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Trace Levels of Lead Shown to Lower IQs

Posted by michael on from the duh dept.

constantnormal writes "This government study explains a lot of things, from the American public's propensity to elect the worst candidates, to the decreasing fraction of students who bother to study the "hard" sciences, to the overwhelming power advertising holds over their apparently simple minds. I think it was all the leaded gasoline burned in this country prior to the 1970s.
Homer Simpson IS the archetypal American -- Thinking and Reasoning is just too doggoned difficult."

3 of 78 comments (clear)

  1. Correlation != Causation by Ieshan · · Score: 5, Insightful

    The study says that lead levels are LINKED, slightly, to lower IQs. It says little about causation.

    While the researchers do say on a few occasions, correctly, that lead is a toxin which may be affecting children, it appears as if they correctly realize that their study is correlative and cannot be directly linked, therefore, to causation.

    All studies that deal with correlation cannot be linked to causation because the experimenters do not have direct control over the independant variable, nor can they tell which variable is independant in some cases. While the researchers did control for a variety of things in this experiment (The study followed 172 children in the Rochester, N.Y., area whose blood lead was assessed at 6, 12, 18, 24, 36, 48, and 60 months, and who were tested for IQ at both 3 and 5 years of age. The researchers controlled for many other factors that contribute to a child's intellectual functioning, such as birth weight, mother's intelligence, income, education, and amount of stimulation in the home)... it appears that they did not account for lead exposure by location - the first thing I might suggest.

    For instance, suppose that equal income housing varies greatly in Rochester, NY, and that certain children are growing up in worse or older neighborhoods than others? These worse neighborhoods might have a higher lead exposure than others, which might cause the subsequent decline more than the lead.

    Obviously, the children must be getting lead exposure from somewhere - have they accounted for school district (lead piping or building location of a particular school)?

    It's not that I don't believe in the study, I'd just be hesitant to scream causality.

  2. Maybe that's because.... by tha_mink · · Score: 5, Funny

    Maybe, just maybe, only stupid people eat paint.

    --
    You'll have that sometimes...
  3. causation already established! by js7a · · Score: 5, Informative
    ...their study is correlative and cannot be directly linked, therefore, to causation.

    No, the causation is well established.

    The correlation in question has been known since the early 1960s and confirmed repeatedly in the medical literature. Because of this, lead was removed from the ingredients of paint and gasoline in the 1970s. The causation has been confirmed since at least the publication of this 1994 meta-analysis:

    ... Lead interferes with GABAergic and dopaminergic neurotransmission. It has been shown to bind to the NMDA receptor and inhibit long-term potentiation in the hippocampal region of the brain. Moreover, experimental studies have demonstrated that blood levels of 10 micrograms/dl interfere with a broad range of cognitive function in primates. Given this support, these associations in humans should be considered causal.

    The important results from the new research cited in the article is that the threshold of activity is much lower than had previously been understood.