A prohibited chemical that was once used in toys, clothing, food packaging and cosmetics can lead to fertility problems, according to a study of worms.
Scientists are afraid of diethylhexyl phthalate, making plastics flexible and still being used in recycled PVC, damaging the DNA.
Previous studies have claimed that DEHP can make both men and women less fertile, but the way it could do this is not well understood.
A roundworm study revealed that it increases the risk of DNA strands while the body tries to make sperm or eggs.
It also made them less able to repair broken DNA and led to defects in the chromosomes, which subsequently caused genetic problems that prevented the sperm and eggs from growing properly and reduced the ability of embryos to develop.
Scientists who were not involved in the study said there was no evidence that the same problems would happen to people and older research had suggested that they would not.
The chemical diethylhexyl phthalate (DEHP) was used to make plastics until the EU banned it in 2015, although it is still permitted in new items made from recycled PVC and is present in the environment in items made before the ban or in countries where it is still legal (stock image)
A team at Harvard University in Boston, Massachusetts, did the research by exposing the creatures to DEHP in a lab.
DEHP was used for the construction, automobile production and production of food packages, as well as medical devices and electrical cables.
Because DEHP was classified as a ‘reproductive toxicant’ – meaning that it could impair fertility – it was banned in 2015 according to European legislation.
But EU members voted the following year to continue using it in the production of recycled PVC.
The move means that it is still used in new items and that it occurs in the environment in items made before the ban or in countries where it is still legal.
In their research, the researchers did experiments to see how the chemical affected a type of worm called Caenorhabditis elegans (C. elegans).
They used amounts of DEHP that they said were “within the reach of the human population” – the chemical was detected in people’s urine.
Although the worms are small and only around 1 mm long, their genes are very similar to those of humans, so they are useful for DNA testing.
The study found that when worms were exposed to DEHP, their DNA was more likely to break and less likely to repair themselves.
Due to the genetic defects that resulted, embryos could grow less and the worms were less fertile.
WHAT IS REPRODUCTIVE TOXICITY?
Reproduction toxicity is when a chemical is known to have harmful effects on a person’s reproductive system.
This can be due to damage to a person’s reproductive organs, such as their sexual organs or sperm or eggs, by disrupting their hormones or by damaging DNA.
If a chemical makes a person more infertile, or if the cells damage the genetics passed on to a child, it can be considered toxic to reproduction.
Known toxic chemicals include lead, which can damage the brain and nervous system of a fetus and, in non-pregnant women, cause irregular menstrual cycles or cause an early menopause.
Thalidomide, a chemical that was once used in a morning sickness pill, is also toxic and has been shown to cause limb deformities in babies.
A chemical called bisphenol A (BPA), which is widely used in plastic bottles, is also reported to disrupt hormones and possibly reduce male fertility when it enters the body.
“[DEHP affects chromosomes] partly by changing chromatin [genetic material] during the production of eggs and sperm, “said Dr. Mónica Colaiácovo, who led the research.
“Our studies link this change to increased levels of double-stranded DNA breaks and a reduced ability to properly repair these breaks.
“This underlines the importance of identifying better alternatives for replacing DEHP.”
The researchers said other studies had shown that “doses relevant to human exposure” had shown that the chemical could damage fertility in mice.
Dr. Oliver Jones, from RMIT University in Melbourne, was not involved in the research, but said: “The work is entirely based on the roundworm of Caenorhabditis elegans and not on people.
‘Although Caenorhabditis elegans is an extremely useful model for biological research, it is not a mini-human and should not be treated as such.
“Second, the worms in this study were continuously exposed to DEHP throughout their lives – from eggs to adulthood.
“This is not the same type of exposure that people get to this chemical (which has been around for a long time).
“As with any chemical, it’s not really a question of whether something is toxic or not (everything is toxic in a sufficient dose, even water), but whether it is toxic at the level to which we are exposed. I think the jury is still behind this for DEHP. “
Dr. Rod Mitchell of the University of Edinburgh said: ‘Caution is required when translating these results into people.
“Although these studies have shown germ cell loss [sex cells] after DEHP exposure in worms, similar studies on the effect of DEHP exposure using developing human ovarian tissues in culture have shown no loss of germ cells. “
And his colleague, Professor Richard Sharpe, added: “It is unclear whether these findings can be translated to humans, but since germ cells (eggs) are the source of the next generation, we must be especially careful with any exposure that has the potential to has to impact germ cells. “
Dr. Harvard Colaiácovo said she would continue to investigate the effects of other phthalates – similar chemicals, also used in cosmetics – on fertility.
The research is published in the journal PLOS Genetics.