among the most studied are polybrominated diphenyl ethers, or pbdes. scientists have linked pbdes to a wide range of conditions, from delayed development to learning problems and diminished intelligence. >> the neuro-developmental effects--so that's exposures during pregnancy or early in life, linking to neuro-developmental effects in animals, have now been evaluated in two human studies. so there's one in a population in new york and one in a population in california. and what they find is actually remarkably similar. these developmental exposures to pbdes are actually linked to detriments in i.q. >> two pbdes, penta and octa, were taken off the u.s. market voluntarily in 2004 because of growing health concerns. production of the pbde deca is in the process of being terminated. >> the problem with all of these pbdes is that they are very persistent in the environment. >> the issue with pbdes is that they've been replaced withther types of chemicals that may have very similar concerns and perhaps even the same mechanism of action, in terms of their abi