Roger Masters, a retired professor of government at Dartmouth, a
maverick researcher with no formal scientific training who has been
studying the link between pollution and violent crime, argues that
metal toxins in the brain can lead to murders, rapes and robberies.

"Nobody makes the connection between metals, brain chemistry,
behavior and crime," Masters says.

"There's the broader issue of how chemicals are affecting the brain
and the things we do. It goes beyond the idea that watching
television causes crime."

Study of the dangers of heavy metals and their effects on the brain
has been going on for some time. The effects of lead exposure,
suspected since antiquity, are probably the best known of all metal
poisoning; the first study linking lead poisoning and violent
behavior appeared in 1943.

In 1979 Herbert Needleman, then a Harvard Medical School professor,
did a groundbreaking study showing that kids with higher lead
residues in their teeth performed worse on IQ tests and had poorer
attention spans and less-developed language skills. His article
helped lead to the banning of leaded gasoline.

Since then, studies have shown that exposure to toxins like mercury
and polychlorinated biphenyls (PCBs) can play a role in developmental
disabilities such as intellectual retardation, attention
deficit/hyperactivity disorder and autism.

In 1997 Masters found that counties with releases of lead and
manganese and high rates of alcoholism-related deaths had three times
more violent crime than areas with no releases and few deaths from
alcoholism.

(His study controlled for factors like poverty and family
disintegration so that he could more accurately test the effects of
environmental poisons.)

Masters argues that the interaction of pollution with brain
chemistry, poverty, family disintegration and poor diet can put some
people at risk for "sub-clinical toxicity" -- a condition that can
interfere with impulse control, lowering the mental barrier.

http://www.salon.com/books/it/1999/06/18/littleton/