Endocrine disruptors and endometriosis: what the evidence shows

Endometriosis affects roughly 1 in 10 women of reproductive age worldwide — a chronic, often painful condition in which tissue similar to the uterine lining grows outside the uterus [1]. Its exact cause is still unknown, but for over 30 years researchers have investigated whether exposure to endocrine-disrupting chemicals (EDCs) — substances that interfere with hormone signaling — helps drive its development. Here’s what the science actually says, and where it’s still uncertain.

The founding evidence: a monkey study that started it all

The dioxin–endometriosis hypothesis traces back to a landmark 1993 study by Rier and colleagues. Rhesus monkeys were fed 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, the most toxic dioxin) daily for four years. The result was dose-dependent: 43% of monkeys exposed to a low dose (5 ppt) developed moderate-to-severe endometriosis, compared with 71% of those exposed to a higher dose (25 ppt) [2][3]. A follow-up study published in 2001 examined the same animals 13 years after exposure ended and found that those with endometriosis still had elevated serum levels of dioxin-like PCBs, and that disease severity correlated with serum concentrations of specific PCB congeners [4]. This was the first strong experimental evidence that an endocrine disruptor could cause endometriosis-like lesions in a primate, and it set the research agenda for the decades that followed.

What human studies show, by chemical class

Human evidence is observational — mostly case-control studies comparing chemical levels in women with surgically confirmed endometriosis to women without it — so it can show associations but can’t prove cause and effect on its own. With that caveat, the picture that emerges is not uniform across EDCs:

Dioxins, PCBs, and organochlorine pesticides have the most consistent evidence. A meta-analysis found significantly increased odds of endometriosis associated with PCBs (odds ratio 1.58) and organochlorine pesticides (odds ratio 1.40) [5]. A 2023 systematic review of 27 studies likewise concluded that dioxins, organochlorine pesticides, and PCBs showed a “solid connection” to endometriosis, while evidence for bisphenol A and phthalates was more mixed [6].

Phthalates, used as plasticizers and often found in fragranced products, show a weaker and less consistent signal. A meta-analysis of eight studies found that one specific metabolite, MEHHP, was associated with modestly higher odds of endometriosis (OR 1.25, 95% CI 1.00–1.55), while four other phthalate metabolites showed no significant association [7]. The association with MEHHP was also stronger in Asian study populations than in U.S. ones, hinting that exposure levels, genetics, or other regional factors matter [7]. A broader meta-analysis lumping phthalate esters together as a class found an overall odds ratio of 1.27 [5]. An earlier 2015 meta-analysis spanning 30 studies and four EDC classes found an overall odds ratio of 1.41 across all exposures combined [8].

Bisphenol A (BPA), one of the most-studied EDCs, has not shown a significant association with endometriosis risk in meta-analysis, despite being linked to other reproductive effects [5].

PFAS (“forever chemicals”) are the newest addition to this research. A 2025 study — the first to measure PFAS directly in endometrial tissue — found no association between PFAS and overall endometriosis risk, but among women who already had endometriosis, higher levels of certain PFAS (PFOS, PFOSA, and PFHxS) were associated with more advanced-stage disease [9][10]. A separate case-control study (the ENDEA study) found that exposure to perfluorotridecanoic acid (PFTrDA) specifically was associated with higher odds of an endometriosis diagnosis [11].

Why these chemicals might matter biologically

There are plausible mechanisms connecting EDCs to endometriosis, which is part of why researchers take the epidemiological signal seriously even where it’s inconsistent. EDCs can bind to and activate estrogen receptors, and endometriosis is a fundamentally estrogen-dependent condition — lesions grow in response to estrogen. Several EDCs also appear to promote progesterone resistance, which impairs the body’s normal ability to counterbalance estrogen’s effects on endometrial tissue [12][13]. Separately, EDCs can alter immune function — changing the activity of macrophages, natural killer cells, and T cells — creating a more inflammatory environment that may allow displaced endometrial-like tissue to survive and grow instead of being cleared by the immune system, as it normally would be [13]. Some research also points to epigenetic changes: dioxin exposure has been linked to altered gene expression patterns relevant to endometriosis pathogenesis [14].

The Endocrine Society, in its 2009 and 2015 scientific statements on EDCs, concluded more broadly that evidence from animal models, clinical observation, and epidemiology converges to implicate EDCs as a significant concern across multiple aspects of female reproductive health, not endometriosis alone [15][16].

