By Catherine Clabby
Just as federal regulators are urging consumers and manufacturers to steer clear from an entire class of flame-retardants, Duke researchers have preliminary evidence linking some of the chemicals to increased risk of thyroid cancer.
Thyroid cancer, on average, remains rare in the United States, with only about 14 people out of every 100,000 being diagnosed with the disease. But thyroid malignancies, including fatal cases, have been on the rise.
“We are winning the war on cancer with some exceptions. Thyroid cancer is one of those exceptions,” said Julie Ann Sosa, chief of Endocrine Surgery and director of the Surgical Center for Outcomes Research at Duke.
Incidence of papillary carcinoma – the most common form of thyroid cancer – has increased an average of 7 percent for the past two decades Sosa said. Advances in imaging gear such as ultrasound scans that improve detection of the cancers don’t explain the increased number of diagnoses, Sosa’s research has concluded.
Environmental causes, including expanded exposure to some organohalogen flame retardants over decades, may be in play. The compounds invite suspicions because so many people carry traces of them.
And at a molecular level, the flame-retardants resemble hormones and sometimes interact with human cells in a disruptive way. Some compounds have been shown to alter normal endocrine processes, particularly in the thyroid.
In a pilot study published this summer, Sosa and Duke environmental scientist Heather Stapleton found reasons to dig deeper into this potential link. They found that people in a relatively small research cohort of 140 subjects who were exposed to decabromodiphenyl ether (BDE-209) and tris (2-chloroethyl) phosphate in dust in their homes had increased odds of also having papillary hybrid cancer.
“I’m not sure this is going to explain everything but it may explain something,” Sosa said of the increased rate of thyroid cancer.
Invisible but everywhere
Just last month, the U.S. Consumer Product Safety Commission urged consumers and manufacturers to steer clear of organohalogen flame retardants (OFRs) able to seep into the environment. Members also recommended that importers, distributors and retailers confirm the absence of those OFRs before purchasing products to sell. Pregnant women and families with young children should obtain assurances that products do not contain OFRs, commissioners counseled.
Petitioned by pediatricians, environmental groups and others, commission members by a 3-to-2 vote also agreed to study whether the compounds should be banned, a move opposed by chemical industry groups, whose leadership argues it could make people more vulnerable to injury from fire.
Children may be most vulnerable because their brains and other organs are still developing, says the information page on the substances published by the National Institute of Environmental Health Sciences, based in Research Triangle Park.
Manufacturers have used chemical treatments since the 1970s to suppress fire on countless objects we live among: upholstered furniture, mattresses, carpets, computers, televisions parts, insulation for wires, cables and homes, auto parts, and more.
Generally not integrated into the products they are intended to protect, the compounds leach into the environment. Once there, they don’t break down easily. As a result, most people in the U.S. have traces of flame-retardant chemicals in their blood and tissue. Amounts can accumulate over time.
Adverse health effects associated with the chemicals include reproductive impairments, reduced sperm count among men, decreased IQ in children, impaired memory, and learning deficits. In addition to interfering with normal thyroid functions regulated by hormones, the chemicals may contribute to obesity and diabetes, cancer, and immune disorders, the U.S. Consumer Product Safety Commission noted in a publication in the Federal Register explaining its vote.
Stapleton, Sosa’s research partner, is a veteran investigator of both flame-retardant exposure and its possible health effects.
In one crowd-sourced project, she invited people from all over the country to send her lab snips of fabric and other materials from their home suspected to contain the chemicals. The lab analyzed what they received, informing people of what was in their homes, and expanding a database of the chemical contamination at the same time.
For the thyroid cancer study, Sosa, Stapleton and colleagues recruited 140 study subjects. Some had thyroid cancer and some did not.
The research teams scoured participants’ medical records and the lists of chemical contaminants detected in their blood. They also asked participants to not vacuum their homes for a couple of days before they visited. With a Eureka Mighty Might vacuum, they sucked up dust in the homes themselves, wrapping what they found in aluminum foil and freezing it until it could be analyzed in Stapleton’s lab.
Exposures to two chemicals — decabromodiphenyl ether (BDE-209) and tris (2-chloroethyl) phosphate (TCEP) in dust— were most strongly associated with higher odds of having papillary thyroid cancer, the researchers found.
Looking at the role of an environmental exposure in an endocrine cancer is a new research avenue for Sosa, whose work is usually more oriented to clinical trials of drugs and surgical procedures. But she is convinced this is worthwhile.
“You have to partner or collaborate with other experts who have the complete skill set,” she said. “I hope more physicians and surgeons will think about this.”
More to learn
Both scientists emphasize that their findings are preliminary and need to be confirmed by more research. They hope to land federal funding to expand the research to do that and more.
In the meantime, the Duke professors’ outreach to thyroid cancer patients continues, including a project aimed at getting a glimpse of how much exposure to flame retardants occurs outside the home. They are asking people recently diagnosed with thyroid cancer at Duke to wear silicone bracelets, resembling those handed out by charities.
Research has shown the material absorbs some chemicals it comes in contact with, Stapleton said.
Stapleton was among the experts on the risks from flame retardants who spoke before the U.S. Consumer Product Safety Commission before it decided to take steps against the compounds. So was Linda Birnbaum, the director of NIEHS and a longtime researcher in this arena.
Stapleton said she hopes funding for such work remains available under a U.S. Presidential administration that is explicitly trying to adjust some regulation to favor industry over environmental groups.
Both houses of the U.S. Congress so far have rejected a Trump Administration bid to reduce the National Institutes of Health (NIH) budget by $7.7 billion (22 percent) for the coming fiscal year. But uncertainty remains regarding federal funding support for related costs, such as paying for research facilities and administration.
And Stapleton isn’t confident that the Consumer Product Safety Commission will pursue a ban on flame-retardants, despite the recent vote to start that process.
The term of one supportive commissioner who participated in the 3-to-2 vote has expired and a new Trump Administration appointee may not endorse the move, she said.
The push to address this problem may falter, Stapleton said, but the exposure isn’t disappearing. “It’s not like anyone can walk in a home and figure out what is used where,” Stapleton said. “But we detect them in almost every single home, some in larger quantities than others.”