By David Liu, Ph.D.

Sunday June 26, 2011 (foodconsumer.org) -- A study in the June 17, 2011 issue of Environmental Research confirms that exposure to flame retardants like polychlorinated biphenyls (PCBs) may increase risk of type 2 diabetes mellitus.

Previous studies have already shown an association of polychlorinated biphenyl exposure with risk of diabetes and insulin resistance.  The current study found exposure to PCBs was significantly correlated with history of diabetes, but not insulin resistance in non-diabetics.

Victoria Persky of University of Illinois School of Public Health in Chicago, IL and colleagues found the association after analyzing data collected in 1996 from 118 postmenopausal women who previously worked for a capacitor manufacturer, meaning that they were exposed to PCBs.

The data "included a survey of exposure and medical history, height, weight and collection of blood and urine for measurements of lipids, liver function, hematologic markers and endogenous hormones," the researchers reported.

In addition to the association of exposure to PCBs with history of diabetes, the researchers also found diabetes was inversely correlated with hormones like follicle stimulating hormone, dehydroepiandrosterone sulfate and triiodothyronine.

This is not the first time PCBs were correlated with higher risk of diabetes mellitus.

Dr. Yueliang Leon Guo of the National Taiwan University and colleagues found a similar association in 2008 after comparing 378 adults who were exposed to PCBs with 370 of their neighbors who were not for their incidences of type 2 diabetes mellitus.

Women who used cooking oil tainted with PCBs were found twice as likely as controls to develop type 2 diabetes during a period of 24 years.  Those who were severely affected by PCB exposure were four times as likely to develop the disease.

But no association was found among men.

It has been known for a long time that flame retardants disrupts the balance of certain hormones like thyroid hormones such as triiodothyronine.  Health effects of flame retardants include altered gene expression, reduced fertility, slowed fetal growth and high risk of ADHD, thyroid disease, colon cancer, and low IQ.

PCBs widely used as flame retardants were banned in 1970s because of their toxicity.  Successors to PCBs are polybrominated flame retardants such as polybrominated diphenyl ethers or PBDEs.  Both types of chemicals are chemically similar.  It is not surprising that studies have shown PBDEs may boost risk of diabetes mellitus as well.

One study led by Korean researchers found exposure to brominated flame retardants was also associated with increased risk of diabetes mellitus.

For the study, J.S. Lim of Kyungpook National University in Daegu, Korea and colleagues quantified the association of brominated flame retardants with diabetes and metabolic syndrome based on data collected from 1367 adults who participated in the National Health and Nutrition Examination Survey 2003 -2004.

Lim et al. found that compared to those whose serum concentrations of PBB-153 and PBDE-153 - two types of brominated flame retardants in the lowest quartile, adults who had their serum concentrations of these chemicals in the highest quartile were 90 percent and 80 percent more likely to be diagnosed with diabetes mellitus, respectively.

Similarly, PBB-153 and PBDE-153 can boost the risk of metabolic syndrome by up to 200 percent.

The study was published in 2008 in Diabetes Care.

Flame retardants can be used in any household products that may otherwise catch fire including CD/DVD cases, computers, furniture, carpets, toys, TV and many products made of plastics. They can also be used in baby products such as car seats, nursing pillows, high chairs, strollers, and bassinet mattresses.

Flame retardants are found in 98 percent pregnant women in the United States, according to Environmental Working Group.  Children have higher levels of flame retardants, compared with  adults.  Women may be at a higher risk from flame retardants, compared with men.  Some flame retardants are carcinogens.