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Talk about unintended consequences. A compound called BPA is being phased out of plastic packaging due to fears it may disrupt our hormones – but a replacement for it may be just as harmful.

BPA, or bisphenol A, is often found in disposable water bottles and babies’ milk bottles and cups. Small amounts can dissolve into the food and drink inside these containers.

This is a concern because a host of studies have shown that BPA can mimic the actions of oestrogen, binding to the same receptor in the body. Oestrogen is normally involved in breast development, regulating periods and maintaining pregnancies. Animals exposed to BPA develop abnormal reproductive systems, but it is unclear if people are exposed to high enough doses to be affected.

Due to public pressure – and bans in a few countries – many manufacturers have started replacing BPA. One substitute, fluorene-9-bisphenol, or BHPF, is already widely used in a variety of materials.

But of Peking University in Beijing and her team have found that BHPF also binds to the body’s oestrogen receptors. Unlike BPA, it does this without stimulating them, instead blocking their normal activity. In tests on female mice, BHPF caused the animals to have smaller wombs and smaller pups than controls, and in some cases miscarriages.

If BHPF binds to the same receptor in humans, it has the potential to cause fertility problems. “That’s pretty scary,” says Frederick vom Saal of the University of Missouri.

Detected in blood

As food and drink containers don’t usually reveal detailed information about what they are made from, Hu’s team tested a variety of plastic bottles labelled “BPA-free” to see if they released BHPF into hot water stored inside, as heat encourages such compounds to dissolve.

They found the compound was released from 23 of the 52 items tested, including all three babies’ bottles they examined.

When they took blood samples from 100 college students who regularly drank water from plastic bottles, Hu’s team detected low levels of BHPF in seven people.

It is unknown if the compound came from their drinking water – as there are many materials containing BHPF in the environment – nor if that would be high enough to cause harm. But vom Saal says even low levels could in theory disrupt our hormonal systems.

Vom Saal says he tries to use plastic as little as possible, and avoids putting plastic containers in the microwave or dishwasher, as they degrade under heat.