• A chemical called DEHP can trigger a chain reaction that causes uterine fibroids, a new paper finds. 
• DEHP is used to make plastic flexible in many products, such as shower curtains and food packaging.
• Fibroids can cause infertility and pregnancy complications, as well as severe pelvic pain and bleeding.

A new paper found a chemical used in plastic can stimulate a serious of chain reactions that cause uterine fibroids, or tumors in the uterus. 

DEHP — or, di(2-ethylhexyl) phthalate — is a synthetic chemical added to thousands of products to make plastic flexible. It is found in shower curtains, shoes, garden hoses, rain wear, dolls, and packaging for processed food. 

These chemicals show up in small amounts, but research has increasingly found constant exposure over time could lead to health consequences like diabetes risk and obesity. The most common way people are exposed to DEHP is likely through food that was packaged in plastic, the Environmental Protection Agency says. 

A new paper, published Monday in the Proceedings of the National Academy of Sciences, zooms in on the particular risk plastics pose to people with a uterus, increasing the risk of benign yet sometimes debilitating tumors called fibroids.

Dr. Serdar Bulun, chair of the department of obstetrics and gynecology at Northwestern University’s school of medicine and the study’s main author, said other papers had established a link between high DEHP levels and uterine fibroid growth, but his was the first to understand how the chemical can directly lead to the tumor’s growth. 

“What we found was a subtle effect, but the fibroid growth is also a subtle process,” Bulun said. “The fact that you’re not seeing cancer or things like that immediately in somebody who had exposure [to phthalates] doesn’t mean that they’re innocent and they don’t cause problems.”

Fibroids can cause pregnancy complications, intense pain, and bleeding

Uterine fibroids are non-cancerous tumors that grow in or outside the uterus. They can cause infertility and pregnancy complications, as well as severe pelvic pain and bleeding, STAT News reported.

About 26 million Americans will have fibroids in their lifetime — roughly equivalent to the number of Americans diagnosed with diabetes, per the National Institutes of Health. They are more common in Black women, and typically affect people during their menstruating years.

As Insider has previously reported, fibroids have been something of a medical mystery for years due to scant research. To this day, the exact cause of uterine fibroids are unknown, though scientists believe vitamin D deficiency, alcohol use, and a family history of the tumors increase your risk.

How plastics fuel fibroids

A major breakthrough in fibroid research occurred in 2011: Researchers in Finland discovered a gene (MED12) that increases a person’s risk of developing uterine fibroids.

Bulun has spent years trying to explain how that happens. Years ago, he published research showing that MED12 carriers sometimes convert nutrients from foods (such as milk and turkey) into a hormone. Once converted, that hormone can activate dormant receptors, causing fibroid tumor growth. 

In the new study, Bulun’s team exposed fibroid cells to different types of phthalates, and they found exposure to DEHP can trigger this whole fibroid-forming process.

“If a woman already has a few small fibroids, through exposure to phthalates over the years, these tumors grow,” Bulun said. 

Bulun said he will continue to study how environmental pollutants increase tumor growth — and wants other researchers to do the same. 

“We all, including legislators, should be advocating for more research for environmental pollutants. I think the money and efforts spent in this area would be very impactful,” he said.