Friday, December 11, 2009

Retardants are Retardants

It has always been suspected that polybrominated diphenyl ethers (PBDEs) might have potential neurological effects much like other halogenated organic compounds. Reported in EHP this month, a study of healthy school-aged children were measured for various motor, cognition and behavioral endpoints and correlated with their mothers’ prenatal levels of various organohalogenated compounds. Exposures to higher levels of PBDEs lead to both positive and negative neurological outcomes.

PBDEs are everywhere. They are used as flame retardants and found in fabrics, textiles, furniture, electronics, foams etc...So from everything including the computer chair I’m sitting on, to the bed I plan on crashing into tonight, are loaded with PBDEs. It has been shown previously that a measurable percentage of the air we breathe indoors are PBDEs (there are reasons why indoor air pollution is worse than outdoors). Now make no question about it - PBDEs save lives. Much like DDT which successfully reduces malaria in some parts of the world, we must not overlook the beneficial impact these chemicals can have. In fact, the federal government requires manufacturers to include these compounds because house fires are common and flame retardants save lives.

Much like any halogenated compound, the bonds in PBDEs are very strong and they do not degrade readily in the environment. In addition, they are hydrophobic, leading to accumulation in fat reserves and their ultimate fate is bioaccumulation and biomagnification. PBDEs are a conservative pollutant, meaning once they are released, they can be considered as a permanent addition to the environment. The frightening thing is, because they are so ubiquitous, PBDEs can be measured in our bodies and the concentration doubling times are as little as 5 years!

But back to the study, this is the first time a cohort study had been performed on healthy school-aged children (5-6yr) looking at prenatal exposure to halogenated compounds. Mothers were first measured for serum background levels of several organohalogenated compounds at the 35th week of pregnancy. What was found in their children, now years later, that exposure to prenatal PBDEs leads to permanent neurological disruption, such as shortened attention span and poor fine motor skills. However, unlike exposure to prenatal PCBs, there was no impairment of cognitive function. In addition, exposure to PBDEs also led to increased coordination and better behavior. Because of the diverse neurological effects seen, both positive and negative, it is difficult to determine the implications of these findings. Also in laboratory studies, it has been found PBDEs can cause worsening neurological impairment with age. So this leaves open the question of how these children will be affected as they grow.

Both Penta- and Octo- BDE have been banned in the EU and US, and Deca- being only banned in the EU. While these are considered the most persistent forms of PBDE, our high volume of production still puts us all potentially at risk, even if we are only exposed to just background levels.

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