I’ve written frequently about the well-established link between environmental toxins and this country’s skyrocketing obesity rate. Persistent organic pollutants (POPs), which resist bio-degradation and are ubiquitous in the environment and food chain, are stored in human fat tissue and subsequently found in much higher levels in obese individuals than normal-weight folks. There’s little doubt that repeated exposure to endocrine-disrupting POPs is a major factor in both the type 2 diabetes mellitus and obesity pandemics.
Throwing fuel on the fire, a new study out of Duke University has found that certain chemicals in household dust may trigger a key receptor tied to obesity. This study adds to a growing body of evidence that a wide range of chemical mixtures, including those used in flame retardants, lubricants, hydraulic fluids and plastics bind to something known as the PPARgamma receptor and, under the right conditions, activate it. PPARgamma is short for “peroxisome proliferator-activated nuclear receptor gamma.” It’s known as the “master receptor” and is part of a group of receptor proteins that regulate fat metabolism, cell proliferation and cell death (apoptosis).
The researchers found that activation of the PPARgamma receptor during early development “may be a key factor in obesity.” Previous studies have shown that widely used organophosphates (found in insecticides) and polybrominated diphenyl ether (PDBE) metabolites( used as flame retardant coating in clothing, mattresses, and electronic equipment) also bind to the PPARgamma, but didn’t always activate it.
To better understand whether environmental exposures can trigger the PPARgamma, “on switch”, the Duke researchers conducted a study using something called a reporter gene assay, which measures the ability of an unknown DNA-sequence, to activate the PPARgamma receptor. The researchers choose to study the chemicals in house dust samples because indoor dust is an important pathway through which humans—especially young children—are exposed to environmental contaminants. Infants and toddlers, as example, ingest about 50 milligrams of house dust a day, at least according to EPA estimates.
The study showed that 28 of 30 compounds commonly found in indoor dust were “weak or moderate” PPARgamma agonists—meaning they could bind to and potentially activate the receptor. What most interested the researchers, however, was that the level of activation observed following exposure to a mixture of the contaminants in the dust samples. Indeed, the researchers found discovered that more than half of the dust samples collected from homes, offices and gyms were capable of activating the signs of significant PPARgamma receptor activation in more than half of the 25 dust samples collected from homes, offices and gyms, at a level of exposure that would be similar to a child’s daily dose at home. That is very disconcerting.
I’ve been telling patients for years that household dust is a pathway for the uptake of environmental contaminants, and that pregnant women and young children are at greatest risk. And this study shows how something as seemingly innocuous as household dust can contribute to a myriad of health problems, including obesity.