Scientists at Northwestern Medicine have established a causal link between exposure to phthalates, toxic chemicals found in everyday products such as cosmetics and food packaging, and increased growth of uterine fibroids in women.

Phthalates are a group of chemicals used to make plastic more durable and are commonly used by manufacturers in a range of industrial and consumer products. DEHP, particularly, has been the most widely used phthalate. It is utilized as a plasticizer in everything from shower curtains and car upholstery to lunchboxes and shoes. They can also be found in a range of cosmetics and personal care products, including nail polish, hairspray, shampoo and perfumes. A study even detected elevated levels of phthalates, including DEHP, in sanitary pads and disposable diapers, which, according to the researchers, could cause developmental or reproductive harm.

Uterine fibroids are the most common tumors among women – around 80% of women develop fibroids at some point in their life. A quarter of these cases are symptomatic, accompanied by excessive or uncontrolled uterine bleeding, miscarriages, anemia, infertility and large abdominal tumours that require technically-challenging surgeries, researchers at Northwestern University noted in a press release.

Their study, published in the journal Proceedings of the National Academy of Sciences, found that women with high exposure to certain phthalates such as DEHP are at higher risk for developing symptomatic fibroids. While previous research has associated phthalate exposure with uterine fibroid growth, this is the first study that explains how these chemicals activate growth of these tumors in women.

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Scientists found that exposure to DEHP could activate a hormonal pathway, which in turn activates an environmentally responsive receptor (AHR) that binds to DNA and facilitates the increased growth of fibroids.

“Interestingly, AHR was cloned in the early ’90s as the receptor for dioxin, the key toxin in the agent orange… 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 said.

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

Common consumer products gradually release DEHP indoors where it can settle on the floor or other surfaces while also accumulating in dust and remaining suspended in the air. DEHP can also pass from the mother to the baby during pregnancy. When used in food packaging, phthalates can leach into the food – these chemicals have previously been detected in milk and spices.

These chemicals can then enter the human body through ingestion, inhalation, skin contact, or even exposure to contaminated air. Once absorbed, these phthalates are metabolized and excreted in urine — a primary biomarker of phthalate exposure.

The risks associated with phthalates have raised widespread concern over the years. A 2021 study said that chronic exposure to phthalates could negatively affect the endocrine system and the functioning of multiple organs, causing long-term impacts on pregnancy, child growth and reproductive systems in children and adolescents. Since these toxins act as hormone disruptors, they may increase the risk of miscarriages and gestational diabetes.

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In children, exposure to phthalates could cause early onset of puberty, neurodevelopmental effects, and has even been linked to impairment of social functioning.

Still, the wide prevalence of these chemicals in everyday products shows they have not been subject to the kind of regulation that might be needed. Certain regulatory restrictions have been put in place in European Union countries, where phthalate concentrations have been limited to less than 0.1% in cosmetics, children’s toys, electronic devices and medical devices.

The US Environmental Protection Agency has classified DEHP as a possible carcinogen. Many countries, including India, have also restricted the use of phthalates in children’s toys. Despite such restrictions, phthalates continue to be widely used in several products, especially food packaging and health products, the researchers noted. A fact sheet by Toxics Link stated that standards are lacking in India to restrict phthalate concentrations in several commonly used products, drinking water and air. It also underscored the need for guidelines on product labelling of phthalates.

The links between these toxic chemicals and increased uterine fibroid growth then adds to an existing body of knowledge on the health hazards posed by phthalates, pointing to a need for greater regulatory restrictions that could reduce individual exposure to such toxins.