Cat food, house dust, human breast milk, televisions, and sperm whales all have one thing in common: They are laced with a group of flame retardants known as polybrominated diphenyl ethers or PBDEs.

There are three common commercial forms in this group. Two were voluntarily phased-out of production in 2005 in the U.S. because of toxicity concerns, but one still remains.

The third and most widely used molecule, known as deca-BDE for its 10 bromine atoms, can still be found anywhere and everywhere that researchers have looked. It is an additive in electronics, especially televisions, as well as textiles and furniture. Because the chemical is not bound to materials it can leak out into the environment. Until recently it was thought deca-BDE was an innocuous member of the trio, but a growing body of evidence and increasing political action is questioning that assumption.

“In the last two or three years there’s been paper after paper that deca does the same thing as these other chemicals,” said Deborah Rice, a toxicologist at the Maine Center for Disease Control and Prevention. “They’re persistent, they’re bioaccumulative and they’re toxic.”

A recent study found a correlation between PBDE exposure and hyperthyroidism in cats. The condition is the leading cause of death in pet cats, according to researchers.

Hyperthyroidism in cats has increased dramatically in the past few decades, just as PBDEs have become ubiquitous. “We did not prove a link,” said Janice Dye, a research biologist at the Environmental Protection Agency and lead author of the study. “But the link did show that maybe it could be a factor."

Cats who ate canned food, which had high levels of the two PBDEs that have been phased out, had a “significantly higher risk” for thyroid problems, she said.

Even with the prohibition on some PBDEs, the threat remains. The study found deca-BDE was pervasive in house dust, and also in dry cat food. Researchers discovered the cats were metabolizing deca-BDE into more toxic forms, such as the two PBDEs that have already been banned.

House-bound felines may serve as live-in sentinels for human exposure to deca-BDE, but it is not just house cats that are metabolizing this chemical. Studies have found that mice, wild fish and birds and humans can also break it down into more toxic forms. Research has also found that it deteriorates in sunlight, which may explain how its degraded forms are ending up in the environment and wild animals.

While PBDEs are correlated with thyroid problems in cats, there are other adverse health effects seen in animal models. Recent studies have found that deca-BDE, even before it is broken down, slows neurological development, including learning and memory in rats.

Deca-BDE and its by-products seem to affect “brain, endocrine, and possibly cause cancer in very high doses,” said Dr. Arnold Schecter of the University of Texas School of Public Health, who has studied PBDE levels in humans and the environment.

To date, there have been limited human studies regarding deca-BDE, but Schecter said, generally in toxicity studies, “what holds up in animals holds up in humans as well.” The U.S. has the highest levels of PBDEs in the world, 10 to 30 times higher than Europeans, and it is clear that “PBDEs are going up, and going up fairly rapidly,” he said.

The swell of new studies focusing on the rising rates of deca-BDE and its ability to break down has garnered the attention of legislators.

In Europe, Denmark, Germany and Sweden are locked in a battle over the European Union’s decision to ban the other two commercial PBDEs while allowing for deca-BDE to remain in use. That decision was made in 2003, before the newest research illustrating that deca-BDE is even more toxic as it breaks down.

In the U.S., Washington State and Maine have passed legislation to ban deca-BDE, and Illinois is debating similar action.

John Kyte, North American program director of the Bromine Science and Environmental Forum, an international organization representing PBDE manufacturers, said in an email that the move is premature, because the efficacy and health safety of alternatives to deca-BDE have not been proven.

“That’s why we’re being very cautious about it,” explained Denise LaFlamme, a toxicologist at the Washington State Department of Health, which is assessing alternatives. Both Maine and Washington have provisions that deca-BDE will not be phased out until an alternative can be named.

States and non-profit groups, such as Clean Production Action, are leaning towards phosphate alternatives. Many of these phosphate alternatives are already being produced by the same manufactures that make deca-BDE, and are equally effective flame retardants.

There is some evidence that they are safer than deca-BDE, although states are looking for more information before making a final decision. Both Illinois and Maine found that changing the type of plastic used in televisions can greatly reduce the need for flame retardants. LaFlamme notes that using phosphate flame retardants, in conjunction with different plastics, should not cost much more than deca-BDE, only adding a few dollars to the final price of an item.

Toxicologists agree that PBDEs look a lot like another infamous chemical, PCBs. Levels of PCBs in humans have been declining since they were banned in the 1970s in light of toxicity concerns.

As levels of PCBs have dropped off in the environment, they have been replaced by rising rates of deca-BDE and all of its related chemicals. “They look like PCBs, and act like PCBs,” said Schecter. “So if you want to err on the side of caution, you would ban them.”