Researchers from the Yale University School of Medicine and Ontario Veterinary College, studying the effects of bisphenol-A (BPA), an ingredient of polycarbonate plastic used to make common everyday items for storing food and medicines, found it caused loss of connections between brain cells in primates and may lead to disruption in memory and learning as well as depression. Previous studies have looked at the effect of BPA on rodents, but this is the first to look at what happens to primates. It is also the first to use lower levels of the chemical. In fact the daily dose used in the study corresponded to the US EPA's reference safe daily limit.

For the study, the researchers gave each primate a daily dose of 50 micrograms per kg of body weight of BPA for 28 days. They also gave them estradiol, a human estrogen hormone that is involved in the control of synaptic connections between brain cells. Previous research has shown this hormone is not only produced in the ovaries but also in the brain, where it contributes to the development and working of the hippocampus and prefrontal cortex, two parts of the brain that regulate mood and help form memories.

Using an electron microscope to count synaptic connections, they found that BPA stopped connections forming in the hippocampus and prefrontal cortex. Remodelling of spine synapses is crucial to cognitive and mood function, and if, as shown, BPA interferes with building synapse connections, it could have ‘profound implications’. This study is the first to demonstrate an adverse effect of BPA on the brain in a non-human primate model and further amplifies concerns about the widespread use of BPA in medical equipment, and in food preparation and storage.

While the average person is unlikely to reach the daily exposure limit set by the EPA, the researchers were concerned about cumulative exposure to BPA and also that the negative effects could be worse in people with lower than normal estradiol levels, such as babies and the elderly.

Based on their findings the scientists suggest the US Environmental Protection Agency lower the current safe limit for human daily exposure to BPA.

The study was published online on 3rd September in the Proceedings of the National Academy of Sciences.

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First Publishedin October 2008

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