Science News included a report that certain cat foods, especially fish-flavored canned entries, deliver substantial quantities of brominated flame retardants to the pets' diets. The finding helps explain why blood concentrations of these ubiquitous chemicals—known as polybrominated diphenyl ethers (PBDEs)
Several studies show that both children and adults can accumulate substantial amounts of these hormone-perturbing agents. Certain foods can deliver significant quantities, especially fish, chicken livers, and certain sausages. Moreover, recent studies have found that mothers typically pass PBDEs along to their baby—both in the womb and during breastfeeding.
In general, manufacturers add PBDEs to plastics and foam products to reduce the likelihood they will catch fire. However, treated products can shed the chemicals into air, water, and dust. Through exposure routes that remain somewhat sketchy, PBDEs have been entering in food supply.
What's emerging as an apparently far greater source of human exposure is ingestion of PBDE-laced house dust. That puts toddlers at greatest risk of accumulating the chemicals because of the time they spend crawling on carpets and mouthing toys and other items that are indoor-dust magnets.
Indeed, authors of the new cat study argue in an upcoming issue of Environmental Science & Technology that house cats "may serve as sentinels to better assess human exposure and adverse health outcomes related to low-level but chronic PBDE exposure."
What are those risks?
Studies have shown that at least in young animals, brief, early PBDE exposures can mildly impair learning and reduce thyroid-hormone concentrations in blood. Exposures later in life can delay puberty in male rodents, and adult exposures can block the activity of cellular receptors for male sex hormones. Then there's the new cat study. PBDE exposures can bring a potentially lethal thyroid disease.
No one knows whether these flame retardants pose similar risks to people—and if so, what concentrations might be harmful. The data just aren't in. Until they are, the animal data suggest that cautious parents might want to vacuum frequently and limit their small children's intake of certain foods.
The role of dust
Both the new study of house cats PBDE contamination in supermarket foods present a conundrum.Toxicologist with the Environmental Protection Agency both studies, explains that the two sets of data indicate that food doesn't account for much of the amount of flame-retardants found in either people or pets.
Indeed, her team has calculated a likely daily PBDE intake from the foods and found it unimpressive. The total intake would probably lead to blood-PBDE values of less than 10 ppb, the researchers note. Yet the average blood value exceeds 30 ppb in U.S. residents, and 5 percent of people have blood-PBDE values 10 to 100 times that amount.
Such numbers "suggest that house dust is an important source [of PBDEs], Supporting that suspicion are data from a study published in the March 1 Environmental Science & Technology. Thomas F. Webster of Boston University and his colleagues showed that among new mothers in the Boston area, PBDE concentrations "in breast milk and house dust were strongly and positively correlated."
Overall, breast milk from women whose homes contained house dust rich in flame-retardant residues had PBDE concentrations 2.6 times those of milk from women whose homes had low PBDE concentrations in dust.
Birnbaum and her collaborators say that because house cats may occupy the same environmental niche around the home as young children—both crawling around and getting dirt in their mouths— a better understanding of how cats become exposed to flame retardants and the hormonal impacts of those exposures "may have public health ramifications for both veterinary and human patients alike."
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