Study in roundworms finds how phthalates in plastic affect egg cell quality, impact fertility

New Delhi, Oct 25 (PTI) Phthalate, a common ingredient in plastic, damages the DNA in egg cells by causing breaks in strands, thereby altering the chromosome numbers and deteriorating quality of egg cells, a new study conducted in roundworms has found.

The chemical ‘benzyl butyl phthalate (BBP)’ is known to make plastic more flexible and durable. It is found in common consumer goods, such as food packaging, hygiene products and children’s toys.

The worm species present an effective model for studying the impacts of phthalate in people, as we found that roundworms metabolise the plastic ingredient in the same manner as mammals and are affected at similar plastic levels seen to occur in humans, researchers from Harvard Medical School, US, said.

In recent months, increasing instances of microplastics being detected in human semen and genitalia have been reported in studies.

While previous studies have shown that phthalates can interfere with hormones and affect human reproduction, details related to how the chemical impacts reproduction have been unclear, the researchers said.

The findings, published in the journal PLoS Genetics, highlighted the toxic nature of the common plastic ingredient and the damage it inflicts on animal reproduction, the authors said.

For the study, the researchers tested a range of doses of the phthalate chemical on the ‘nematode Caenorhabditis elegans’ species (roundworms) and looked for abnormal changes in egg cells — sex cells of female species.

At levels similar to those detected in humans, phthalate was found to interfere with how newly copied chromosomes are distributed into the sex cells.

Phthalate caused oxidative stress and broke DNA strands, resulting in cell death and a wrong number of chromosomes in egg cells, the researchers explained.

They, therefore, suggested that exposure to phthalates changed gene expression in roundworms in ways that caused significant damage to the DNA, ultimately leading to lower-quality egg cells with abnormal chromosomes.

“Here, examining the female germline in the nematode C. elegans, this study found that a level of exposure within the range detected in human serum and urine alters gene expression linking increased germline oxidative stress with compromised genomic integrity and errors in meiotic chromosome segregation,” the authors wrote.

“Taken together, we propose that C. elegans exposure to BBP leads to increased oxidative stress and double-strand break formation, thereby compromising germline genomic integrity and chromosome segregation,” they wrote.