Environmental lead

Overview
This page is about the presence of the chemical element lead (Pb) in the environment, and its effects.

from the brin-l mailing list
...The specific harms done by environmental lead are difficult to quantify. It is known that children are much more apt to absorb the neurotoxic metal than adults, and it is suspected to have stricken many children with behavior problems, learning difficulties, hyperactivity, and breathing complications. Even more troubling, a number of recent studies have shown a strong correlation between atmospheric lead levels and crime rates. A study published in the peer-reviewed journal Environmental Research, which used data spanning more than fifty years, reported a "very strong association" between the exposure of young children to lead, and crime rates twenty years later when they became young adults. This correlation holds true for a wide variety of locales, social conditions, and models of government. The sharp decline in US crime rates which began in the early 1990s dovetails perfectly with the reduction of leaded gasoline in the early 1970s; and other countries which followed suit saw similar declines, also delayed by twenty years. It seems that the lawmakers who claim credit for crime-reducing legislation during that time are probably misplacing their congratulations. In another study, Pittsburgh University researchers found that juvenile delinquents had lead levels four times higher on average than law-abiding adolescents...

There have been several studies that show decreased IQ with even very low levels of lead in children; IIRC it was in the 2-4ug/dl range, with the grosser effects of lead poisoning manifesting at greater than ~40ug/dl.

...Over time, even low levels of lead exposure can harm a child's mental development. The possible health problems get worse as the level of lead in the blood gets higher. Possible complications include:
 * Reduced IQ
 * Slowed body growth
 * Hearing problems
 * Behavior or attention problems
 * Failure at school
 * Kidney damage

A more detailed article from the Mayo Clinic: "...Lead levels in the blood are measured in micrograms per deciliter (mcg/dL). An unsafe level is 10 mcg/dL or higher – a guideline set by the CDC."

This was set in 1991; the articles I cited some years ago about subtle effects at very low levels were from the late nineties to early 21st, IIRC.

http://www.yale.edu/ynhti/curriculum/units/1993/5/93.05.06.x.html#r [Has the 1991 CDC guidelines in addition to even more detail on lead poisoning and prevention.]

but another poster says: Brazil was one of the first countries to ban lead (because of ethanol, whose octane rating is high), and we don't have nice numbers on crime.