Where the evidence is weaker than headlines suggest

It’s worth being honest about the limitations, because this is an area where the science is easy to overstate:

• Most human studies are case-control, not longitudinal. They typically measure chemical levels after a woman already has an endometriosis diagnosis, which raises the possibility of reverse causation — the disease process itself, or its treatment, could plausibly affect chemical metabolism or where chemicals accumulate in the body.
• Non-persistent chemicals are hard to measure accurately. Phthalates and BPA are metabolized within 24–48 hours, so a single urine sample — which is what most studies use — may not reflect a person’s actual long-term exposure [17].
• Results are inconsistent even within the same chemical class, likely due to differences in which metabolites were measured, how studies adjusted for confounders like creatinine, and differences in study populations [17].
• Despite thousands of participants across dozens of studies, no EDC has been definitively established as a cause of endometriosis. The consistent findings for dioxins, PCBs, and organochlorine pesticides are the strongest signal, but even here, researchers describe the relationship as an association requiring further mechanistic and longitudinal confirmation, not a proven causal pathway [6][17].

The practical takeaway

Endometriosis has many contributing factors — genetics, retrograde menstruation, immune function, and likely a combination of environmental exposures rather than any single chemical. That said, reducing avoidable exposure to the EDC classes with the most consistent evidence is a reasonable, low-cost precaution while research continues. In practice, that means being more mindful of the phthalates and synthetic fragrance ingredients (often hidden under “parfum” on labels) common in cosmetics and personal care products, choosing BPA-free food and drink containers, and being aware that older organochlorine pesticides and dioxins persist in the environment and in animal fats even where use is now restricted. Scanning ingredient labels on the products you use daily is one concrete way to reduce your personal exposure load to the chemicals researchers are actively studying.

Sources

1. World Health Organization, Endometriosis fact sheet
2. Rier, S.E. et al., “Endometriosis in Rhesus Monkeys (Macaca mulatta) Following Chronic Exposure to 2,3,7,8-Tetrachlorodibenzo-p-dioxin,” Fundamental and Applied Toxicology, 1993 — ScienceDirect
3. Rier, S., “The Physiopathology of Endometriosis: Pollution and Dioxin,” Gynecologic and Obstetric Investigation, 1999 — PubMed
4. “Serum Levels of TCDD and Dioxin-like Chemicals in Rhesus Monkeys Chronically Exposed to Dioxin: Correlation of Increased Serum PCB Levels with Endometriosis,” Toxicological Sciences, 2001 — PubMed / Oxford Academic
5. Meta-analysis of EDC exposure classes and endometriosis risk (PCB, organochlorine pesticide, and phthalate ester odds ratios) — Frontiers in Public Health
6. “Exploring the Effects of Endocrine-Disrupting Chemicals and miRNA Expression in the Pathogenesis of Endometriosis by Unveiling the Pathways: A Systematic Review,” 2024 — PubMed
7. “Association between Phthalate Metabolites and Risk of Endometriosis: A Meta-Analysis,” International Journal of Environmental Research and Public Health, 2019 — PMC
8. Meta-analysis of 30 studies across four EDC classes and endometriosis (2015) — referenced in Frontiers in Physiology review
9. Marroquin, J. et al., “Per- and Polyfluoroalkyl Substances in Eutopic Endometrium Tissue and Risk of Endometriosis: Findings from the IMPLANT Study,” Environmental Health Perspectives, 2025 — EHP
10. George Mason University College of Public Health, “Unavoidable Forever Chemicals May Be Associated with Severe Endometriosis,” 2025
11. “Association between Exposure to Perfluoroalkyl Substances (PFAS) and Endometriosis in the ENDEA Case-Control Study” — PubMed
12. “Endocrine Disruptors and Endometriosis,” Fertility and Sterility — ScienceDirect
13. “Unraveling the Core of Endometriosis: The Impact of Endocrine Disruptors,” International Journal of Molecular Sciences, 2025 — MDPI
14. “Correlation between Dioxin and Endometriosis: An Epigenetic Route to Unravel the Pathogenesis of the Disease,” Archives of Gynecology and Obstetrics — Springer
15. Diamanti-Kandarakis, E. et al., “Endocrine-Disrupting Chemicals: An Endocrine Society Scientific Statement,” Endocrine Reviews, 2009 — PMC
16. Gore, A.C. et al., “EDC-2: The Endocrine Society’s Second Scientific Statement on Endocrine-Disrupting Chemicals,” Endocrine Reviews, 2015 — Oxford Academic
17. “Environmental Exposure to Non-Persistent Endocrine Disrupting Chemicals and Endometriosis: A Systematic Review” — PMC

This article summarizes current research for educational purposes and is not medical advice. If you have symptoms of endometriosis, talk to a gynecologist or your primary care provider.