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According to a new mouse study published in Current Biology on Thursday, plastic products that boast of being "BPA free" are not necessarily safer for us. The chemicals used to replace BPA in these plastics can still escape and affect the sperm and eggs of both male and female mice. And these same effects could occur in people.
Bisphenol A, or BPA, is a chemical commonly used to create polycarbonate plastics and epoxy resins. These transparent white plastics are themselves used in food and beverage packaging, as well as in consumer products and medical devices, while resins are used to coat metal products such as canned foods. When these products break down or are damaged (for example, when they are heated repeatedly in a microwave oven), they can eliminate BPA, which exposes us to it. As a result, it is estimated that 93% of Americans have some level of BPA in their system.
This is troubling, as there is more and more research showing that exposure to BPA can have subtle but real effects on our health. It is one of many chemicals that can interfere with our endocrine system, which regulates how hormones affect everything from our fertility to brain development. BPA in particular has been implicated as a possible cause of genital deformity in men, early puberty in women, and developmental problems among the very young; it could also contribute to metabolic disorders like obesity and some cancers.
As a result of this bad publicity, companies have begun to refrain from using plastics containing BPA, particularly in products for the very young, such as baby bottles and infant formula packaging.
The researchers behind this study were among the first to notice the potential dangers of BPA – although their discovery was an accident. Twenty years ago, while studying the genetics of mice, they discovered that the female mice they used as controls produced more unhealthy eggs than usual. Later, they found that these mice were kept in damaged plastic crates and drank damaged plastic water bottles, both of which leached BPA into their environment.
Incredibly, it seems that something similar has happened on a smaller scale. While working on another project, the authors began to see some of their control mice, men and women, but not all, developing reproductive problems. Although the mice kept polysulfone and not polycarbonate cages, the researchers noticed a whitish residue in some of the cages, indicating that they had been damaged and that chemicals were leached.
"There was definitely that feeling of" Oh no, not yet, "Patricia Hunt, senior author at the University of Washington's Center for Reproductive Biology, told Gizmodo.
When Hunt and his team analyzed the chemical signatures of the damaged cages, they found both BPA and BPS, a bisphenol that largely replaces BPA. The crates were made of polysulfone plastic, manufactured in part from BPA, but it is reported to be more resistant to heat and chemicals than polycarbonate and therefore less likely to degrade. Polysulfone is not thought to degrade to BPS, but Hunt's team found that if certain chemical bonds in the plastic were broken in the right way, the BPS could form.
In their initial experiments with BPA, the Hunt team exposed more mice to low doses of BPS and compared their reproductive health with mice exposed to BPA and mice raised in new cages. BPS mice had more defects in ova and sperm than control mice, but the lesion level was similar to that observed in mice exposed to the same dose of BPA alone.
"These replacements behaved pretty much exactly as BPA did," Hunt said.
Although manufacturers have refrained from making explicit statements that BPA substitutes are safer, Hunt noted, customers have certainly assumed that they are safer. But although the study is only the latest to suggest that there is no real difference between these chemicals and their potential harm, proving that this effect is real in humans is another problem.
"We can almost never demonstrate a cause-and-effect in humans," Hunt said, noting that even the well-established link between smoking and cancer relies heavily on circumstantial evidence. "But to what extent would you be confident if I told you that we have seen this effect in mice, nematodes, and rhesus monkeys? I would say it's a very good bet that we would see it in humans as well if we could do the same kind of experiments. "
If that is not enough, other studies have suggested that the effects of BPA could be inherited. And when the Hunt team raised some of the original male mice exposed to BPS with healthy females, that's exactly what they found: the second generation of mice continued to have more genetic problems than normal. It was only by the third and fourth generation that these mice looked completely like healthy mice.
Regulatory agencies such as the Food and Drug Administration maintain that current levels of BPA exposure in foods are not of concern to human health, indicating that people metabolize BPA faster than mice, reducing possible toxic effects. But Hunt says that this hypothesis is largely based on traditional methods of toxicology, which could miss the more subtle effects caused by low doses of BPA and similar chemicals.
"You could expect a linear answer – the more you give, the worse it is. But these types of chemicals do not behave this way. they behave like hormones or medications that we take, where a little bit can exert a powerful effect, but bumping the dose can abolish that effect or induce a new one, "said Hunt. "And yet, the FDA does not want to believe that there is a low-dose effect, although there is evidence of this in its data."
Hurt is referring to a future government report on BPA, known as CLARITY-BPA. The report, in response to criticism from researchers such as Hunt, aims to combine data from more traditional toxicological studies and more recent methods.
The final results of the first half of the report, based on the old type of research, should be announced today. The study should confirm the FDA's conclusion that exposure to BPA from our food is not necessarily a health problem. But the final report, incorporating these new methods, will only be published next year.
Because of the pervasiveness of these chemicals in our lives, it is possible that no meaningful action can eliminate them in the near future, even if the FDA wanted to do something about it. The ease with which similar chemical analogues can be developed far exceeds the ability of health organizations to study and regulate them effectively, Hunt said.
And as BPA tends to persist in the environment, it may take decades before its impact disappears completely. Some researchers have speculated that these long-term effects could even explain the decline in collective fertility of Western men.
It's very dark. But Hunt still believes there is a way for the public to better protect themselves.
"People have to think about plastics differently. Because now, we tend to think of them as things that will last a very long time, "she said. "But if you see signs of damage, you should get rid of it. I also recommend people never put plastic in the dishwasher or microwave because the heat is only an invitation to migrate these chemicals.
"If it's damaged, it starts to leak chemicals and you do not want to be around," she added.
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