Phthalates cause uterine fibroids, in vitro study confirms

Toxic chemicals that are in a slew of consumer products are to blame for uterine fibroids, a new study finds.

Phthalates, chemicals known to be toxic that are in everything from medical supplies and makeup to food and hair products, are linked to the tumors, which are non-cancerous but highly common in women. (Phthalates, a term that may give you flashbacks to high school chemistry, is pronounced thal-ates.)

The study marks the first time that researchers have established that phthalates cause uterine fibroids. 

Related: Your biggest questions about fibroids and pregnancy, answered

Up to 80% of women may have a fibroid tumor during their lives, says study author Dr. Serdar Bulun, who heads up the department of obstetrics and gynecology at Northwestern University Feinberg School of Medicine, in a statement. About a quarter of the women show symptoms of fibroids, which can range from anemia and miscarriages to infertility and bleeding. In some cases, women have to have the tumors removed.

“[Phthalates] are more than simply environmental pollutants. They can cause specific harm to human tissues,” Dr. Bulun notes in the statement.

The report was published in the Proceedings of the National Academy of Sciences (PNAS).

The news comes just weeks after another large study linked hair straightening chemicals to uterine cancer. The chemicals in the products can include phthalates (as well as formaldehyde, cyclosiloxanes, parabens, and more).

How phthalates can cause fibroids

In the report, the researchers found that women who were exposed a lot to phthalates such as di-(2-ethylhexyl) phthalate or DEHP (a plasticizer that makes plastics stronger) had a high risk for having a symptomatic fibroid.

Previous studies have shown that there’s a link between phthalate exposure and fibroids, as well as steroid hormone levels and reproductive function. In a lab study (in vitro) on human tumor cells, Dr. Bulun and his team’s experiments showed that DEHP can trigger a hormonal pathway in the tumor cells, turning on a receptor (known as AHR) that binds to DNA and encourages the tumors to grow. 

Dr. Bulun notes that AHR was cloned in the early ’90s to be a receptor for dioxin, which is the toxin in Agent Orange. That was used during the Vietnam War, and caused significant reproductive abnormalities in those who were exposed. 

DEHP is just one phthalate, but it’s the most widely used one. It’s not banned in the U.S., but has been in other countries. Some phthalates are known carcinogens–meaning we know they cause cancer.

Related: Here’s why we need an expanded definition of infertility

You’re not just exposed if you touch a plastic item. Phthalate particles can gradually release and settle on surfaces; they can even accumulate in the air. DEHP can pass from mother to baby. (And kids under 3 are most at risk because they are exposed to a lot of plastic–and they tend to like to put items in their mouths a lot.)

Dr. Bulun tells Motherly that his team will do more studies on the topic. They want to see if there’s a link between phthalate levels in urine and activation of the AHR pathway in fibroids. 

Phthalates are called “everywhere chemicals” because, well, they’re kind of everywhere. But you can try to limit your exposure.

How to spot phthalates in products

Want to lower your exposure to phthalates? Dr. Bulun says to be mindful to read product labels, especially those of cosmetics, hair products like shampoo and hairspray, as well as trying to avoid plastic food packaging. And remember, products may not be labeled as “phthalate-free,” so you may have to know exactly what to look for.

Related: 12 signs you might be having fertility struggles, according to experts

Here’s what to keep an eye out for when trying to find out if a product contains phthalates:

• On storage containers or food wrap, check for a number 3 inside the universal recycling symbol along with the  “V” or “PVC” below the arrows. The logo usually is molded into the plastic 
• Opt for items with the numbers 1, 2, 4 and 5 within the arrows. Polypropylene (PP) is a phthalate-free substance
• Remember that most products don’t advertise that they contain phthalates. Look for these acronyms, which indicate that the product does (or includes phthalate metabolites):
• BBP: butyl benzyl phthalate 
• MBzP: mono benzyl phthalate 
• DBP: di-n-butyl phthalate
• MBP: mono-n-butyl phthalate 
• MiBP: mono-isobutyl phthalate 
• DEHP: di-(2-ethylhexyl) phthalate 
• MEHP: mono-(2-ethylhexyl) phthalate 
• DEP: diethyl phthalate 
• MEP: monoethyl phthalate 
• DiDP: di-isodecyl phthalate 
• DiNP: di-isononyll phthalate 
• DnHP: di-n- hexyl phthalate 
• DnOP: di-n-octyl phthalate

Sources

California Department of Toxic Substances Control: Work Plan Implementation: Chemicals in Hair Straightening  Products Background Document.

Iizuka T, et al. Mono-(2-ethyl-5-hydroxyhexyl) phthalate promotes uterine leiomyoma cell survival through tryptophan-kynurenine-AHR pathway activation. 2022. PNAS. doi:10.1073/pnas.2208886119. 

Northwestern Now: Uterine fibroid growth activated by chemicals found in everyday products.
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