents and non-human primates to fully characterize how BPA is processed in the body.

In general, these studies show that BPA is efficiently converted to a biologically inactive substance as it is absorbed into the body. This process occurs in both the intestine and the liver. This substance is then rapidly eliminated from the body in urine with a half-life of only a few hours. FDA’s research also shows that BPA does not accumulate or persist in the body and, in particular, does not accumulate in fat.

The efficient process to metabolize and eliminate BPA occurs not only in adults, but also during developmental life stages including pregnancy, infancy and childhood. During pregnancy, the fetus is protected by maternal metabolism and elimination of BPA, while fetal capability to metabolize BPA increases throughout gestation. A study in non-human primates shows that the capability to metabolize BPA is present just after birth with an efficiency level similar to adults.

These findings were confirmed for adult humans in a study conducted jointly by the Pacific Northwest National Laboratory, FDA and CDC, with funding from EPA. This clinical study on human volunteers found that BPA itself could not be detected in blood after exposure to an atypically high level of BPA through the diet, which is how people are typically exposed to BPA. Only the biologically inactive substance could be transiently detected in blood before it was quickly eliminated in urine.

Overall, the federal government pharmacokinetic studies show that BPA is efficiently converted to a biologically inactive substance, which is then eliminated from the body within a day after exposure. Based on the way that BPA is processed in the body, these results indicate that exposure to BPA at real-life levels is unlikely to cause health effects.

In early 2014, FDA researchers published the results of what may be the largest-scale toxicity study ever conducted on BPA. In this subchronic study (i.e., less than a full lifetime in duration), rats were exposed to BPA during pregnancy and continuing through 90 days after birth, which covers all developmental life stages. The study included 7 low doses of BPA, which are most relevant for evaluating the safety of BPA, two high doses, and two doses of a positive control. Multiple reproductive and developmental effects were examined in the study.

The study design allowed the researchers to evaluate many of the claims from previous small-scale studies that BPA could cause health effects at low doses. Notably, no significant reproductive or developmental effects were found at any of the 7 low doses. Effects consistent with previous studies were found only for the positive control and high doses of BPA, which confirm the validity of the study.

The subchronic study also included extensive pharmacokinetic measurements, which help to interpret and further validate the study results. These measurements confirm that BPA is efficiently metabolized and rapidly eliminated from the body, which provides strong support for the lack of effects at low doses and the presence of effects only at very high doses of BPA that are approximately a million times higher than real-world exposure levels.

In addition to the many reproductive and developmental effects examined in the FDA subchronic study, separate studies conducted by FDA and EPA examined the potential for low doses of BPA to cause neurobehavioral effects. Neither of these well-designed and conducted studies found evidence for neurobehavioral effects from exposure to BPA as had been reported in previous small-scale, preliminary studies.

Overall, the results of toxicity studies conducted by FDA and EPA are consistent with what we know from pharmacokinetic studies. The way that BPA is processed in the body makes it very unlikely that BPA could cause health effects at real-life exposure levels. These studies confirm that BPA does not cause health effects at any dose even remotely close to typical consumer exposure levels.