Polybrominated biphenyls (PBBs) are a class of highly stable brominated flame retardants that were once used in the manufacturing of plastics and electronics. Although the production of PBBs has ceased in the United States as of the 1970s, health concerns remain due to their persistence in the environment, their ability to accumulate in food products, and their long biological half-life (United States Environmental Protection Agency, 2017; Hood et al., 2023; Terrell et al., 2008). There is also evidence that PBB has estrogen-mimicking endocrine disrupting properties (Curtis et al., 2019), which could have long-term impacts on individuals exposed in-utero (Small et al., 2011). Previous studies have already demonstrated that those exposed to PBB, and its endocrine disrupting properties, in-utero are at higher risk for lower birthweight (Givens et al., 2007), low 1-min Apgar score (Terrell et al., 2015), earlier menarche (Blanck et al., 2000), and adverse pregnancy outcomes (Small et al., 2011).

The Michigan PBB registry is one of the longest-running cohort studies in the country and was established to examine the health effects of the widespread environmental contamination with PBBs. During the early 1970s, PBBs were accidently introduced into the food supply when it was shipped in place of an animal feed supplement. Research based on the Michigan PBB registry has shown associations between exposure to PBB and many reproductive health outcomes (Small et al., 2011). In 2005, a menstrual function prevalence study among women exposed to PBBs from their diet suggested that higher exposure was associated with shorter menstrual cycle length and longer bleed length among women with past year weight loss (Davis et al., 2005). A follow-up prospective study published in 2019 showed that PBB concentrations measured during early childhood were associated with lower concentrations of endogenous estradiol metabolites throughout the menstrual cycle in adulthood (Howards et al., 2019).

Because the Michigan PBB registry is multigenerational, there is the rare opportunity to use the data collected from the registry to assess health outcomes in individuals exposed in-utero. There is evidence that in-utero exposure to PBBs is associated with health outcomes like increased odds of spontaneous abortion (Small et al., 2011), delayed puberty in males (Small et al., 2009), and earlier age at menarche (Blanck et al., 2000). However, there is limited research on the effects of in-utero exposure to PBBs or similar chemicals, specifically for menstrual cycle function and reproductive hormone levels (sex steroids and gonadotropins). Therefore, our objective was to examine the association between in-utero exposure to PBBs and menstrual cycle function in adulthood.