Most teenagers exposed to chemical allegedly linked ...

The Mail Online reports "chemicals linked to breast and prostate cancer" are found in 86% of teenagers' bodies.

The research concerns the chemical bisphenol A (BPA), found in many plastic products.

BPA is detectable in the urine of most people, and several laboratory studies have raised concerns that it may disrupt hormone balance.

Some commentators have claimed that exposure to BPA may be partially responsible for the drop in average sperm counts seen in developed countries over the last 40 years, an issue we looked at in 2017.

This study included just 94 teenagers aged 17 to 19 from the south-west of England. BPA was detected in the urine of 86% of them.

The teenagers and researchers then collaborated to develop dietary guidelines they could follow to try to reduce their BPA exposure over the course of a week.

Following these guidelines made no difference to BPA levels in their urine.

This sample is far too small to be representative of all teenagers nationally.

But it does seem to confirm what we already know – that, as the researchers put it, there's a "pervasiveness of BPA in our food chain".

They concluded their study by calling for better labelling on food and drink packaging to highlight the presence of BPA in certain products.

What's still uncertain is whether BPA at current exposure levels actually poses any health risk.

Both the European and UK Food Standards Agency say that there's no appreciable health risk.

Where did the story come from?

The study was conducted by researchers from the University of Exeter and the Royal Devon and Exeter NHS Foundation Trust.

It was funded by a Wellcome Trust People Award and the Natural Environment Research Council.

The study was published in the peer-reviewed journal BMJ Open and is free to read online.

The UK media's coverage is correct on the 86% exposure figure. But the news stories go on to discuss the possible health risks BPA may pose, which the study didn't actually look at.

Many sources contained a statement from a spokesperson for the British Plastic Federation, who stressed that the European Food Standards Agency had concluded that "at current exposure levels, plastics containing BPA pose no consumer health risks for any age group".

What kind of research was this?

This experimental study set out to see whether it's possible to manipulate people's diets to reduce their exposure to BPA.

Various studies have linked BPA with potential hormonal effects, but to date no studies have proved a direct link.

In 2015 the Endocrine Society concluded that BPA may have links with several cardiovascular, reproductive and metabolic traits in humans.

And the European Food Standards Agency said there was "sufficient uncertainty", meaning it isn't possible to exclude an effect (which isn't the same thing as saying there's clear evidence of health risks).

There's been a lot of interest in reducing exposure to BPA, particularly given that food and drink packaging is the main source.

This study aimed to investigate whether this could be possible in a real-world community setting. The main limitation is that this is a very small study in a specific sample.

What did the research involve?

The study recruited 108 student volunteers aged 17 to 19 from 6 schools and colleges in south-west England.

It was designed by University of Exeter researchers in collaboration with these young people, who put together all the study materials, food diaries and questionnaires.

Based on the available literature on BPA, they developed a set of dietary guidelines that aimed to minimise their BPA intake over the course of a week while maintaining calorie intake.

Food items were scored according to their risk of BPA contamination.

Students also provided other health and lifestyle data. Urine samples were collected before and after the attempted 7-day dietary intervention for measurement of BPA.

The final data set included 94 students (44% male) with complete data available.

What were the basic results?

BPA was detected in the urine of 86% of the teenagers prior to the dietary intervention, at an average level of 1.22ng per ml of urine.

There was no significant change in the urine BPA content after the intervention (an average change of 0.05ng per ml only).

There was no link between urine BPA levels and the students' measure of BPA risk score of the items they were eating.

The only link observed was that those with the highest urinary BPA prior to the intervention were more likely to have a reduced BPA afterwards.

The majority of students (91%) found that trying to manipulate their diet to reduce BPA exposure restricted their food choice. Two-thirds said it would be hard to follow the diet in the long term.

One notable difficulty is that it was often hard to know whether the food packaging contained BPA or not.

How did the researchers interpret the results?

The researchers concluded: "We found no evidence in this self-administered intervention study that it was possible to moderate BPA exposure by diet in a real-world setting.

"Furthermore, our study participants indicated that they would be unlikely to sustain such a diet long term, due to the difficulty in identifying BPA-free foods."

Conclusion

This study demonstrates a couple of things. It supports current understanding – that the majority of people are exposed to BPA through food and drink packaging, and that BPA can be detected in urine.

It also shows how difficult it would be to try to manipulate our diets to reduce BPA exposure.

But it can't really tell us a great deal more than this.

There are also some drawbacks to this study. Even though it seems to support what we already know, it doesn't show that 86% of all teenagers have BPA in their urine – only that this is the case among a very small, select sample from one area of the country.

Ninety-four people is too few to get an accurate indication of what proportion of teenagers excrete BPA in their urine.

For an accurate indication, you'd need a nationally representative sample ideally of several thousand people from across the country.

The study doesn't show that teenagers are exposed to BPA more than other people – this just happens to be the only sample the researchers looked at as part of this study.

This study doesn't provide any evidence that BPA has "gender-bending" (as the Mail clumsily puts it) effects or harms – this idea comes from previous studies, which weren't able to prove this definitively either.

The research was essentially a student-designed attempt to restrict dietary BPA, where students developed dietary guidance with the researchers.

That's not to say it's impossible to limit BPA exposure, but it may require a different approach.

And the study only looked at the effect of BPA over a week-long period, which may be too short a timeframe to detect a noticeable difference.

After public consultation on the possible risks of BPA from 2013-14, the UK Food Standards Agency supported the conclusion of the European Food Standards Agency that "on the balance of evidence, at current levels of exposure there is no appreciable health risk".

It's likely that there needs to be a change in national policy around BPA in plastic packaging to make a real difference to our exposure. Such a move would only come when there's firmer evidence that BPA is a health risk.