Preliminary tests show bisphenol-A reduces memory and scent discrimination in tests of rat olfactory performance

Abstract

Over 10% of the 260 million tons of plastic produced each year ends up in Earth's oceans. Despite worldwide efforts to limit plastic waste, many organisms have already been exposed to plastic waste for prolonged periods. Plastic degradation releases biologically active compounds (e.g. bisphenol-A (BPA)). Studies have demonstrated that BPA can affect brain development and function, but little is known about its impact on physiological activity or brain function. The aim of this research is to assess the effect of BPA on olfaction in order to understand how BPA might affect marine organisms that are critically dependent on olfaction for survival. Operant conditioning was used to train two groups of laboratory rats (Rattus norvegicus) to detect the scent of lemon juice. Rats in the experimental group received water containing 0.05 mg/kg/day of BPA for five weeks, and then 0.10 mg/kg of BPA for nine weeks. Performance variables measured included sensitivity, scent discrimination, and memory. Data analysis with a general linear mixed model found a small significant difference (based on p-value) in performance between the two groups of rats before BPA administration, and a stronger difference in scent discrimination afterward. After BPA administration, repeated measures tests found significant differences within the experimental group in the rats' ability to remember the target scent. These preliminary results suggest a need for expanded testing. If these results are then confirmed, we recommend additional research examining the effects of plastic waste on the olfactory capabilities and survival of terrestrial and marine species in their native habitats.