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Areas for Future Lead
Research
The following is an extract from "The Health
Effects of Low Level Exposure to Lead" by Prof H.L. Needleman & Dr. D. Bellinger.
First published in Annual Review of Public Health 1991 12:111-40. © 1991 by Annual Review
Inc
Most studies of childhood lead exposure have focused on psychometric intelligence, i.e.
reading and math achievement. Little attention has been paid to higher order behavior,
such as ability to get along with peers and to accept the prevailing social mores. There
is growing evidence that lead-exposed children have difficulty in attention (64);p some
evidence suggests that exposure is associated with aggressiveness (48). Attention deficit
with hyperactivity, coupled with antisocial behavior, is a strong predictor of criminality
(52, 55). Criminal behavior has been found to be higher in males, blacks, and urban
dwellers. It displays itself early in life; criminals are more likely to have been
hyperactive as young children and to have come from disorderly homes with poor
housekeeping (106). All of these factors are associated with lead exposure. Carefully
designed case control and forward studies of the association of lead exposure with
antisocial behavior are clearly warranted.
The studies of Kitchen et al (42, 4 1) and Nation et al (6 1) suggest
that studies of lead exposure in drug and alcohol abusers are worth pursuit. Case control
studies of older individuals who are past the ages of peak exposure should benefit from
new advances in the technology of in vivo lead measurement.
Almost all studies of lead toxicity have focused on
young children, and more recently on fetuses in utero. Because the fetus clearly is not
protected from lead, maternal exposure has become a subject of considerable interest.
Hormonal changes associated with pregnancy might mobilize lead stores, which would create
an endogenous source of fetal exposure, even if external exposure during pregnancy is low
(56, 100). Less attention has been paid to paternal exposure and its consequences for the
father and his potential offspring, despite evidence that suggests that lead is a
gametoxin. Studies of male productive function and fetal consequences of paternal exposure
are needed.
Another ignored issue is the effect of early lead exposure on the aged. Most lead is
deposited in bone, where it is relatively inert. But with aging, bone demineralizes, which
possibly provides an 'endogenous source of ongoing exposure (96). No information on the
sites of redistribution of bone lead is available. Does some of this lead get to the CNS?
Is lead one factor in the disordered memory and cognition found in some older patients?
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