Flame retardants may cause neurodevelopmental problems in children

By Helen Albert, Senior medwireNews Reporter

Children exposed to high levels of polybrominated diphenyl ethers (PBDEs) either prenatally or during childhood have poorer attention, fine motor coordination, and intelligence quotients (IQs) than those exposed to low levels, show results from two studies.

Results from one of the studies also showed disrupted levels of the thyroid hormones free triiodothyronine 3 and 4 (FT3 and 4) and thyroid stimulating hormone (TSH) in adolescents exposed to high levels of PBDEs.

In a study published in Environmental Health Perspectives, Brenda Eskenazi (University of California at Berkeley, USA) and colleagues assessed levels of PBDEs, key components of flame retardants, in blood samples taken from 279 women during pregnancy or at delivery and from 272 of the children when aged 7 years.

The team found that high (highest quartile) maternal PBDE levels were significantly associated with impaired attention at age 5 years, measured using a continuous performance task, and with poorer fine motor coordination in the hands (particularly the non-dominant hand) at age 5 and 7 years. In addition, children of mothers with high blood levels of PBDEs had decreased verbal and full-scale IQ scores compared with children with no or lower exposure levels (mothers in lowest quartile of PBDE levels).

Similarly, high (highest quartile) levels of blood PBDE at age 7 years were associated with increased teacher reports of attention problems, reductions in processing speed and perceptual reasoning, and lower decreased verbal and full-scale IQ scores compared with low or undetectable (lowest quartile) blood PBDE levels at this age.

"This new study is very important because it confirms earlier published research on the neurodevelopmental effects of PBDE exposure," commented independent expert Heather Stapleton (Duke University, Durham, North Carolina, USA) in a press statement.

In the other study, published in Environmental Health, Tim Nawrot (Hasselt University, Diepenbeek, Belgium) and colleagues carried out a cross sectional survey of PBDE levels in 515 adolescents (13.6-17.0 years).

They found that a twofold increase in serum PBDEs was linked to a 5.31-fold decrease in the number of taps made with the preferred hand in the Finger Tapping test, a measure of fine motor coordination.

They also found that adolescents with high levels of serum PBDEs had significantly decreased FT3 levels (by 0.15-0.18 pg/mL), and increased TSH (by 10.1% on average) compared with adolescents with serum PBDE below the level of quantification.

"Consistently with experimental animal data, PBDE exposure was associated with changes in the motor function and the serum levels of the thyroid hormones," say Nawrot and team.

However, "our observations need to be further elucidated in other age groups preferably using prospectively designed studies," concede the authors.

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