Middle-aged White women who had higher levels of some breakdown products of phthalates – a class of endocrine disrupting chemicals (EDCs), or “forever chemicals,” that act as plasticizers – had a significantly greater risk of developing type 2 diabetes over a 6-year period compared with other similar women.
However, this association was not seen among Black or Asian middle-aged women.
These findings from the Study of Women’s Health Across the Nation – Multipollutant Study (SWAN-MPS), by Mia Q. Peng, PhD, MPH, and colleagues, have been published online in the Journal of Clinical Endocrinology & Metabolism.
“Overall, our study has added some evidence to support the potential diabetogenic effects of phthalates, but it also highlights that much is still unknown about the metabolic effects of these chemicals,” the group noted.
“The apparent racial/ethnic differences in the associations between phthalates and incident diabetes should be investigated in future studies,” they cautioned.
Recruiting younger participants and observing them longer, they suggested, “will also help us understand the effects of phthalates on different stages of the diabetogenic process, including whether body fat gain is an important mediator.”
Phthalates are all around us
Low-molecular-weight phthalates are frequently added to personal care products, such as fragrance, nail polish, and some feminine hygiene products, as solvents, plasticizers, and fixatives, the researchers explained.
And high-molecular-weight phthalates are frequently added to polyvinyl chloride plastic products, such as plastic food packaging, clothing, and vinyl flooring, as plasticizers.
Phthalates have been hypothesized to contribute to the development of diabetes, but longitudinal evidence in humans was limited.
“Given widespread exposure to phthalates and the enormous costs of diabetes to individuals and societies, ongoing investments in the research on phthalates’ metabolic effects are warranted,” the researchers concluded.
Racial differences in phthalates and incident diabetes
“A new finding is that we observed some phthalates are associated with a higher risk of diabetes development, especially in White women [that] were not seen in Black or Asian women,” senior author Sung Kyun Park, ScD, MPH, of the University of Michigan, Ann Arbor, told this news organization.
“We were surprised to see the racial/ethnic differences,” added Dr. Peng, formerly of the University of Michigan and now at Lifecourse Epidemiology of Adiposity and Diabetes Center, University of Colorado Anschutz Medical Campus.
A possible explanation is that “compared to White women, Black women develop diabetes at a younger age and are exposed to higher levels of several phthalates,” and this study excluded women who already had diabetes by midlife, she noted.
“Although our study was conducted in a cohort of women,” Dr. Park stressed, “we hope that our findings are not interpreted that only women should be concerned of phthalates. Our findings add to the current literature that phthalates may be a potential risk factor for type 2 diabetes.
“Certain phthalates are prohibited in children’s toys and child care articles,” Dr. Peng noted, as explained by the U.S. Consumer Product Safety Commission. In addition, a bill has been introduced in Congress to ban phthalates in food contact substances.
“If phthalates are removed from plastics and other consumer products,” she cautioned, “we do have to be careful in the process to avoid replacing them with some other potentially harmful chemicals.”
A well-known example of this type of “regrettable substitution,” Dr. Park added, “is ‘BPA-free’ plastics that replaced bisphenol A with other bisphenols such as bisphenol-F (BPF) or bisphenol-S (BPS). The product has a label of ‘BPA-free’, but those replaced chemicals turned out to be equally toxic. Science is slow to determine if a new chemical introduced to the market is safe and can replace a regulated chemical.”
And studies have shown that a diet rich in meat, fat, and ultraprocessed foods is associated with increased exposures to some phthalates, especially when the foods are obtained away from home, such as fast foods, Dr. Peng observed. In addition, some phthalates are added to personal care products such as fragrance.
“As a first step,” she said, “I think reducing consumption of ultraprocessed foods packaged in plastics may help reduce phthalate exposure.”
A 2020 report from the Endocrine Society and the International Pollutants Elimination Network (IPEN), titled, “Plastics, EDCs, and Health,” summarizes research on bisphenol A, per- and polyfluoroalkyl substances (PFAS), phthalates, and other EDCs that leach from plastics. The Endocrine Society website also has a link to a 2-page summary.