Diabetes could be linked to phthalates, chemical in common household products, study suggests

By Deborah Kotz, Globe Staff

More than twice as many Americans have type 2 diabetes than 30 years ago, and new research suggests that our sedentary lifestyle habits and overconsumption of calories may not be the only reasons. Certain chemicals called phthalates -- ubiquitous in soft plastic packaging, fragrances, and cosmetics -- could be contributing to a rise in diabetes rates, according to a study from Brigham and Women’s Hospital.

It’s one of a handful of recent studies that found a statistical association between high levels of phthalates and an increased risk of diabetes, but it couldn’t determine whether there was a causal effect, in part because phthalate levels were measured at one point in time -- after the study participants had already been diagnosed with the disease.

The study, published Friday in the journal Environmental Health Perspectives, examined data from a government study of 2,350 women ages 20 to 80 and found that those with the highest levels of certain types of phthalates in their urine had up to twice the likelihood of having diabetes compared with those with the lowest.

About 9 percent of those with a high level of one type, called mono-isobutyl phthalate, had diabetes compared with 5 percent of those with the lowest levels of this chemical. But phthalates are found in medical tubing, IV bags, and certain medications, so it could be that those with diabetes are more likely to have higher levels due to the fact that they take more medications and have more medical treatments.

“What we really need to do now is to start exploring phthalate levels over time,” said study author Tamarra James-Todd, an epidemiologist at Brigham and Women’s, “to determine whether high levels actually lead to a greater risk of becoming obese and developing diabetes down the line.”

Phthalates are a class of chemicals called endocrine disrupters because they bind to cells and can alter the production of certain hormones such as insulin or estrogen.

“This study certainly has important public health implications,” said Nikki Gillum Posnack, a George Washington University phthalate researcher who wasn’t involved in the study. “It adds support to the claim that phthalate exposure is associated with metabolic diseases in humans, including insulin resistance and diabetes.”

About 75 percent of Americans have detectable levels of phthalates in their urine, and whether or how much of an impact these chemicals have had on our diabetes rates isn’t known.

It’s also tough to avoid phthalates since they’re in everything from nail polish to deodorant to plastic packaging. “A moisturizer can say it’s phthalate-free, but it’s packaging can still contain the chemical, which can leech into the cream,” said James-Todd. “The bigger issue is whether the government should take steps to limit the use of phthalates in products.”