Brominated flame retardants, the chemicals found in household items like furniture cushions and carpet pads, can alter thyroid hormones in pregnant women that may hamper the baby’s growth and brain development, a new study has claimed.
Flame-retarding chemicals known as polybrominated diphenyl ethers, or PBDEs, are a class of toxic chemicals in wide use to prevent the spread of fire.
Earlier research suggested that 97 per cent of Americans get exposed to PBDE which causes an array of adverse health effects including thyroid hormone disruption.
The new study, published in the journal Environmental Health Perspectives, is considered important because it is the first human research showing a link between the ubiquitous chemicals and altered levels of the hormones in pregnant women.
Though its effects on babies are unknown, researchers said it might lead to smaller foetuses, and reduce children’s intelligence and motor skills.
“Normal maternal thyroid hormone levels are essential for normal foetal growth and brain development, so our findings could have significant public health implications,” said lead researcher Jonathan Chevrier of the University of California, Berkeley.
“These results suggest that a closer examination between PBDEs and these outcomes is needed.” Jonathan Chevrier added.
Brenda Eskenazi, the co-author of the study, said despite the prevalence of these flame retardants, there are few studies that have examined their impact on human health.
“Our results suggest that exposure to PBDE flame retardants may have unanticipated human health risks.” Brenda Eskenazi said.
For their study, the researchers analysed blood samples from 270 women taken around the end of their second trimester of pregnancy.
They measured concentrations of 10 PBDE chemicals, two types of thyroxine (T4) and thyroid-stimulating hormone (TSH).
They controlled for such factors as maternal smoking, alcohol and drug use, and exposure to lead and pesticides.
The analysis focused on the five PBDE chemicals that were detected most frequently and are components of a mixture called pentaBDE.
The researchers found that a 10-fold increase in each of the PBDE chemicals was associated with decreases in TSH ranging from 10.9 per cent to 18.7 per cent. When the five PBDEs were analysed together, a tenfold increase was linked to a 16.8 per cent decrease in TSH.
“Low TSH and normal T4 levels are an indication of subclinical hyperthyroidism, which is often the first step leading toward clinical hyperthyroidism,” said Chevrier.
“Though the health effect of subclinical hyperthyroidism during pregnancy is not well understood, maternal clinical hyperthyroidism is linked to altered fetal neurodevelopment, increased risk of miscarriage, premature birth and intrauterine growth retardation.”
Exactly how flame retardants influence TSH levels is unclear, but the researchers said animal studies have shown that certain PBDEs can mimic thyroid hormones.
