Plastic is a durable, tough material that has been adopted for use in countless products. That widespread use has also led to the problem of plastic pollution; since it doesn't easily degrade or dissolve into natural products, plastic just breaks apart into ever-smaller bits called microplastics, which are plastic particles under 5 millimeters long, and nanoplastics, which are less that one micron long. These tiny particles have made their way into seemingly everything, from water and air to the human body. Now scientists are trying to learn more about the potential health impacts of microplastics and nanoplastics. A new study reported in the Journal of the Endocrine Society has used a mouse model to show that a father's exposure to microplastics could affect his children's metabolic health.
In this study, the researchers studied mice that had been fed a high-fat diet, to mimic eating habits that can bring out metabolic disorders such as excess body fat, high blood sugar, and high blood pressure. Some of these mice were also exposed to microplastics. The scientists also analyzed the offspring of these male mice, which were also fed a high-fat diet.
This showed that whiel all of the offspring ate the same high-fat diet, the risk of metabolic disorders was significantly increased in female mice who were offspring of males that had been exposed to microplastics. These female offspring also had lower muscle mass and an increased risk of diabetes. Genes linked to diabetes were shown to be more active in their livers.
Małe offspring did not show an increased risk of diabetes or increased expression of diabetes-linked genes, but did show a decrease in fat mass.
"The exact reasons for this sex-specific effect are still unclear," said senior study author Changcheng Zhou, a professor of biomedical sciences at the University of California, Riverside.
Additional work showed that the microplastics seemed to affect molecules that control gene expression in the sperm of mouse fathers. Molecules known as small RNAs, which often do not code for protein, were altered in this sperm. These changes in small RNAs may be affecting the expression of genes in offspring during development.
"To our knowledge, ours is the first study to show that paternal exposure to microplastics can affect sperm small noncoding RNA profiles and induce metabolic disorders in offspring," Zhou said.
Although these findings have to be confirmed in humans, they suggest that exposure to microplastics may be affecting human health in ways that we have not understood or appreciated. These impacts may also go beyond the person who is initially exposed; they could have a negative influence on future generations too.
"Our discovery opens a new frontier in environmental health, shifting the focus toward how both parents' environments contribute to the health of their children," said Zhou. "These findings from a mouse study likely have implications for humans. Men planning to have children should consider reducing their exposure to harmful substances like microplastics to protect both their health and that of their future children."
Sources: University of California Riverside, Journal of the Endocrine Society