Chemicals From Everyday Products Can Activate Uterine Fibroid Growth

A new study has, for the first time, demonstrated a link between phthalates – a group of chemicals found in many consumer products – and the increased growth of uterine tumors known as fibroids. The study is published in PNAS.

Possible dangers of phthalate exposure

Phthalates, a type of plasticizer, are often added to plastics to make them soft, flexible and durable. Environmental phthalates are used by manufacturers to produce many different industrial and consumer products from shower curtains to car upholstery, lunchboxes and shoes.

Nevertheless, phthalates are also known to be toxic. Despite their detection in the packaging for products such as food and medical equipment and the implementation of regulatory restrictions in some countries in the European Union, they are not currently banned in the US.

One of the most extensively used phthalates, di(2- ethylhexyl) phthalate (DEHP), has been shown to be gradually released from consumer products to indoor environments like homes, schools, offices and cars. Here, DEHP gathers in air and dust particles before settling on floors and surfaces.

“These toxic pollutants are everywhere, including food packaging, hair and makeup products, and more, and their usage is not banned,” explained Dr. Serdar Bulun, the study’s senior author and chair of the department of obstetrics and gynecology at Northwestern University Feinberg School of Medicine. “These are more than simply environmental pollutants. They can cause specific harm to human tissues.”

Consequences for fibroid growth

In the current study, Bulun and colleagues found that women who experienced high exposure to phthalates such as DEHP and its metabolites have a high risk of developing what is known as a symptomatic fibroid.

Fibroids are an incredibly common type of benign tumor that develops in the uterus, with up to 80% of women developing a fibroid during their lifetime. Of these, around 25% result in symptoms such as heavy uterine bleeding, anemia, miscarriages and infertility. Particularly large fibroids may even require surgery, which can be incredibly difficult to perform.

Previous studies have shown an association between exposure to phthalates and uterine fibroids. However, this is the first study to demonstrate the mechanisms underpinning this relationship. The researchers suggest DEHP exposure may stimulate a hormonal signaling pathway, thereby activating the DNA-binding aryl hydrocarbon receptor (AHR). This culminates in the promotion of fibroid growth.

“Interestingly, AHR was cloned in the early ’90s as the receptor for dioxin, the key toxin in the Agent Orange,” Bulun added. “The use of Agent Orange during the Vietnam war caused significant reproductive abnormalities in the exposed populations, and dioxin and AHR were thought to be responsible for this.” Bulun suggests that these findings offer additional evidence in support of these theories.

Reference: Iizuka T, Yin P, Zuberi A, et al. Mono-(2-ethyl-5-hydroxyhexyl) phthalate promotes uterine leiomyoma cell survival through tryptophan-kynurenine-AHR pathway activation. PNAS. 2022;119(47):e2208886119. doi: 10.1073/pnas.2208886119

This article is a rework of a press release issued by Northwestern University. Material has been edited for length and content.