March 1, 2017

BPA-free plastic and mice

A new study in Nature Communications reports that fluorene-9-bisphenol – a Bisphenol A substitute – has anti-oestrogenic effects in mice. Roundup comments accompany this analysis.

Title, Date of Publication & Journal

Fluorene-9-bisphenol is anti-oestrogenic and may cause adverse pregnancy outcomes in mice.

Published on 28^th February 2017 in Nature Communications

Study’s main claims – and are they supported by the data

In mice there was a correlation between increased levels of BHPF and reduced pregnancy weight gain, decreased pup birth weight, low uterine weight and adverse pregnancy outcomes.

Measurable amounts of BHPF are leached from some polycarbonate containers for food/drink into water stored in them. It isn’t clear how these levels relate to those that could potentially be found in humans.

Most importantly, there is no suggestion of any untoward effects at potential human exposure levels and it is not clear if BHPF is currently used in materials that come into contact with food: as the authors themselves says, “whether BHPF is also used in materials or containers that come into contact with food-including milk bottles, children’s bottles and sippy cups – and whether humans are exposed to BHPF remains unclear”.

Strengths/Limitations

Strengths

Even though the authors performed multiple tests, the in vitro evidence for what they found is quite good.

Everything is sensible in terms of internal consistency, e.g. dose responses and randomisation/blinding of the investigators.

In vivo data seems to support anti-oestrogenic activity, but these are large doses and may be unrealistic in humans or in the real world.

Limitations

BHPF was detectable in 7 out of 100 students’ serum who drink water regularly from bottles. This was not compared to students who did not drink regularly from water bottles and therefore we cannot tell if it was other factors that could have affected these levels found. (For example, if those who drunk regularly from a bottle of water were more likely to go to the gym then it could be that the gym shower water increased the amount of BHPF in the serum).

As the press release correctly states the bottles of water were not measured to gauge their levels of BHPF. So we do not know how much BHPF the bottled water contained, if any at all.

How the BHPF got into their serum is not known and therefore this finding could be as a result of anything/from anywhere – i.e. maybe it didn’t come from the bottles at all.

The concentrations used in mice weren’t justified or explained what the equivalent levels would be in humans i.e. is 50mg/kg the dose expected to be the safe/normal levels in humans?

The bottles were filled with hot water and then left to cool, because people in China usually use water in this way. This is not the case in the UK. So does the heating affect the BHPF levels released into the water?  In other words, are these findings applicable to the UK even if they are real?

Before The Headlines is a service provided to the SMC by volunteer statisticians: members of the Royal Statistical Society (RSS), Statisticians in the Pharmaceutical Industry (PSI) and experienced statisticians in academia and research. A list of contributors, including affiliations, is available here.