'Things are going wrong': Stand-in plastics can harm eggs and sperm
Advertisement

'Things are going wrong': Stand-in plastics can harm eggs and sperm

The safety of BPA-free plastic is being questioned after new research suggested any plastic with signs of ageing or damage could be harmful.

A study which tested the impact of "BPA-free" products on mice, indicates they have almost the same effects on reproduction as BPA itself.

The dangers of BPA plastics have been known for a while. Now there's a fresh threat.

The dangers of BPA plastics have been known for a while. Now there's a fresh threat.

Photo: Washington Post

BPA-free or not, "plastic products that show physical signs of damage or ageing cannot be considered safe,” says Professor Patricia Hunt, the Washington State University researcher who led the study.

But other researchers caution that just because these chemicals are bad for mice, it does not necessarily mean they are bad for humans.

BPA (Bisphenol A) is found in many plastic bottles, receipts and food packaging. After public concerns grew about its health impacts, manufacturers have replaced it with similar chemicals including BPS, BPF and BPAF.

Advertisement

But there is a growing body of evidence that mice, zebrafish, rats and human cells are affected by exposure to these replacement chemicals.

In humans, large studies have found sperm counts have fallen by as much as 60 per cent in the Western world in the past four decades.

Some scientists have linked that to exposure to chemicals such as BPA – they even believe chemicals in plastics are increasing penis defects and shrinking human penis sizes.

But the research community is split on whether they truly are having an effect on human health.

Loading

“Rats and mice process BPA – and probably BPS – very, very differently to humans,” says Dr Amy Heffernan, a chartered member of the Royal Australian Chemical Institute and expert in BPA.

“The human body is excellent at detoxifying chemicals of all sorts. Because BPA is so rapidly metabolised by the body, we have nothing to worry about.”

It was Professor Hunt's lab that first revealed to the world the damage BPA can do to a mouse's reproductive cells.

Back in 1998, the lab noticed something odd was going on with its mice. The egg cells in juvenile female rats did not look right – their chromosomes were all scrambled up.

This image, from the Hunt lab's 2003 paper, shows mouse oocyte cells. Image A is normal. Image B shows the type of abnormalities exposure to BPA can induce.

This image, from the Hunt lab's 2003 paper, shows mouse oocyte cells. Image A is normal. Image B shows the type of abnormalities exposure to BPA can induce.

Photo: Current Biology / Supplied

They couldn’t work out what it was, until someone thought to look at the cages – and found the plastic was starting to wear down. Bits were flaking off and getting into the mice’s food.

Now, 15 years later, it is happening again.

“It was like Groundhog Day,” says Tegan Horan, the paper’s lead author.

“We were doing a normal experiment, and suddenly all our data started to look strange – like we were getting another exposure.”

And they were.

An undamaged cage, left, and a degraded cage, right, from the research lab.

An undamaged cage, left, and a degraded cage, right, from the research lab.

Photo: Cell Press / Supplied

They eventually traced the source to a white residue on the plastic cages. The residue turned out to be BPS (Bisphenol S), a chemical manufacturers have introduced to replace BPA since the world became concerned about its health impacts.

To determine BPS was the culprit, the team then gave mice tiny doses of the chemical, as well as BPF and BPAF, two other BPA replacements. The doses were way below safe daily intake levels set by governments.

All the chemicals had effects nearly identical to BPA.

“These are pretty subtle effects. We like to think of them as canaries in the coal mine. They are really just the first sign that things are going wrong,” says Ms Horan.