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Living on Earth: Flouride in Drinking Water and Other Chemical Risks

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CURWOOD: It's Living on Earth, I'm Steve Curwood. Lead. Mercury. Arsenic. PCBs. Toluene. These are common chemicals that researchers know can damage developing brains. Now a new study in the journal Lancet Neurology evaluates earlier research involving six different but also widely used chemicals that seem to affect brain function.

Perhaps most startling, this review raises more questions about fluoride in drinking water, suggesting that despite its dental benefits, fluoride could permanently impair cognitive development in children. The additional chemicals documented as neurotoxins in this article include PERC, which is used as dry cleaning fluid, manganese, used as a gasoline additive, certain fire retardants, and the insecticides Dursban and DDT. Dr. Philippe Grandjean of the Harvard School of Public Health, was the lead author.

GRANDJEAN: We looked at every single industrial chemical that we could find information on, and our conclusion is that we're now up to 12 industrial chemicals where we have evidence that they can damage the human brain development.

CURWOOD: When you say 'damage human brain development,' what do you mean?

GRANDJEAN: Well, what we have seen with these chemicals with that the effects may be cognitive, meaning that they may relate to higher brain functions, they may relate to motor control, they may relate to a behavior. There is evidence that they can also be related to depression, so we're talking about a range of different aspects of brain function, if a child is exposed to the chemical during early life or if the exposure happens in the mother's womb, then we can see later on that the child does not have optimal brain functioning.

CURWOOD: In the United States, how many children do you estimate are exposed to these chemicals at meaningful levels?

GRANDJEAN: We're all exposed to levels that can actually interfere with brain development in humans. Of course, it's a matter of the dose, how much we are exposed, because we get pesticide residues from the fruits and vegetables unless they're organic, we get mercury even if we avoid tuna and other large fish, we're still exposed to a little bit of mercury. And my message is let's minimize those exposures, we know how to do it. Let's do the best we can as soon as possible, and then do the systematic testing of industrial chemicals so that we can figure out which additional ones to control.

CURWOOD: You say these chemicals are in general circulation, and that virtually everyone is getting exposed to them at meaningful high levels. How do they relate to what we see in terms of the high number of kids with autism, a lot of discussion about ADHD, Attention Deficit Hyperactivity Disorder?

GRANDJEAN: Well, we have actually not quite convincing evidence in regard to which chemicals contribute to autism and ADHD, but I suspect that the very same chemicals that are causing the dysfunctions and deficits - where we have convincing evidence - I suspect that the very same chemicals can also trigger the disease development in the kids that end up with, for example, autism. But because the etiology of those diseases is complex we haven't quite been able to extract the convincing evidence yet.

CURWOOD: What do you think exposure to toxic chemicals is costing our society?

GRANDJEAN: Quite clearly, if a child is losing IQ points, then that child will have a lesser chance of completing high school, getting a higher education, etcetera, and landing a well paying job. So economists are saying that one IQ point is worth about $15,000. If you then look at the lead exposures in this country - exposures to lead - that translates to a loss of about $50 billion dollars per year. Mercury is something like $5 billion dollars, pesticides somewhat more. So this problem is easily 100 billion dollars per year.

CURWOOD: Professor, let's talk about fluoride. Fluoride is something that I think everyone is familiar with. It's in toothpaste. It's in a lot of drinking water. What harm, if any, is this perhaps bringing to children?

GRANDJEAN: Fluoride appears to be just like the other chemicals that damage brain development, but most of that evidence comes from China. We looked at more than 20 studies from China where they have compared children exposed to high fluoride content in the water and low. And on the average, the difference in the performance among those kids was seven IQ points. That's a sizable difference. And obviously some of the kids have been exposed to substantial fluoride concentrations in water, some of them were just a little bit above what's in this country, therefore I find that evidence very worrysome, and we need to follow up and determine if there is any risk in regard to fluoride exposure under US conditions.   
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