November 23, 2007
Even Low Blood Lead Levels Lower IQ?
Lead toxicity to the brain appears to kick in at pretty low blood levels of lead.
Even very small amounts of lead in children's blood -- amounts well below the current federal standard -- are associated with reduced IQ scores, finds a new six-year Cornell study.
The study examined the effect of lead exposure on cognitive function in children whose blood-lead levels (BLLs) were below the Centers for Disease Control and Prevention (CDC) standard of 10 micrograms per deciliter (mcg/dl) -- about 100 parts per billion. The researchers compared children whose BLLs were between 0 and 5 mcg/dl with children in the 5-10 mcg/dl range.
"Even after taking into consideration family and environmental factors known to affect a child's cognitive performance, blood lead played a significant role in predicting nonverbal IQ scores," says Richard Canfield, a senior researcher in Cornell's Division of Nutritional Sciences and senior author of the study in the journal Environmental Health Perspectives. "We found that the average IQ scores of children with BLLs of only 5 to 10 mcg/dl were about 5 points lower than the IQ scores of children with BLLs less than 5 mcg/dl. This indicates an adverse effect on children who have a BLL substantially below the CDC standard, suggesting the need for more stringent regulations," he said.
Vitamin C (ascorbic acid) and B1 (thiamine) enhance lead excretion. Screening of children in high risk neighborhoods might identify neighborhoods where children should take a multivitamin that will raise their IQs by reducing lead toxicity. A 5 point IQ jump would pay back the cost of the screening and vitamins many times over.
Randall, maybe you could retitle the post "Even low..." I saw it, and I thought that having low, as opposed to high lead levels would make me dumber. It might mean I have too much lead in though.
I thought it was going to be the connection where the higher levels of blood lead meant higher fish consumption.
Lead sucks. It really, really sucks. It just screams out for sustained government action. Abatement, abatement, abatement, no matter the apparent upfront price (which, for the record, looks like a rounding error on the Iraq war).
That the US government largely doesn't is among the stronger indictments I know of any and all political parties.
wcw, I agree.
Anon, The problem with fish is mercury, not lead.
Thanks for the pointer to the journal Environmental Health Perspectives--the articles can be freely downloaded as PDFs, which makes the journal a great resource for my statistics classes.
Looking at the article, the evidence for this effect seems fairly strong, which should get the CDC motivated to improve their standard on lead. The missing piece of the puzzle, which I suspect someone has somewhere, is what proportion of our overall population is exposed to these low, but potentially damaging levels of lead. I suspect it's not everyone, but that it's considerable.
Does anything enhance mercury excretion?
I wonder if this contributes to the black-white IQ gap?
I have to be skeptical about these results, due to the difficulty of eliminating confounding factors.
I hate to throw water on this but if you look at the Vitamine B1 and C study closely, it only shows about a 1/3 reduction in lead levels, from very high to still too high (For Vitamine B1, from 39 to 24 micrograms per deciliter, and for Vitamine C, from 31 to 20 micrograms per deciliter). Still more than double the currently acceptable level, which as you point out is itself too high. I've heard that pretty much any detectable level for lead (and mercury, etc) is hazardous. It's very interesting and suggests further inquiry, but by itself this study is inconclusive.
Meanwhile, lead acetate is sold as a hair coloring agent
and fully approved by our regulatory authorities.
(See Wikipedia, Grecian Formula.)
Don't touch grandpa's hair, junior!
That is interesting sort of study with blood. I wouldn't have thought of that as viable. I like that someone did the study.