Phthalates are chemical compounds used in plastics to provide flexibility and durability, and are most commonly found in polyvinyl chloride (PVC). Phthalates are also found in cosmetics such as nail polish, shampoos, perfumes, and hair sprays. In addition, they can be found in pill coatings, plastic bottles, detergents, box packaging, paints, waxes, and textile materials. Phthalates are ubiquitously present. As a result, most people that are tested for the presence of phthalates in their urine are found to have trace levels. Women who use beauty care products, such as nail polish, have been found to have higher levels of phthalates than the average for the population at large. In rodent laboratory studies, exposure to high levels of phthalates has been shown to cause changes in hormone levels and cause birth defects. Exposure to high levels of phthalates been linked to human health problems through observational studies, but no definitive evidence to support this has been documented.
Researchers, lead by Dr. Tamarra James-Todd from Brigham and Women’s Hospital in Boston, have found that women who have the highest levels of phthalates had more than double the probability of having the endocrine disorder diabetes. The results of their research were published in the journal Environmental Health Perspectives. The investigation was conducted as a cross-sectional study and involved 2,350 women aged 20 to 80 years who were enrolled in the NHANES study (National Health and Nutrition Examination Survey) from 2001 to 2008. The researchers analyzed urinary concentrations of phthalates and self reported cases of diabetes among the women. Women with the highest levels of phthalates had almost twice the odds of developing diabetes when compared to those women who had the lowest levels. In addition, women with moderate levels of phthalates had 70% increased risk of developing diabetes compared to those when with the lowest levels. There was also a correlation between phthalate levels and risk of having insulin resistance, which is considered a precursor to the development of diabetes. These results were consistent even after adjusting for possible confounding factors such as family history, diet, and social factors.
The authors wrote, “urinary levels of [phthalates] were associated with diabetes in women. In women without diagnosed diabetes, some phthalate metabolites were positively associated with [fasting blood glucose] and [insulin resistance]. These findings suggest the need to further explore the association between phthalates, insulin resistance, and diabetes. If future studies determine causal links between phthalates and diabetes, then reducing phthalate exposure could decrease the risk of diabetes in women”.
This study adds to previous research which has shown negative health consequences from exposure to phthalates. It has been previously shown that phthalate exposure increases insulin resistance in male NHANES participants, and that a geriatric population had an increased incidence of diabetes when exposed to phthalates. Future studies will need to focus on the exact mechanism which causes this observational link between diabetes and phthalate exposure. If additional studies continue to document health risks with exposure to phthalates, governmental health regulatory agencies will need to intervene to limit exposure to phthalates and decrease their negative health consequences.
Tamarra James-Todd et al. “Urinary Phthalate Metabolite Concentrations and Diabetes among Women in the National Health and Nutrition Examination Survey (NHANES) 2001-2008” Environ Health Perspect 2012 doi:10.1289/ehp.1104717