(Reuters Health) - Two toxic chemicals banned in the U.S. in 2005 are still finding their way into the bloodstreams of California women, suggesting that sources of exposure persist in homes and in the environment, researchers say.
The flame retardant chemicals called Polybrominated Diphenyl Ethers, or PBDEs, were used to treat polyurethane foam, hard plastics, textiles, glues and wire insulation, among other products, until 2006 in the U.S. They were banned a few years earlier in Europe.
“We don’t fully understand the health consequences of exposures to these chemicals in humans. Laboratory studies in animals, however, have shown that PBDEs can interfere with normal development of the neurologic system, disrupt the proper functioning of the immune and hormonal systems, and may promote cancer” lead author Susan Hurley told Reuters Health in an email.
“Concerns that similar effects might occur in people led to the voluntary phase-out and banning of these chemicals,” said Hurley, a researcher with the Cancer Prevention Institute of California, in Berkeley.
Small studies in the past, almost entirely focused on young women, suggested that PBDE levels in people dropped immediately after the chemicals were banned, Hurley said.
To check more recent levels in a larger and different population, the researchers analyzed blood samples from 1,253 women participating in an ongoing study of California teachers. The participants, mostly between the ages of 60 and 79, provided blood samples regularly between May 2011 and August 2015.
Exposure to PBDEs was common, Hurley said, “(they) were found in at least three-quarters of the women we tested.” And there was a small, but statistically meaningful increase in the blood levels of both chemicals over the four-year study period, the study team reports in Environmental Science and Technology.
“Our results . . . which focus on a more recent time period, suggest that there may be a recent shift in exposure pathways such that the diet may be becoming more important,” Hurley said.
Before the ban, people were primarily exposed to the chemicals by ingesting and inhaling dust from furniture and other PBDE-laden products, Hurley said.
“As the ban took effect and these products have been replaced with newer PBDE-free products, exposures from indoor dust probably have declined. However, as the old products are now being disposed of in landfills and incinerators, it is likely that the outdoor environment is becoming increasingly contaminated,” she said.
PBDEs aren’t easily broken down in the environment, Hurley noted, so they eventually find their way into the food chain.
“This is exactly what we witnessed with PCBs, a class of toxic pollutants that were banned nearly 40 years ago. While initially PCB body burden levels declined, they eventually leveled off and remained steady for decades as people have been continually exposed through the food they eat. It appears that exposures to PBDEs may be following a similar trajectory,” she said.
“If our findings of sustained and possibly increasing PBDE body burden levels are replicated in other contemporary populations, it will underscore the urgency to take additional regulatory actions to manage the safe disposal of PBDE-laden furniture and other PBDE-laced products to reduce environmental contamination and minimize dietary exposures,” she said.
“Although there are some limitations in the study, the findings have significant public health implications, suggesting that human exposure to PBDEs are still existing,” said Dr. Yawei Zhang, a researcher at the Yale School of Public Health in New Haven, Connecticut, who wasn’t involved in the study.
“Although the PBDEs have been phased out, people may be exposed to these chemicals continuously due to their persistence, ubiquity, and bioaccumulation,” said Zhang, who is currently investigating serum concentrations of PBDEs and risk of thyroid cancer in military personnel.
“While the commercial formulations containing these particular chemicals have been banned, they have been replaced with similar compounds whose health effects are not yet fully understood,” Hurley noted.
Avoiding the use of substitutions that will pose similar problems in the future is a goal of California’s Safer Consumer Products Program (bit.ly/O1SYsM), Hurley said.
SOURCE: bit.ly/2p5jkNt Environmental Science and Technology, online March 17, 2017.