Industry groups are skeptical of the significance of the new findings.
“The phthalate data are derived from a single (spot) sample. For substances like phthalates that are rapidly broken down and eliminated from the body, depending on a spot urine sample is a significant design flaw,” said Steve Risotto, senior director of the American Chemistry Council, a trade association for chemical manufacturers.
A group representing cosmetics and fragrance manufacturers doubts personal care products have a role in diabetes.
“Diethyl phthalate, also known as DEP, is the only phthalate with significant use in cosmetics. The study found no association between DEP and diabetes,” noted Linda Loretz, a director of the Personal Care Product Council.
Nail polish used to contain high levels, but most manufacturers voluntarily eliminated phthalates in recent years. The chemicals also have been banned in children’s toys.
Black women in the study had more than double the concentrations of DEP, the phthalate in cosmetics, and DBP, the phthalate in adhesives and lacquers that was linked to a double rate of diabetes, when compared with white women. Mexican-American women had 75 percent higher concentrations of DEP. Poor women had up to 78 percent higher levels of BBP – the phthalate in vinyl flooring that was associated with a double rate of diabetes – than women living above poverty level.
The racial and economic trends were in line with those of another recent study. Published in April, it found that women ranking lowest in socioeconomic status (based on race, education, income and food security measurements) had up to 83 percent more BBP than women with the highest socioeconomic status.
Non-white women had significantly more DBP, the phthalate in adhesives and lacquers that was linked to diabetes in the new research, and DEP, the primary phthalate associated with cosmetics, than their white counterparts. Women with lower levels of education and income had more BBP, the vinyl flooring phthalate linked to diabetes in the study.
Consumer behavior patterns might explain these disparities, Stahlhut said. For example, if black women use more hair care products or cosmetics, they would likely have higher levels of DEP in their bodies. But it’s impossible to distill trends like these from the current data, Stahlhut said.
“It’s difficult to interpret these patterns,” said Roni Kobrosly, an epidemiology researcher at the University of Rochester who led the socioeconomic study published in the journal Environmental Research. “They suggest that, on a large public health level, patterns of phthalate exposure vary with socioeconomic factors. But it’s premature to talk about the implications on an individual or cultural level.”
Because neither study included long-term follow-up with the women, the researchers cannot determine whether high phthalate concentrations actually led the women to develop diabetes or other diseases. Still, the findings are an important first step in sorting out the relationships between these chemicals and chronic diseases such as diabetes, experts say.
Several other pollutants have been linked to type 2 diabetes risks. Polychlorinated biphenyls (PCBs) and bisphenol A (BPA) are thought to disrupt the endocrine system by interfering with hormone signals. Studies suggest that phthalates may hinder glucose metabolism and stimulate fat cell production.
“With phthalates, the story is really still emerging,” said Kristina Thayer, a researcher with the National Institute of Environmental Health Sciences and the National Toxicology Program. “Studies like these are considered exploratory, but they seem to be consistent.”
“More needs to be done to really fill in this question of potential causality, and the roles that specific phthalates may play,” she added.