Common Plastic Chemical Can Wreak Havoc on The Sex Cells of Worms

A chemical that's been long used in soft, flexible plastics like PVC might be messing with the sex cells of some animals and possibly even humans, a new study suggests.

Researchers exposed roundworms (Caenorhabditis elegans) to the chemical benzyl butyl phthalate (BBP) at levels within a range previously detected in samples of human urine, semen, blood, umbilical cord blood, breast milk, and amniotic fluid.

The team, led by researchers at Harvard Medical School, found BPP and its byproducts were internalized in worms at similar levels to what is seen in humans, and that the plastic chemical had the strongest negative effect on the animals' sex cells, including DNA breakage.

BBP was, and in some cases still is, used widely in products like vinyl flooring and furniture, exercise balls, carpet backing, children's toys and other childcare products, car care products, and cosmetics.

While the chemical has been somewhat restricted in the US, Canada, and the European Union, it is often only prohibited at certain concentrations in certain circumstances, like cosmetics or children's products. And many of us live surrounded by furniture, flooring, and other materials produced before concerns about BBP arose.

"Whether topically applied, sprayed, or consumed, the various uses of BBP-containing products introduce three main routes of exposure for humans: dermal absorption, inhalation, and ingestion," the authors write.

We've known BBP disrupts the endocrine system for quite some time. And yet, as the authors point out, very few studies have addressed the direct effects of endocrine-disrupting chemicals like BBP on that key process which forms our reproductive cells, meiosis.

The researchers, led by reproductive toxicologist Ayana Henderson from Harvard Medical School, exposed roundworms to 1, 10, 100, and 500 micrometer BBP doses and took a closer look at the impacts this had on the worms' sex cells using mass spectrometry and RNA sequencing.

Throughout the cells, double-strand DNA breaks formed at increased levels. There were also defects in meiosis (cell division that reduces the chromosomes in sex cells), with nuclei forming too soon. Chromosome segregation was inaccurate, which can lead to offspring having an abnormal number of chromosomes.

Basically, it was a bit of a horror show.

The study found BPP does its damage by causing oxidative stress, during which the body's shield of antioxidants can't keep up with their task of neutralizing the highly reactive toxin. With this antioxidant carnage, the toxin can rip at the body's cells instead. In the gonads, where eggs and sperm form, this can have very serious consequences for the next generation.

"The fact that internal levels of BBP and its primary metabolites detected in the worms are comparable to levels found in various human female biological samples underscore the relevance of using C. elegans for studying the reprotoxic effects of exposure to BBP," the authors write.

"Exposure to these endocrine-disrupting chemicals may pose a threat to human health, both to those directly exposed as well as to unexposed subsequent generations."

This research was published in PLOS Genetics.