By Dr. Becker
A study published last year in the Journal of Toxicology and Environmental Health1 indicates that flame retardant chemicals (polybrominated diphenyl ethers, or PBDEs) in house dust are linked to the growing problem of thyroid disease in pet cats. The study was conducted by researchers at the Department of Veterinary Biosciences, College of Veterinary Medicine, University of Illinois at Urbana-Champaign.
Hyperthyroidism is the most common endocrine disorder of housecats, with over 10 percent of kitties over the age of 10 diagnosed with the disease. Since hyperthyroidism was discovered fairly recently (1979), the sudden appearance and rapid increase in cases in both humans and cats has generated several studies in a search for potential causes.
PBDEs are used as flame retardants in furniture and electronics. The compounds can leak from these products into the environment.
PBDEs are known endocrine and thyroid disruptors, so it's likely no coincidence that widespread use of these flame retardant chemicals began right before the first diagnoses of hyperthyroidism.
Researchers Evaluate PBDE Levels in Canned Cat Food and House Dust
The purpose of the University of Illinois study was to explore the role of PBDEs in the development of hyperthyroidism in cats. The researchers evaluated the diet (canned cat food), environment (specifically, house dust) and blood serum of kitties that were hyperthyroid as well as cats with normal thyroid function. A small number of feral cats were also used in the study.
They set out to discover whether toxin loads in the blood of same age cats correlated with thyroid dysfunction in the hyperthyroid kitties.
They also measured commercial canned cat foods and house dust for PBDE content to determine which likely posed the greater risk.
Third, they looked for a link between blood PBDE levels, environmental or nutritional PBDE exposure, and thyroid function.
What the Study Showed
Blood PBDE concentrations in the cats with normal thyroids were not all that different from those of hyperthyroid kitties. However, as you might expect, concentrations were much lower in feral cats than in either of the groups of pet cats.
Total PBDEs in canned cat food had a range of 0.42 to 3.1 ng/g. In house dust, the range was much higher at 510 to 95,000 ng/g.
And here's where it gets interesting. The level of PBDEs in the dust of homes of cats with normal thyroids was from 510 to 4,900 ng/g, while the level in the homes of hyperthyroid cats ranged from 1,100 to 95,000 ng/g – a great deal higher. In addition, the level of dust PBDEs was closely linked to serum total blood T4 concentrations. Dust PBDEs and serum total T4 concentrations were also significantly related. (Greater than normal levels of the thyroid hormone thyroxine, or T4, in the blood signify an overactive thyroid.)
These study results indicate housecats are primarily exposed to flame retardant chemicals by ingesting house dust – which of course occurs every time they groom themselves. These findings are similar to studies linking feline malignant lymphoma with cats that live with cigarette smokers.
Dogs Also Have Significant Exposure to PBDEs
A 2007 study conducted at Indiana University2 revealed significant blood concentrations of PBDEs in pet dogs. Dogs had levels 5 to 10 times higher than those of humans living in North America, and previous studies have shown levels in cats that are 20 to 100 higher than are found in humans.
Dogs appear to metabolize these chemicals faster than cats do. In addition, dogs produce an enzyme that breaks down organochlorine pesticides, and researchers theorize something similar could be going on with the breakdown of PBDEs.
PBDEs have been added to consumer products since the 1970s as fire retardants. These compounds inside certain products increase the temperature it takes to make them burn, which makes the products more flame-resistant.
Items around your home and office that may contain PBDEs include:
Polyurethane foam products – upholstered furniture, mattresses, pillows Computers, printers, copiers, scanners, faxes Carpet padding Toner cartridges Vehicle seat covers TVs and TV remote controls Kitchen appliances Video equipment Fans Blow dryers Water heaters Cell phones
PBDEs leak from products when they heat up during use or when the product begins to deteriorate.
Avoiding PDBE Exposure
Fortunately, most new foam products are not likely to have PBDEs added. If you have foam items in your home, office or vehicle that were purchased before 2005, however, they probably contain PBDEs. These items might include: carpet padding, upholstered couches and chairs, mattresses and mattress pads, foam-filled pillows and the seats in your vehicle.
The Environmental Working Group offers some excellent tips to help limit your family's and pet's exposure to PBDE-containing products:
- Exercise caution with foam items. Replace any item in which the foam is exposed or misshapen (an indicator the foam is breaking down and releasing toxic compounds into the environment).
- Use only vacuums with HEPA filters, which are better at trapping small dust particles and are more efficient at removing contaminants and allergens from your home or office. The same principle applies to indoor air cleaners with HEPA filters.
- Replace rather than reupholster foam furniture. Even PBDE-free furniture can contain other types of fire retardants with potentially harmful effects.
- Remove old carpet with care. The padding beneath may contain PBDEs.
- When buying a new product, ask what type of fire retardant it contains. Try to avoid purchasing items containing brominated flame retardants (BFRs). Go with less flammable materials, for example, cotton, wool and leather. Keep in mind that 'natural' latex foam and natural cotton are flammable and by law require the addition of a fire retardant.