A controversial chemical commonly found in food containers has again been linked to poor health outcomes – this time in a study of embryos. The synthetic chemical Bisphenol A, known as BPA, is found in some plastic food and drink containers, old baby bottles, the resin lining of some tin cans and cash register receipts. Ingested through contaminated food and drink or even by handling receipts, BPA is considered an endocrine disruptor: a class of chemicals that interfere with the normal hormonal processes in the body. In the case of BPA, its chemical composition means it works on the oestrogen hormone pathway. To date, most studies have focused on adult or foetal development following BPA exposure. Few have looked at the impact of BPA on an embryo. Those studies that have, have focused on toxicity. “The real novelty of our study is that it looks at environmental levels and the early embryo and the metabolic effects of exposure,” said Melbourne University reproductive biologist Mark Green. Published in the journal Scientific Reports recently, the study found exposing cow embryos to BPA in the first days after fertilisation resulted in a substantial rise in glucose consumption, the embryo’s main source of food. This could increase the risk of obesity and type 2 diabetes later in life. “It could be enough to set the embryo on a different trajectory,” Dr Green said. The study used cattle because they are animals with a similar gestation period to humans, ovulate one egg per cycle and produce an egg with similar metabolic characteristics to humans. The cow embryo was exposed to BPA between day three to seven – the equivalent stage for humans at day five. The amount of BPA exposure over four days reflected what is considered “environmentally relevant levels” – doses that an average population would experience. “It was between 1 to 15 nanograms per millilitre which is reasonably high for an endocrine disruptor but that reflects the pervasive nature of BPA,” Dr Green said. Tests in humans have shown evidence of BPA in more than 95 per cent of urine samples. The pervasive nature of BPA means that pregnant women would be exposed to BPA throughout pregnancy, while the cow embryos were only exposed to BPA for four days. “You could see a much greater effect if there was exposure to BPA throughout a pregnancy,” Dr Green said. Used primarily in plastics, BPA is a synthetic chemical which has been associated with obesity, thyroid dysfunction, breast cancer, asthma and poor behavioural outcomes. The European Union, United States and Canada have banned BPA use in baby bottles. In Australia, a voluntary phase out of BPA use in polycarbonate baby bottles was announced in 2010. In January, Food Standards Australia New Zealand released its 2nd phase of the 24th Australian Total Diet Study, which screens food for 30 packaging chemicals, including BPA. The food standards authority did not identify any public health and safety concerns for BPA. However, Dr Green said it was not clear what a safe level of exposure was for a developing embryo. “I guess this is raising a flag to say that we really do need to have thorough testing of chemicals and their affect all through development,” he said.
The Age, 14 July 2016 ;http://www.theage.com.au ;